99 results on '"membrane channels"'
Search Results
2. Structural insights into the orthosteric inhibition of P2X receptors by non-ATP analog antagonists
- Author
-
Danqi Sheng, Chen-Xi Yue, Fei Jin, Yao Wang, Muneyoshi Ichikawa, Ye Yu, Chang-Run Guo, and Motoyuki Hattori
- Subjects
membrane channels ,receptors ,electron microscopy ,electrophysiology ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
P2X receptors are extracellular ATP-gated ion channels that form homo- or heterotrimers and consist of seven subtypes. They are expressed in various tissues, including neuronal and nonneuronal cells, and play critical roles in physiological processes such as neurotransmission, inflammation, pain, and cancer. As a result, P2X receptors have attracted considerable interest as drug targets, and various competitive inhibitors have been developed. However, although several P2X receptor structures from different subtypes have been reported, the limited structural information of P2X receptors in complex with competitive antagonists hampers the understanding of orthosteric inhibition, hindering the further design and optimization of those antagonists for drug discovery. We determined the cryogenic electron microscopy (cryo-EM) structures of the mammalian P2X7 receptor in complex with two classical competitive antagonists of pyridoxal-5'-phosphate derivatives, pyridoxal-5'-phosphate-6-(2'-naphthylazo-6'-nitro-4',8'-disulfonate) (PPNDS) and pyridoxal phosphate-6-azophenyl-2′,5′-disulfonic acid (PPADS), and performed structure-based mutational analysis by patch-clamp recording as well as molecular dynamics (MD) simulations. Our structures revealed the orthosteric site for PPADS/PPNDS, and structural comparison with the previously reported apo- and ATP-bound structures showed how PPADS/PPNDS binding inhibits the conformational changes associated with channel activation. In addition, structure-based mutational analysis identified key residues involved in the PPNDS sensitivity of P2X1 and P2X3, which are known to have higher affinity for PPADS/PPNDS than other P2X subtypes.
- Published
- 2024
- Full Text
- View/download PDF
3. Proteome and Membrane Channels
- Author
-
Pasquarelli, Alberto and Pasquarelli, Alberto
- Published
- 2021
- Full Text
- View/download PDF
4. Anesthetics and Cell–Cell Communication: Potential Ca 2+ -Calmodulin Role in Gap Junction Channel Gating by Heptanol, Halothane and Isoflurane.
- Author
-
Peracchia, Camillo
- Subjects
- *
ISOFLURANE , *CAFFEINE , *ANESTHETICS , *PHORBOL esters , *ION channels , *FORSKOLIN , *CALMODULIN , *THEOPHYLLINE - Abstract
Cell–cell communication via gap junction channels is known to be inhibited by the anesthetics heptanol, halothane and isoflurane; however, despite numerous studies, the mechanism of gap junction channel gating by anesthetics is still poorly understood. In the early nineties, we reported that gating by anesthetics is strongly potentiated by caffeine and theophylline and inhibited by 4-Aminopyridine. Neither Ca2+ channel blockers nor 3-isobutyl-1-methylxanthine (IBMX), forskolin, CPT-cAMP, 8Br-cGMP, adenosine, phorbol ester or H7 had significant effects on gating by anesthetics. In our publication, we concluded that neither cytosolic Ca2+i nor pHi were involved, and suggested a direct effect of anesthetics on gap junction channel proteins. However, while a direct effect cannot be excluded, based on the potentiating effect of caffeine and theophylline added to anesthetics and data published over the past three decades, we are now reconsidering our earlier interpretation and propose an alternative hypothesis that uncoupling by heptanol, halothane and isoflurane may actually result from a rise in cytosolic Ca2+ concentration ([Ca2+]i) and consequential activation of calmodulin linked to gap junction proteins. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. The murburn precepts for cellular ionic homeostasis and electrophysiology.
- Author
-
Manoj, Kelath Murali, Bazhin, Nikolai, and Tamagawa, Hirohisa
- Subjects
- *
MOLECULAR structure , *HOMEOSTASIS , *MONOVALENT cations , *CALCIUM ions , *ACTION potentials , *SOLUBILIZATION , *ELECTROPHYSIOLOGY - Abstract
Starting from the basic molecular structure and redox properties of its components, we build a macroscopic cellular electrophysiological model. We first present a murburn purview that could explain ion distribution in bulk‐milieu/membrane‐interface and support the origin of trans‐membrane potential (TMP) in cells. In particular, the discussion focuses on how cells achieve disparity in the distribution of monovalent and divalent cations within (K+ > Na+ > Mg2+ > Ca2+) and outside (Na+ > K+ > Ca2+ > Mg2+). We explore how TMP could vary for resting/graded/action potentials generation and project a model for impulse conduction in neurons. Outcomes based on murburn bioenergetic equilibriums leading to solubilization of ion‐pairs, membrane's permittivity, protein channels' fluxes, and proteins' innate ability to bind/adsorb ions selectively are projected as the integral rationale. We also provide experimental modalities to ratify the projections. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
6. Digging into the biophysical features of cell membranes with lipid-DNA conjugates.
- Author
-
Ali, Ahsan Ausaf, Bagheri, Yousef, and You, Mingxu
- Subjects
- *
CELL membranes , *BIOPHYSICS , *MEMBRANE lipids , *DNA probes - Abstract
Lipid-DNA conjugates have emerged as highly useful tools to modify the cell membranes. These conjugates generally consist of a lipid anchor for membrane modification and a functional DNA nanostructure for membrane analysis or regulation. There are several unique properties of these lipid-DNA conjugates, especially including their programmability, fast and efficient membrane insertion, and precise sequence-specific assembly. These unique properties have enabled a broad range of biophysical applications on live cell membranes. In this review, we will mainly focus on recent tremendous progress, especially during the past three years, in regulating the biophysical features of these lipid-DNA conjugates and their key applications in studying cell membrane biophysics. Some insights into the current challenges and future directions of this interdisciplinary field have also been provided. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. Molecular mechanism of thiamine pyrophosphate import into mitochondria: a molecular simulation study.
- Author
-
Van Liefferinge, F., Krammer, E.-M., Waeytens, J., and Prévost, M.
- Subjects
- *
THIAMIN pyrophosphate , *MOLECULAR dynamics , *PLANT mitochondria , *MITOCHONDRIA , *BINDING sites , *MITOCHONDRIAL membranes - Abstract
The import of thiamine pyrophosphate (TPP) through both mitochondrial membranes was studied using a total of 3-µs molecular dynamics simulations. Regarding the translocation through the mitochondrial outer membrane, our simulations support the conjecture that TPP uses the voltage-dependent anion channel, the major pore of this membrane, for its passage to the intermembrane space, as its transport presents significant analogies with that used by other metabolites previously studied, in particular with ATP. As far as passing through the mitochondrial inner membrane is concerned, our simulations show that the specific carrier of TPP has a single binding site that becomes accessible, through an alternating access mechanism. The preference of this transporter for TPP can be rationalized mainly by three residues located in the binding site that differ from those identified in the ATP/ADP carrier, the most studied member of the mitochondrial carrier family. The simulated transport mechanism of TPP highlights the essential role, at the energetic level, of the contributions coming from the formation and breakage of two networks of salt bridges, one on the side of the matrix and the other on the side of the intermembrane space, as well as the interactions, mainly of an ionic nature, formed by TPP upon its binding. The energy contribution provided by the cytosolic network establishes a lower barrier than that of the matrix network, which can be explained by the lower interaction energy of TPP on the matrix side or possibly a uniport activity. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
8. A Visible‐Light‐Regulated Chloride Transport Channel Inspired by Rhodopsin.
- Author
-
Quan, Jiaxin, Zhu, Fei, Dhinakaran, Manivannan Kalavathi, Yang, Yingying, Johnson, Robert P., and Li, Haibing
- Subjects
- *
CHLORIDE channels , *RHODOPSIN , *BIOLOGICAL transport , *CHEMICAL models , *VISIBLE spectra , *CUCURBITURIL - Abstract
Inspired by the light‐regulating capabilities of naturally occurring rhodopsin, we have constructed a visible‐light‐regulated Cl−‐transport membrane channel based on a supramolecular host–guest interaction. A natural retinal chromophore, capable of a visible‐light response, is used as the guest and grafted into the artificial channel. Upon introduction of an ethyl‐urea‐derived pillar[6]arene (Urea‐P6) host, threading or de‐threading of the retinal and selective bonding of Cl− can be utilized to regulate ion transport. Based on the visible‐light responsiveness of the host–guest interaction, Cl− transport can be regulated by visible light between ON and OFF states. Visible‐light‐regulated Cl− transport as a chemical model permits to understand comparable biological ion‐selective transport behaviors. Furthermore, this result also supplies a smart visible‐light‐responsive Cl− transporter, which may have applications in natural photoelectric conversion and photo‐controlled delivery systems. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
9. Structural insights into the orthosteric inhibition of P2X receptors by non-ATP analog antagonists.
- Author
-
Sheng D, Yue CX, Jin F, Wang Y, Ichikawa M, Yu Y, Guo CR, and Hattori M
- Subjects
- Animals, Mammals, Molecular Dynamics Simulation, Adenosine Triphosphate chemistry
- Abstract
P2X receptors are extracellular ATP-gated ion channels that form homo- or heterotrimers and consist of seven subtypes. They are expressed in various tissues, including neuronal and nonneuronal cells, and play critical roles in physiological processes such as neurotransmission, inflammation, pain, and cancer. As a result, P2X receptors have attracted considerable interest as drug targets, and various competitive inhibitors have been developed. However, although several P2X receptor structures from different subtypes have been reported, the limited structural information of P2X receptors in complex with competitive antagonists hampers the understanding of orthosteric inhibition, hindering the further design and optimization of those antagonists for drug discovery. We determined the cryogenic electron microscopy (cryo-EM) structures of the mammalian P2X7 receptor in complex with two classical competitive antagonists of pyridoxal-5'-phosphate derivatives, pyridoxal-5'-phosphate-6-(2'-naphthylazo-6'-nitro-4',8'-disulfonate) (PPNDS) and pyridoxal phosphate-6-azophenyl-2',5'-disulfonic acid (PPADS), and performed structure-based mutational analysis by patch-clamp recording as well as molecular dynamics (MD) simulations. Our structures revealed the orthosteric site for PPADS/PPNDS, and structural comparison with the previously reported apo- and ATP-bound structures showed how PPADS/PPNDS binding inhibits the conformational changes associated with channel activation. In addition, structure-based mutational analysis identified key residues involved in the PPNDS sensitivity of P2X1 and P2X3, which are known to have higher affinity for PPADS/PPNDS than other P2X subtypes., Competing Interests: DS, CY, FJ, YW, MI, YY, CG, MH No competing interests declared, (© 2023, Sheng, Yue et al.)
- Published
- 2024
- Full Text
- View/download PDF
10. Effects of Moderate Static Magnetic Field on Neural Systems Is a Non-invasive Mechanical Stimulation of the Brain Possible Theoretically?
- Author
-
Antonio Hernando, Fernando Galvez, Miguel A. García, Vanesa Soto-León, Carlos Alonso-Bonilla, Juan Aguilar, and Antonio Oliviero
- Subjects
static magnetic field ,Zeeman energy ,membrane channels ,non-invasive brain stimulation ,mechanical stimulation ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Static magnetic fields have been shown to induce effects on the human brain. Different experiments seem to support the idea that moderate static magnetic field can exert some influence on the gating processes of the membrane channels. In this article we visit the order of magnitude of the energy magnetic terms associated with moderate applied field (between 10 and 200 milliteslas). It is shown that gradients of the Zeeman energy associated with the inhomogeneous applied fields can induce pressures of the order of 10–2Pa. The surface tension generated by the magnetic pressure, on the surface delimiting the brain region subject to relevant field and gradients, is found to range between 10–1 and 1 mN⋅m–1. These pressures seem to be strong enough to interfere with the elastic and electrostatic energies involved in the channel activation-inactivation-deactivation mechanisms of biological membranes. It has been described that small mechanical force can activate voltage gated potassium channels. Moreover, stretch-activated ion channels are widely described in different biological tissues. Virtually, all these channels can modify their activity if stressed by a sufficient pressure delivered for enough time. We propose mechanical stimulation – possibly not exclusively – as a candidate mechanism how static magnetic field can produce effects in biological systems. It must be emphasized, that such field gradients were not previously proposed as a possible source of neural activity modification.
- Published
- 2020
- Full Text
- View/download PDF
11. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity
- Author
-
Joseph A Giovinazzo, Russell P Thomson, Nailya Khalizova, Patrick J Zager, Nirav Malani, Enrique Rodriguez-Boulan, Jayne Raper, and Ryan Schreiner
- Subjects
protein trafficking ,membrane channels ,ion channel ,apolipoprotein l1 ,polymorphism ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Recently evolved alleles of Apolipoprotein L-1 (APOL1) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na+ and Ca2+. We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease.
- Published
- 2020
- Full Text
- View/download PDF
12. Direct binding of phosphatidylglycerol at specific sites modulates desensitization of a ligand-gated ion channel
- Author
-
Ailing Tong, John T Petroff II, Fong-Fu Hsu, Philipp AM Schmidpeter, Crina M Nimigean, Liam Sharp, Grace Brannigan, and Wayland WL Cheng
- Subjects
mass spectrometry ,membrane channels ,phospholipids ,desensitization ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Pentameric ligand-gated ion channels (pLGICs) are essential determinants of synaptic transmission, and are modulated by specific lipids including anionic phospholipids. The exact modulatory effect of anionic phospholipids in pLGICs and the mechanism of this effect are not well understood. Using native mass spectrometry, coarse-grained molecular dynamics simulations and functional assays, we show that the anionic phospholipid, 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG), preferentially binds to and stabilizes the pLGIC, Erwinia ligand-gated ion channel (ELIC), and decreases ELIC desensitization. Mutations of five arginines located in the interfacial regions of the transmembrane domain (TMD) reduce POPG binding, and a subset of these mutations increase ELIC desensitization. In contrast, a mutation that decreases ELIC desensitization, increases POPG binding. The results support a mechanism by which POPG stabilizes the open state of ELIC relative to the desensitized state by direct binding at specific sites.
- Published
- 2019
- Full Text
- View/download PDF
13. Effects of Moderate Static Magnetic Field on Neural Systems Is a Non-invasive Mechanical Stimulation of the Brain Possible Theoretically?
- Author
-
Hernando, Antonio, Galvez, Fernando, García, Miguel A., Soto-León, Vanesa, Alonso-Bonilla, Carlos, Aguilar, Juan, and Oliviero, Antonio
- Subjects
BRAIN stimulation ,CYBERNETICS ,MAGNETIC fields ,BIOLOGICAL membranes ,POTASSIUM channels ,TISSUES - Abstract
Static magnetic fields have been shown to induce effects on the human brain. Different experiments seem to support the idea that moderate static magnetic field can exert some influence on the gating processes of the membrane channels. In this article we visit the order of magnitude of the energy magnetic terms associated with moderate applied field (between 10 and 200 milliteslas). It is shown that gradients of the Zeeman energy associated with the inhomogeneous applied fields can induce pressures of the order of 10
–2 Pa. The surface tension generated by the magnetic pressure, on the surface delimiting the brain region subject to relevant field and gradients, is found to range between 10–1 and 1 mN⋅m–1 . These pressures seem to be strong enough to interfere with the elastic and electrostatic energies involved in the channel activation-inactivation-deactivation mechanisms of biological membranes. It has been described that small mechanical force can activate voltage gated potassium channels. Moreover, stretch-activated ion channels are widely described in different biological tissues. Virtually, all these channels can modify their activity if stressed by a sufficient pressure delivered for enough time. We propose mechanical stimulation – possibly not exclusively – as a candidate mechanism how static magnetic field can produce effects in biological systems. It must be emphasized, that such field gradients were not previously proposed as a possible source of neural activity modification. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
14. Calmodulin-Mediated Regulation of Gap Junction Channels.
- Author
-
Peracchia, Camillo
- Subjects
- *
CALMODULIN , *CONNEXINS , *CELL death , *NINETEENTH century - Abstract
Evidence that neighboring cells uncouple from each other as one dies surfaced in the late 19th century, but it took almost a century for scientists to start understanding the uncoupling mechanism (chemical gating). The role of cytosolic free calcium (Ca2+ i) in cell–cell channel gating was first reported in the mid-sixties. In these studies, only micromolar [Ca2+]i were believed to affect gating—concentrations reachable only in cell death, which would discard Ca2+ i as a fine modulator of cell coupling. More recently, however, numerous researchers, including us, have reported the effectiveness of nanomolar [Ca2+]i. Since connexins do not have high-affinity calcium sites, the effectiveness of nanomolar [Ca2+]i suggests the role of Ca-modulated proteins, with calmodulin (CaM) being most obvious. Indeed, in 1981 we first reported that a CaM-inhibitor prevents chemical gating. Since then, the CaM role in gating has been confirmed by studies that tested it with a variety of approaches such as treatments with CaM-inhibitors, inhibition of CaM expression, expression of CaM mutants, immunofluorescent co-localization of CaM and gap junctions, and binding of CaM to peptides mimicking connexin domains identified as CaM targets. Our gating model envisions Ca2+-CaM to directly gate the channels by acting as a plug (“Cork” gating model), and probably also by affecting connexin conformation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
15. Major regulatory mechanisms involved in sperm motility
- Author
-
Rute Pereira, Rosália Sá, Alberto Barros, and Mário Sousa
- Subjects
antioxidants ,calcium ,membrane channels ,protein kinases ,sperm genetic abnormalities ,sperm motility ,Diseases of the genitourinary system. Urology ,RC870-923 - Abstract
The genetic bases and molecular mechanisms involved in the assembly and function of the flagellum components as well as in the regulation of the flagellar movement are not fully understood, especially in humans. There are several causes for sperm immotility, of which some can be avoided and corrected, whereas other are related to genetic defects and deserve full investigation to give a diagnosis to patients. This review was performed after an extensive literature search on the online databases PubMed, ScienceDirect, and Web of Science. Here, we review the involvement of regulatory pathways responsible for sperm motility, indicating possible causes for sperm immotility. These included the calcium pathway, the cAMP-dependent protein kinase pathway, the importance of kinases and phosphatases, the function of reactive oxygen species, and how the regulation of cell volume and osmolarity are also fundamental components. We then discuss main gene defects associated with specific morphological abnormalities. Finally, we slightly discuss some preventive and treatments approaches to avoid development of conditions that are associated with unspecified sperm immotility. We believe that in the near future, with the development of more powerful techniques, the genetic causes of sperm immotility and the regulatory mechanisms of sperm motility will be better understand, thus enabling to perform a full diagnosis and uncover new therapies.
- Published
- 2017
- Full Text
- View/download PDF
16. TMC1 is an essential component of a leak channel that modulates tonotopy and excitability of auditory hair cells in mice
- Author
-
Shuang Liu, Shufeng Wang, Linzhi Zou, Jie Li, Chenmeng Song, Jiaofeng Chen, Qun Hu, Lian Liu, Pingbo Huang, and Wei Xiong
- Subjects
TMC1 ,mechanotransduction ,leak conductance ,membrane channels ,tonotopy ,hair cells ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate biological processes other than MET in invertebrates, ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized four amino acids that are required for the leak conductance. The leak conductance is graded in a frequency-dependent manner along the length of the cochlea and is indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and -intensity.
- Published
- 2019
- Full Text
- View/download PDF
17. Structural and functional characterization of an otopetrin family proton channel
- Author
-
Qingfeng Chen, Weizhong Zeng, Ji She, Xiao-chen Bai, and Youxing Jiang
- Subjects
otopetrin ,proton ,membrane channels ,cryo-EM ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The otopetrin (OTOP) proteins were recently characterized as proton channels. Here we present the cryo-EM structure of OTOP3 from Xenopus tropicalis (XtOTOP3) along with functional characterization of the channel. XtOTOP3 forms a homodimer with each subunit containing 12 transmembrane helices that can be divided into two structurally homologous halves; each half assembles as an α-helical barrel that could potentially serve as a proton conduction pore. Both pores open from the extracellular half before becoming occluded at a central constriction point consisting of three highly conserved residues – Gln232/585-Asp262/Asn623-Tyr322/666 (the constriction triads). Mutagenesis shows that the constriction triad from the second pore is less amenable to perturbation than that of the first pore, suggesting an unequal contribution between the two pores to proton transport. We also identified several key residues at the interface between the two pores that are functionally important, particularly Asp509, which confers intracellular pH-dependent desensitization to OTOP channels.
- Published
- 2019
- Full Text
- View/download PDF
18. Structural basis of Ca2+-dependent activation and lipid transport by a TMEM16 scramblase
- Author
-
Maria E Falzone, Jan Rheinberger, Byoung-Cheol Lee, Thasin Peyear, Linda Sasset, Ashleigh M Raczkowski, Edward T Eng, Annarita Di Lorenzo, Olaf S Andersen, Crina M Nimigean, and Alessio Accardi
- Subjects
Scrambling ,membrane structure ,membrane channels ,phospholipids ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The lipid distribution of plasma membranes of eukaryotic cells is asymmetric and phospholipid scramblases disrupt this asymmetry by mediating the rapid, nonselective transport of lipids down their concentration gradients. As a result, phosphatidylserine is exposed to the outer leaflet of membrane, an important step in extracellular signaling networks controlling processes such as apoptosis, blood coagulation, membrane fusion and repair. Several TMEM16 family members have been identified as Ca2+-activated scramblases, but the mechanisms underlying their Ca2+-dependent gating and their effects on the surrounding lipid bilayer remain poorly understood. Here, we describe three high-resolution cryo-electron microscopy structures of a fungal scramblase from Aspergillus fumigatus, afTMEM16, reconstituted in lipid nanodiscs. These structures reveal that Ca2+-dependent activation of the scramblase entails global rearrangement of the transmembrane and cytosolic domains. These structures, together with functional experiments, suggest that activation of the protein thins the membrane near the transport pathway to facilitate rapid transbilayer lipid movement.
- Published
- 2019
- Full Text
- View/download PDF
19. Structure and Function of Ion Channels Regulating Sperm Motility—An Overview
- Author
-
Karolina Nowicka-Bauer and Monika Szymczak-Cendlak
- Subjects
sperm motility ,ion channels ,membrane channels ,calcium ,potassium ,chloride ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Sperm motility is linked to the activation of signaling pathways that trigger movement. These pathways are mainly dependent on Ca2+, which acts as a secondary messenger. The maintenance of adequate Ca2+ concentrations is possible thanks to proper concentrations of other ions, such as K+ and Na+, among others, that modulate plasma membrane potential and the intracellular pH. Like in every cell, ion homeostasis in spermatozoa is ensured by a vast spectrum of ion channels supported by the work of ion pumps and transporters. To achieve success in fertilization, sperm ion channels have to be sensitive to various external and internal factors. This sensitivity is provided by specific channel structures. In addition, novel sperm-specific channels or isoforms have been found with compositions that increase the chance of fertilization. Notably, the most significant sperm ion channel is the cation channel of sperm (CatSper), which is a sperm-specific Ca2+ channel required for the hyperactivation of sperm motility. The role of other ion channels in the spermatozoa, such as voltage-gated Ca2+ channels (VGCCs), Ca2+-activated Cl-channels (CaCCs), SLO K+ channels or voltage-gated H+ channels (VGHCs), is to ensure the activation and modulation of CatSper. As the activation of sperm motility differs among metazoa, different ion channels may participate; however, knowledge regarding these channels is still scarce. In the present review, the roles and structures of the most important known ion channels are described in regard to regulation of sperm motility in animals.
- Published
- 2021
- Full Text
- View/download PDF
20. Biomimetic DNA Nanotubes: Nanoscale Channel Design and Applications.
- Author
-
Liu, Xiaoguo, Zhao, Yan, Liu, Pi, Wang, Lihua, Lin, Jianping, and Fan, Chunhai
- Subjects
- *
NANOTUBES , *DNA , *DNA nanotechnology , *CONSTRUCTION materials , *DNA primers - Abstract
Biomacromolecular nanotubes play important physiological roles in transmembrane ion/molecule channeling, intracellular transport, and inter‐cellular communications. While genetically encoded protein nanotubes are prevalent in vivo, the in vitro construction of biomimetic DNA nanotubes has attracted intense interest with the rise of structural DNA nanotechnology. The abiotic use of DNA assembly provides a powerful bottom‐up approach for the rational construction of complex materials with arbitrary size and shape at the nanoscale. More specifically, a typical DNA nanotube can be assembled either with parallel‐aligned DNA duplexes or by closing DNA tile lattices. These artificial DNA nanotubes can be tailored and site‐specifically modified to realize biomimetic functions including ionic or molecular channeling, bioreactors, drug delivery, and biomolecular sensing. In this Minireview, we aim to summarize recent advances in design strategies, including the characterization and applications of biomimetic DNA nanotubes. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
21. Small‐Molecule Permeation across Membrane Channels: Chemical Modification to Quantify Transport across OmpF.
- Author
-
Wang, Jiajun, Bafna, Jayesh Arun, Bhamidimarri, Satya Prathyusha, and Winterhalter, Mathias
- Subjects
- *
CURRENT fluctuations , *BACTERIAL cell membranes , *ACTIVATION energy , *NORFLOXACIN - Abstract
Biological channels facilitate the exchange of molecules across membranes, but general tools to quantify transport are missing. Electrophysiology is the method of choice to study the functional properties of channels. However, analyzing the current fluctuation of channels typically does not identify successful transport, that is, distinguishing translocation from binding. To distinguish both processes, we added an additional barrier at the channel exit acting as a molecular counter. To identify permeation, we compare the molecule residence time in the native channel with one that is chemically modified at the exit. We use the well‐studied outer membrane channel from E. coli, OmpF. Position 181, which is below the constriction region, was subsequently mutated into cysteine (E181C) in an otherwise cysteine‐free system, then functionalized by covalent binding with one of the two blockers MTSES or GLT. We measured the passage of model peptides, mono‐, tri‐, hepta‐arginine and of norfloxacin, as an example for antibiotic permeation. A molecule counter, added at the channel exit of a bacterial cell membrane pore creates an additional energy barrier to quantify molecules that permeate. The efficiency with charged peptides was tested. In a second series the antibiotic norfloxacin was tested. Introducing the partial channel blocker allows to distinguish binding from translocation for a broad range of molecules. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
22. Calmodulin-Mediated Regulation of Gap Junction Channels
- Author
-
Camillo Peracchia
- Subjects
gap junctions ,connexins ,innexins ,calmodulin ,membrane channels ,channel gating ,calcium ,ph ,chemical gating ,voltage gating ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Evidence that neighboring cells uncouple from each other as one dies surfaced in the late 19th century, but it took almost a century for scientists to start understanding the uncoupling mechanism (chemical gating). The role of cytosolic free calcium (Ca2+i) in cell−cell channel gating was first reported in the mid-sixties. In these studies, only micromolar [Ca2+]i were believed to affect gating—concentrations reachable only in cell death, which would discard Ca2+i as a fine modulator of cell coupling. More recently, however, numerous researchers, including us, have reported the effectiveness of nanomolar [Ca2+]i. Since connexins do not have high-affinity calcium sites, the effectiveness of nanomolar [Ca2+]i suggests the role of Ca-modulated proteins, with calmodulin (CaM) being most obvious. Indeed, in 1981 we first reported that a CaM-inhibitor prevents chemical gating. Since then, the CaM role in gating has been confirmed by studies that tested it with a variety of approaches such as treatments with CaM-inhibitors, inhibition of CaM expression, expression of CaM mutants, immunofluorescent co-localization of CaM and gap junctions, and binding of CaM to peptides mimicking connexin domains identified as CaM targets. Our gating model envisions Ca2+-CaM to directly gate the channels by acting as a plug (“Cork” gating model), and probably also by affecting connexin conformation.
- Published
- 2020
- Full Text
- View/download PDF
23. Cation selectivity of the presequence translocase channel Tim23 is crucial for efficient protein import
- Author
-
Niels Denkert, Alexander Benjamin Schendzielorz, Mariam Barbot, Lennart Versemann, Frank Richter, Peter Rehling, and Michael Meinecke
- Subjects
mitochondria ,protein trafficking ,Tim23 ,electrophysiology ,mitochondrial biogenesis ,membrane channels ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Virtually all mitochondrial matrix proteins and a considerable number of inner membrane proteins carry a positively charged, N-terminal presequence and are imported by the TIM23 complex (presequence translocase) located in the inner mitochondrial membrane. The voltage-regulated Tim23 channel constitutes the actual protein-import pore wide enough to allow the passage of polypeptides with a secondary structure. In this study, we identify amino acids important for the cation selectivity of Tim23. Structure based mutants show that selectivity is provided by highly conserved, pore-lining amino acids. Mutations of these amino acid residues lead to reduced selectivity properties, reduced protein import capacity and they render the Tim23 channel insensitive to substrates. We thus show that the cation selectivity of the Tim23 channel is a key feature for substrate recognition and efficient protein import.
- Published
- 2017
- Full Text
- View/download PDF
24. Major regulatory mechanisms involved in sperm motility.
- Author
-
Pereira, Rute, Sá, Rosália, Barros, Alberto, and Sousa, Mário
- Abstract
The genetic bases and molecular mechanisms involved in the assembly and function of the flagellum components as well as in the regulation of the flagellar movement are not fully understood, especially in humans. There are several causes for sperm immotility, of which some can be avoided and corrected, whereas other are related to genetic defects and deserve full investigation to give a diagnosis to patients. This review was performed after an extensive literature search on the online databases PubMed, ScienceDirect, and Web of Science. Here, we review the involvement of regulatory pathways responsible for sperm motility, indicating possible causes for sperm immotility. These included the calcium pathway, the cAMP‑dependent protein kinase pathway, the importance of kinases and phosphatases, the function of reactive oxygen species, and how the regulation of cell volume and osmolarity are also fundamental components. We then discuss main gene defects associated with specific morphological abnormalities. Finally, we slightly discuss some preventive and treatments approaches to avoid development of conditions that are associated with unspecified sperm immotility. We believe that in the near future, with the development of more powerful techniques, the genetic causes of sperm immotility and the regulatory mechanisms of sperm motility will be better understand, thus enabling to perform a full diagnosis and uncover new therapies. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
25. Proton currents constrain structural models of voltage sensor activation
- Author
-
Aaron L Randolph, Younes Mokrab, Ashley L Bennett, Mark SP Sansom, and Ian Scott Ramsey
- Subjects
proton transport ,membrane channels ,channel gating ,voltage sensor ,protein structure ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic ‘aqueous’ H+ conductance (GAQ). Mutation of a highly conserved ‘gating charge’ residue in the S4 helix (R1H) confers a resting-state H+ ‘shuttle’ conductance (GSH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute GSH in Hv1 without abrogating GAQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate GSH and GAQ gating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on GSH and GAQ are used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H+ transfer mechanisms in Hv1.
- Published
- 2016
- Full Text
- View/download PDF
26. Low noise patch‐clamp current amplification by nanoparticles plasmonic–photonic coupling (analysis and modelling).
- Author
-
Haberal, E. O., SalmanOgli, A., and Nasseri, B.
- Abstract
In this article, a patch‐clamp low noise current amplification based on nanoparticles plasmonic radiation is analyzed. It is well‐known, a very small current is flowing from different membrane channels and so, for extra processing the current amplification is necessary. It is notable that there are some problems in traditional electronic amplifier due to its noise and bandwidth problem. Because of the important role of the patch‐clamp current in cancer research and especially its small amplitude, it is vital to intensify it without adding any noises. In this study, the current amplification is performed firstly: from the excitement of nanoparticles by the patch‐clamp pico‐ampere current and then, the effect of nanoparticles plasmonic far‐field radiation on conductor's carriers, which will cause the current amplification. This relates to the plasmonic‐photonic coupling and their effect on conductor carriers as the current perturbation agent. In the steady state, the current amplification can reach to 1000 times of initial level. Furthermore, we investigated the nanoparticles morphology changing effect such as size, nanoparticles inter‐distance, and nanoparticles distance from the conductor on the amplifier parameters. Finally, it should note that the original aim is to use nanoparticles plasmonic engineering and their coupling to photonics for output current manipulating. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
27. Peroxisomal Pex11 is a pore-forming protein homologous to TRPM channels.
- Author
-
Mindthoff, Sabrina, Grunau, Silke, Steinfort, Laura L., Girzalsky, Wolfgang, Hiltunen, J. Kalervo, Erdmann, Ralf, and Antonenkov, Vasily D.
- Subjects
- *
PEROXISOMES , *LIPID metabolism , *TRP channels , *GENETIC mutation , *GENETIC overexpression , *MEMBRANE proteins , *ORIGIN of life - Abstract
More than 30 proteins (Pex proteins) are known to participate in the biogenesis of peroxisomes—ubiquitous oxidative organelles involved in lipid and ROS metabolism. The Pex11 family of homologous proteins is responsible for division and proliferation of peroxisomes. We show that yeast Pex11 is a pore-forming protein sharing sequence similarity with TRPM cation-selective channels. The Pex11 channel with a conductance of Λ = 4.1 nS in 1.0 M KCl is moderately cation-selective ( P K + / P Cl − = 1.85) and resistant to voltage-dependent closing. The estimated size of the channel's pore (r ~ 0.6 nm) supports the notion that Pex11 conducts solutes with molecular mass below 300–400 Da. We localized the channel's selectivity determining sequence. Overexpression of Pex11 resulted in acceleration of fatty acids β-oxidation in intact cells but not in the corresponding lysates. The β-oxidation was affected in cells by expression of the Pex11 protein carrying point mutations in the selectivity determining sequence. These data suggest that the Pex11-dependent transmembrane traffic of metabolites may be a rate-limiting step in the β-oxidation of fatty acids. This conclusion was corroborated by analysis of the rate of β-oxidation in yeast strains expressing Pex11 with mutations mimicking constitutively phosphorylated (S165D, S167D) or unphosphorylated (S165A, S167A) protein. The results suggest that phosphorylation of Pex11 is a mechanism that can control the peroxisomal β-oxidation rate. Our results disclose an unexpected function of Pex11 as a non-selective channel responsible for transfer of metabolites across peroxisomal membrane. The data indicate that peroxins may be involved in peroxisomal metabolic processes in addition to their role in peroxisome biogenesis. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
28. Introduction to the Theme on Membrane Channels
- Author
-
von Heijne, Gunnar and von Heijne, Gunnar
- Abstract
This volume of the Annual Review of Biochemistry contains three reviews on membrane channel proteins: the first by Szczot et al., titled The Form and Function of PIEZO2; the second by Ruprecht & Kunji, titled Structural Mechanism of Transport of Mitochondrial Carriers; and the third by McIlwain et al., titled Membrane Exporters of Fluoride Ion. These reviews provide nice illustrations of just how far evolution has been able to play with the basic helix-bundle architecture of integral membrane proteins to produce membrane channels and transporters of widely different functions.
- Published
- 2021
- Full Text
- View/download PDF
29. Molecular mechanism of thiamine pyrophosphate import into mitochondria: a molecular simulation study
- Author
-
Van Liefferinge, François, Krammer, Eva-Maria, Waeytens, Jehan, Prévost, Martine, Van Liefferinge, François, Krammer, Eva-Maria, Waeytens, Jehan, and Prévost, Martine
- Abstract
The import of thiamine pyrophosphate (TPP) through both mitochondrial membranes was studied using a total of 3-µs molecular dynamics simulations. Regarding the translocation through the mitochondrial outer membrane, our simulations support the conjecture that TPP uses the voltage-dependent anion channel, the major pore of this membrane, for its passage to the intermembrane space, as its transport presents significant analogies with that used by other metabolites previously studied, in particular with ATP. As far as passing through the mitochondrial inner membrane is concerned, our simulations show that the specific carrier of TPP has a single binding site that becomes accessible, through an alternating access mechanism. The preference of this transporter for TPP can be rationalized mainly by three residues located in the binding site that differ from those identified in the ATP/ADP carrier, the most studied member of the mitochondrial carrier family. The simulated transport mechanism of TPP highlights the essential role, at the energetic level, of the contributions coming from the formation and breakage of two networks of salt bridges, one on the side of the matrix and the other on the side of the intermembrane space, as well as the interactions, mainly of an ionic nature, formed by TPP upon its binding. The energy contribution provided by the cytosolic network establishes a lower barrier than that of the matrix network, which can be explained by the lower interaction energy of TPP on the matrix side or possibly a uniport activity., SCOPUS: ar.j, info:eu-repo/semantics/published
- Published
- 2021
30. The Ciliary Muscle and Zonules of Zinn Modulate Lens Intracellular Hydrostatic Pressure Through Transient Receptor Potential Vanilloid Channels
- Author
-
Paul J. Donaldson, Caterina Sellitto, Thomas W. White, Richard T. Mathias, Leping Li, Junyuan Gao, and Yadi Chen
- Subjects
0301 basic medicine ,TRPV4 ,membrane transport ,Hydrostatic pressure ,TRPV1 ,microcirculation ,TRPV ,03 medical and health sciences ,Transient receptor potential channel ,Lens ,0302 clinical medicine ,Ciliary body ,Transient Receptor Potential Channels ,Lens, Crystalline ,medicine ,Hydrostatic Pressure ,Chemistry ,lens epithelium ,Ciliary Body ,Accommodation, Ocular ,membrane channels ,030104 developmental biology ,medicine.anatomical_structure ,Ciliary muscle ,030221 ophthalmology & optometry ,Biophysics ,Intracellular - Abstract
Purpose Lenses have an intracellular hydrostatic pressure gradient to drive fluid from central fiber cells to surface epithelial cells. Pressure is regulated by a feedback control system that relies on transient receptor potential vanilloid (TRPV)1 and TRPV4 channels. The ciliary muscle transmits tension to the lens through the zonules of Zinn. Here, we have examined if ciliary muscle tension influenced the lens intracellular hydrostatic pressure gradient. Methods We measured the ciliary body position and intracellular hydrostatic pressures in mouse lenses while pharmacologically causing relaxation or contraction of the ciliary muscle. We also used inhibitors of TRPV1 and TRPV4, in addition to phosphoinositide 3-kinase (PI3K) p110α knockout mice and immunostaining of phosphorylated protein kinase B (Akt), to determine how changes in ciliary muscle tension resulted in altered hydrostatic pressure. Results Ciliary muscle relaxation increased the distance between the ciliary body and the lens and caused a decrease in intracellular hydrostatic pressure that was dependent on intact zonules and could be blocked by inhibition of TRPV4. Ciliary contraction moved the ciliary body toward the lens and caused an increase in intracellular hydrostatic pressure and Akt phosphorylation that required intact zonules and was blocked by either inhibition of TRPV1 or genetic deletion of the p110α catalytic subunit of PI3K. Conclusions These results show that the hydrostatic pressure gradient within the lens was influenced by the tension exerted on the lens by the ciliary muscle through the zonules of Zinn. Modulation of the gradient of intracellular hydrostatic pressure in the lens could alter the water content, and the gradient of refractive index.
- Published
- 2019
31. BK channel overexpression on plasma membrane of fibroblasts from Hutchinson-Gilford progeria syndrome
- Author
-
Gastone Castellani, Giovanna Lattanzi, Entele Gavoci, Isabella Zironi, Angela Virelli, Daniel Remondini, Fabrizio Amorini, Zironi, Isabella, Gavoçi, Entelë, Lattanzi, Giovanna, Virelli, Angela, Amorini, Fabrizio, Remondini, Daniel, and Castellani, Gastone
- Subjects
0301 basic medicine ,Adult ,BK channel ,congenital, hereditary, and neonatal diseases and abnormalities ,Adolescent ,patch clamp ,LMNA ,03 medical and health sciences ,K current + ,Young Adult ,0302 clinical medicine ,Progeria ,Gene expression ,medicine ,Cell Adhesion ,Humans ,Large-Conductance Calcium-Activated Potassium Channels ,LMNA gene ,Child ,Aged ,Cell Proliferation ,cellular proliferation ,Aged, 80 and over ,biology ,membrane channel ,integumentary system ,Chemistry ,aging ,Cell Membrane ,nutritional and metabolic diseases ,Cell Biology ,Fibroblasts ,medicine.disease ,Progerin ,Lamin Type A ,K+ current ,Potassium channel ,Chromatin ,Cell biology ,membrane channels ,030104 developmental biology ,Gene Expression Regulation ,030220 oncology & carcinogenesis ,gene LMNA ,biology.protein ,Hutchinson-Gilford Progeria Syndrome (HGPS) ,Lamin ,Research Paper - Abstract
Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare genetic disorder wherein symptoms resembling aspects of aging are manifested at a very early age. It is a genetic condition that occurs due to a de novo mutation in the LMNA gene encoding for the nuclear structural protein lamin A. The lamin family of proteins are thought to be involved in nuclear stability, chromatin structure and gene expression and this leads to heavy effects on the regulation and functionality of the cell machinery. The functional role of the large-conductance calcium-activated potassium channels (BKCa) is still unclear, but has been recently described a strong relationship with their membrane expression, progerin nuclear levels and the ageing process. In this study, we found that: i) the outward potassium membrane current amplitude and the fluorescence intensity of the BKCa channel probe showed higher values in human dermal fibroblast obtained from patients affected by HGPS if compared to that from healthy young subjects; ii) this result appears to correlate with a basic cellular activity such as the replicative boost. We suggest that studying the HGPS also from the electrophysiological point of view might reveal new clues about the normal process of aging.
- Published
- 2018
32. Efim Liberman toward the comprehension of the phenomenon of life.
- Author
-
Skulachev, Vladimir P.
- Subjects
- *
BIOLOGICAL membranes , *OXIDATIVE phosphorylation , *ARTIFICIAL membranes , *BIOPHYSICS , *CELL membranes - Abstract
Efim Liberman was a proud scholar of biophysics—a genuine scientific discipline that strives for high accuracy in contrast to descriptive biology. He played a major role at the Pushchino Institute of Biophysics and participated in Gelfand's famous seminar. He developed a groundbreaking model of neural impulses and discovered the decisive role of cell membranes and membrane channels in neural cell excitation. Efim Liberman studied artificial and biological membranes, and conducted seminal experiments to proof Mitchell's hypothesis of oxidative phosphorylation. He discovered penetrating ions in pioneering studies of mitochondrial electrical energetics. He put forward a trailblazing idea of an intracell analog-digital molecular computer capable of using genetically coded algorithms for processing information. His ideas and research gave impetus to academic studies in various areas, such as a role of small RNАs as universal regulators of life. Efim Liberman was an outstanding, versatile and bright personality whose lifelong journey was to pursue the comprehension of the Universe and to understand the phenomenon of life. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
33. Effect of lauric arginate, nisin Z, and a combination against several food-related bacteria.
- Author
-
Rinrada Pattanayaiying, Aran H.-Kittikun, and Cutter, Catherine N.
- Subjects
- *
ANTI-infective agents , *NISIN , *ESCHERICHIA coli O157:H7 , *SCANNING electron microscopy , *TRANSMISSION electron microscopy , *LYSIS , *FOOD microbiology , *BACTERIOCINS - Abstract
The effects of lauric arginate (LAE) and nisin Z, alone or in combination, on cell damage were investigated against Escherichia coli O157:H7, Listeria monocytogenes and Brochothrix thermosphacta, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations, efflux of potassium and phosphate ions, and growth inhibition. A combination of LAE with nisin Z caused severe and dramatic changes in the cytoplasmic membrane and cell lysis of both Gram-positive and Gram-negative bacteria. The combination treatment also caused significant potassium and phosphate ion leakage of E. coli O157:H7, L. monocytogenes and B. thermosphacta, when compared with other treatments: 16.62 ± 1.05, 50.35 ± 0.81 and 45.47 ± 1.15 mg/L of potassium ion and 122.66 ± 8.81, 97.96 ± 3.31 and 26.47 ± 13.97 mg/L of phosphate ion after treatment for 6 h, respectively. Bacteria were reduced by approximately 7 log10 CFU/mL within the first hour of treatment and then cells were unable to grow for the remainder of the experiment. Treatment with LAE alone resulted in changes in cellular morphology, coagulation of the cytoplasm, and low level leakage of potassium and phosphate ions in all bacteria tested. Treatment of L. monocytogenes and B. thermosphacta with nisin Z (320 AU/mL of final concentration) resulted in the formation of membrane channels and leakage of potassium and phosphate ions at rather high levels; but the bacteriocin was not effective against E. coli O157:H7. LAE or nisin Z reduced growth of both L. monocytogenes and B. thermosphacta by approximately 7 log10 CFU/mL. Conversely, E. coli O157:H7 was not inhibited by treatments with nisin Z, but decreased by approximately 4.45 log10 CFU/mL after treatment with LAE. These findings provide additional information on the mode of action of these compounds on bacterial populations. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
34. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity
- Author
-
Enrique Rodriguez-Boulan, Jayne Raper, Nirav Malani, Patrick J. Zager, Nailya Khalizova, Russell Thomson, Ryan Schreiner, and Joseph A Giovinazzo
- Subjects
0301 basic medicine ,Apolipoprotein B ,Apolipoprotein L1 ,030232 urology & nephrology ,Endoplasmic Reticulum ,Kidney ,Ion Channels ,polymorphism ,0302 clinical medicine ,Risk Factors ,Biology (General) ,education.field_of_study ,Cell Death ,biology ,Cytotoxins ,General Neuroscience ,General Medicine ,Hydrogen-Ion Concentration ,membrane channels ,Cell biology ,Medicine ,Kidney Diseases ,Apolipoprotein L ,protein trafficking ,Research Article ,Human ,Programmed cell death ,QH301-705.5 ,Science ,Population ,CHO Cells ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Cricetulus ,medicine ,Animals ,Humans ,Human Biology and Medicine ,education ,Ion channel ,apolipoprotein l1 ,General Immunology and Microbiology ,Sodium ,Cell Membrane ,Cell Biology ,medicine.disease ,HEK293 Cells ,030104 developmental biology ,Microscopy, Fluorescence ,ion channel ,Potassium ,biology.protein ,Membrane channel ,Kidney disease - Abstract
Recently evolved alleles of Apolipoprotein L-1 (APOL1) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na+and Ca2+. We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease.
- Published
- 2020
35. Direct binding of phosphatidylglycerol at specific sites modulates desensitization of a ligand-gated ion channel
- Author
-
Fong-Fu Hsu, Grace Brannigan, Ailing Tong, Wayland W.L. Cheng, Liam Sharp, Crina M. Nimigean, Philipp A. M. Schmidpeter, and John T. Petroff
- Subjects
Protein Conformation ,QH301-705.5 ,Structural Biology and Molecular Biophysics ,Science ,DNA Mutational Analysis ,Phospholipid ,desensitization ,Molecular Dynamics Simulation ,Synaptic Transmission ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Desensitization (telecommunications) ,Allosteric Regulation ,None ,Biology (General) ,Ion channel ,phospholipids ,030304 developmental biology ,mass spectrometry ,Phosphatidylglycerol ,0303 health sciences ,General Immunology and Microbiology ,General Neuroscience ,Phosphatidylglycerols ,General Medicine ,Ligand-Gated Ion Channels ,membrane channels ,Transmembrane domain ,chemistry ,Structural biology ,Biophysics ,Membrane channel ,Ligand-gated ion channel ,Medicine ,lipids (amino acids, peptides, and proteins) ,030217 neurology & neurosurgery ,Research Article ,Protein Binding - Abstract
Pentameric ligand-gated ion channels (pLGICs) are essential determinants of synaptic transmission, and are modulated by specific lipids including anionic phospholipids. The exact modulatory effect of anionic phospholipids in pLGICs and the mechanism of this effect are not well understood. Using native mass spectrometry, coarse-grained molecular dynamics simulations and functional assays, we show that the anionic phospholipid, 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG), preferentially binds to and stabilizes the pLGIC, Erwinia ligand-gated ion channel (ELIC), and decreases ELIC desensitization. Mutations of five arginines located in the interfacial regions of the transmembrane domain (TMD) reduce POPG binding, and a subset of these mutations increase ELIC desensitization. In contrast, a mutation that decreases ELIC desensitization, increases POPG binding. The results support a mechanism by which POPG stabilizes the open state of ELIC relative to the desensitized state by direct binding at specific sites.
- Published
- 2019
36. TMC1 is an essential component of a leak channel that modulates tonotopy and excitability of auditory hair cells in mice
- Author
-
Chenmeng Song, Shuang Liu, Jiaofeng Chen, Linzhi Zou, Shufeng Wang, Qun Hu, Lian Liu, Wei Xiong, Pingbo Huang, and Jie Li
- Subjects
0301 basic medicine ,Leak ,hair cells ,Mouse ,QH301-705.5 ,Science ,leak conductance ,Mechanotransduction, Cellular ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Mice ,0302 clinical medicine ,Sensation ,Hair Cells, Auditory ,otorhinolaryngologic diseases ,Animals ,Cysteine ,Biology (General) ,Mechanotransduction ,tonotopy ,Cochlea ,mechanotransduction ,General Immunology and Microbiology ,Chemistry ,General Neuroscience ,Conductance ,Membrane Proteins ,TMC1 ,General Medicine ,Cell Biology ,Transmembrane protein ,Cell biology ,membrane channels ,030104 developmental biology ,Medicine ,Membrane channel ,Tonotopy ,030217 neurology & neurosurgery ,Research Article ,Neuroscience - Abstract
Hearing sensation relies on the mechano-electrical transducer (MET) channel of cochlear hair cells, in which transmembrane channel-like 1 (TMC1) and transmembrane channel-like 2 (TMC2) have been proposed to be the pore-forming subunits in mammals. TMCs were also found to regulate biological processes other than MET in invertebrates, ranging from sensations to motor function. However, whether TMCs have a non-MET role remains elusive in mammals. Here, we report that in mouse hair cells, TMC1, but not TMC2, provides a background leak conductance, with properties distinct from those of the MET channels. By cysteine substitutions in TMC1, we characterized four amino acids that are required for the leak conductance. The leak conductance is graded in a frequency-dependent manner along the length of the cochlea and is indispensable for action potential firing. Taken together, our results show that TMC1 confers a background leak conductance in cochlear hair cells, which may be critical for the acquisition of sound-frequency and -intensity.
- Published
- 2019
37. Lens Connexin Channels Have Differential Permeability to the Second Messenger cAMP
- Author
-
Thomas W. White, Peter R. Brink, and Virginijus Valiunas
- Subjects
0301 basic medicine ,Patch-Clamp Techniques ,Cell division ,Connexin ,Transfection ,Second Messenger Systems ,Connexins ,Permeability ,03 medical and health sciences ,Cyclic nucleotide ,chemistry.chemical_compound ,Lens ,0302 clinical medicine ,Lens, Crystalline ,Cyclic AMP ,Humans ,Patch clamp ,Fluorescent Dyes ,Chemistry ,lens epithelium ,Gap junction ,Gap Junctions ,General Medicine ,membrane channels ,030104 developmental biology ,Permeability (electromagnetism) ,030220 oncology & carcinogenesis ,Connexin 43 ,Second messenger system ,Biophysics ,sense organs ,Ion Channel Gating ,Intracellular ,HeLa Cells - Abstract
Purpose Gap junction channels exhibit connexin specific biophysical properties, including the selective intercellular passage of larger solutes, such as second messengers. Here, we have examined the cyclic nucleotide permeability of the lens connexins, which could influence events like epithelial cell division and differentiation. Methods We compared the cAMP permeability through channels composed of Cx43, Cx46, or Cx50 using simultaneous measurements of junctional conductance and intercellular transfer. For cAMP detection, the recipient cells were transfected with a cAMP sensor gene, the cyclic nucleotide-modulated channel from sea urchin sperm (SpIH). cAMP was introduced via patch pipette into the cell of the pair that did not express SpIH. SpIH-derived currents were recorded from the other cell of a pair that expressed SpIH. cAMP permeability was also directly visualized in transfected cells using a chemically modified fluorescent form of the molecule. Results cAMP transfer was observed for homotypic Cx43 channels over a wide range of junctional conductance. Homotypic Cx46 channels also transferred cAMP, but permeability was reduced compared with Cx43. In contrast, homotypic Cx50 channels exhibited extremely low permeability to cAMP, when compared with either Cx43, or Cx46. Conclusions These data show that channels made from Cx43 and Cx46 result in the intercellular delivery of cAMP in sufficient quantity to activate cyclic nucleotide-modulated channels. The data also suggest that the greatly reduced cAMP permeability of Cx50 channels could play a role in the regulation of cell division in the lens.
- Published
- 2019
38. Structural and functional characterization of an otopetrin family proton channel
- Author
-
Youxing Jiang, Ji She, Weizhong Zeng, Qingfeng Chen, and Xiao Chen Bai
- Subjects
QH301-705.5 ,Protein Conformation ,Cryo-electron microscopy ,Science ,Xenopus ,Structural Biology and Molecular Biophysics ,Protein subunit ,DNA Mutational Analysis ,Ion Channels ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,0302 clinical medicine ,Proton transport ,Animals ,Biology (General) ,030304 developmental biology ,0303 health sciences ,General Immunology and Microbiology ,biology ,Chemistry ,General Neuroscience ,Cryoelectron Microscopy ,General Medicine ,biology.organism_classification ,membrane channels ,Transmembrane domain ,Structural biology ,Membrane protein ,Mutagenesis ,Biophysics ,Medicine ,cryo-EM ,Membrane channel ,otopetrin ,Protein Multimerization ,030217 neurology & neurosurgery ,Research Article ,proton - Abstract
The otopetrin (OTOP) proteins were recently characterized as proton channels. Here we present the cryo-EM structure of OTOP3 from Xenopus tropicalis (XtOTOP3) along with functional characterization of the channel. XtOTOP3 forms a homodimer with each subunit containing 12 transmembrane helices that can be divided into two structurally homologous halves; each half assembles as an α-helical barrel that could potentially serve as a proton conduction pore. Both pores open from the extracellular half before becoming occluded at a central constriction point consisting of three highly conserved residues – Gln232/585-Asp262/Asn623-Tyr322/666 (the constriction triads). Mutagenesis shows that the constriction triad from the second pore is less amenable to perturbation than that of the first pore, suggesting an unequal contribution between the two pores to proton transport. We also identified several key residues at the interface between the two pores that are functionally important, particularly Asp509, which confers intracellular pH-dependent desensitization to OTOP channels.
- Published
- 2019
39. Structural basis of Ca2+-dependent activation and lipid transport by a TMEM16 scramblase
- Author
-
Olaf S. Andersen, Byoung-Cheol Lee, Crina M. Nimigean, Jan Rheinberger, Linda Sasset, Thasin Peyear, Edward T. Eng, Maria Falzone, Alessio Accardi, A. Di Lorenzo, and Ashleigh M. Raczkowski
- Subjects
Phospholipid scramblase ,QH301-705.5 ,Science ,Phospholipid ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,membrane structure ,Biology (General) ,Lipid bilayer ,Lipid Transport ,phospholipids ,030304 developmental biology ,0303 health sciences ,General Immunology and Microbiology ,Chemistry ,General Neuroscience ,Membrane structure ,Lipid bilayer fusion ,General Medicine ,Phosphatidylserine ,Transmembrane protein ,Scrambling ,membrane channels ,Biophysics ,Medicine ,030217 neurology & neurosurgery - Abstract
The lipid distribution of plasma membranes of eukaryotic cells is asymmetric and phospholipid scramblases disrupt this asymmetry by mediating the rapid, nonselective transport of lipids down their concentration gradients. As a result, phosphatidylserine is exposed to the outer leaflet of membrane, an important step in extracellular signaling networks controlling processes such as apoptosis, blood coagulation, membrane fusion and repair. Several TMEM16 family members have been identified as Ca2+-activated scramblases, but the mechanisms underlying their Ca2+-dependent gating and their effects on the surrounding lipid bilayer remain poorly understood. Here, we describe three high-resolution cryo-electron microscopy structures of a fungal scramblase from Aspergillus fumigatus, afTMEM16, reconstituted in lipid nanodiscs. These structures reveal that Ca2+-dependent activation of the scramblase entails global rearrangement of the transmembrane and cytosolic domains. These structures, together with functional experiments, suggest that activation of the protein thins the membrane near the transport pathway to facilitate rapid transbilayer lipid movement.
- Published
- 2019
40. Functional Properties of Oligomeric and Monomeric Forms of Helicobacter pylori VacA Toxin.
- Author
-
Caso GC, McClain MS, Erwin AL, Truelock MD, Campbell AM, Leasure CS, Nagel M, Schey KL, Lacy DB, Ohi MD, and Cover TL
- Subjects
- Bacterial Proteins genetics, Bacterial Toxins genetics, Protein Binding, Protein Interaction Domains and Motifs, Structure-Activity Relationship, Bacterial Proteins chemistry, Bacterial Proteins metabolism, Bacterial Toxins chemistry, Bacterial Toxins metabolism, Protein Conformation, Protein Multimerization
- Abstract
Helicobacter pylori VacA is a secreted toxin that assembles into water-soluble oligomeric structures and forms anion-selective membrane channels. Acidification of purified VacA enhances its activity in cell culture assays. Sites of protomer-protomer contact within VacA oligomers have been identified by cryoelectron microscopy, and in the current study, we validated several of these interactions by chemical cross-linking and mass spectrometry. We then mutated amino acids at these contact sites and analyzed the effects of the alterations on VacA oligomerization and activity. VacA proteins with amino acid charge reversals at interprotomer contact sites retained the capacity to assemble into water-soluble oligomers and retained cell-vacuolating activity. Introduction of paired cysteine substitutions at these sites resulted in formation of disulfide bonds between adjacent protomers. Negative-stain electron microscopy and single-particle two-dimensional class analysis revealed that wild-type VacA oligomers disassemble when exposed to acidic pH, whereas the mutant proteins with paired cysteine substitutions retain an oligomeric state at acidic pH. Acid-activated wild-type VacA caused vacuolation of cultured cells, whereas acid-activated mutant proteins with paired cysteine substitutions lacked cell-vacuolating activity. Treatment of these mutant proteins with both low pH and a reducing agent resulted in VacA binding to cells, VacA internalization, and cell vacuolation. Internalization of a nonoligomerizing mutant form of VacA by host cells was detected without a requirement for acid activation. Collectively, these results enhance our understanding of the molecular interactions required for VacA oligomerization and support a model in which toxin activity depends on interactions of monomeric VacA with host cells.
- Published
- 2021
- Full Text
- View/download PDF
41. Major regulatory mechanisms involved in sperm motility
- Author
-
Alberto Barros, Mário Sousa, Rosália Sá, and Rute Pereira
- Subjects
0301 basic medicine ,Male ,antioxidants ,calcium ,membrane channels ,protein kinases ,sperm genetic abnormalities ,sperm motility ,Web of science ,Ubiquinone ,Urology ,Sperm immotility ,Review ,Flagellum ,Biology ,lcsh:RC870-923 ,03 medical and health sciences ,Humans ,Vitamin E ,Protein kinase A ,Gene ,Sperm motility ,Cell Size ,Genetics ,Kinase ,Osmolar Concentration ,General Medicine ,Vitamins ,lcsh:Diseases of the genitourinary system. Urology ,Cyclic AMP-Dependent Protein Kinases ,Spermatozoa ,Cell biology ,030104 developmental biology ,Sperm Tail ,Sperm Motility ,Reactive Oxygen Species ,Function (biology) ,Metabolic Networks and Pathways - Abstract
The genetic bases and molecular mechanisms involved in the assembly and function of the flagellum components as well as in the regulation of the flagellar movement are not fully understood, especially in humans. There are several causes for sperm immotility, of which some can be avoided and corrected, whereas other are related to genetic defects and deserve full investigation to give a diagnosis to patients. This review was performed after an extensive literature search on the online databases PubMed, ScienceDirect, and Web of Science. Here, we review the involvement of regulatory pathways responsible for sperm motility, indicating possible causes for sperm immotility. These included the calcium pathway, the cAMP-dependent protein kinase pathway, the importance of kinases and phosphatases, the function of reactive oxygen species, and how the regulation of cell volume and osmolarity are also fundamental components. We then discuss main gene defects associated with specific morphological abnormalities. Finally, we slightly discuss some preventive and treatments approaches to avoid development of conditions that are associated with unspecified sperm immotility. We believe that in the near future, with the development of more powerful techniques, the genetic causes of sperm immotility and the regulatory mechanisms of sperm motility will be better understand, thus enabling to perform a full diagnosis and uncover new therapies.
- Published
- 2015
42. Structural basis of Ca
- Author
-
Maria E, Falzone, Jan, Rheinberger, Byoung-Cheol, Lee, Thasin, Peyear, Linda, Sasset, Ashleigh M, Raczkowski, Edward T, Eng, Annarita, Di Lorenzo, Olaf S, Andersen, Crina M, Nimigean, and Alessio, Accardi
- Subjects
Models, Molecular ,Binding Sites ,Protein Conformation ,Aspergillus fumigatus ,Structural Biology and Molecular Biophysics ,S. cerevisiae ,Biological Transport ,Ceramides ,Ligands ,Lipids ,Scrambling ,membrane channels ,Fungal Proteins ,Membrane Lipids ,membrane structure ,Nanoparticles ,Calcium ,Amino Acid Sequence ,Phospholipid Transfer Proteins ,phospholipids ,Research Article - Abstract
The lipid distribution of plasma membranes of eukaryotic cells is asymmetric and phospholipid scramblases disrupt this asymmetry by mediating the rapid, nonselective transport of lipids down their concentration gradients. As a result, phosphatidylserine is exposed to the outer leaflet of membrane, an important step in extracellular signaling networks controlling processes such as apoptosis, blood coagulation, membrane fusion and repair. Several TMEM16 family members have been identified as Ca2+-activated scramblases, but the mechanisms underlying their Ca2+-dependent gating and their effects on the surrounding lipid bilayer remain poorly understood. Here, we describe three high-resolution cryo-electron microscopy structures of a fungal scramblase from Aspergillus fumigatus, afTMEM16, reconstituted in lipid nanodiscs. These structures reveal that Ca2+-dependent activation of the scramblase entails global rearrangement of the transmembrane and cytosolic domains. These structures, together with functional experiments, suggest that activation of the protein thins the membrane near the transport pathway to facilitate rapid transbilayer lipid movement.
- Published
- 2018
43. Introduction to the Theme on Membrane Channels.
- Author
-
von Heijne G
- Subjects
- Adenosine Diphosphate metabolism, Adenosine Triphosphate metabolism, Fluorides metabolism, Ion Channels chemistry, Ion Channels metabolism
- Abstract
This volume of the Annual Review of Biochemistry contains three reviews on membrane channel proteins: the first by Szczot et al., titled The Form and Function of PIEZO2; the second by Ruprecht & Kunji, titled Structural Mechanism of Transport of Mitochondrial Carriers; and the third by McIlwain et al., titled Membrane Exporters of Fluoride Ion. These reviews provide nice illustrations of just how far evolution has been able to play with the basic helix-bundle architecture of integral membrane proteins to produce membrane channels and transporters of widely different functions.
- Published
- 2021
- Full Text
- View/download PDF
44. (A)/(B) Tim23- (A) or Tim23N150A-containing (B) proteoliposomes were fused with planar lipid bilayers and single-channel activity was characterized by electrophysiological current recordings. (C) Gating event histograms for Tim23 (left) and Tim23N150A (right) were calculated from constant-voltage recordings (as depicted in A) with at least 2000 gating events each. The three most prominent classes of conductance changes were modeled with a Gaussian fit. (D) I-V curves at asymmetrical buffer conditions were recorded for Tim23 (left) and Tim23N150A (right) with indicated reversal potential Urev for 12.5-fold KCl-gradient. (E)/(F) I-V curves (left) and open probabilities (right) were determined for bilayer incorporated Tim23 (E) or Tim23N150A (F) before (black) and after (red) addition of 700 nM Tim50IMS to IMS-side of the channel. Error bars represent standard deviation (SD, n = 3)
- Author
-
Alexander Benjamin Schendzielorz, Frank Richter, Niels Denkert, Lennart Versemann, Michael Meinecke, Mariam Barbot, and Peter Rehling
- Subjects
0301 basic medicine ,mitochondrial biogenesis ,Structural Biology and Molecular Biophysics ,Amino Acid Motifs ,S. cerevisiae ,Gene Expression ,Phosphatidylinositols ,medicine.disease_cause ,Substrate Specificity ,Mitochondrial Precursor Protein Import Complex Proteins ,Protein targeting ,Translocase ,Biology (General) ,Cloning, Molecular ,Inner mitochondrial membrane ,Membrane Potential, Mitochondrial ,chemistry.chemical_classification ,biology ,Membrane transport protein ,General Neuroscience ,General Medicine ,Recombinant Proteins ,membrane channels ,Mitochondria ,Amino acid ,Biochemistry ,Phosphatidylcholines ,Medicine ,protein trafficking ,Research Article ,Protein Binding ,Saccharomyces cerevisiae Proteins ,QH301-705.5 ,Cardiolipins ,Science ,Proteolipids ,Genetic Vectors ,Phosphatidylserines ,Saccharomyces cerevisiae ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,Mitochondrial membrane transport protein ,Biochemistry and Chemical Biology ,Escherichia coli ,medicine ,Protein Interaction Domains and Motifs ,Tim23 ,biochemistry ,biophysics ,electrophysiology ,mitochondria ,structural biology ,Binding Sites ,General Immunology and Microbiology ,Phosphatidylethanolamines ,Membrane Transport Proteins ,Biological Transport ,Kinetics ,030104 developmental biology ,chemistry ,Structural biology ,Mutation ,Translocase of the inner membrane ,biology.protein - Abstract
Virtually all mitochondrial matrix proteins and a considerable number of inner membrane proteins carry a positively charged, N-terminal presequence and are imported by the TIM23 complex (presequence translocase) located in the inner mitochondrial membrane. The voltage-regulated Tim23 channel constitutes the actual protein-import pore wide enough to allow the passage of polypeptides with a secondary structure. In this study, we identify amino acids important for the cation selectivity of Tim23. Structure based mutants show that selectivity is provided by highly conserved, pore-lining amino acids. Mutations of these amino acid residues lead to reduced selectivity properties, reduced protein import capacity and they render the Tim23 channel insensitive to substrates. We thus show that the cation selectivity of the Tim23 channel is a key feature for substrate recognition and efficient protein import., eLife digest The cells of animals, plants and other eukaryotic organisms contain compartments known as organelles that play many different roles. For example, compartments called mitochondria are responsible for supplying the chemical energy cells need to survive and grow. Two membranes surround each mitochondrion and energy is converted on the surface of the inner one. Mitochondria contain over 1,000 different proteins, most of which are produced in the main part of the cell and have to be transported into the mitochondria. A transport protein called Tim23 is part of a larger group or ‘complex’ of proteins that helps to import many other proteins into the mitochondria. This complex sits in the inner membrane, with the Tim23 protein forming a large, water-filled pore through its core that provides a route for proteins to pass through the membrane. Proteins are made of building blocks called amino acids. The proteins transported by the complex containing Tim23 all have a short chain of amino acids at one end known as an N-terminal presequence. However, it is not clear how the inside of the Tim23 channel identifies and transports this presequence to allow the right proteins to pass through the inner membrane. Denkert, Schendzielorz et al. studied the normal and mutant versions of a Tim23 channel from yeast to find out which parts of the protein are involved in detecting the N-terminal presequence after it enters the pore. The experiments show that there are several amino acids in Tim23 that play important roles in this process. Furthermore, mitochondria containing mutant Tim23 channels, that are less able to identify the N-terminal presequence, are impaired in their ability to import proteins. Tim23 proteins in humans and other organisms also contain most or all of the specific amino acids identified in this study, suggesting that the findings of Denkert, Schendzielorz et al. will also apply to other species. Furthermore, the experimental strategy used in this study could be adapted to investigate transport proteins in other cell compartments.
- Published
- 2017
45. Structure and Function of Ion Channels Regulating Sperm Motility-An Overview.
- Author
-
Nowicka-Bauer K and Szymczak-Cendlak M
- Subjects
- Animals, Calcium metabolism, Calcium Channels chemistry, Calcium Channels genetics, Calcium Channels metabolism, Calcium Signaling, Chloride Channels chemistry, Chloride Channels genetics, Chloride Channels metabolism, Humans, Ion Channels genetics, Male, Potassium Channels chemistry, Potassium Channels genetics, Potassium Channels metabolism, Sodium Channels chemistry, Sodium Channels genetics, Sodium Channels metabolism, Structure-Activity Relationship, Ion Channel Gating, Ion Channels chemistry, Ion Channels metabolism, Sperm Motility, Spermatozoa physiology
- Abstract
Sperm motility is linked to the activation of signaling pathways that trigger movement. These pathways are mainly dependent on Ca
2+ , which acts as a secondary messenger. The maintenance of adequate Ca2+ concentrations is possible thanks to proper concentrations of other ions, such as K+ and Na+ , among others, that modulate plasma membrane potential and the intracellular pH. Like in every cell, ion homeostasis in spermatozoa is ensured by a vast spectrum of ion channels supported by the work of ion pumps and transporters. To achieve success in fertilization, sperm ion channels have to be sensitive to various external and internal factors. This sensitivity is provided by specific channel structures. In addition, novel sperm-specific channels or isoforms have been found with compositions that increase the chance of fertilization. Notably, the most significant sperm ion channel is the cation channel of sperm (CatSper), which is a sperm-specific Ca2+ channel required for the hyperactivation of sperm motility. The role of other ion channels in the spermatozoa, such as voltage-gated Ca2+ channels (VGCCs), Ca2+ -activated Cl-channels (CaCCs), SLO K+ channels or voltage-gated H+ channels (VGHCs), is to ensure the activation and modulation of CatSper. As the activation of sperm motility differs among metazoa, different ion channels may participate; however, knowledge regarding these channels is still scarce. In the present review, the roles and structures of the most important known ion channels are described in regard to regulation of sperm motility in animals.- Published
- 2021
- Full Text
- View/download PDF
46. Proton currents constrain structural models of voltage sensor activation
- Author
-
Mark S.P. Sansom, Aaron Randolph, Ashley L. Bennett, Ian Scott Ramsey, and Younes Mokrab
- Subjects
0301 basic medicine ,Models, Molecular ,Patch-Clamp Techniques ,QH301-705.5 ,Protein Conformation ,Science ,channel gating ,Mutation, Missense ,Gating ,General Biochemistry, Genetics and Molecular Biology ,Ion Channels ,03 medical and health sciences ,Protein structure ,Proton transport ,None ,Humans ,Biology (General) ,protein structure ,Ion channel ,General Immunology and Microbiology ,Chemistry ,General Neuroscience ,Conductance ,General Medicine ,Biophysics and Structural Biology ,membrane channels ,voltage sensor ,030104 developmental biology ,HEK293 Cells ,Structural biology ,Biochemistry ,Helix ,Biophysics ,Membrane channel ,Medicine ,Mutant Proteins ,proton transport ,Protons ,Research Article - Abstract
The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic ‘aqueous’ H+ conductance (GAQ). Mutation of a highly conserved ‘gating charge’ residue in the S4 helix (R1H) confers a resting-state H+ ‘shuttle’ conductance (GSH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute GSH in Hv1 without abrogating GAQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate GSH and GAQ gating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on GSH and GAQ are used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H+ transfer mechanisms in Hv1. DOI: http://dx.doi.org/10.7554/eLife.18017.001
- Published
- 2016
47. Sperm Membrane Channels, Receptors and Kinematics : Using boar spermatozoa for drug toxicity screening
- Author
-
Alejandro Vicente Carrillo
- Subjects
boar ,endocrine system ,membrane receptors ,BOAR ,Sperm membrane ,Cellbiologi ,Cell- och molekylärbiologi ,education ,Pharmacology and Toxicology ,Biology ,Internal fertilization ,Pharmaceutical Sciences ,Veterinärmedicin ,spermatozoa ,medicine ,Receptor ,Drug toxicity ,Spermatozoon ,urogenital system ,Biochemistry and Molecular Biology ,Cell Biology ,Oocyte ,Farmakologi och toxikologi ,Farmaceutiska vetenskaper ,Zygote formation ,Cell biology ,membrane channels ,medicine.anatomical_structure ,kinematics ,3Rprinciples ,Veterinary Science ,Cell and Molecular Biology ,Biokemi och molekylärbiologi ,Plasma membrane - Abstract
Internal fertilization usually implies that a spermatozoon, with intact attributes for zygote formation, passes all hurdles during its transport through the female genitalia and reaches the oocyte. During this journey, millions to billions of other spermatozoa perish. Spermatozoa are highly differentiated motile cells without synthetic capabilities. They generate energy via glycolysis and oxidative phosphorylation to sustain motility and to maintain the stability and functionality of their plasma membrane. In vivo, they spend their short lifespan bathing in female genital tract fluids of different origins, or are in vitro exposed to defined media during diverse sperm handling i.e. extension, cryopreservation, in vitro fertilization, etc. Being excitable cells, spermatozoa respond in vivo to various stimuli during pre-fertilization (capacitation, hyperactivation, oocyte location) and fertilization (acrosome reaction, interaction with the oocyte) events, mediated via diverse membrane ion-conducting channels and ligand-gated receptors. The present Thesis has mapped the presence and reactivity (sperm intactness and kinematics) of selected receptors, water and ion channels in ejaculated boar spermatozoa. The final aim was to find a relevant alternative cell type for in vitro bioassays that could ease the early scrutiny of candidate drugs as well as decreasing our needs for experimental animals according to the 3R principles. Spermatozoa are often extended, cooled and thawed to warrant their availability as fertile gametes for breeding or in vitro testing. Such manipulations stress the cells via osmotic variations and hence spermatozoa need to maintain membrane intactness by controlling the exchange of water and the common cryoprotectant glycerol, via aquaporins (AQPs). Both AQPs-7 and -9 were studied for membrane domain changes in cauda- and ejaculated spermatozoa (un-processed, extended, chilled or frozen-thawed). While AQP-9 maintained location through source and handling, thawing of ejaculated spermatozoa clearly relocated the labelling of AQP-7, thus appearing as a relevant marker for non-empirical studies of sperm cryopreservation. Alongside water, spermatozoa interact with calcium (Ca2+) via the main Ca2+ sperm channel CatSper. Increments in intracellular Ca2+ initiate motility hyperactivation and the acrosome reaction. The four subunits of the CatSper channel were present in boar spermatozoa, mediating changes in sperm motility under in vitro capacitation-inducing conditions (increased extracellular Ca2+ availability and bicarbonate) or challenge by the CatSper antagonists mibefradil and NNC 55-0396. Uterine and oviduct fluids are richest in endogenous opioids as β-endorphins during mating and ovulation. Both μ- and δ- opioid receptors were present in boar spermatozoa modulating sperm motility, as in vitro challenge with known agonists (μ: morphine; δ: DPDPE and κ: U 50488) and antagonists (μ: naloxone; δ: naltrindole and κ: nor-binaltrorphimine) showed that the μ-opioid receptor maintained or increased motility while the δ-opioid receptor mediated decreased motility over time. Finally, boar spermatozoa depicted dose-response effects on sperm kinematics and mitochondrial potential following in vitro challenge with 130 pharmacological drugs and toxic compounds as well as with eight known mito-toxic compounds. In conclusion, boar spermatozoa expressing functional water (AQPs-7 and -9) and ion (CatSper 1-4) channels as well as μ- and δ-opioid receptors are able to adapt to stressful environmental variations, capacitation and pharmacological compounds and drug components. Ejaculated sperm suspensions are easily and painlessly obtained from breeding boars, and are suitable biosensors for in vitro drug-induced testing, complying with the 3R principles of reduction and replacement of experimental animals, during early toxicology screening.
- Published
- 2016
48. Sperm Membrane Channels, Receptors and Kinematics : Using boar spermatozoa for drug toxicity screening
- Author
-
Vicente Carrillo, Alejandro and Vicente Carrillo, Alejandro
- Abstract
Internal fertilization usually implies that a spermatozoon, with intact attributes for zygote formation, passes all hurdles during its transport through the female genitalia and reaches the oocyte. During this journey, millions to billions of other spermatozoa perish. Spermatozoa are highly differentiated motile cells without synthetic capabilities. They generate energy via glycolysis and oxidative phosphorylation to sustain motility and to maintain the stability and functionality of their plasma membrane. In vivo, they spend their short lifespan bathing in female genital tract fluids of different origins, or are in vitro exposed to defined media during diverse sperm handling i.e. extension, cryopreservation, in vitro fertilization, etc. Being excitable cells, spermatozoa respond in vivo to various stimuli during pre-fertilization (capacitation, hyperactivation, oocyte location) and fertilization (acrosome reaction, interaction with the oocyte) events, mediated via diverse membrane ion-conducting channels and ligand-gated receptors. The present Thesis has mapped the presence and reactivity (sperm intactness and kinematics) of selected receptors, water and ion channels in ejaculated boar spermatozoa. The final aim was to find a relevant alternative cell type for in vitro bioassays that could ease the early scrutiny of candidate drugs as well as decreasing our needs for experimental animals according to the 3R principles. Spermatozoa are often extended, cooled and thawed to warrant their availability as fertile gametes for breeding or in vitro testing. Such manipulations stress the cells via osmotic variations and hence spermatozoa need to maintain membrane intactness by controlling the exchange of water and the common cryoprotectant glycerol, via aquaporins (AQPs). Both AQPs-7 and -9 were studied for membrane domain changes in cauda- and ejaculated spermatozoa (un-processed, extended, chilled or frozen-thawed). While AQP-9 maintained location through source and handl
- Published
- 2016
- Full Text
- View/download PDF
49. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity.
- Author
-
Giovinazzo JA, Thomson RP, Khalizova N, Zager PJ, Malani N, Rodriguez-Boulan E, Raper J, and Schreiner R
- Subjects
- Animals, Apolipoprotein L1 genetics, CHO Cells, Cell Death, Cell Membrane metabolism, Cricetulus, Endoplasmic Reticulum metabolism, HEK293 Cells, Humans, Hydrogen-Ion Concentration, Kidney Diseases etiology, Microscopy, Fluorescence, Potassium metabolism, Risk Factors, Sodium metabolism, Apolipoprotein L1 metabolism, Cytotoxins metabolism, Ion Channels metabolism, Kidney Diseases metabolism
- Abstract
Recently evolved alleles of Apolipoprotein L-1 ( APOL1 ) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na
+ and Ca2+ . We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease., Competing Interests: JG, RT, NK, PZ, NM, ER, JR, RS No competing interests declared, (© 2020, Giovinazzo et al.)- Published
- 2020
- Full Text
- View/download PDF
50. Degradation Products of Amyloid Protein: Are They The Culprits?
- Author
-
Zaretsky DV and Zaretskaia M
- Subjects
- Cell Membrane, Flow Cytometry, Humans, Neurons pathology, Phosphatidylserines, Alzheimer Disease pathology, Amyloid beta-Peptides metabolism, Amyloidogenic Proteins metabolism, Amyloidosis metabolism, Calcium metabolism, Mitochondria metabolism
- Abstract
Objectives: Beta-amyloid (Aβ) peptides are most toxic to cells in oligomeric form. It is commonly accepted that oligomers can form ion channels in cell membranes and allow calcium and other ions to enter cells. The activation of other mechanisms, such as apoptosis or lipid peroxidation, aggravates the toxicity, but it itself can result from the same initial point, that is, ion disturbance due to an increased permeability of membranes. However, experimental studies of membrane channels created by Aβ are surprisingly limited., Methods: Here, we report a novel flow cytometry technique which can be used to detect increased permeability of membranes to calcium induced by the exposure to amyloid peptides. Calcium entry into the liposome is monitored using calcium-sensitive fluorescent probe. Undamaged lipid membranes are not permeable to calcium. Liposomes that are prepared in a calcium-free medium become able to accumulate calcium in a calcium-containing medium only after the formation of channels., Results: Using this technique, we demonstrated that the addition of short amyloid fragment Ab25-35, which is known for its extreme toxicity on cultured neurons, readily increased membrane permeability to calcium. However, neither similarly sized peptide Ab22-35 nor full-length peptide Aβ1-42 were producing channels. The formation of channels was observed in the membranes made of phosphatidylserine, a negatively charged lipid, but not in membranes made of the neutral phosphatidylcholine., Discussion: We have analyzed several issues which could be critical for understanding the pathogenesis of Alzheimer's disease, specifically 1) the need for a negatively charged membrane to produce the ion channel; 2) the potential role of the aggregated form in cellular toxicity of Aβ peptides; 3) channelforming ability of multiple degradation products of amyloid; 4) non-specificity of ion channels formed by amyloid peptides. Potential targets of channel-forming oligomers appear to be intracellular and are organelles well-known for dysfunction in Alzheimer's disease (mitochondria and lysosomes). In fact, lysosomes can also be the producers of degraded amyloid. Provided speculations support the hypothesis that neuronal toxicity can be caused by the degradation products of beta-amyloid., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)
- Published
- 2020
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.