40 results on '"raft"'
Search Results
2. GPI-anchored proteins at the node of Ranvier
- Author
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Labasque, Marilyne and Faivre-Sarrailh, Catherine
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GLYCOLIPIDS , *CELL adhesion molecules , *MYELINATION , *ENDOPLASMIC reticulum , *MEMBRANE proteins , *NEUROLOGICAL disorders , *MULTIPLE sclerosis - Abstract
Abstract: Contactin and TAG-1 are glycan phosphatidyl inositol (GPI)-anchored cell adhesion molecules that play a crucial role in the organization of axonal subdomains at the node of Ranvier of myelinating fibers. Contactin and TAG-1 mediate axo-glial selective interactions in association with Caspr-family molecules at paranodes and juxtaparanodes, respectively. How membrane proteins can be confined in these neighbouring domains along the axon has been the subject of intense investigations. This review will specifically examine the properties conferred by the lipid microenvironment to regulate trafficking and selective association of these axo-glial complexes. Increasing evidences from genetic and neuropathological models point to a role of lipid rafts in the formation or stabilization of the paranodal junctions. [Copyright &y& Elsevier]
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- 2010
- Full Text
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3. Cholesterol but not association with detergent resistant membranes is necessary for the transport function of MRP2/ABCC2
- Author
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Ito, Kousei, Hoekstra, Dick, and van IJzendoorn, Sven C.D.
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ATP-binding cassette transporters , *BIOLOGICAL membranes , *BIOLOGICAL transport , *BLOOD cholesterol , *ANIONS , *SURFACE active agents - Abstract
Abstract: MRP2(/ABCC2) excretes amphiphilic organic anions into bile, and associates with detergent-resistant bile canalicular membrane domains (DRM). Here, we have evaluated sensitivities of MRP2 transport function and DRM association by titrating the cellular cholesterol content. We demonstrate that the role of cholesterol in the partitioning of MRP2 to DRM can be separated from the role of cholesterol in the function of MRP2, such that (i) cholesterol is not necessary for the polarized distribution of MRP2 at the canalicular membrane, (ii) partitioning into DRM is not required for MRP2 function, yet (iii) the presence of cholesterol is necessary for transport activity. [Copyright &y& Elsevier]
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- 2008
- Full Text
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4. Variable actin dynamics requirement for the exit of different cargo from the trans-Golgi network
- Author
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Lázaro-Diéguez, Francisco, Colonna, Cecilia, Cortegano, Miguel, Calvo, María, Martínez, Susana E., and Egea, Gustavo
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ACTIN , *MICROTUBULES , *GOLGI apparatus , *ORGANELLES - Abstract
Abstract: Efficient post-Golgi trafficking depends on microtubules, but actin filaments and actin-associated proteins are also postulated. Here we examined, by inverse fluorescence recovery after photobleaching, the role of actin dynamics in the exit from the TGN of fluorescent-tagged apical or basolateral and raft or non-raft-associated cargoes. Either the actin-stabilizing jasplakinolide or the actin-depolymerising latrunculin B variably but significantly inhibited post-Golgi traffic of non-raft associated apical p75NTR and basolateral VSV-G cargoes. The TGN-exit of the apical-destined VSV-G mutant was impaired only by latrunculin B. Strikingly, the raft-associated GPI-anchor protein was not affected by either actin toxin. Results indicate that actin dynamics participates in the TGN egress of both apical- and basolateral-targeted proteins but is not needed for apical raft-associated cargo. [Copyright &y& Elsevier]
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- 2007
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5. About lipids and toxins
- Author
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Reig, Núria and van der Goot, F.Gisou
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ANTIGENS , *METABOLITES , *ANTITOXINS , *BIOLOGICALS - Abstract
Abstract: Many mono or multicellular organisms secrete soluble proteins, referred to as protein toxins, which alter the behavior of foreign, or target cells, possibly leading to their death. These toxins affect either the cell membrane by forming pores or modifying lipids, or some intracellular target. To reach this target, they must cross one of the cellular membranes, generally that of an intracellular organelle. As described in this minireview, lipids play crucial roles in the intoxication process of most if not all toxins, by allowing/promoting binding, endocytosis, trafficking and/or translocation into the cytoplasm. [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
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6. PSPN/GFRα4 has a significantly weaker capacity than GDNF/GFRα1 to recruit RET to rafts, but promotes neuronal survival and neurite outgrowth
- Author
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Yang, Jianmin, Lindahl, Maria, Lindholm, Päivi, Virtanen, Heidi, Coffey, Eleanor, Runeberg-Roos, Pia, and Saarma, Mart
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NERVOUS system , *BACTERIOPHAGES , *NEUROTROPHINS , *CELL membranes - Abstract
Previously, it was shown that the recruitment of RET into lipid rafts by glial cell line-derived neurotrophic factor (GDNF)/GFRα1 is crucial for efficient signal transduction. Here, we show that the mouse GFRα4 is a functional, N-glycosylated, glycosylphosphatidylinositol (GPI)-anchored protein, which mediates persephin (PSPN)-induced phosphorylation of RET, but has an almost undetectable capacity to recruit RET into the 0.1% Triton X-100 insoluble membrane fraction. In spite of this, PSPN/mGFRα4 promotes neurite outgrowth in PC6-3 cells and survival of cerebellar granule neurons. As we show that also human PSPN/GFRα4 is unable to recruit RET into lipid rafts, we propose that the mammalian GFRα4 in this respect differs from GFRα1. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
- View/download PDF
7. Prion protein is a component of the multimolecular signaling complex involved in T cell activation
- Author
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Mattei, Vincenzo, Garofalo, Tina, Misasi, Roberta, Circella, Annapia, Manganelli, Valeria, Lucania, Giuseppe, Pavan, Antonio, and Sorice, Maurizio
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PRIONS , *PROTEINS , *GANGLIOSIDES , *T cells - Abstract
In this study we analyzed the interaction of prion protein PrPC with components of glycosphingolipid-enriched microdomains in lymphoblastoid T cells. PrPC was distributed in small clusters on the plasma membrane, as revealed by immunoelectron microscopy. PrPC is present in microdomains, since it coimmunoprecipitates with GM3 and the raft marker GM1. A strict association between PrPC and Fyn was revealed by scanning confocal microscopy and coimmunoprecipitation experiments. The phosphorylation protein ZAP-70 was immunoprecipitated by anti-PrP after T cell activation. These results demonstrate that PrPC interacts with ZAP-70, suggesting that PrPC is a component of the multimolecular signaling complex within microdomains involved in T cell activation. [Copyright &y& Elsevier]
- Published
- 2004
- Full Text
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8. Lipid rafts determine efficiency of NADPH oxidase activation in neutrophils
- Author
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Shao, Dongmin, Segal, Anthony W., and Dekker, Lodewijk V.
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LIPID metabolism , *OXIDASES , *NEUTROPHILS , *PROTEIN kinase C - Abstract
We have investigated the contribution of lipid rafts to activation of the NADPH oxidase enzyme system in neutrophils. Membrane-bound NADPH oxidase subunits are present in the lipid raft compartment of neutrophils. Cytosolic NADPH oxidase components are mainly absent from but are recruited to rafts upon Fcγ receptor activation. In parallel, protein kinase C isotypes are recruited to the rafts. Kinetic analysis of NADPH oxidase activation revealed that rafts determine the onset but not the maximal rate of enzyme activity. Thus lipid rafts serve to physically juxtapose the NADPH oxidase effector, protein kinase C and Fcγ receptor, resulting in efficient coupling. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
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9. Munc18-2/syntaxin3 complexes are spatially separated from syntaxin3-containing SNARE complexes
- Author
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Pombo, Isabel, Rivera, Juan, and Blank, Ulrich
- Subjects
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EXOCYTOSIS , *MEMBRANE fusion , *MAST cells , *PROTEIN binding - Abstract
Exocytosis of mast cell granules requires a vesicular- and plasma membrane-associated fusion machinery. We examined the distribution of SNARE membrane fusion and Munc18 accessory proteins in lipid rafts of RBL mast cells. SNAREs were found either excluded (syntaxin2), equally distributed between raft and non-raft fractions (syntaxin4, VAMP-8, VAMP-2), or selectively enriched in rafts (syntaxin3, SNAP-23). Syntaxin4-binding Munc18-3 was absent, whereas small amounts of the syntaxin3-interacting partner Munc18-2 consistently distributed into rafts. Cognate SNARE complexes of syntaxin3 with SNAP-23 and VAMP-8 were enriched in rafts, whereas Munc18-2/syntaxin3 complexes were excluded. This demonstrates a spatial separation between these two types of complexes and suggests that Munc18-2 acts in a step different from SNARE complex formation and fusion. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
10. Sphingomyelin is much more effective than saturated phosphatidylcholine in excluding unsaturated phosphatidylcholine from domains formed with cholesterol
- Author
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van Duyl, Bianca Y., Ganchev, Dragomir, Chupin, Vladimir, de Kruijff, Ben, and Killian, J. Antoinette
- Subjects
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CHOLESTEROL , *NUCLEAR magnetic resonance , *ATOMIC force microscopy - Abstract
In this study, we compared domain formation in raft-like mixtures of cholesterol and dioleoylphosphatidylcholine (DOPC) with either sphingomyelin (SM) or dipalmitoylphosphatidylcholine (DPPC). Using 2H nuclear magnetic resonance, we studied the properties of the lipid enriched in the fluid phase, DOPC. We found that acyl chain 2H-labeled DOPC is much less ordered in SM-containing mixtures than in those containing DPPC, suggesting that DOPC in the SM-containing mixture senses a lower concentration of cholesterol in its direct environment. Atomic force microscopy experiments demonstrated large differences in the size and shape of domains in the different mixtures. We propose that these various differences are a consequence of the preferential interaction of cholesterol for sphingolipids over glycerophospholipids. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
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11. AKT1/PKBα is recruited to lipid rafts and activated downstream of PKC isotypes in CD3-induced T cell signaling
- Author
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Bauer, Birgit, Jenny, Marcel, Fresser, Fiedrich, Überall, Florian, and Baier, Gottfried
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T cells , *PROTEIN kinase C - Abstract
Protein kinase (PK) Cθ and Akt/PKBα cooperate in T cell receptor/CD28-induced T cell signaling. We here demonstrate the recruitment of endogenous Akt1 and PKCθ to lipid rafts in CD3-stimulated T cells. Further we show that Myr-PKCθ mediates translocation of endogenous Akt1 to the plasma membrane as well as to lipid rafts, most likely explained by the observed complex formation of both protein kinases. In addition, in peripheral mouse T cells, the PKC inhibitor Go¨6850 could partially block Akt1 activation in CD3-induced signaling, placing PKC isotype(s) upstream of Akt1. However, T cells derived from PKCθ knockout mice were not impaired in CD3- or phorbol ester-induced Akt1 activity. Taken together, the results of this study give new insights into the functional link of Akt1 and PKCθ in T cell signaling, demonstrating the co-recruitment of the two kinases and showing a novel pathway leading to Akt1 transactivation where PKC isotype(s) are involved but PKCθ is not essential. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
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12. Role of sphingomyelinase and ceramide in modulating rafts: do biophysical properties determine biologic outcome?
- Author
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Cremesti, Aida E., Goni, Felix M., and Kolesnick, Richard
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BIOLOGICAL systems , *SPHINGOLIPIDS - Abstract
Recent biophysical data suggest that the properties of ceramide observed in model membranes may apply to biological systems. In particular, the ability of ceramide to form microdomains, which coalesce into larger platforms or macrodomains, appears to be important for some cellular signaling processes. Several laboratories have now demonstrated similar reorganization of plasma membrane sphingolipid rafts, via ceramide generation, into macrodomains. This event appeared necessary for signaling upon activation of a specific set of cell surface receptors. In this article, we review the properties and functions of rafts, and the role of sphingomyelinase and ceramide in the biogenesis and re-modeling of these rafts. As clustering of some cell surface receptors in these domains may be critical for signal transduction, we propose a new model for transmembrane signal transmission. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
13. Doppel and PrPC do not share the same membrane microenvironment
- Author
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Shaked, Yuval, Hijazi, Nuha, and Gabizon, Ruth
- Subjects
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PROTEINS , *AFFINITY chromatography - Abstract
Doppel is a paralog of the normal prion protein, PrPC. It has been suggested that Doppel can compensate for the absence of PrPC in PrP0/0 mice. In this work, we tested whether Doppel and PrPC share the same cell location, thereby sharing the same neighboring cell components, probably required to share the same cell function. Our results show that, at detergent conditions in which membrane rafts were intact, neither PrPC and Doppel co-immunoprecipitate with the appropriate antibodies, nor was Doppel retained by a Cu2+IMAC resin, as PrPC does. This indicates that, although Doppel is a raft-associated protein as is PrPC, both proteins are not present in the same membrane microenvironment, and they probably do not perform the same function. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
14. Influence of hydrophobic mismatch and palmitoylation on the association of transmembrane α-helical peptides with detergent-resistant membranes
- Author
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van Duyl, Bianca Y., Rijkers, Dirk T.S., de Kruijff, Ben, and Killian, J. Antoinette
- Subjects
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PROTEINS , *BIOLOGICAL membranes , *LIQUIDS , *LIPIDS - Abstract
The aim of this study was to gain insight into the mechanism through which transmembrane proteins are targeted to liquid ordered (Lo) phase domains or rafts. This was investigated by analyzing the Triton X-100 resistance of designed transmembrane peptides in model membranes of 1,2-dioleoyl-sn-glycero-3-phosphocholine, sphingomyelin and cholesterol (1/1/1, molar ratio), which contain both Lo phase domains and fluid bilayers. By using peptides with one or two palmitate chains covalently linked to their N-terminus or with variable hydrophobic lengths, the roles of protein palmitoylation and of mismatch between the transmembrane segment of the protein and the bilayer thickness, respectively, were investigated. The results show that neither hydrophobic matching nor palmitoylation is sufficient for partitioning of peptides into Lo phase domains. It is concluded that the Lo phase itself, due to the tight packing of the lipids, constitutes an unfavorable environment for accommodation of protein transmembrane segments. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
15. Mechanisms of RNA loading into exosomes
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Maja M. Janas, Karolina Sapoń, Tadeusz Janas, and Teresa Janas
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Ceramide ,Biophysics ,Biology ,Exosomes ,Models, Biological ,Biochemistry ,Intraluminal vesicles ,Membrane Lipids ,chemistry.chemical_compound ,Rafts ,Membrane Microdomains ,Structural Biology ,microRNA ,Genetics ,Extracellular ,Animals ,Humans ,Molecular Biology ,Vesicle ,Cell Membrane ,Membrane ,Multivesicular Bodies ,RNA-Binding Proteins ,RNA ,MicroRNA ,Cell Biology ,Raft ,Microvesicles ,Cell biology ,chemistry ,Cytoplasm ,lipids (amino acids, peptides, and proteins) - Abstract
Upon fusion of multivesicular bodies (MVBs) with the plasma membrane, intraluminal vesicles (ILVs) are released into the extracellular space as exosomes. Since the lipid composition of the exosomal membrane resembles that of raft microdomains, the inward budding process involves the raft-like region of the MVB limiting membrane. Although published research suggests that cellular RNAs may be selectively sorted into exosomes, the molecular mechanisms remain elusive. In this review, we suggest that there is a continuous interaction of cellular RNAs with the outer (cytoplasmic) surface of MVBs and that the selection for incorporation of these RNAs into ILVs is based on their affinity to the raft-like region in the outer layer of the MVB membrane.
- Published
- 2015
16. Membrane rafting: From apical sorting to phase segregation
- Author
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Kai Simons and Uenal Coskun
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Detergents ,Phase separation ,Biophysics ,Biology ,Fatty Acid-Binding Proteins ,Models, Biological ,Biochemistry ,Phase Transition ,Membrane Microdomains ,Structural Biology ,Phase (matter) ,Genetics ,Animals ,Humans ,Membrane organisation ,Apical transport ,Resting state ,Molecular Biology ,Lipid raft ,Lipid rafts ,Membrane heterogeneity ,Cyclodextrins ,Cell Polarity ,Biological Transport ,Cell Biology ,Raft ,Lipid Metabolism ,Sphingolipid ,Cell Compartmentation ,Cell biology ,Cholesterol ,Membrane ,Apical sorting ,lipids (amino acids, peptides, and proteins) ,Function (biology) - Abstract
In this review we describe the history of the development of the raft concept for membrane sub-compartmentalization. From its early beginnings as a mechanism for apical sorting in epithelial cells the concept has evolved to a general principle for membrane organisation. After a shaky start with crude methodology based on detergent extraction the field has become increasingly sophisticated, employing a host of different methods that support the existence of dynamic raft domains in membranes. These are composed of fluctuating nanoscale assemblies of sphingolipid, cholesterol and proteins that can be stabilized to coalesce, forming platforms that function in membrane signalling and trafficking.
- Published
- 2009
17. The characterization of plasma membrane Ca2+-ATPase in rich sphingomyelin-cholesterol domains
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Yuhong Pang, Hua Zhu, Ping Wu, and Jianwen Chen
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Proteolipids ,Biophysics ,Calcium-Transporting ATPases ,Biochemistry ,Fluorescence ,Phase Transition ,Cell membrane ,Plasma membrane Ca2+-ATPase ,Structural Biology ,Caveolae ,Genetics ,Membrane fluidity ,medicine ,Conformation ,Molecular Biology ,Lipid raft ,Lipid rafts ,Acrylamide ,Liposome ,Chemistry ,Cell Membrane ,Tryptophan ,Cell Biology ,Raft ,Sphingomyelins ,Cholesterol ,Spectrometry, Fluorescence ,medicine.anatomical_structure ,Phosphatidylcholines ,Plasma membrane Ca2+ ATPase ,lipids (amino acids, peptides, and proteins) ,Sphingomyelin - Abstract
According to the raft hypothesis, sphingolipid-cholesterol (CHOL) microdomains are involved in numerous cellular functions. Here, we have prepared liposomes to simulate the lipid composition of rafts/caveolae using phosphatidylchone, sphingomyelin (SPM)-CHOL in vitro. Experiments of both 1,6-diphenyl-1,3,5-hexatriene and merocyanine-540 fluorescence showed that a phase transition from l(d) to l(o) can be observed clearly. In particular, we investigated the behavior of a membrane protein, plasma membrane Ca(2+)-ATPase (PMCA), in lipid rafts (l(o) phase). Three complementary approaches to characterize the physical appearance of PMCA were employed in the present study. Tryptophan intrinsic fluorescence increase, fluorescence quenching by both acrylamid and hypocrellin B decrease, and MIANS fluorescence decrease, indicate that the conformation of PMCA embedded in lipid l(o) phase is more compact than in lipid l(d) phase. Also, our results showed that PMCA activity decreased with the increase of SPM-CHOL content, in other words, with the increase of l(o) phase. This suggests that the specific domains containing high SPM-CHOL concentration are not a favorable place for PMCA activity. Finally, a possible explanation about PMCA molecules concentrated in caveolae/rafts was discussed.
- Published
- 2005
18. The effect of raft lipid depletion on microvilli formation in MDCK cells, visualized by atomic force microscopy
- Author
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Kai Simons, Doris Meder, Kate Poole, and Daniel J. Müller
- Subjects
Laser scanning confocal microscopy ,Biophysics ,Microvillus ,Raft lipid ,Microscopy, Atomic Force ,Biochemistry ,Cell Line ,Atomic force microscopy ,chemistry.chemical_compound ,Dogs ,Membrane Microdomains ,Structural Biology ,Madin–Darby canine kidney ,Monolayer ,Image Processing, Computer-Assisted ,Genetics ,Confocal laser scanning microscopy ,medicine ,Animals ,Molecular Biology ,Sphingolipids ,Microscopy, Confocal ,Microvilli ,Cholesterol ,Lasers ,Cell Membrane ,Cell Biology ,Buffer solution ,Raft ,Sphingolipid ,Actins ,Cell biology ,medicine.anatomical_structure ,chemistry ,lipids (amino acids, peptides, and proteins) - Abstract
We have investigated whether raft lipids of Madin–Darby canine kidney (MDCK) cells play any role in microvilli maintenance using a combination of atomic force microscopy (AFM) and laser scanning confocal microscopy. MDCK cells were treated to reduce the amount of sphingolipids, cholesterol, or both and subsequently imaged, in buffer solution, using AFM. It was observed that inhibition of either sphingolipid or cholesterol biosynthesis led to a reduction in the number of microvilli on the surface of MDCK cells. However, this effect was not uniform across the monolayer, with some cells resembling those in untreated controls. The subsequent extraction of cholesterol from cells grown in the presence of inhibitors led to a further reduction in microvilli on the surface of the cells and, in some cases, resulted in monolayers devoid of full length microvilli. Significantly, smaller spikes were observed on the surface of the smoother cells.
- Published
- 2004
19. Detergents as tools for the purification and classification of lipid rafts
- Author
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Luke H. Chamberlain
- Subjects
Detergent ,Octoxynol ,Detergents ,Biophysics ,Biochemistry ,Sphingolipid ,Polyethylene Glycols ,03 medical and health sciences ,Membrane Microdomains ,Structural Biology ,Genetics ,Molecular Biology ,Lipid raft ,030304 developmental biology ,0303 health sciences ,Chemistry ,030302 biochemistry & molecular biology ,Cell Biology ,Raft ,6. Clean water ,Cholesterol ,Membrane ,Solubility ,lipids (amino acids, peptides, and proteins) - Abstract
The relative insolubility of lipid rafts in cold non-ionic detergents is the most widely used method to purify these fascinating membrane domains from intact cells or membranes. Most of what we know about lipid raft function has been derived from experiments utilising detergent insolubility as the basis for raft purification. Recently, a wider range of detergents have been used to purify ‘rafts’, and rafts have been subclassified based on their differential solubility in different detergents. This minireview critically examines the use of detergents as tools for raft isolation and for the subclassification of rafts.
- Published
- 2004
20. Concurrent increase of cholesterol, sphingomyelin and glucosylceramide in the spleen from non-neurologic Niemann-Pick type C patients but also patients possibly affected with other lipid trafficking disorders
- Author
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Klaus Harzer, Eckhart Fröhlich, and Gero Massenkeil
- Subjects
Adult ,Spleen lipid ,Ceramide ,Pathology ,medicine.medical_specialty ,Niemann–Pick type C disease ,Biophysics ,Biology ,Ceramides ,Glucosylceramides ,Biochemistry ,Sphingolipid ,chemistry.chemical_compound ,Structural Biology ,Genetics ,medicine ,Lysosomal storage disease ,Humans ,Child ,Molecular Biology ,Lipid raft ,Cells, Cultured ,Raft ,Niemann-Pick Diseases ,Lipid metabolism ,Cell Biology ,Fibroblasts ,Middle Aged ,Lipid Metabolism ,medicine.disease ,Sphingomyelins ,stomatognathic diseases ,Cholesterol ,chemistry ,Child, Preschool ,Immunology ,lipids (amino acids, peptides, and proteins) ,NPC1 ,Niemann–Pick disease ,Sphingomyelin ,Spleen - Abstract
Niemann–Pick type C disease (NPC) is a neurovisceral (or, extremely rarely, only visceral) lipidosis caused by mutations in the NPC1 gene or, in a few patients, the HE1 gene, which encode sterol regulating proteins. NPC is characterised by a complex lipid anomaly including a disturbed cellular trafficking of cholesterol but also multi-lipid storage in visceral organs and brain. Lipids were studied using conventional methods in enlarged spleens that had been removed from five patients for different therapeutic and diagnostic reasons and found to have microscopic signs of lysosomal storage disease not suspected clinically. The spleen lipid findings with a concurrent accumulation of cholesterol, sphingomyelin and glucosylceramide (Acc-CSG) allowed us to suggest NPC diagnoses for these patients, who were free of neurologic symptoms. From two patients no material for confirmatory studies was available, but in two other patients NPC diagnoses could be confirmed with the filipin cytochemical cholesterol assay and NPC1 gene analysis, respectively. However, these tests and also HE1 gene analysis were negative in a third patient. Since the Acc-CSG lipid pattern seems to indicate a multi-lipid trafficking defect rather than being highly specific for NPC, this patient, if not affected with very atypical NPC, may be a candidate for a different lipid trafficking disorder. The Acc-CSG pattern was considered to be similar to the lipid pattern known for the lipid rafts, these functional cell structures being probably disorganised and accumulated in late endosomes and lysosomes of NPC cells.
- Published
- 2003
21. Doppel and PrPCdo not share the same membrane microenvironment
- Author
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Ruth Gabizon, Yuval Shaked, and Nuha Hijazi
- Subjects
Prions ,animal diseases ,Cell ,Biophysics ,Biology ,GPI-Linked Proteins ,Biochemistry ,Chromatography, Affinity ,Mice ,Structural Biology ,mental disorders ,Genetics ,medicine ,Animals ,PrPC Proteins ,Prion protein ,Molecular Biology ,Raft ,PrP ,Doppel ,Cell Biology ,Immobilized metal affinity chromatography ,Precipitin Tests ,Cell function ,Protein Structure, Tertiary ,nervous system diseases ,Cell biology ,Membrane ,medicine.anatomical_structure ,Prion ,Function (biology) - Abstract
Doppel is a paralog of the normal prion protein, PrP(C). It has been suggested that Doppel can compensate for the absence of PrP(C) in PrP(0/0) mice. In this work, we tested whether Doppel and PrP(C) share the same cell location, thereby sharing the same neighboring cell components, probably required to share the same cell function. Our results show that, at detergent conditions in which membrane rafts were intact, neither PrP(C) and Doppel co-immunoprecipitate with the appropriate antibodies, nor was Doppel retained by a Cu(2+)IMAC resin, as PrP(C) does. This indicates that, although Doppel is a raft-associated protein as is PrP(C), both proteins are not present in the same membrane microenvironment, and they probably do not perform the same function.
- Published
- 2002
22. Influence of hydrophobic mismatch and palmitoylation on the association of transmembrane α-helical peptides with detergent-resistant membranes
- Author
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Bianca Y. van Duyl, J. Antoinette Killian, Dirk T. S. Rijkers, and Ben de Kruijff
- Subjects
Model membrane ,Octoxynol ,Palmitates ,Biophysics ,Biochemistry ,Sphingolipid ,Protein Structure, Secondary ,Membrane Lipids ,Hydrophobic mismatch ,Palmitoylation ,Structural Biology ,Genetics ,Protein palmitoylation ,Molecular Biology ,Raft ,Binding Sites ,Membranes ,Triton X-100 ,Chemistry ,Bilayer ,technology, industry, and agriculture ,Membrane Proteins ,Membranes, Artificial ,Cell Biology ,Transmembrane protein ,Sphingomyelins ,Transmembrane domain ,Cholesterol ,Membrane ,Phosphatidylcholines ,lipids (amino acids, peptides, and proteins) ,Peptides ,Sphingomyelin ,Hydrophobic and Hydrophilic Interactions - Abstract
The aim of this study was to gain insight into the mechanism through which transmembrane proteins are targeted to liquid ordered (Lo) phase domains or rafts. This was investigated by analyzing the Triton X-100 resistance of designed transmembrane peptides in model membranes of 1,2-dioleoyl-sn-glycero-3-phosphocholine, sphingomyelin and cholesterol (1/1/1, molar ratio), which contain both Lo phase domains and fluid bilayers. By using peptides with one or two palmitate chains covalently linked to their N-terminus or with variable hydrophobic lengths, the roles of protein palmitoylation and of mismatch between the transmembrane segment of the protein and the bilayer thickness, respectively, were investigated. The results show that neither hydrophobic matching nor palmitoylation is sufficient for partitioning of peptides into Lo phase domains. It is concluded that the Lo phase itself, due to the tight packing of the lipids, constitutes an unfavorable environment for accommodation of protein transmembrane segments.
- Published
- 2002
23. Membrane microdomains in immunoreceptor signaling
- Author
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Matous Hrdinka and Vaclav Horejsi
- Subjects
T-cell receptor ,Biophysics ,Receptors, Antigen, T-Cell ,Cell Biology ,Raft ,Leukocyte ,Biology ,Biochemistry ,Cell biology ,Lipid raft ,Membrane ,Membrane Microdomains ,Structural Biology ,Immunoreceptor signaling ,Genetics ,Animals ,Humans ,lipids (amino acids, peptides, and proteins) ,Functional studies ,Receptor ,Molecular Biology ,Signal Transduction - Abstract
Membrane microdomains denoted commonly as lipid rafts (or membrane rafts) have been implicated in T-cell receptor (TCR), and more generally immunoreceptor, signaling for over 25years. However, this area of research has been complicated by doubts about the real nature (and even existence) of these membrane entities, especially because of methodological problems connected with possible detergent artefacts. Recent progress in biophysical approaches and functional studies of raft resident proteins apparently clarified many controversial aspects in this area. At present, the prevailing view is that these membrane microdomains are indeed involved in many aspects of cell biology, including immunoreceptor signaling. Moreover, several other types of raft-like microdomains (perhaps better termed nanodomains) have been described, which apparently also play important biological roles.
- Published
- 2014
24. Mutation of a raft-targeting signal in the transmembrane region retards transport of influenza virus hemagglutinin through the Golgi
- Author
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Andreas Herrmann, Stephanie Engel, Michael Veit, and Maren de Vries
- Subjects
Biophysics ,Hemagglutinin (influenza) ,Golgi Apparatus ,Hemagglutinin Glycoproteins, Influenza Virus ,Biology ,Protein Sorting Signals ,medicine.disease_cause ,Biochemistry ,Exocytosis ,Cell Line ,symbols.namesake ,Dogs ,Membrane Microdomains ,Palmitoylation ,Structural Biology ,Golgi ,Genetics ,medicine ,Animals ,Hemagglutinin ,Molecular Biology ,Raft ,Mutation ,Vesicular transport ,Cell Biology ,Golgi apparatus ,Apical membrane ,Transport protein ,Cell biology ,Vesicular transport protein ,Protein Transport ,Transmembrane region ,symbols ,biology.protein ,lipids (amino acids, peptides, and proteins) ,Influenza virus - Abstract
Inclusion of proteins into membrane-rafts favours interactions required for virus assembly but has also been proposed to facilitate vesicular transport of proteins. The hemagglutinin (HA) of influenza virus contains a raft-targeting sequence in the outer leaflet of its transmembrane region. We report that its mutation enhances co-localization of HA with a cis-Golgi marker and retards Golgi-localized processing, such as acquisition of Endo-H resistant carbohydrates and proteolytic cleavage. In contrast, trimerization of the molecule in the ER and transport to the apical membrane were not affected. The second signal for raft-targeting, S-acylation at cytoplasmic cysteines, did not retard HA transport.
- Published
- 2011
25. Formation and regulation of lipid microdomains in cell membranes: theory, modeling, and speculation
- Author
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Jun Fan, Mikko Haataja, and Maria Sammalkorpi
- Subjects
Lipid microdomain ,Biophysics ,Biology ,Biochemistry ,Models, Biological ,Cell membrane ,Membrane Microdomains ,Structural Biology ,Genetics ,medicine ,Animals ,Humans ,Theory ,Spatial localization ,Molecular Biology ,Lipid raft ,Cell Membrane ,Modeling ,Membrane structure ,Cell Biology ,Raft ,Models, Theoretical ,Lipid Metabolism ,Cell biology ,Membrane ,medicine.anatomical_structure ,lipids (amino acids, peptides, and proteins) ,Membrane biophysics - Abstract
Compositional lipid microdomains (“lipid rafts”) in plasma membranes are believed to be important components of many cellular processes. The biophysical mechanisms by which cells regulate the size, lifetime, and spatial localization of these domains are rather poorly understood at the moment. Over the years, experimental studies of raft formation have inspired several phenomenological theories and speculations incorporating a wide variety of thermodynamic assumptions regarding lipid–lipid and lipid–protein interactions, and the potential role of active cellular processes on membrane structure. Here we critically review and discuss these theories, models, and speculations, and present our view on future directions.
- Published
- 2009
26. GPI-anchored proteins at the node of Ranvier
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Marilyne Labasque, Catherine Faivre-Sarrailh, Centre de recherche en neurobiologie - neurophysiologie de Marseille (CRN2M), and Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)
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Glycosylphosphatidylinositols ,MESH: Membrane Microdomains ,Biochemistry ,Myelin ,0302 clinical medicine ,Structural Biology ,Paranode ,Contactin ,MESH: Animals ,Axon ,Lipid raft ,0303 health sciences ,Node of Ranvier ,Cell adhesion molecule ,MESH: Glycosylphosphatidylinositols ,Cell biology ,medicine.anatomical_structure ,Intercellular Junctions ,lipids (amino acids, peptides, and proteins) ,MESH: Membrane Proteins ,Glycan ,MESH: Axons ,MESH: Biological Transport ,Biophysics ,Biology ,Models, Biological ,03 medical and health sciences ,Membrane Microdomains ,Ranvier's Nodes ,Genetics ,medicine ,Animals ,Humans ,TAG-1 ,[SDV.BBM.BC]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biochemistry [q-bio.BM] ,Molecular Biology ,Raft ,030304 developmental biology ,MESH: Humans ,Endoplasmic reticulum ,MESH: Models, Biological ,Membrane Proteins ,Biological Transport ,Cell Biology ,Axons ,Membrane protein ,nervous system ,biology.protein ,MESH: Ranvier's Nodes ,030217 neurology & neurosurgery ,MESH: Intercellular Junctions - Abstract
International audience; Contactin and TAG-1 are glycan phosphatidyl inositol (GPI)-anchored cell adhesion molecules that play a crucial role in the organization of axonal subdomains at the node of Ranvier of myelinating fibers. Contactin and TAG-1 mediate axo-glial selective interactions in association with Caspr-family molecules at paranodes and juxtaparanodes, respectively. How membrane proteins can be confined in these neighbouring domains along the axon has been the subject of intense investigations. This review will specifically examine the properties conferred by the lipid microenvironment to regulate trafficking and selective association of these axo-glial complexes. Increasing evidences from genetic and neuropathological models point to a role of lipid rafts in the formation or stabilization of the paranodal junctions.
- Published
- 2009
27. Cholesterol but not association with detergent resistant membranes is necessary for the transport function of MRP2/ABCC2
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Kousei Ito, Dick Hoekstra, Sven C.D. van IJzendoorn, Nanotechnology and Biophysics in Medicine (NANOBIOMED), Groningen Institute for Gastro Intestinal Genetics and Immunology (3GI), and Center for Liver, Digestive and Metabolic Diseases (CLDM)
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HepG2 ,LIPID MICRODOMAINS ,PROTEINS ,Detergents ,Biophysics ,ABCC2 ,Biochemistry ,digestive system ,Detergent resistant membrane ,Cell Line ,chemistry.chemical_compound ,Membrane Microdomains ,Structural Biology ,Amphiphile ,Genetics ,Humans ,EXPORT PUMP ,Molecular Biology ,CANALICULAR MEMBRANES ,Raft ,P-glycoprotein ,CHOLESTATIC RAT-LIVER ,DRUG-RESISTANCE ,biology ,Cholesterol ,Multidrug resistance-associated protein 2 ,Lipid microdomain ,MRP2 ,P-GLYCOPROTEIN ,Biological Transport ,Cell Biology ,Multidrug Resistance-Associated Protein 2 ,Membrane ,chemistry ,CELLS ,biology.protein ,Triton X-100 insoluble fraction ,lipids (amino acids, peptides, and proteins) ,TAUROURSODEOXYCHOLIC ACID INSERTS ,Multidrug Resistance-Associated Proteins ,Organic anion - Abstract
MRP2(/ABCC2) excretes amphiphilic organic anions into bile, and associates with detergent-resistant bile canalicular membrane domains (DRM). Here, we have evaluated sensitivities of MRP2 transport function and DRM association by titrating the cellular cholesterol content. We demonstrate that the role of cholesterol in the partitioning of MRP2 to DRM can be separated from the role of cholesterol in the function of MRP2, such that (i) cholesterol is not necessary for the polarized distribution of MRP2 at the canalicular membrane, (ii) partitioning into DRM is not required for MRP2 function, yet (iii) the presence of cholesterol is necessary for transport activity. (c) 2008 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.
- Published
- 2008
28. Lipid rafts and membrane traffic
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Michael Hanzal-Bayer and John F. Hancock
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Biophysics ,Biology ,Biochemistry ,Exocytosis ,Rafts ,Membrane Microdomains ,Structural Biology ,Cell Movement ,Liquid-ordered ,Genetics ,Molecular Biology ,Lipid raft ,Membrane microstructure ,Cell Membrane ,Cell Biology ,Raft ,Compartmentalization (psychology) ,Endocytosis ,Cell biology ,Pleckstrin homology domain ,Transmembrane domain ,Protein Transport ,Membrane ,Förster resonance energy transfer ,Signalling ,Cholesterol-facilitated ,lipids (amino acids, peptides, and proteins) - Abstract
Membrane rafts are regions of increased lipid acyl chain order that differ in their lipid and protein composition from the surrounding membrane. By providing an additional level of compartmentalization they have been proposed to serve many functions in cellular signal transduction and trafficking. We will review their potential involvement in different forms of membrane traffic, explicitly excluding signalling, and discuss select aspects of the raft hypothesis in its current form.
- Published
- 2007
29. Munc18-2/syntaxin3 complexes are spatially separated from syntaxin3-containing SNARE complexes
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Isabel Pombo, Ulrich Blank, and Juan Rivera
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Munc18 Proteins ,Macromolecular Substances ,Biophysics ,Vesicular Transport Proteins ,Membrane fusion ,Nerve Tissue Proteins ,Biology ,Biochemistry ,Munc18 ,Exocytosis ,R-SNARE Proteins ,Membrane Microdomains ,Structural Biology ,Genetics ,Animals ,Mast Cells ,Qc-SNARE Proteins ,Molecular Biology ,Lipid raft ,Raft ,Cells, Cultured ,Qa-SNARE Proteins ,Receptors, IgE ,Lipid bilayer fusion ,Membrane Proteins ,Proteins ,Reproducibility of Results ,Cell Biology ,Qb-SNARE Proteins ,Phosphoproteins ,Precipitin Tests ,Cell biology ,Rats ,SNARE ,lipids (amino acids, peptides, and proteins) ,SNARE complex ,Carrier Proteins ,SNARE Proteins - Abstract
Exocytosis of mast cell granules requires a vesicular- and plasma membrane-associated fusion machinery. We examined the distribution of SNARE membrane fusion and Munc18 accessory proteins in lipid rafts of RBL mast cells. SNAREs were found either excluded (syntaxin2), equally distributed between raft and non-raft fractions (syntaxin4, VAMP-8, VAMP-2), or selectively enriched in rafts (syntaxin3, SNAP-23). Syntaxin4-binding Munc18-3 was absent, whereas small amounts of the syntaxin3-interacting partner Munc18-2 consistently distributed into rafts. Cognate SNARE complexes of syntaxin3 with SNAP-23 and VAMP-8 were enriched in rafts, whereas Munc18-2/syntaxin3 complexes were excluded. This demonstrates a spatial separation between these two types of complexes and suggests that Munc18-2 acts in a step different from SNARE complex formation and fusion.
- Published
- 2003
30. Role of sphingomyelinase and ceramide in modulating rafts: do biophysical properties determine biologic outcome?
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Félix M. Goñi, Richard Kolesnick, and Aida Cremesti
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Ceramide ,Cell signaling ,Capping ,Biophysics ,Biology ,Ceramides ,Biochemistry ,Models, Biological ,Biophysical Phenomena ,chemistry.chemical_compound ,Membrane Microdomains ,Structural Biology ,Cell surface receptor ,Genetics ,Animals ,Humans ,Molecular Biology ,Raft ,Sphingolipids ,Cell Membrane ,Cell Biology ,Sphingolipid ,Transmembrane protein ,Cell biology ,Protein Structure, Tertiary ,Sphingomyelin Phosphodiesterase ,chemistry ,Sphingomyelinase ,Signal transduction ,Sphingomyelin ,Biogenesis ,Signal Transduction - Abstract
Recent biophysical data suggest that the properties of ceramide observed in model membranes may apply to biological systems. In particular, the ability of ceramide to form microdomains, which coalesce into larger platforms or macrodomains, appears to be important for some cellular signaling processes. Several laboratories have now demonstrated similar reorganization of plasma membrane sphingolipid rafts, via ceramide generation, into macrodomains. This event appeared necessary for signaling upon activation of a specific set of cell surface receptors. In this article, we review the properties and functions of rafts, and the role of sphingomyelinase and ceramide in the biogenesis and re-modeling of these rafts. As clustering of some cell surface receptors in these domains may be critical for signal transduction, we propose a new model for transmembrane signal transmission.
- Published
- 2002
31. Cardiolipin: a proton trap for oxidative phosphorylation
- Author
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Norbert A. Dencher and Thomas H. Haines
- Subjects
Chemiosmotic ,Cardiolipins ,Lipid Bilayers ,Biophysics ,Oxidative phosphorylation ,Mitochondrion ,Biochemistry ,Models, Biological ,Oxidative Phosphorylation ,chemistry.chemical_compound ,Structural Biology ,Genetics ,Cardiolipin ,Molecular Biology ,Raft ,Membranes ,ATP synthase ,biology ,Cardiolipin pK ,Chemiosmosis ,Biological membrane ,Cell Biology ,Hydrogen-Ion Concentration ,Proton Pumps ,Mitochondria ,Membrane ,chemistry ,Membrane protein ,Deoxy-cardiolipin ,biology.protein ,lipids (amino acids, peptides, and proteins) ,Protons ,Protein Binding - Abstract
The role of specific lipid structures in biological membranes has been elusive. There are hundreds of them in nature. Why has nature made them? How do they aid in the functioning of membrane proteins? Genetics with its ‘knock out’ organisms declares that functions persist in the absence of any particular lipid. Nonetheless some lipids, such as cardiolipin (CL), are associated with particular functions in the cell. It may merely expand the variety of culture conditions (pH, temperature, etc.) under which the wild-type organism survives. This article explores a unique role of CL as a proton trap within membranes that conduct oxidative phosphorylation and therefore the synthesis of ATP. CL’s pK2 (above 8.0) provides a role for it as a headgroup proton trap for oxidative phosphorylation. It suggests why CL is found in membranes that pump protons. The high pK2 also indicates that the headgroup has but one negative charge in the neutral pH range. Data on the binding of CL to all of the oxidative phosphorylation proteins suggest that the CL may aggregate the oxidative phosphorylation proteins into a patch while it restricts pumped protons within its headgroup domain – supplying protons to the ATP synthase with minimal changes in the bulk phase pH.
- Published
- 2002
32. Interaction between two adapter proteins, PAG and EBP50: a possible link between membrane rafts and actin cytoskeleton
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Václav Hořejší, Ladislav Anděra, Tomas Brdicka, Jiřı́ Špička, Sharon L. Milgram, Pavla Angelisova, and Naděžda Brdičková
- Subjects
Sodium-Hydrogen Exchangers ,Moesin ,PDZ domain ,Biophysics ,macromolecular substances ,Biology ,Cell Fractionation ,Biochemistry ,Cell Line ,Jurkat Cells ,Ezrin ,Dogs ,Membrane Microdomains ,Structural Biology ,Radixin ,Genetics ,Animals ,Humans ,Actin-binding protein ,Microdomain ,Adapter protein ,Cytoskeleton ,Molecular Biology ,Raft ,Adaptor Proteins, Signal Transducing ,Membrane Proteins ,Cell Biology ,Actin cytoskeleton ,Phosphoproteins ,Actins ,Cell biology ,nervous system ,Membrane protein ,biology.protein ,Carrier Proteins ,Plasmids - Abstract
Phosphoprotein associated with GEMs (PAG), also known as Csk-binding protein (Cbp), is a broadly expressed palmitoylated transmembrane adapter protein found in membrane rafts, also called GEMs (glycosphingolipid-enriched membrane microdomains). PAG is known to bind and activate the essential regulator of Src-family kinases, cytoplasmic protein tyrosine kinase Csk. In the present study we used the yeast 2-hybrid system to search for additional proteins which might bind to PAG. We have identified the abundant cytoplasmic adapter protein EBP50 (ezrin/radixin/moesin (ERM)-binding phosphoprotein of 50 kDa), also known as NHERF (Na+/H+ exchanger regulatory factor), as a specific PAG-binding partner. The interaction involves the C-terminal sequence (TRL) of PAG and N-terminal PDZ domain(s) of EBP50. As EBP50 is known to interact via its C-terminal domain with the ERM-family proteins, which in turn bind to actin cytoskeleton, the PAG–EBP50 interaction may be important for connecting membrane rafts to the actin cytoskeleton.
- Published
- 2001
33. Visualizing detergent resistant domains in model membranes with atomic force microscopy
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Jan P. J. M. van der Eerden, Margot M. E. Snel, Ben de Kruijff, and Hilde A. Rinia
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Percolating ,Liquid ordered phase ,Octoxynol ,Eggs ,Detergents ,Lipid Bilayers ,Phase separation ,Biophysics ,Microscopy, Atomic Force ,Biochemistry ,Sphingolipid ,chemistry.chemical_compound ,Membrane Microdomains ,Structural Biology ,Phosphatidylcholine ,Genetics ,Animals ,Lipid bilayer ,Molecular Biology ,Raft ,Chromatography ,Calorimetry, Differential Scanning ,Chemistry ,Bilayer ,Cell Biology ,Sphingomyelins ,Planar lipid bilayer ,Membrane ,Cholesterol ,Solubility ,Phosphatidylcholines ,lipids (amino acids, peptides, and proteins) ,Chromatography, Thin Layer ,Sphingomyelin - Abstract
Evidence is accumulating that in cell membranes microdomains exist, also referred to as rafts or detergent resistant membranes. In this study, atomic force microscopy is used to study supported lipid bilayers, consisting of a fluid phosphatidylcholine, sphingomyelin and cholesterol. Domains were visualized of which the morphology and size depended on the cholesterol concentration. The presence of cholesterol was found to induce bilayer coupling. At 30 mol% cholesterol, a change in percolation phase was observed, and at 50 mol%, when both fluid lipids and solid lipids are saturated with cholesterol, phase separation was still observed. In addition, we were able to directly visualize the resistance of domains against non-ionic detergent.
- Published
- 2001
34. Fluorescence microscopy studies on islet amyloid polypeptide fibrillation at heterogeneous and cellular membrane interfaces and its inhibition by resveratrol
- Author
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Diana Radovan, Roland Winter, and Norbert Opitz
- Subjects
endocrine system ,Islet amyloid polypeptide ,Amyloid ,endocrine system diseases ,Type II diabetes mellitus ,Cytotoxicity ,Biophysics ,Amylin ,Resveratrol ,Fibril ,Biochemistry ,Cell Line ,Extracellular matrix ,Membrane Lipids ,chemistry.chemical_compound ,Structural Biology ,Stilbenes ,Genetics ,Fluorescence microscope ,Animals ,Humans ,Model raft mixture ,Molecular Biology ,Fluorescence microscopy ,geography ,geography.geographical_feature_category ,Chemistry ,Cell Membrane ,Cell Biology ,Raft ,Islet ,Giant unilamellar lipid vesicle ,Diabetes Mellitus, Type 2 ,Microscopy, Fluorescence - Abstract
Type II diabetes mellitus (T2DM) is a disease characterized by progressive deposition of amyloid in the extracellular matrix of β-cells. We investigated the interaction of the islet amyloid polypeptide (IAPP) with lipid model raft mixtures and INS-1E cells using fluorescence microscopy techniques. Following preferential partitioning of IAPP into the fluid lipid phase, the membrane suffers irreversible damage and predominantly circularly-shaped lipid-containing IAPP amyloid is formed. Interaction studies with the pancreatic β-cell line INS-1E revealed that growing IAPP fibrils also incorporate substantial amounts of cellular membranes in vivo. Additionally, the inhibitory effect of the red wine compound resveratrol on IAPP fibril formation has been studied, alluding to its potential use in developing therapeutic strategies against T2DM.
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35. Involvement of caveolin-2 in caveolar biogenesis in MDCK cells
- Author
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Paul Verkade, Ulla Lahtinen, Kai Simons, Robert G. Parton, and Masanori Honsho
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Caveolin 2 ,Biophysics ,Fluorescent Antibody Technique ,Biology ,Caveolae ,Biochemistry ,Caveolins ,03 medical and health sciences ,Dogs ,Caveolin-2 ,Caveolin-1 ,Structural Biology ,Caveolin ,Genetics ,Animals ,Electrophoresis, Gel, Two-Dimensional ,Molecular Biology ,030304 developmental biology ,Epithelial polarity ,0303 health sciences ,Vesicle ,030302 biochemistry & molecular biology ,Caveola ,Cell Biology ,Raft ,Apical membrane ,Cell biology ,Microscopy, Electron ,Caveolin 1 ,MDCK - Abstract
Caveolins have been identified as key components of caveolae, specialized cholesterol-enriched raft domains visible as small flask-shaped invaginations of the plasma membrane. In polarized MDCK cells caveolin-1 and -2 are found together on basolateral caveolae whereas the apical membrane, where only caveolin-1 is present, lacks caveolae. Expression of a caveolin mutant prevented the formation of the large caveolin-1/-2 hetero-oligomeric complexes, and led to intracellular retention of caveolin-2 and disappearance of caveolae from the basolateral membrane. Correspondingly, in MDCK cells over-expressing caveolin-2 the basolateral membrane exhibited an increased number of caveolae. These results indicate the involvement of caveolin-2 in caveolar biogenesis.
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36. About lipids and toxins
- Author
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F. Gisou van der Goot and Núria Reig
- Subjects
Biophysics ,Biology ,Pore-forming ,Endocytosis ,Biochemistry ,Membrane Fusion ,Cell membrane ,Anthrax ,Intracellular organelle ,Structural Biology ,AB toxin ,Genetics ,medicine ,Animals ,Humans ,Toxins ,Secretion ,Molecular Biology ,Raft ,Toxins, Biological ,Lysenin ,Cell Membrane ,Cholera toxin ,Lipid metabolism ,Biological Transport ,Cell Biology ,Lipid Metabolism ,Cell biology ,medicine.anatomical_structure ,Cytoplasm ,Intracellular - Abstract
Many mono or multicellular organisms secrete soluble proteins, referred to as protein toxins, which alter the behavior of foreign, or target cells, possibly leading to their death. These toxins affect either the cell membrane by forming pores or modifying lipids, or some intracellular target. To reach this target, they must cross one of the cellular membranes, generally that of an intracellular organelle. As described in this minireview, lipids play crucial roles in the intoxication process of most if not all toxins, by allowing/promoting binding, endocytosis, trafficking and/or translocation into the cytoplasm.
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37. AKT1/PKBα is recruited to lipid rafts and activated downstream of PKC isotypes in CD3-induced T cell signaling
- Author
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Florian Überall, Birgit Bauer, Marcel Jenny, Fiedrich Fresser, and Gottfried Baier
- Subjects
CD3 Complex ,T-Lymphocytes ,Protein kinase Cθ ,Biochemistry ,Jurkat cells ,Jurkat Cells ,Mice ,0302 clinical medicine ,Structural Biology ,Lipid raft ,Protein Kinase C ,Mice, Knockout ,0303 health sciences ,Chemistry ,CD28 ,Cell biology ,Isoenzymes ,Protein Transport ,medicine.anatomical_structure ,embryonic structures ,Signal transduction ,Signal Transduction ,T cell ,Biophysics ,Protein Serine-Threonine Kinases ,03 medical and health sciences ,Akt-1 ,Membrane Microdomains ,CD28 Antigens ,Proto-Oncogene Proteins ,Genetics ,medicine ,Animals ,Humans ,Nuclear factor κB ,Protein kinase A ,Molecular Biology ,Protein kinase B ,Protein kinase C ,Raft ,030304 developmental biology ,T cell receptor signaling ,Cell Membrane ,Cell Biology ,Molecular biology ,Enzyme Activation ,Protein Kinase C-theta ,Mutation ,Proto-Oncogene Proteins c-akt ,030215 immunology - Abstract
Protein kinase (PK) Ctheta and Akt/PKBalpha cooperate in T cell receptor/CD28-induced T cell signaling. We here demonstrate the recruitment of endogenous Akt1 and PKCtheta to lipid rafts in CD3-stimulated T cells. Further we show that Myr-PKCtheta mediates translocation of endogenous Akt1 to the plasma membrane as well as to lipid rafts, most likely explained by the observed complex formation of both protein kinases. In addition, in peripheral mouse T cells, the PKC inhibitor Gö6850 could partially block Akt1 activation in CD3-induced signaling, placing PKC isotype(s) upstream of Akt1. However, T cells derived from PKCtheta knockout mice were not impaired in CD3- or phorbol ester-induced Akt1 activity. Taken together, the results of this study give new insights into the functional link of Akt1 and PKCtheta in T cell signaling, demonstrating the co-recruitment of the two kinases and showing a novel pathway leading to Akt1 transactivation where PKC isotype(s) are involved but PKCtheta is not essential.
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38. PSPN/GFRα4 has a significantly weaker capacity than GDNF/GFRα1 to recruit RET to rafts, but promotes neuronal survival and neurite outgrowth
- Author
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Heidi Virtanen, Pia Runeberg-Roos, Eleanor T. Coffey, Maria Lindahl, Päivi Lindholm, Mart Saarma, and Jianmin Yang
- Subjects
endocrine system diseases ,Biochemistry ,Cell survival ,Mice ,0302 clinical medicine ,Structural Biology ,Neurotrophic factors ,Glial cell line-derived neurotrophic factor ,Cloning, Molecular ,Lipid raft ,Neurons ,0303 health sciences ,Membrane Glycoproteins ,Neurite outgrowth ,Recombinant Proteins ,Cell biology ,Proto-Oncogene Proteins c-ret ,GFRα4 ,lipids (amino acids, peptides, and proteins) ,Signal transduction ,Glial Cell Line-Derived Neurotrophic Factor Receptors ,Neurite ,Persephin ,Biophysics ,Nerve Tissue Proteins ,Receptors, Nerve Growth Factor ,Biology ,Transfection ,Cell Line ,03 medical and health sciences ,Membrane Microdomains ,Proto-Oncogene Proteins ,Neurites ,Genetics ,Animals ,Humans ,Glial Cell Line-Derived Neurotrophic Factor ,Nerve Growth Factors ,Molecular Biology ,Raft ,030304 developmental biology ,Cell Membrane ,Receptor Protein-Tyrosine Kinases ,Cell Biology ,Rats ,biology.protein ,RET ,GDNF family of ligands ,030217 neurology & neurosurgery - Abstract
Previously, it was shown that the recruitment of RET into lipid rafts by glial cell line-derived neurotrophic factor (GDNF)/GFRalpha1 is crucial for efficient signal transduction. Here, we show that the mouse GFRalpha4 is a functional, N-glycosylated, glycosylphosphatidylinositol (GPI)-anchored protein, which mediates persephin (PSPN)-induced phosphorylation of RET, but has an almost undetectable capacity to recruit RET into the 0.1% Triton X-100 insoluble membrane fraction. In spite of this, PSPN/mGFRalpha4 promotes neurite outgrowth in PC6-3 cells and survival of cerebellar granule neurons. As we show that also human PSPN/GFRalpha4 is unable to recruit RET into lipid rafts, we propose that the mammalian GFRalpha4 in this respect differs from GFRalpha1.
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39. Towards the in vitro reconstitution of caveolae. Asymmetric incorporation of glycosylphosphatidylinositol (GPI) and gangliosides into liposomal membranes
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Alicia Alonso, Ana-Victoria Villar, Isabel Varela-Nieto, Covadonga Pañeda, Urs Brodbeck, and Félix M. Goñi
- Subjects
Time Factors ,Glycosylphosphatidylinositols ,education ,Biophysics ,Neuraminidase ,Phospholipase ,In Vitro Techniques ,Biochemistry ,Permeability ,Structural Biology ,Caveolae ,Gangliosides ,Genetics ,Phospholipase D ,Animals ,Molecular Biology ,Raft ,Liposome ,Ganglioside ,Chemistry ,Bilayer ,Vesicle ,Hydrolysis ,Caveola ,Asymmetry ,Cell Biology ,Rats ,carbohydrates (lipids) ,Glycosylphosphatidylinositol ,Membrane ,Liver ,alpha-Galactosidase ,Liposomes ,lipids (amino acids, peptides, and proteins) - Abstract
Large unilamellar vesicles consisting of phospholipids with or without cholesterol have been prepared containing GPI and/or gangliosides asymmetrically located in the outer leaflet of the bilayer. Such asymmetric distribution of GPI and gangliosides is found in 'rafts' and caveolae. Using these vesicles, GPI can be readily hydrolysed by phospholipases. Both cholesterol and ganglioside are seen to inhibit, in an additive way, the hydrolytic activity of GPI-specific phospholipase D. Copyright (C) 1999 Federation of European Biochemical Societies., This work was supported in part by funds from CICYT (Grant PB96/0171), the Basque Government (Grants EX98/28 and PI98/32), and the University of the Basque Country (G03/98). A.-V.V. is the recipient of a scholarship from the University of the Basque Country.
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40. Variable actin dynamics requirement for the exit of different cargo from the trans-Golgi network
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Cecilia Colonna, Gustavo Egea, Francisco Lázaro-Diéguez, Maria Calvo, Susana E. Martínez, and Miguel Cortegano
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Time Factors ,Biophysics ,Polarized transport ,Biological Transport, Active ,Arp2/3 complex ,macromolecular substances ,Transfection ,Biochemistry ,Actin remodeling of neurons ,symbols.namesake ,Structural Biology ,Chlorocebus aethiops ,Genetics ,Animals ,Cycloheximide ,Fluorescent Antibody Technique, Indirect ,Cytoskeleton ,Molecular Biology ,Actin ,Raft ,Protein Synthesis Inhibitors ,Microscopy, Confocal ,Microscopy, Video ,biology ,Chemistry ,Actin remodeling ,Cell Biology ,Golgi apparatus ,iFRAP ,Actins ,Cell biology ,Profilin ,COS Cells ,symbols ,biology.protein ,Latrunculin ,lipids (amino acids, peptides, and proteins) ,MDia1 ,Fluorescence Recovery After Photobleaching ,trans-Golgi Network - Abstract
Efficient post-Golgi trafficking depends on microtubules, but actin filaments and actin-associated proteins are also postulated. Here we examined, by inverse fluorescence recovery after photobleaching, the role of actin dynamics in the exit from the TGN of fluorescent-tagged apical or basolateral and raft or non-raft-associated cargoes. Either the actin-stabilizing jasplakinolide or the actin-depolymerising latrunculin B variably but significantly inhibited post-Golgi traffic of non-raft associated apical p75NTR and basolateral VSV-G cargoes. The TGN-exit of the apical-destined VSV-G mutant was impaired only by latrunculin B. Strikingly, the raft-associated GPI-anchor protein was not affected by either actin toxin. Results indicate that actin dynamics participates in the TGN egress of both apical- and basolateral-targeted proteins but is not needed for apical raft-associated cargo.
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