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Connexin hemichannels were identified as the first members of the eukaryotic large-pore channel family that mediate permeation of both atomic ions and small molecules between the intracellular and extracellular environments. The conventional view is that their pore is a large passive conduit through which both ions and molecules diffuse in a similar manner. In stark contrast to this notion, we demonstrate that the permeation of ions and of molecules in connexin hemichannels can be uncoupled and differentially regulated. We find that human connexin mutations that produce pathologies and were previously thought to be loss-of-function mutations due to the lack of ionic currents are still capable of mediating the passive transport of molecules with kinetics close to those of wild-type channels. This molecular transport displays saturability in the micromolar range, selectivity, and competitive inhibition, properties that are tuned by specific interactions between the permeating molecules and the N-terminal domain that lies within the pore-a general feature of large-pore channels. We propose that connexin hemichannels and, likely, other large-pore channels, are hybrid channel/transporter-like proteins that might switch between these two modes to promote selective ion conduction or autocrine/paracrine molecular signaling in health and disease processes.

Junyu Wang,1 Lu Yun,1 Hong Zhao,1 Xiangpeng Li2 1Department of Pharmacy, Qingdao Central Hospital, Qingdao, 266042, Shandong, People’s Republic of China; 2Department of Pharmacy, The Affiliated Hospital of Qingdao University, Qingdao, 266003, Shandong, People’s Republic of ChinaCorrespondence: Xiangpeng LiDepartment of Pharmacy, The Affiliated Hospital of Qingdao University, 16 Jiangsu Road, Shinan District, Qingdao, 266003, Shandong, People’s Republic of ChinaTel +86-532-82912182; +86-18661809083Email XiangpengLi021966@163.comBackground: Pseudomonas aeruginosa (P. aeruginosa) is an uncommon but fatal causative pathogen for community-acquired pneumonia (CAP). Few case reports described the previously healthy individuals with CAP caused by P. aeruginosa.Case Presentation: A 67-year-old male farmer was referred to our hospital with a 6-day history of fever and shortness of breath. The radiologic findings revealed a dense consolidation site in the right lung, considering infection lesion, accompanying with mediastinal and right hilar lymphadenopathy. Sputum sample results showed P. aeruginosa and multidrug-resistant Acinetobacter baumannii. The combination of polymyxin B and amikacin was given to him based on the lab results, the manifestations of the patient were alleviated and he returned to his home after a 35-day hospitalization.Conclusion: We need to keep close attention to community-acquired P. aeruginosa pneumonia due to its high mortality, further studies are needed to identify the infectious source, effective examination, and optimal therapy including medications and duration.Keywords: Pseudomonas aeruginosa, community-acquired pneumonia, polymyxin B and amikacin, a case report

Inle Lake is an ancient lake in Myanmar, which is an important area with unique and diverse fauna. Its ichthyofauna is believed to have formed non‐radiatively, but the historical processes are poorly understood. To elucidate the mechanisms that shape species diversity in this moderately isolated biogeographical 'island', this study focused on a typical endemic fish of Inle Lake, Channa harcourtbutleri (Channidae, Anabantiformes), with its widely distributed sister species, C. limbata, and estimated the historical distribution and diversification processes of the endemic fish based on genome‐wide polymorphism (MIG‐seq) and mitochondrial DNA data. Channa harcourtbutleri contained two genetically and morphologically distinct groups inhabiting Inle Lake and the surrounding rivers respectively. These two groups were genetically the closest to each other; however, the riverine group showed some similarity to the closely related species, C. limbata from Southeast Asia. The mtDNA haplotypes of the endemic species were not monophyletic; most of the riverine group had haplotypes identical or close to those of C. limbata from the upper Irrawaddy and Salween rivers. The time tree suggested that C. harcourtbutleri diverged from C. limbata in the early Pleistocene and then experienced secondary contact with C. limbata in the late Pleistocene. Genetic and morphological differentiation within C. harcourtbutleri suggests that local adaptation to different environments has played an important role for the coexistence of its two forms with some reproductive isolation. Further, the results highlight the importance of multiple colonization and allopatric speciation in shaping biodiversity in the long‐term, moderately isolated environments. [ABSTRACT FROM AUTHOR]

The diagnosis of sleep disorders such as narcolepsy and insomnia currently requires experts to interpret sleep recordings (polysomnography). Here, the authors introduce a neural network analysis method for polysomnography that could reduce time spent in sleep clinics and automate narcolepsy diagnosis.

Angiotensin II type 1 receptor (AT1R) blockers (ARBs) are among the most prescribed drugs. However, ARB effectiveness varies widely, which may be due to non-synonymous single nucleotide polymorphisms (nsSNPs) within the AT1R gene. The AT1R coding sequence contains over 100 nsSNPs; therefore, this study embarked on determining which nsSNPs may abrogate the binding of selective ARBs. The crystal structure of olmesartan-bound human AT1R (PDB:4ZUD) served as a template to create an inactive apo-AT1R via molecular dynamics simulation (n = 3). All simulations resulted in a water accessible ligand-binding pocket that lacked sodium ions. The model remained inactive displaying little movement in the receptor core; however, helix 8 showed considerable flexibility. A single frame representing the average stable AT1R was used as a template to dock Olmesartan via AutoDock 4.2, MOE, and AutoDock Vina to obtain predicted binding poses and mean Boltzmann weighted average affinity. The docking results did not match the known pose and affinity of Olmesartan. Thus, an optimization protocol was initiated using AutoDock 4.2 that provided more accurate poses and affinity for Olmesartan (n = 6). Atomic models of 103 of the known human AT1R polymorphisms were constructed using the molecular dynamics equilibrated apo-AT1R. Each of the eight ARBs was then docked, using ARB-optimized parameters, to each polymorphic AT1R (n = 6). Although each nsSNP has a negligible effect on the global AT1R structure, most nsSNPs drastically alter a sub-set of ARBs affinity to the AT1R. Alterations within N298 -L314 strongly effected predicted ARB affinity, which aligns with early mutagenesis studies. The current study demonstrates the potential of utilizing in silico approaches towards personalized ARB therapy. The results presented here will guide further biochemical studies and refinement of the model to increase the accuracy of the prediction of ARB resistance in order to increase overall ARB effectiveness.

Abstract Background Smad4 is a critical effector of TGF-β signaling that regulates a variety of cellular functions. However, its role in the brain has rarely been studied. Here, we examined the molecular mechanisms underlying the post-translational regulation of Smad4 function by SUMOylation, and its role in spatial memory formation. Results In the hippocampus, Smad4 is SUMOylated by the E3 ligase PIAS1 at Lys-113 and Lys-159. Both spatial training and NMDA injection enhanced Smad4 SUMOylation. Inhibition of Smad4 SUMOylation impaired spatial learning and memory in rats by downregulating TPM2, a gene associated with skeletal myopathies. Similarly, knockdown of TPM2 expression impaired spatial learning and memory, while TPM2 mRNA and protein expression increased after spatial training. Among the TPM2 mutations associated with skeletal myopathies, the TPM2E122K mutation was found to reduce TPM2 expression and impair spatial learning and memory in rats. Conclusions We have identified a novel role of Smad4 SUMOylation and TPM2 in learning and memory formation. These results suggest that patients with skeletal myopathies who carry the TPM2E122K mutation may also have deficits in learning and memory functions.

Mechanosensitive PIEZO channels constitute potential pharmacological targets for multiple clinical conditions, spurring the search for potent chemical PIEZO modulators. Among them is Yoda1, a widely used synthetic small molecule PIEZO1 activator discovered through cell-based high-throughput screening. Yoda1 is thought to bind to PIEZO1's mechanosensory arm domain, sandwiched between two transmembrane regions near the channel pore. However, how the binding of Yoda1 to this region promotes channel activation remains elusive. Here, we first demonstrate that cross-linking PIEZO1 repeats A and B with disulfide bridges reduces the effects of Yoda1 in a redox-dependent manner, suggesting that Yoda1 acts by perturbing the contact between these repeats. Using molecular dynamics-based absolute binding free energy simulations, we next show that Yoda1 preferentially occupies a deeper, amphipathic binding site with higher affinity in PIEZO1 open state. Using Yoda1's binding poses in open and closed states, relative binding free energy simulations were conducted in the membrane environment, recapitulating structure-activity relationships of known Yoda1 analogs. Through virtual screening of an 8 million-compound library using computed fragment maps of the Yoda1 binding site, we subsequently identified two chemical scaffolds with agonist activity toward PIEZO1. This study supports a pharmacological model in which Yoda1 activates PIEZO1 by wedging repeats A and B, providing a structural and thermodynamic framework for the rational design of PIEZO1 modulators. Beyond PIEZO channels, the three orthogonal computational approaches employed here represent a promising path toward drug discovery in highly heterogeneous membrane protein systems. [ABSTRACT FROM AUTHOR]

Post-translational modifications of methyl-CpG-binding protein 2 (MeCP2) are important for its function and dysfunction in Rett syndrome. Here, Tai et al. show a functional interaction between MeCP2 SUMOylation and phosphorylation in rodent behavior and synaptic plasticity.

Alzheimer’s disease (AD) is a neurodegenerative disorder that affects approximately 35 million people worldwide, and diet has been reported to influence the prevalence/incidence of AD. Colorectal cancer is among the most common cancers in Western populations, and the correlation between constipation and the occurrence of colorectal cancer has been identified in a number of studies, which show that a Westernized diet is a mutual risk factor. Constipation is a growing health problem, particularly in middle-aged and older adults. As the most common gastrointestinal disorder in adults, constipation affects 2–20% of the world population, and it is associated with several diseases, such as diabetes, Parkinson’s disease, and others. Comparing the epidemiological data on colorectal cancer and AD, we find that colorectal cancer and AD have similar epidemiologic feature, which is both disease correlate with high prevalence of constipation. Therefore, we hypothesized that constipation may influence Alzheimer’s disease in a similar way that it contributes to colorectal cancer. This review aimed to systemically elucidate the evidence that constipation contributes to Alzheimer’s disease progression.

Previous studies showed that the serum- and glucocorticoid-inducible kinase ("sgk") gene plays an important role in long-term memory formation. The present study further examined the role of SGK in long-term potentiation (LTP). The dominant-negative mutant of "sgk," SGKS422A, was used to inactivate SGK. Results revealed a time-dependent increase in SGK phosphorylation after tetanization with a significant effect observed 3 h and 5 h later. Transfection of SGKS422A impaired the expression, but not the induction, of LTP. Furthermore, the constitutively active "sgk," SGKS422D, up-regulated postsynaptic density-95 expression in the hippocampus. These results together support the role of SGK in neuronal plasticity. (Contains 3 figures.)

Disturbance of L‐carnitine (LC) activity dissipates metabolic energy production in living cells. LC deficiency regards to malabsorption and biosynthetic and transport deficiencies, either due to dietary or metabolic factors. Metal ions interact with LC molecule or its metabolic system elements such as building blocks (lysine and methionine), biosynthetic enzymes (trimethyllysine hydroxylase, TMLH; γ‐butyrobetaine dioxygenase, γ‐BBD) and LC transporters (carnitine acetyl transferase, CAT; organic cation transporter novel 2, OCTN2). Metals such as Cu2+, Ca2+ and Mg2+ form complexes with LC, while Pb2+ and Ni form complexes with methionine and lysine. Also, Mg2+ and Mn ions inhibit TMLH and γ‐BBD activities. On the other hand, Ca2+ ions induce TMLH activity while LC forms a complex with it. Also, boron stabilizes B6 and C vitamins as they are co‐enzymes for LC biosynthetic enzymes activity. Metals affect LC homeostasis via affecting its transporters CAT and OCTN2, that Na+ shortage affects OCTN2 activity, while Cu2+ inhibit CAT activity. Dietary fibres mediate ions toxicity by forming complexes with ions, which increase LC absorption in small intestine, while fibre fermentation liberates the bounded minerals and enrich bacterial biomass in large intestine, but the microbiome sequent metals intra‐ and extracellularly increasing LC absorption, in addition to the dietary sparing effect on LC from bacterial consumption as nitrogen source. This review aimed to illustrate effect of metal ions toxicity on LC activity and the mediating effect of dietary fibres. To the best of our knowledge, this is the first review to illustrate the ion toxicity on LC activity in monogastrics and fish. [ABSTRACT FROM AUTHOR]