151
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Inoue H, Ha VL, Prekeris R, Randazzo PA. Arf GTPase-activating protein ASAP1 interacts with Rab11 effector FIP3 and regulates pericentrosomal localization of transferrin receptor-positive recycling endosome. Mol Biol Cell 2008; 19:4224-37. [PMID: 18685082 DOI: 10.1091/mbc.e08-03-0290] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
ADP-ribosylation factors (Arfs) and Arf GTPase-activating proteins (GAPs) are key regulators of membrane trafficking and the actin cytoskeleton. The Arf GAP ASAP1 contains an N-terminal BAR domain, which can induce membrane tubulation. Here, we report that the BAR domain of ASAP1 can also function as a protein binding site. Two-hybrid screening identified FIP3, which is a putative Arf6- and Rab11-effector, as a candidate ASAP1 BAR domain-binding protein. Both coimmunoprecipitation and in vitro pulldown assays confirmed that ASAP1 directly binds to FIP3 through its BAR domain. ASAP1 formed a ternary complex with Rab11 through FIP3. FIP3 binding to the BAR domain stimulated ASAP1 GAP activity against Arf1, but not Arf6. ASAP1 colocalized with FIP3 in the pericentrosomal endocytic recycling compartment. Depletion of ASAP1 or FIP3 by small interfering RNA changed the localization of transferrin receptor, which is a marker of the recycling endosome, in HeLa cells. The depletion also altered the trafficking of endocytosed transferrin. These results support the conclusion that ASAP1, like FIP3, functions as a component of the endocytic recycling compartment.
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Affiliation(s)
- Hiroki Inoue
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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152
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Yoo CM, Wen J, Motes CM, Sparks JA, Blancaflor EB. A class I ADP-ribosylation factor GTPase-activating protein is critical for maintaining directional root hair growth in Arabidopsis. PLANT PHYSIOLOGY 2008; 147:1659-74. [PMID: 18539780 PMCID: PMC2492602 DOI: 10.1104/pp.108.119529] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2008] [Accepted: 05/27/2008] [Indexed: 05/18/2023]
Abstract
Membrane trafficking and cytoskeletal dynamics are important cellular processes that drive tip growth in root hairs. These processes interact with a multitude of signaling pathways that allow for the efficient transfer of information to specify the direction in which tip growth occurs. Here, we show that AGD1, a class I ADP ribosylation factor GTPase-activating protein, is important for maintaining straight growth in Arabidopsis (Arabidopsis thaliana) root hairs, since mutations in the AGD1 gene resulted in wavy root hair growth. Live cell imaging of growing agd1 root hairs revealed bundles of endoplasmic microtubules and actin filaments extending into the extreme tip. The wavy phenotype and pattern of cytoskeletal distribution in root hairs of agd1 partially resembled that of mutants in an armadillo repeat-containing kinesin (ARK1). Root hairs of double agd1 ark1 mutants were more severely deformed compared with single mutants. Organelle trafficking as revealed by a fluorescent Golgi marker was slightly inhibited, and Golgi stacks frequently protruded into the extreme root hair apex of agd1 mutants. Transient expression of green fluorescent protein-AGD1 in tobacco (Nicotiana tabacum) epidermal cells labeled punctate bodies that partially colocalized with the endocytic marker FM4-64, while ARK1-yellow fluorescent protein associated with microtubules. Brefeldin A rescued the phenotype of agd1, indicating that the altered activity of an AGD1-dependent ADP ribosylation factor contributes to the defective growth, organelle trafficking, and cytoskeletal organization of agd1 root hairs. We propose that AGD1, a regulator of membrane trafficking, and ARK1, a microtubule motor, are components of converging signaling pathways that affect cytoskeletal organization to specify growth orientation in Arabidopsis root hairs.
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Affiliation(s)
- Cheol-Min Yoo
- Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401
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153
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Felkl M, Leube RE. Interaction assays in yeast and cultured cells confirm known and identify novel partners of the synaptic vesicle protein synaptophysin. Neuroscience 2008; 156:344-52. [PMID: 18706977 DOI: 10.1016/j.neuroscience.2008.07.033] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 07/16/2008] [Accepted: 07/16/2008] [Indexed: 01/15/2023]
Abstract
Synaptophysin (SYP) is a major protein of neurotransmitter-containing vesicles spanning the membrane four times and contributing to various aspects of the synaptic vesicle cycle. The split-ubiquitin yeast two-hybrid system was used to characterize molecular interactions of membrane-bound, full-length murine SYP. In this way, the known homophilic SYP-SYP association could be confirmed and heterophilic binding of SYP to other tetraspan vesicle membrane proteins of the secretory carrier-associated membrane- and synaptogyrin-type could be detected for the first time. SYP-binding was also observed for the vSNARE synaptobrevin2 and various membrane and membrane-associated proteins. Double labeling immunofluorescence microscopy of murine retina, co-immunoprecipitation experiments and fluorescence energy resonance transfer (FRET) analyses between fluorescent protein-tagged polypeptides were carried out to validate and further characterize the association of SYP with the tetraspan vesicle membrane proteins secretory carrier-associated membrane protein 1 and synaptogyrin3, with synaptobrevin2, and the newly identified binding partners phospholipase D4, stathmin-like3, Rho family GTPase2 and ADP-ribosylation factor interacting protein2. It was observed that the carboxyterminus of SYP is dispensable for association with integral membrane proteins while it is needed for binding to membrane-associated polypeptides. The latter appears to be regulated by phosphorylation, since src homology 2-domains were shown to attach to the multiple carboxyterminal phosphotyrosine residues of SYP. In conclusion, the association of SYP with different tetraspan vesicle membrane proteins suggests shared functions and the multiple other interactions identify SYP as part of a membrane platform acting as a facilitator of various steps of the synaptic vesicle cycle.
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Affiliation(s)
- M Felkl
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany
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154
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Hara S, Kiyokawa E, Iemura SI, Natsume T, Wassmer T, Cullen PJ, Hiai H, Matsuda M. The DHR1 domain of DOCK180 binds to SNX5 and regulates cation-independent mannose 6-phosphate receptor transport. Mol Biol Cell 2008; 19:3823-35. [PMID: 18596235 DOI: 10.1091/mbc.e08-03-0314] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
DOCK180 is the archetype of the DOCK180-family guanine nucleotide exchange factor for small GTPases Rac1 and Cdc42. DOCK180-family proteins share two conserved domains, called DOCK homology region (DHR)-1 and -2. Although the function of DHR2 is to activate Rac1, DHR1 is required for binding to phosphoinositides. To better understand the function of DHR1, we searched for its binding partners by direct nanoflow liquid chromatography/tandem mass spectrometry, and we identified sorting nexins (SNX) 1, 2, 5, and 6, which make up a multimeric protein complex mediating endosome-to-trans-Golgi-network (TGN) retrograde transport of the cation-independent mannose 6-phosphate receptor (CI-MPR). Among these SNX proteins, SNX5 was coimmunoprecipitated with DOCK180 most efficiently. In agreement with this observation, DOCK180 colocalized with SNX5 at endosomes. The RNA interference-mediated knockdowns of SNX5 and DOCK180, but not Rac1, resulted in the redistribution of CI-MPR from TGN to endosomes. Furthermore, expression of the DOCK180 DHR1 domain was sufficient to restore the perturbed CI-MPR distribution in DOCK180 knockdown cells. These data suggest that DOCK180 regulates CI-MPR trafficking via SNX5 and that this function is independent of its guanine nucleotide exchange factor activity toward Rac1.
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Affiliation(s)
- Shigeo Hara
- Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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155
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Bossers K, Meerhoff G, Balesar R, van Dongen JW, Kruse CG, Swaab DF, Verhaagen J. Analysis of gene expression in Parkinson's disease: possible involvement of neurotrophic support and axon guidance in dopaminergic cell death. Brain Pathol 2008; 19:91-107. [PMID: 18462474 DOI: 10.1111/j.1750-3639.2008.00171.x] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra. We have studied alterations in gene expression in the substantia nigra, the caudate nucleus and putamen of four PD patients and four matched controls using custom designed Agilent microarrays. To gain insight into changes in gene expression during early stages of dopaminergic neurodegeneration, we selectively investigated the relatively spared parts of the PD substantia nigra, and correlated gene expression changes with alterations in neuronal density. We identified changes in the expression of 287 transcripts in the substantia nigra, 16 transcripts in the caudate nucleus and four transcripts in the putamen. For selected transcripts, transcriptional alterations were confirmed with qPCR on a larger set of seven PD cases and seven matched controls. We detected concerted changes in functionally connected groups of genes. In the PD substantia nigra, we observed strong evidence for a reduction in neurotrophic support and alterations in axon guidance cues. As the changes occur in relatively spared parts of the PD substantia nigra, they suggest novel disease mechanisms involving neurotrophic support and axon guidance in early stages of cellular stress events, ultimately leading to dopaminergic cell death in PD.
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Affiliation(s)
- Koen Bossers
- Laboratory for Neuroregeneration, Netherlands Institute for Neuroscience, Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands.
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156
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Lim KB, Bu W, Goh WI, Koh E, Ong SH, Pawson T, Sudhaharan T, Ahmed S. The Cdc42 effector IRSp53 generates filopodia by coupling membrane protrusion with actin dynamics. J Biol Chem 2008; 283:20454-72. [PMID: 18448434 DOI: 10.1074/jbc.m710185200] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Cdc42 effector IRSp53 is a strong inducer of filopodia formation and consists of an Src homology domain 3 (SH3), a potential WW-binding motif, a partial-Cdc42/Rac interacting binding region motif, and an Inverse-Bin-Amphiphysins-Rvs (I-BAR) domain. We show that IRSp53 interacts directly with neuronal Wiskott-Aldrich syndrome protein (N-WASP) via its SH3 domain and furthermore that N-WASP is required for filopodia formation as IRSp53 failed to induce filopodia formation in N-WASP knock-out (KO) fibroblasts. IRSp53-induced filopodia formation can be reconstituted in N-WASP KO fibroblasts by full-length N-WASP, by N-WASPDeltaWA (a mutant unable to activate the Arp2/3 complex), and by N-WASPH208D (a mutant unable to bind Cdc42). IRSp53 failed to induce filopodia in mammalian enabled (Mena)/VASP KO cells, and N-WASP failed to induce filopodia when IRSp53 was knocked down with RNA interference. The IRSp53 I-BAR domain alone induces dynamic membrane protrusions that lack actin and are smaller than normal filopodia ("partial-filopodia") in both wild-type N-WASP and N-WASP KO cells. We propose that IRSp53 generates filopodia by coupling membrane protrusion through its I-BAR domain with actin dynamics through SH3 domain binding partners, including N-WASP and Mena.
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Affiliation(s)
- Kim Buay Lim
- Institute of Medical Biology, 8A Biomedical Grove, Immunos, Singapore
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157
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ICA69 is a novel Rab2 effector regulating ER–Golgi trafficking in insulinoma cells. Eur J Cell Biol 2008; 87:197-209. [DOI: 10.1016/j.ejcb.2007.11.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 11/22/2007] [Accepted: 11/22/2007] [Indexed: 11/24/2022] Open
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158
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Atkinson J, Epand RF, Epand RM. Tocopherols and tocotrienols in membranes: a critical review. Free Radic Biol Med 2008; 44:739-64. [PMID: 18160049 DOI: 10.1016/j.freeradbiomed.2007.11.010] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Revised: 11/09/2007] [Accepted: 11/12/2007] [Indexed: 12/14/2022]
Abstract
The familiar role of tocols (tocopherols and tocotrienols) as lipid-soluble chain-terminating inhibitors of lipid peroxidation is currently in the midst of a reinterpretation. New biological activities have been described for tocols that apparently are not dependent on their well-established antioxidant behaviour. These activities could well be real, but there remain large gaps in our understanding of the behaviour of tocols in membranes, especially when it comes to the alpha-, beta-, gamma-, delta-chroman methylation patterns and the seemingly special nature of tocotrienols. It is inappropriate to make conclusions and develop models based on in vivo (or cell culture) results with reference to in vitro measurements of antioxidant activity. When present in biological membranes, tocols will experience a large variation in the local composition of phospholipids and the presence of neutral lipids such as cholesterol, both of which would be expected to change the efficiency of antioxidant action. It is likely that tocols are not homogeneously dispersed in a membrane, but it is still not known whether any specific combination of lipid head group and acyl chains are conferred special protection from peroxidation, nor do we currently appreciate the structural role that tocols play in membranes. Tocols may enhance curvature stress or counteract similar stresses generated by other lipids such as lysolipids. This review will outline what is known about the location and behaviour of tocols in phospholipid bilayers. We will draw mainly from the biophysical literature, but will attempt to extend the discussion to biologically relevant phenomena when appropriate. We hope that it will assist researchers when designing new experiments and when critically assessing the results, in turn providing a more thorough understanding of the biochemistry of tocols.
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Affiliation(s)
- Jeffrey Atkinson
- Department of Chemistry and Centre for Biotechnology, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada.
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159
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Querin L, Sanvito R, Magni F, Busti S, Van Dorsselaer A, Alberghina L, Vanoni M. Proteomic analysis of a nutritional shift-up in Saccharomyces cerevisiae identifies Gvp36 as a BAR-containing protein involved in vesicular traffic and nutritional adaptation. J Biol Chem 2007; 283:4730-43. [PMID: 18156177 DOI: 10.1074/jbc.m707787200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Yeast cells undergoing a nutritional shift-up from a poor to a rich carbon source take several hours to adapt to the novel, richer carbon source. The budding index is a physiologically relevant "global" parameter that reflects the complex links between cell growth and division that are both coordinately and deeply affected by nutritional conditions. We used changes in budding index as a guide to choose appropriate, relevant time points during an ethanol to glucose nutritional shift-up for preparation of samples for the analysis of proteome by two-dimensional electrophoresis/mass spectrometry. About 600 spots were detected. 90 spots, mostly comprising proteins involved in intermediary metabolism, protein synthesis, and response to stress, showed differential expression after glucose addition. Among modulated proteins we identified a protein of previously unknown function, Gvp36, showing a transitory increase corresponding to the drop of the fraction of budded cells. A gvp36Delta strain shares several phenotypes (including general growth defects, heat shock, and high salt sensitivity, defects in polarization of the actin cytoskeleton, in endocytosis and in vacuolar biogenesis, defects in entering stationary phase upon nutrient starvation) with secretory pathway mutants and with mutants in genes encoding the two previously known yeast BAR proteins (RSV161 and RSV167). We thus propose that Gvp36 represents a novel yeast BAR protein involved in vesicular traffic and in nutritional adaptation.
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Affiliation(s)
- Lorenzo Querin
- Department of Biotechnology and Biosciences, University Milano-Bicocca, 20126 Milano, Italy
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160
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Chial HJ, Wu R, Ustach CV, McPhail LC, Mobley WC, Chen YQ. Membrane targeting by APPL1 and APPL2: dynamic scaffolds that oligomerize and bind phosphoinositides. Traffic 2007; 9:215-29. [PMID: 18034774 DOI: 10.1111/j.1600-0854.2007.00680.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Human adaptor protein, phosphotyrosine interaction, PH domain and leucine zipper containing 1 (APPL1) and adaptor protein, phosphotyrosine interaction, PH domain and leucine zipper containing 2 (APPL2) are homologous effectors of the small guanosine triphosphatase RAB5 that interact with a diverse set of receptors and signaling proteins and are proposed to function in endosome-mediated signaling. Herein, we investigated the membrane-targeting properties of the APPL1 and APPL2 Bin/Amphiphysin/Rvs (BAR), pleckstrin homology (PH) and phosphotyrosine binding (PTB) domains. Coimmunoprecipitation and yeast two-hybrid studies demonstrated that full-length APPL proteins formed homooligomers and heterooligomers and that the APPL minimal BAR domains were necessary and sufficient for mediating APPL-APPL interactions. When fused to a fluorescent protein and overexpressed, all three domains (minimal BAR, PH and PTB) were targeted to cell membranes. Furthermore, full-length APPL proteins bound to phosphoinositides, and the APPL isolated PH or PTB domains were sufficient for in vitro phosphoinositide binding. Live cell imaging showed that full-length APPL-yellow fluorescent protein (YFP) fusion proteins associated with cytosolic membrane structures that underwent movement, fusion and fission events. Overexpression of full-length APPL-YFP fusion proteins was sufficient to recruit endogenous RAB5 to enlarged APPL-associated membrane structures, although APPL1 was not necessary for RAB5 membrane targeting. Taken together, our findings suggest a role for APPL proteins as dynamic scaffolds that modulate RAB5-associated signaling endosomal membranes by their ability to undergo domain-mediated oligomerization, membrane targeting and phosphoinositide binding.
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Affiliation(s)
- Heidi J Chial
- Department of Cancer Biology, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, USA.
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161
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The PX-BAR membrane-remodeling unit of sorting nexin 9. EMBO J 2007; 26:4788-800. [PMID: 17948057 DOI: 10.1038/sj.emboj.7601889] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Accepted: 09/19/2007] [Indexed: 11/08/2022] Open
Abstract
Sorting nexins (SNXs) form a family of proteins known to interact with components in the endosomal system and to regulate various steps of vesicle transport. Sorting nexin 9 (SNX9) is involved in the late stages of clathrin-mediated endocytosis in non-neuronal cells, where together with the GTPase dynamin, it participates in the formation and scission of the vesicle neck. We report here crystal structures of the functional membrane-remodeling unit of SNX9 and show that it efficiently tubulates lipid membranes in vivo and in vitro. Elucidation of the protein superdomain structure, together with mutational analysis and biochemical and cell biological experiments, demonstrated how the SNX9 PX and BAR domains work in concert in targeting and tubulation of phosphoinositide-containing membranes. The study provides insights into the SNX9-induced membrane modulation mechanism.
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162
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Li J, Mao X, Dong LQ, Liu F, Tong L. Crystal structures of the BAR-PH and PTB domains of human APPL1. Structure 2007; 15:525-33. [PMID: 17502098 DOI: 10.1016/j.str.2007.03.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 03/21/2007] [Accepted: 03/23/2007] [Indexed: 10/23/2022]
Abstract
APPL1 interacts with adiponectin receptors and other important signaling molecules. It contains a BAR and a PH domain near its N terminus, and the two domains may function as a unit (BAR-PH domain). We report here the crystal structures of the BAR-PH and PTB domains of human APPL1. The structures reveal novel features for BAR domain dimerization and for the interactions between the BAR and PH domains. The BAR domain dimer of APPL1 contains two four-helical bundles, whereas other BAR domain dimers have only three helices in each bundle. The PH domain is located at the opposite ends of the BAR domain dimer. Yeast two-hybrid assays confirm the interactions between the BAR and PH domains. Lipid binding assays show that the BAR, PH, and PTB domains can bind phospholipids. The ability of APPL1 to interact with multiple signaling molecules and phospholipids supports an important role for this adaptor in cell signaling.
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Affiliation(s)
- Jiang Li
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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163
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Abstract
Remarkable strides have been made over the past 20 years in elucidating the molecular basis of membrane trafficking. Indeed, a combination of biochemical and genetic approaches have determined the identity and function of many of the core constituents needed for protein secretion and endocytosis. But much remains to be learned. This review highlights underlying themes in membrane traffic to help us refocus and solve many remaining and newly emerging issues that are fundamental to mammalian cell biology and human physiology.
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Affiliation(s)
- Suzanne R Pfeffer
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307, USA.
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164
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Saito T, Jones CC, Huang S, Czech MP, Pilch PF. The interaction of Akt with APPL1 is required for insulin-stimulated Glut4 translocation. J Biol Chem 2007; 282:32280-7. [PMID: 17848569 DOI: 10.1074/jbc.m704150200] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
APPL1 (adaptor protein containing PH domain, PTB domain, and leucine zipper motif 1) is an Akt/protein kinase B-binding protein involved in signal transduction and membrane trafficking pathways for various receptors, including receptor tyrosine kinases. Here, we establish a role for APPL1 in insulin signaling in which we demonstrate its interaction with Akt2 by co-immunoprecipitation and pulldown assays. In primary rat adipocytes and skeletal muscle, APPL1 and Akt2 formed a complex that was dissociated upon insulin stimulation in both tissues. To investigate possible APPL1 function in adipocytes, we analyzed Akt phosphorylation, 2-deoxyglucose uptake, and Glut4 translocation by immunofluorescence following APPL1 knockdown by small interfering and short hairpin RNAs. We show that APPL1 knockdown suppressed Akt phosphorylation, glucose uptake, and Glut4 translocation. We also tested the effect in 3T3-L1 adipocytes of expressing full-length APPL1 or an N- or a C-terminal APPL1 construct. Interestingly, expression of full-length APPL1 and its N terminus suppressed insulin-stimulated 2-deoxyglucose uptake and Glut4 translocation to roughly the same extent (40-60%). We confirmed by cellular fractionation that Glut4 translocation was substantially blocked in 3T3-L1 adipocytes transfected with full-length APPL1. By cellular fractionation, APPL1 was localized mainly in the cytosol, and it showed a small degree of re-localization to the light microsomes and nucleus in response to insulin. By immunofluorescence, we also show that APPL1 partially co-localized with Glut4. These data suggest that APPL1 plays an important role in insulin-stimulated Glut4 translocation in muscle and adipose tissues and that its N-terminal portion may be critical for APPL1 function.
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Affiliation(s)
- Tsugumichi Saito
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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165
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Manna D, Albanese A, Park WS, Cho W. Mechanistic basis of differential cellular responses of phosphatidylinositol 3,4-bisphosphate- and phosphatidylinositol 3,4,5-trisphosphate-binding pleckstrin homology domains. J Biol Chem 2007; 282:32093-105. [PMID: 17823121 DOI: 10.1074/jbc.m703517200] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2) and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) are lipid second messengers that regulate various cellular processes by recruiting a wide range of downstream effector proteins to membranes. Several pleckstrin homology (PH) domains have been reported to interact with PtdIns(3,4)P2 and PtdIns(3,4,5)P3. To understand how these PH domains differentially respond to PtdIns(3,4)P2 and PtdIns(3,4,5)P3 signals, we quantitatively determined the PtdIns(3,4)P2 and PtdIns(3,4,5)P3 binding properties of several PH domains, including Akt, ARNO, Btk, DAPP1, Grp1, and C-terminal TAPP1 PH domains by surface plasmon resonance and monolayer penetration analyses. The measurements revealed that these PH domains have significant different phosphoinositide specificities and affinities. Btk-PH and TAPP1-PH showed genuine PtdIns(3,4,5)P3 and PtdIns(3,4)P2 specificities, respectively, whereas other PH domains exhibited less pronounced specificities. Also, the PH domains showed different degrees of membrane penetration, which greatly affected the kinetics of their membrane dissociation. Mutational studies showed that the presence of two proximal hydrophobic residues on the membrane-binding surface of the PH domain is important for membrane penetration and sustained membrane residence. When NIH 3T3 cells were stimulated with platelet-derived growth factor to generate PtdIns(3,4,5)P3, reversible translocation of Btk-PH, Grp1-PH, ARNO-PH, DAPP1-PH, and its L177A mutant to the plasma membrane was consistent with their in vitro membrane binding properties. Collectively, these studies provide new insight into how various PH domains would differentially respond to cellular PtdIns(3,4)P2 and PtdIns(3,4,5)P3 signals.
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Affiliation(s)
- Debasis Manna
- Department of Chemistry, University of Illinois, Chicago, Illinois 60607, USA
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166
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Henne WM, Kent HM, Ford MGJ, Hegde BG, Daumke O, Butler PJG, Mittal R, Langen R, Evans PR, McMahon HT. Structure and Analysis of FCHo2 F-BAR Domain: A Dimerizing and Membrane Recruitment Module that Effects Membrane Curvature. Structure 2007; 15:839-52. [PMID: 17540576 DOI: 10.1016/j.str.2007.05.002] [Citation(s) in RCA: 218] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 05/15/2007] [Accepted: 05/16/2007] [Indexed: 10/23/2022]
Abstract
A spectrum of membrane curvatures exists within cells, and proteins have evolved different modules to detect, create, and maintain these curvatures. Here we present the crystal structure of one such module found within human FCHo2. This F-BAR (extended FCH) module consists of two F-BAR domains, forming an intrinsically curved all-helical antiparallel dimer with a Kd of 2.5 microM. The module binds liposomes via a concave face, deforming them into tubules with variable diameters of up to 130 nm. Pulse EPR studies showed the membrane-bound dimer is the same as the crystal dimer, although the N-terminal helix changed conformation on membrane binding. Mutation of a phenylalanine on this helix partially attenuated narrow tubule formation, and resulted in a gain of curvature sensitivity. This structure shows a distant relationship to curvature-sensing BAR modules, and suggests how similar coiled-coil architectures in the BAR superfamily have evolved to expand the repertoire of membrane-sculpting possibilities.
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Affiliation(s)
- William Mike Henne
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB1 0QH, United Kingdom
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167
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Zhu G, Chen J, Liu J, Brunzelle JS, Huang B, Wakeham N, Terzyan S, Li X, Rao Z, Li G, Zhang XC. Structure of the APPL1 BAR-PH domain and characterization of its interaction with Rab5. EMBO J 2007; 26:3484-93. [PMID: 17581628 PMCID: PMC1933402 DOI: 10.1038/sj.emboj.7601771] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Accepted: 05/30/2007] [Indexed: 12/31/2022] Open
Abstract
APPL1 is an effector of the small GTPase Rab5. Together, they mediate a signal transduction pathway initiated by ligand binding to cell surface receptors. Interaction with Rab5 is confined to the amino (N)-terminal region of APPL1. We report the crystal structures of human APPL1 N-terminal BAR-PH domain motif. The BAR and PH domains, together with a novel linker helix, form an integrated, crescent-shaped, symmetrical dimer. This BAR–PH interaction is likely conserved in the class of BAR-PH containing proteins. Biochemical analyses indicate two independent Rab-binding sites located at the opposite ends of the dimer, where the PH domain directly interacts with Rab5 and Rab21. Besides structurally supporting the PH domain, the BAR domain also contributes to Rab binding through a small surface region in the vicinity of the PH domain. In stark contrast to the helix-dominated, Rab-binding domains previously reported, APPL1 PH domain employs β-strands to interact with Rab5. On the Rab5 side, both switch regions are involved in the interaction. Thus we identified a new binding mode between PH domains and small GTPases.
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Affiliation(s)
- Guangyu Zhu
- Crystallography Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Jia Chen
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jay Liu
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Joseph S Brunzelle
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg Medical School, Northwestern University, Chicago, IL, USA
| | - Bo Huang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Nancy Wakeham
- Crystallography Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Simon Terzyan
- Crystallography Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Xuemei Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Zihe Rao
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Guangpu Li
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xuejun C Zhang
- Crystallography Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Crystallography Research Program, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA. Tel.: +1 405 271 7402; Fax: +1 405 271 7953; E-mail:
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168
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Stahelin RV, Karathanassis D, Murray D, Williams RL, Cho W. Structural and membrane binding analysis of the Phox homology domain of Bem1p: basis of phosphatidylinositol 4-phosphate specificity. J Biol Chem 2007; 282:25737-47. [PMID: 17581820 DOI: 10.1074/jbc.m702861200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phox homology (PX) domains, which have been identified in a variety of proteins involved in cell signaling and membrane trafficking, have been shown to interact with phosphoinositides (PIs) with different affinities and specificities. To elucidate the structural origin of the diverse PI specificity of PX domains, we determined the crystal structure of the PX domain from Bem1p that has been reported to bind phosphatidylinositol 4-phosphate (PtdIns(4)P). We also measured the membrane binding properties of the PX domain and its mutants by surface plasmon resonance and monolayer techniques and calculated the electrostatic potentials for the PX domain in the absence and presence of bound PtdIns(4)P. The Bem1p PX domain contains a signature PI-binding site optimized for PtdIns(4)P binding and also harbors basic and hydrophobic residues on the membrane-binding surface. The membrane binding of the Bem1p PX domain is initiated by nonspecific electrostatic interactions between the cationic membrane-binding surface of the domain and anionic membrane surfaces, followed by the membrane penetration of hydrophobic residues. Unlike other PX domains, the Bem1p PX domain has high intrinsic membrane penetrating activity in the absence of PtdIns(4)P, suggesting that the partial membrane penetration may occur before specific PtdIns(4)P binding and last after the removal of PtdIns(4)P under certain conditions. This structural and functional study of the PtdIns(4)P-binding Bem1p PX domain provides new insight into the diverse PI specificities and membrane-binding mechanisms of PX domains.
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Affiliation(s)
- Robert V Stahelin
- Department of Chemistry, University of Illinois, Chicago, Illinois 60607-7061, USA
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169
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Abstract
New work on the ability of IRSp53/MIM domains to induce negative membrane curvature sheds light on the mechanisms used to generate actin-rich cell protrusions.
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Affiliation(s)
- Giles O C Cory
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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170
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Saito K, Williams S, Bulankina A, Höning S, Mustelin T. Association of Protein-tyrosine Phosphatase MEG2 via Its Sec14p Homology Domain with Vesicle-trafficking Proteins. J Biol Chem 2007; 282:15170-8. [PMID: 17387180 DOI: 10.1074/jbc.m608682200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The protein-tyrosine phosphatase PTPMEG2 is located on the cytoplasmic face of the enclosing membrane of secretory vesicles, where it regulates vesicle size by promoting homotypic vesicle fusion by dephosphorylating N-ethylmaleimide-sensitive factor, a key regulator of vesicle fusion. Here we address the question of how PTPMEG2 is targeted to this subcellular location. Using a series of deletion mutants, we pinpointed the N-terminal Sec14p homology (SEC14) domain of PTPMEG2, residues 1-261, as the region containing the secretory vesicle targeting signal. This domain, alone or appended to a heterologous protein, was localized to intracellular vesicle membranes. Yeast two-hybrid screening identified a number of secretory vesicle proteins that interacted directly with the SEC14 domain of PTPMEG2, providing a mechanism for PTPMEG2 targeting to secretory vesicles. Two such proteins, mannose 6-phosphate receptor-interacting protein TIP47 and Arfaptin2, were found to alter PTPMEG2 localization when overexpressed, and elimination of TIP47 resulted in loss of PTPMEG2 function. We conclude that the N terminus of PTPMEG2 is necessary for the targeting of this phosphatase to the secretory vesicle compartment by association with other proteins involved in intracellular transport.
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Affiliation(s)
- Kan Saito
- Program on Inflammatory Disease Research, Infectious and Inflammatory Disease Center, and Program of Signal Transduction, Cancer Center, The Burnham Institute for Medical Research, La Jolla, California 92037, USA
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171
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Lee SH, Kerff F, Chereau D, Ferron F, Klug A, Dominguez R. Structural basis for the actin-binding function of missing-in-metastasis. Structure 2007; 15:145-55. [PMID: 17292833 PMCID: PMC1853380 DOI: 10.1016/j.str.2006.12.005] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 12/08/2006] [Accepted: 12/15/2006] [Indexed: 11/18/2022]
Abstract
The adaptor protein missing-in-metastasis (MIM) contains independent F- and G-actin binding domains, consisting, respectively, of an N-terminal 250 aa IRSp53/MIM homology domain (IMD) and a C-terminal WASP-homology domain 2 (WH2). We determined the crystal structures of MIM's IMD and that of its WH2 bound to actin. The IMD forms a dimer, with each subunit folded as an antiparallel three-helix bundle. This fold is related to that of the BAR domain. Like the BAR domain, the IMD has been implicated in membrane binding. Yet, comparison of the structures reveals that the membrane binding surfaces of the two domains have opposite curvatures, which may determine the type of curvature of the interacting membrane. The WH2 of MIM is longer than the prototypical WH2, interacting with all four subdomains of actin. We characterize a similar WH2 at the C terminus of IRSp53 and propose that in these two proteins WH2 performs a scaffolding function.
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Affiliation(s)
- Sung Haeng Lee
- Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, Philadelphia, PA 19104, USA
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172
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Fei H, Karnezis T, Reimer RJ, Krantz DE. Membrane topology of the Drosophila vesicular glutamate transporter. J Neurochem 2007; 101:1662-71. [PMID: 17394549 DOI: 10.1111/j.1471-4159.2007.04518.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The vesicular glutamate transporters (VGLUTs) are responsible for packaging glutamate into synaptic vesicles, and are part of a family of structurally related proteins that mediate organic anion transport. Standard computer-based predictions of transmembrane domains have led to divergent topological models, indicating the need for experimentally derived predictions. Here we present data on the topology of the VGLUT ortholog from Drosophila melanogaster (DVGLUT). Using immunofluorescence assays of DVGLUT transiently localized to the plasma membrane of heterologously transfected cells, we have determined the accessibility of epitope tags inserted into the lumenal/extracellular face of the protein. Using immunoisolation, we have identified complementary tagged sites that face the cytoplasm. Our data show that DVGLUT contains 10 hydrophobic regions that completely span the membrane (TMs 1-10) and that the amino and carboxyl termini are cytosolic. Importantly, between TMs 4 and 5 is an unforeseen cytosolic loop of some 50 residues. Other domains exposed to the cytosol include loops between TMs 6-7 and 8-9, and regions C-terminal to TM2 and N-terminal to TM3. Between TM2 and 3 is a potentially hydrophobic, but topologically ambiguous region. Lumenal domains include sequences between TMs 1-2, 3-4, 5-6, 7-8 and 9-10. These data provide a basis for determining structure-function relationships for DVGLUT and other related proteins.
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Affiliation(s)
- Hao Fei
- Department of Psychiatry and Biobehavioral Sciences, The David Geffen School of Medicine at UCLA, Gonda (Goldschmied) Center for Genetic and Neuroscience Research, Los Angeles, CA 90095-1761, USA
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173
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Coll PM, Rincon SA, Izquierdo RA, Perez P. Hob3p, the fission yeast ortholog of human BIN3, localizes Cdc42p to the division site and regulates cytokinesis. EMBO J 2007; 26:1865-77. [PMID: 17363901 PMCID: PMC1847667 DOI: 10.1038/sj.emboj.7601641] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Accepted: 02/14/2007] [Indexed: 12/20/2022] Open
Abstract
Cdc42 GTPase is required for polarization in eukaryotic cells, but its spatial regulation is poorly understood. In Schizosaccharomyces pombe, Cdc42p is activated by Scd1p and Gef1p, two guanine-nucleotide exchange factors. Two-hybrid screening identified Hob3p as a Gef1p binding partner. Hob3p is a BAR domain-containing protein ortholog of human Bin3. Hob3p also interacts directly with Cdc42p independently of Gef1p. Hob3p, Cdc42p and Gef1p form a complex, and Hob3p facilitates Gef1p-Cdc42p interaction and activation. Hob3p forms a ring in the division area, similar to that of Gef1p. This localization requires actin polymerization and Cdc15p but is independent of the septation initiation network. Hob3p is required for the concentration of Cdc42p to the division area. The actomyosin ring contraction is slower in hob3Delta than in wild-type cells, and this contributes to its cytokinesis defect. Moreover, this report extends previous evidence that human Bin3 suppresses the cytokinesis phenotype of hob3Delta cells, showing that Bin3 can partially recover the GTP-Cdc42p level and its localization. These results suggest that Hob3p is required to recruit and activate Cdc42p at the cell division site and that this function might be conserved in other eukaryotes.
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Affiliation(s)
- Pedro M Coll
- Consejo Superior de Investigaciones Científicas (CSIC)/Departamento de Microbiología y Genética, Instituto de Microbiología Bioquímica, Universidad de Salamanca, Edificio Departamental, Salamanca 37007, Spain
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174
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Takenawa T, Suetsugu S. The WASP-WAVE protein network: connecting the membrane to the cytoskeleton. Nat Rev Mol Cell Biol 2007; 8:37-48. [PMID: 17183359 DOI: 10.1038/nrm2069] [Citation(s) in RCA: 698] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Wiskott-Aldrich syndrome protein (WASP) and WASP-family verprolin-homologous protein (WAVE) family proteins are scaffolds that link upstream signals to the activation of the ARP2/3 complex, leading to a burst of actin polymerization. ARP2/3-complex-mediated actin polymerization is crucial for the reorganization of the actin cytoskeleton at the cell cortex for processes such as cell movement, vesicular trafficking and pathogen infection. Large families of membrane-binding proteins were recently found to interact with WASP and WAVE family proteins, therefore providing a new layer of membrane-dependent regulation of actin polymerization.
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Affiliation(s)
- Tadaomi Takenawa
- Department of Biochemistry, Institute of Medical Science, University of Tokyo, 4-6-1, Shirokane-dai, Minato-ku, Tokyo 108-8639, Japan.
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175
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Nechamen CA, Thomas RM, Dias JA. APPL1, APPL2, Akt2 and FOXO1a interact with FSHR in a potential signaling complex. Mol Cell Endocrinol 2007; 260-262:93-9. [PMID: 17030088 PMCID: PMC1782224 DOI: 10.1016/j.mce.2006.08.014] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 08/17/2006] [Indexed: 11/23/2022]
Abstract
A number of signaling proteins have been demonstrated to interact with follicle stimulating hormone (FSH) receptor (FSHR), including APPL1, 14-3-3tau and Akt2. To further define the repertoire of proteins involved in FSH-induced signal transduction, several signaling and adapter proteins were examined for the ability to associate with FSHR. This report shows that, in addition to APPL1, FSHR interacts with FOXO1a and APPL2. Moreover, APPL1 and APPL2 associate with one another via the N-terminus of APPL1, presumably via the Bin-Amphiphysin-Rvs (BAR) domain. The interactions between FSHR and APPL2 and between FSHR and FOXO1a evidently are distinct since FOXO1a does not associate with either APPL1 or with APPL2. Though APPL1 and APPL2 show some similarity in primary sequence, APPL1 associates with Akt2, whereas APPL2 does not. This is the first documented difference in function between APPL1 and APPL2. These results suggest that FSHR, APPL1, APPL2, Akt2 and FOXO1a are organized into distinct scaffolding networks in the cell. Accordingly, the spatial organization of signaling and adapter proteins with FSHR likely facilitates and finely regulates the signal transduction induced by FSH.
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Affiliation(s)
- Cheryl A. Nechamen
- Wadsworth Center, David Axelrod Institute for Public Health, New York State Department of Health, Albany, New York 12208
| | - Richard M. Thomas
- Wadsworth Center, David Axelrod Institute for Public Health, New York State Department of Health, Albany, New York 12208
| | - James A. Dias
- Wadsworth Center, David Axelrod Institute for Public Health, New York State Department of Health, Albany, New York 12208
- Department of Biomedical Sciences, State University of New York at Albany, Albany, New York
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176
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Casal E, Federici L, Zhang W, Fernandez-Recio J, Priego EM, Miguel RN, DuHadaway JB, Prendergast GC, Luisi BF, Laue ED. The crystal structure of the BAR domain from human Bin1/amphiphysin II and its implications for molecular recognition. Biochemistry 2006; 45:12917-28. [PMID: 17059209 PMCID: PMC2572078 DOI: 10.1021/bi060717k] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BAR domains are found in proteins that bind and remodel membranes and participate in cytoskeletal and nuclear processes. Here, we report the crystal structure of the BAR domain from the human Bin1 protein at 2.0 A resolution. Both the quaternary and tertiary architectures of the homodimeric Bin1BAR domain are built upon "knobs-into-holes" packing of side chains, like those found in conventional left-handed coiled-coils, and this packing governs the curvature of a putative membrane-engaging concave face. Our calculations indicate that the Bin1BAR domain contains two potential sites for protein-protein interactions on the convex face of the dimer. Comparative analysis of structural features reveals that at least three architectural subtypes of the BAR domain are encoded in the human genome, represented by the Arfaptin, Bin1/Amphiphysin, and IRSp53 BAR domains. We discuss how these principal groups may differ in their potential to form regulatory heterotypic interactions.
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Affiliation(s)
- Eva Casal
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Luca Federici
- Ce.S.I. Centro Studi sull’Invecchiamento and Dipartimento di Scienze Biomediche, Universita’ di Chieti “G. D’Annunzio”, Via dei Vestini 31, 66013 Chieti, Italy
| | - Wei Zhang
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Juan Fernandez-Recio
- Institute of Biomedical Research, Barcelona Science Park, Josep Samitier 1–5, 08028 Barcelona, Spain
| | - Eva-Maria Priego
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Ricardo Nuñez Miguel
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K
| | - James B. DuHadaway
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood PA 19096 USA
| | - George C. Prendergast
- Lankenau Institute for Medical Research, 100 Lancaster Avenue, Wynnewood PA 19096 USA
| | - Ben F. Luisi
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K
- Correspondence to Ben F. Luisi: , phone 44-1223-766019 FAX 44-1223-766002
| | - Ernest D. Laue
- Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, U.K
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177
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Dev KK, Henley JM. The schizophrenic faces of PICK1. Trends Pharmacol Sci 2006; 27:574-9. [PMID: 17011050 PMCID: PMC3314511 DOI: 10.1016/j.tips.2006.09.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Revised: 08/25/2006] [Accepted: 09/14/2006] [Indexed: 01/08/2023]
Abstract
Schizophrenia is a grave psychiatric disorder with psychotic symptoms and an enigmatic etiology. Family studies have strongly indicated that genetic risk factors have a role in this disease. Recent findings, together with previously established evidence, highlight the PDZ-domain-containing protein interacting with C-kinase 1 (PICK1) as a promising candidate for a schizophrenia susceptibility gene. Here, we outline possible molecular mechanisms, discuss clinical case-studies that indicate an unexpected role of PICK1 in schizophrenia and discuss potential avenues for pharmacological manipulation of PICK1.
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Affiliation(s)
- Kumlesh K Dev
- Neuroscience Research, Novartis Institutes for BioMedical Research, Novartis Pharma, WSJ 386-7-43, Lichtstrasse 35, CH-4056 Basel, Switzerland.
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178
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ProFAT: a web-based tool for the functional annotation of protein sequences. BMC Bioinformatics 2006; 7:466. [PMID: 17059594 PMCID: PMC1636073 DOI: 10.1186/1471-2105-7-466] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Accepted: 10/23/2006] [Indexed: 11/18/2022] Open
Abstract
Background The functional annotation of proteins relies on published information concerning their close and remote homologues in sequence databases. Evidence for remote sequence similarity can be further strengthened by a similar biological background of the query sequence and identified database sequences. However, few tools exist so far, that provide a means to include functional information in sequence database searches. Results We present ProFAT, a web-based tool for the functional annotation of protein sequences based on remote sequence similarity. ProFAT combines sensitive sequence database search methods and a fold recognition algorithm with a simple text-mining approach. ProFAT extracts identified hits based on their biological background by keyword-mining of annotations, features and most importantly, literature associated with a sequence entry. A user-provided keyword list enables the user to specifically search for weak, but biologically relevant homologues of an input query. The ProFAT server has been evaluated using the complete set of proteins from three different domain families, including their weak relatives and could correctly identify between 90% and 100% of all domain family members studied in this context. ProFAT has furthermore been applied to a variety of proteins from different cellular contexts and we provide evidence on how ProFAT can help in functional prediction of proteins based on remotely conserved proteins. Conclusion By employing sensitive database search programs as well as exploiting the functional information associated with database sequences, ProFAT can detect remote, but biologically relevant relationships between proteins and will assist researchers in the prediction of protein function based on remote homologies.
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179
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McNiven MA, Thompson HM. Vesicle formation at the plasma membrane and trans-Golgi network: the same but different. Science 2006; 313:1591-4. [PMID: 16973870 DOI: 10.1126/science.1118133] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
An elaborate vesicle transport system supports the active exchange of membranes and protein cargo between the plasma membrane and the trans-Golgi network. Many observations suggest that highly conserved mechanisms are used in vesicle formation and scission. Such similarity is found both at the level of the receptor-ligand sequestration process that uses clathrin and associated polymeric and monomeric adaptor proteins, and in the machinery used to deform and vesiculate lipid membranes.
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Affiliation(s)
- Mark A McNiven
- Department of Biochemistry and Molecular Biology and the Miles and Shirley Fiterman Center for Digestive Diseases, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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180
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Voglmaier SM, Kam K, Yang H, Fortin DL, Hua Z, Nicoll RA, Edwards RH. Distinct endocytic pathways control the rate and extent of synaptic vesicle protein recycling. Neuron 2006; 51:71-84. [PMID: 16815333 DOI: 10.1016/j.neuron.2006.05.027] [Citation(s) in RCA: 304] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 04/21/2006] [Accepted: 05/31/2006] [Indexed: 11/16/2022]
Abstract
Synaptic vesicles have been proposed to form through two mechanisms: one directly from the plasma membrane involving clathrin-dependent endocytosis and the adaptor protein AP2, and the other from an endosomal intermediate mediated by the adaptor AP3. However, the relative role of these two mechanisms in synaptic vesicle recycling has remained unclear. We now find that vesicular glutamate transporter VGLUT1 interacts directly with endophilin, a component of the clathrin-dependent endocytic machinery. In the absence of its interaction with endophilin, VGLUT1 recycles more slowly during prolonged, high-frequency stimulation. Inhibition of the AP3 pathway with brefeldin A rescues the rate of recycling, suggesting a competition between AP2 and -3 pathways, with endophilin recruiting VGLUT1 toward the faster AP2 pathway. After stimulation, however, inhibition of the AP3 pathway prevents the full recovery of VGLUT1 by endocytosis, implicating the AP3 pathway specifically in compensatory endocytosis.
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Affiliation(s)
- Susan M Voglmaier
- Department of Neurology, Graduate Programs in Cell Biology, Neuroscience and Biomedical Sciences, UCSF School of Medicine, 600 16th Street, San Francisco, California 94143, USA
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181
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Childress C, Lin Q, Yang W. Dimerization is required for SH3PX1 tyrosine phosphorylation in response to epidermal growth factor signalling and interaction with ACK2. Biochem J 2006; 394:693-8. [PMID: 16316319 PMCID: PMC1383719 DOI: 10.1042/bj20050576] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
SH3PX1 [SNX9 (sorting nexin 9)] is a member of SNX super-family that is recognized by sharing a PX (phox homology) domain. We have previously shown that SH3PX1, phosphorylated by ACK2 (activated Cdc42-associated tyrosine kinase 2), regulates the degradation of EGF (epidermal growth factor) receptor. In mapping the tyrosine phosphorylation region, we found that the C-terminus of SH3PX1 is required for its tyrosine phosphorylation. Further analysis indicates that this region, known as the coiled-coil domain or the BAR (Bin-amphiphysin-Rvs homology) domain, is the dimerization domain of SH3PX1. Truncation of as little as 13 amino acid residues at the very C-terminus in the coiled-coil/BAR domain of SH3PX1 resulted in no dimerization, no ACK2-catalysed and EGF-stimulated tyrosine phosphorylation and no interaction with ACK2. The intracellular localization of SH3PX1 became dysfunctional upon truncation in the BAR domain. Taken together, our results indicate that the dimerization, which is mediated by the BAR domain, is essential for the intracellular function of SH3PX1.
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Affiliation(s)
- Chandra Childress
- Weis Center for Research, Geisinger Clinic, 100 N. Academy Avenue, Danville, PA 17822, U.S.A
| | - Qiong Lin
- Weis Center for Research, Geisinger Clinic, 100 N. Academy Avenue, Danville, PA 17822, U.S.A
| | - Wannian Yang
- Weis Center for Research, Geisinger Clinic, 100 N. Academy Avenue, Danville, PA 17822, U.S.A
- To whom correspondence should be addressed (email )
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182
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Yoo KW, Kim EH, Jung SH, Rhee M, Koo BK, Yoon KJ, Kong YY, Kim CH. Snx5, as a Mind bomb-binding protein, is expressed in hematopoietic and endothelial precursor cells in zebrafish. FEBS Lett 2006; 580:4409-16. [PMID: 16857196 DOI: 10.1016/j.febslet.2006.07.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Revised: 07/03/2006] [Accepted: 07/04/2006] [Indexed: 12/11/2022]
Abstract
Notch signaling has an evolutionarily conserved function for cell fate determination and stem cell maintenance. Previously, we identified a novel component of the Notch signaling pathway in zebrafish, mind bomb, which encodes an E3 ubiquitin ligase essential for Notch signal activation. Further studies showed that Mind bomb(-/-) mouse embryos exhibited pan-Notch phenotypes in various tissues, suggesting that Mind bomb function is conserved in mammals. Therefore we sought to understand the various molecular partners of Mind bomb using yeast two-hybrid screening. In this search we identified Sorting nexin 5 (Snx5) as a novel interacting partner of Mind bomb. Furthermore we demonstrated that Snx5 colocalizes with Mind bomb in early endosomal compartments, suggesting that Snx5 is important for Mind bomb trafficking. In addition, we identified zebrafish orthologue of Snx5 and showed that snx5 is predominantly expressed in hematopoietic and endothelial precursor cells in zebrafish. We also found defects in hematopoiesis and blood vessel development in snx5 morpholino-injected embryos. Taken together, we show that Snx5, a novel interacting partner of Mind bomb, may have an essential role for cell fate determination in early development.
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Affiliation(s)
- Kyeong-Won Yoo
- Department of Biology, Chungnam National University, Daejeon 305-764, South Korea
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183
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Masuda M, Takeda S, Sone M, Ohki T, Mori H, Kamioka Y, Mochizuki N. Endophilin BAR domain drives membrane curvature by two newly identified structure-based mechanisms. EMBO J 2006; 25:2889-97. [PMID: 16763557 PMCID: PMC1500852 DOI: 10.1038/sj.emboj.7601176] [Citation(s) in RCA: 215] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Accepted: 05/08/2006] [Indexed: 11/09/2022] Open
Abstract
The crescent-shaped BAR (Bin/Amphiphysin/Rvs-homology) domain dimer is a versatile protein module that senses and generates positive membrane curvature. The BAR domain dimer of human endophilin-A1, solved at 3.1 A, has a unique structure consisting of a pair of helix-loop appendages sprouting out from the crescent. The appendage's short helices form a hydrophobic ridge, which runs across the concave surface at its center. Examining liposome binding and tubulation in vitro using purified BAR domain and its mutants indicated that the ridge penetrates into the membrane bilayer and enhances liposome tubulation. BAR domain-expressing cells exhibited marked plasma membrane tubulation in vivo. Furthermore, a swinging-arm mutant lost liposome tubulation activity yet retaining liposome binding. These data suggested that the rigid crescent dimer shape is crucial for the tubulation. We here propose that the BAR domain drives membrane curvature by coordinate action of the crescent's scaffold mechanism and the ridge's membrane insertion in addition to membrane binding via amino-terminal amphipathic helix.
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Affiliation(s)
- Michitaka Masuda
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Soichi Takeda
- Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
- Laboratory of structural biochemistry, RIKEN Harima Institute at SPring-8, Mikazuki-cho, Sayo, Hyogo, Japan
| | - Manami Sone
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Takashi Ohki
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Hidezo Mori
- Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Yuji Kamioka
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Naoki Mochizuki
- Department of Structural Analysis, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
- Department of Structural Analysis, National Cardiovascular Center Research Institute, 5-7-1 Fujishiro-dai, Suita, Osaka 565-8565, Japan. Tel.: +81 6 6833 5012; Fax: +81 6 6835 5461; E-mail:
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184
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Yoon T, Kim M, Lee K. Inhibition of Na,K-ATPase-suppressive activity of translationally controlled tumor protein by sorting nexin 6. FEBS Lett 2006; 580:3558-64. [PMID: 16730713 DOI: 10.1016/j.febslet.2006.05.042] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Revised: 05/11/2006] [Accepted: 05/16/2006] [Indexed: 11/22/2022]
Abstract
Translationally controlled tumor protein (TCTP) has both extra- and intracellular functions. Our group recently reported that TCTP interacts with Na,K-ATPase and suppresses its activity. Our studies led to the identification of sorting nexin 6 (SNX6) which binds with TCTP as a potential negative regulator of TCTP. SNX6 does not interact directly with any cytoplasmic domains of Na,K-ATPase. However, when overexpressed, it restores the Na,K-ATPase activity suppressed by TCTP. This was confirmed by measurements of purified plasma membrane Na,K-ATPase activity after incubation with recombinant TCTP and SNX6. SNX6 alone has no effect on Na,K-ATPase activity, but activates Na,K-ATPase via inhibition of TCTP. Inhibition of endogenous TCTP by the overexpression of SNX6 or knockdown of TCTP expression by siTCTP increased Na,K-ATPase activity above the basal level. The interaction between SNX6 and TCTP thus appears to regulate Na,K-ATPase activity.
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Affiliation(s)
- Taesook Yoon
- College of Pharmacy, Center for Cell Signaling Research and Division of Molecular Life Sciences, Ewha Woman's University, Seoul, Republic of Korea
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185
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Vogel V, Sheetz M. Local force and geometry sensing regulate cell functions. Nat Rev Mol Cell Biol 2006; 7:265-75. [PMID: 16607289 DOI: 10.1038/nrm1890] [Citation(s) in RCA: 1560] [Impact Index Per Article: 86.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The shapes of eukaryotic cells and ultimately the organisms that they form are defined by cycles of mechanosensing, mechanotransduction and mechanoresponse. Local sensing of force or geometry is transduced into biochemical signals that result in cell responses even for complex mechanical parameters such as substrate rigidity and cell-level form. These responses regulate cell growth, differentiation, shape changes and cell death. Recent tissue scaffolds that have been engineered at the micro- and nanoscale level now enable better dissection of the mechanosensing, transduction and response mechanisms.
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Affiliation(s)
- Viola Vogel
- Laboratory for Biologically Oriented Materials, Department of Materials, Swiss Federal Institute of Technology (ETH), Zurich, Wolfgang-Pauli-Strasse 10, ETH Hönggerberg, HCI F443, CH-8093 Zürich, Switzerland.
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186
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Abstract
The response of a cell to the myriad of signals that it receives is varied, and it is dependent on many different factors. The most-studied responses involve growth-factor signalling and these signalling cascades have become key targets for cancer therapy. Recent reports have indicated that growth-factor receptors and associated adaptors can accumulate in the nucleus. Are there novel functions for these proteins that might affect our understanding of their role in cancer and have implications for drug resistance?
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Affiliation(s)
- Charles Massie
- CRUK Uro-Oncology Group, Department of Oncology, University of Cambridge, c/o Hutchison/MRC Cancer Research Centre, Addenbrookes Hospital, Hills Road, Cambridge, CB2 2XZ, UK
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187
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Liu H, Liu ZQ, Chen CXQ, Magill S, Jiang Y, Liu YJ. Inhibitory regulation of EGF receptor degradation by sorting nexin 5. Biochem Biophys Res Commun 2006; 342:537-46. [PMID: 16487940 DOI: 10.1016/j.bbrc.2006.01.179] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2005] [Accepted: 01/20/2006] [Indexed: 12/18/2022]
Abstract
Endosomal trafficking of EGF receptor (EGFR) upon stimulation is a highly regulated process during receptor-mediated signaling. Recently, the sorting nexin (SNX) family has emerged as an important regulator in the membrane trafficking of EGFR. Here, we report the identification of a novel interaction between two members of the family, SNX1 and SNX5, which is mediated by the newly defined BAR domain of both SNXs. We have also shown that the PX domain of SNX5 binds specifically to PtdIns other than to PtdIns(3)P. Furthermore, the BAR domain but not the PX domain of SNX5 is sufficient for its subcellular membrane association. Functionally, overexpression of SNX5 inhibits the degradation of EGFR. This process appears to be independent of its interaction with SNX1. However, overexpression of SNX1 is able to attenuate the effect of SNX5 on EGFR degradation, suggesting the two proteins may play antagonistic roles in regulating endosomal trafficking of the receptor.
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Affiliation(s)
- Hao Liu
- Department of Neurology and Neurobiology, University of Pittsburgh School of Medicine, W958 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15213, USA
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188
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Bhardwaj N, Stahelin RV, Langlois RE, Cho W, Lu H. Structural bioinformatics prediction of membrane-binding proteins. J Mol Biol 2006; 359:486-95. [PMID: 16626739 PMCID: PMC2707359 DOI: 10.1016/j.jmb.2006.03.039] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 02/27/2006] [Accepted: 03/17/2006] [Indexed: 11/25/2022]
Abstract
Membrane-binding peripheral proteins play important roles in many biological processes, including cell signaling and membrane trafficking. Unlike integral membrane proteins, these proteins bind the membrane mostly in a reversible manner. Since peripheral proteins do not have canonical transmembrane segments, it is difficult to identify them from their amino acid sequences. As a first step toward genome-scale identification of membrane-binding peripheral proteins, we built a kernel-based machine learning protocol. Key features of known membrane-binding proteins, including electrostatic properties and amino acid composition, were calculated from their amino acid sequences and tertiary structures, which were then incorporated into the support vector machine to perform the classification. A data set of 40 membrane-binding proteins and 230 non-membrane-binding proteins was used to construct and validate the protocol. Cross-validation and holdout evaluation of the protocol showed that the accuracy of the prediction reached up to 93.7% and 91.6%, respectively. The protocol was applied to the prediction of membrane-binding properties of four C2 domains from novel protein kinases C. Although these C2 domains have 50% sequence identity, only one of them was predicted to bind the membrane, which was verified experimentally with surface plasmon resonance analysis. These results suggest that our protocol can be used for predicting membrane-binding properties of a wide variety of modular domains and may be further extended to genome-scale identification of membrane-binding peripheral proteins.
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Affiliation(s)
- Nitin Bhardwaj
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
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189
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Gorska MM, Cen O, Liang Q, Stafford SJ, Alam R. Differential regulation of interleukin 5-stimulated signaling pathways by dynamin. J Biol Chem 2006; 281:14429-39. [PMID: 16556602 DOI: 10.1074/jbc.m512718200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Through the yeast two-hybrid screen we have identified dynamin-2 as a molecule that interacts with the alpha subunit of the interleukin (IL) 5 receptor. Dynamin-2 is a GTPase that is critical for endocytosis. We have shown that dynamin-2 interacts with the IL-5 receptor-associated tyrosine kinases, Lyn and JAK2, in eosinophils. Tyrosine phosphorylation of dynamin is markedly enhanced upon IL-5 stimulation. The inhibition of tyrosine kinases results in complete abolition of ligand-induced receptor endocytosis. Inhibition of dynamin by a dominant-negative mutant or by small interfering RNA results in enhancement of IL-5-stimulated ERK1/2 signaling and cell proliferation. In contrast, the absence of a functional dynamin does not affect STAT5 or AKT phosphorylation or cell survival. Thus, we have identified specific functions for dynamin in the IL-5 signaling pathway and demonstrated its role in receptor endocytosis and termination of the ERK1/2 signaling pathway.
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Affiliation(s)
- Magdalena M Gorska
- Division of Allergy and Immunology, Department of Medicine, National Jewish Medical and Research Center, Denver, Colorado 80206, USA
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190
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Kessels MM, Qualmann B. Syndapin oligomers interconnect the machineries for endocytic vesicle formation and actin polymerization. J Biol Chem 2006; 281:13285-13299. [PMID: 16540475 DOI: 10.1074/jbc.m510226200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Syndapins were proposed to interconnect the machineries for vesicle formation and actin polymerization, as they interact with dynamin and the Arp2/3 complex activator N-WASP (neural Wiskott-Aldrich syndrome protein). Syndapins, however, have only one Src homology 3 domain mediating both interactions. Here we show that syndapins self-associate via direct syndapin/syndapin interactions, providing a molecular mechanism for the coordinating role of syndapin. Cross-link studies with overexpressed and endogenous syndapins suggest that predominantly dimers form in vivo. Our analyses show that the N-terminal Fes/Cip4 homology domain but not the central coiled-coil domain is sufficient for oligomerization. Additionally, a second interface located further C-terminally mediated interactions with the N terminus. The Src homology 3 domain and the NPF region are not involved and thus available for further interactions interconnecting different syndapin binding partners. Our analyses showed that self-association is crucial for syndapin function. Both syndapin-mediated cytoskeletal rearrangements and endocytosis were disrupted by a self-association-deficient mutant. Consistent with a role of syndapins in linking actin polymerization bursts with endocytic vesicle formation, syndapin-containing complexes had a size of 300-500 kDa in gel filtration analysis and contained both dynamin and N-WASP. The existence of an interconnection of the GTPase dynamin with N-WASP via syndapin oligomers was demonstrated both by coimmunoprecipitations and by reconstitution at membranes in intact cells. The interconnection was disrupted by coexpression of syndapin mutants incapable of self-association. Syndapin oligomers may thus act as multivalent organizers spatially and temporally coordinating vesicle fission with local actin polymerization.
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Affiliation(s)
- Michael M Kessels
- Research Group Membrane Trafficking and Cytoskeleton, Department of Neurochemistry and Molecular Biology, D-39118 Magdeburg, Germany
| | - Britta Qualmann
- Research Group Cell Biology, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany.
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191
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Yan HZ, Liou RF. Selection of internal control genes for real-time quantitative RT-PCR assays in the oomycete plant pathogen Phytophthora parasitica. Fungal Genet Biol 2006; 43:430-8. [PMID: 16531084 DOI: 10.1016/j.fgb.2006.01.010] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Revised: 01/18/2006] [Accepted: 01/27/2006] [Indexed: 11/20/2022]
Abstract
Real-time quantitative reverse transcription-PCR (qRT-PCR) has become one of the most commonly used methods for RNA quantification in recent years. To obtain reliable results with biological significance, it is important that qRT-PCR data are normalized with a proper internal control. In this study, 18 housekeeping genes were selected and evaluated for their potential as a suitable internal control for study of gene expression in the oomycete plant pathogen Phytophthora parasitica. Analysis of qRT-PCR data using the geNorm software indicated that, although commonly used as internal controls, beta-actin (ACT) and translation elongation factor 1alpha (eEF1A) might not be the best choice due to variable expression across different life stages of P. parasitica. Instead, other genes would serve as better controls, including ubiquitin-conjugating enzyme (Ubc), WS21, and beta-tubulin (Tub-b) for 'asexual stage,' Ubc and Tub-b for 'sexual reproduction,' while Ubc and WS21 for the stage of pathogenesis, because of their constant expression levels in each given subset of RNA samples. Although normalization with more than one gene would generate more reliable results, use of a single stably expressed gene as an internal control would suffice for accurate data normalization in some experiments.
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Affiliation(s)
- Hao-Zhi Yan
- Department of Plant Pathology and Microbiology, National Taiwan University, Taipei 106, Taiwan
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192
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Steinberg JP, Takamiya K, Shen Y, Xia J, Rubio ME, Yu S, Jin W, Thomas GM, Linden DJ, Huganir RL. Targeted In Vivo Mutations of the AMPA Receptor Subunit GluR2 and Its Interacting Protein PICK1 Eliminate Cerebellar Long-Term Depression. Neuron 2006; 49:845-60. [PMID: 16543133 DOI: 10.1016/j.neuron.2006.02.025] [Citation(s) in RCA: 225] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Revised: 02/09/2006] [Accepted: 02/28/2006] [Indexed: 11/23/2022]
Abstract
Cerebellar long-term depression (LTD) is a major form of synaptic plasticity that is thought to be critical for certain types of motor learning. Phosphorylation of the AMPA receptor subunit GluR2 on serine-880 as well as interaction of GluR2 with PICK1 have been suggested to contribute to the endocytic removal of postsynaptic AMPA receptors during LTD. Here, we show that targeted mutation of PICK1, the GluR2 C-terminal PDZ ligand, or the GluR2 PKC phosphorylation site eliminates cerebellar LTD in mice. LTD can be rescued in cerebellar cultures from mice lacking PICK1 by transfection of wild-type PICK1 but not by a PDZ mutant or a BAR domain mutant deficient in lipid binding, indicating the importance of these domains in PICK1 function. These results demonstrate that PICK1-GluR2 PDZ-based interactions and GluR2 phosphorylation are required for LTD expression in the cerebellum.
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Affiliation(s)
- Jordan P Steinberg
- Howard Hughes Medical Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
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193
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Ren G, Vajjhala P, Lee JS, Winsor B, Munn AL. The BAR domain proteins: molding membranes in fission, fusion, and phagy. Microbiol Mol Biol Rev 2006; 70:37-120. [PMID: 16524918 PMCID: PMC1393252 DOI: 10.1128/mmbr.70.1.37-120.2006] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Bin1/amphiphysin/Rvs167 (BAR) domain proteins are a ubiquitous protein family. Genes encoding members of this family have not yet been found in the genomes of prokaryotes, but within eukaryotes, BAR domain proteins are found universally from unicellular eukaryotes such as yeast through to plants, insects, and vertebrates. BAR domain proteins share an N-terminal BAR domain with a high propensity to adopt alpha-helical structure and engage in coiled-coil interactions with other proteins. BAR domain proteins are implicated in processes as fundamental and diverse as fission of synaptic vesicles, cell polarity, endocytosis, regulation of the actin cytoskeleton, transcriptional repression, cell-cell fusion, signal transduction, apoptosis, secretory vesicle fusion, excitation-contraction coupling, learning and memory, tissue differentiation, ion flux across membranes, and tumor suppression. What has been lacking is a molecular understanding of the role of the BAR domain protein in each process. The three-dimensional structure of the BAR domain has now been determined and valuable insight has been gained in understanding the interactions of BAR domains with membranes. The cellular roles of BAR domain proteins, characterized over the past decade in cells as distinct as yeasts, neurons, and myocytes, can now be understood in terms of a fundamental molecular function of all BAR domain proteins: to sense membrane curvature, to bind GTPases, and to mold a diversity of cellular membranes.
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Affiliation(s)
- Gang Ren
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland 4072, Australia
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194
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Jin AJ, Prasad K, Smith PD, Lafer EM, Nossal R. Measuring the elasticity of clathrin-coated vesicles via atomic force microscopy. Biophys J 2006; 90:3333-44. [PMID: 16473913 PMCID: PMC1432129 DOI: 10.1529/biophysj.105.068742] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Using a new scheme based on atomic force microscopy (AFM), we investigate mechanical properties of clathrin-coated vesicles (CCVs). CCVs are multicomponent protein and lipid complexes of approximately 100 nm diameter that are implicated in many essential cell-trafficking processes. Our AFM imaging resolves clathrin lattice polygons and provides height deformation in quantitative response to AFM-substrate compression force. We model CCVs as multilayered elastic spherical shells and, from AFM measurements, estimate their bending rigidity to be 285 +/- 30 k(B)T, i.e., approximately 20 times that of either the outer clathrin cage or inner vesicle membrane. Further analysis reveals a flexible coupling between the clathrin coat and the membrane, a structural property whose modulation may affect vesicle biogenesis and cellular function.
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Affiliation(s)
- Albert J Jin
- Division of Bioengineering and Physical Science, Office of Research Services, Office of the Director, National Institutes of Health, Bethesda, Maryland, USA
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195
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Carlton JG, Bujny MV, Peter BJ, Oorschot VMJ, Rutherford A, Arkell RS, Klumperman J, McMahon HT, Cullen PJ. Sorting nexin-2 is associated with tubular elements of the early endosome, but is not essential for retromer-mediated endosome-to-TGN transport. J Cell Sci 2006; 118:4527-39. [PMID: 16179610 PMCID: PMC1904489 DOI: 10.1242/jcs.02568] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sorting nexins are a large family of phox-homology-domain-containing proteins that have been implicated in the control of endosomal sorting. Sorting nexin-1 is a component of the mammalian retromer complex that regulates retrieval of the cation-independent mannose 6-phosphate receptor from endosomes to the trans-Golgi network. In yeast, retromer is composed of Vps5p (the orthologue of sorting nexin-1), Vps17p (a related sorting nexin) and a cargo selective subcomplex composed of Vps26p, Vps29p and Vps35p. With the exception of Vps17p, mammalian orthologues of all yeast retromer components have been identified. For Vps17p, one potential mammalian orthologue is sorting nexin-2. Here we show that, like sorting nexin-1, sorting nexin-2 binds phosphatidylinositol 3-monophosphate and phosphatidylinositol 3,5-bisphosphate, and possesses a Bin/Amphiphysin/Rvs domain that can sense membrane curvature. However, in contrast to sorting nexin-1, sorting nexin-2 could not induce membrane tubulation in vitro or in vivo. Functionally, we show that endogenous sorting nexin-1 and sorting nexin-2 co-localise on high curvature tubular elements of the 3-phosphoinositide-enriched early endosome, and that suppression of sorting nexin-2 does not perturb the degradative sorting of receptors for epidermal growth factor or transferrin, nor the steady-state distribution of the cation-independent mannose 6-phosphate receptor. However, suppression of sorting nexin-2 results in a subtle alteration in the kinetics of cation-independent mannose 6-phosphate receptor retrieval. These data suggest that although sorting nexin-2 may be a component of the retromer complex, its presence is not essential for the regulation of endosome-to-trans Golgi network retrieval of the cation-independent mannose 6-phosphate receptor.
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Affiliation(s)
- Jez G. Carlton
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Miriam V. Bujny
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Brian J. Peter
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
| | - Viola M. J. Oorschot
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Anna Rutherford
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
| | - Rebecca S. Arkell
- Signalling Programme, The Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK
| | - Judith Klumperman
- Cell Microscopy Center, Department of Cell Biology and Institute for Biomembranes, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - Harvey T. McMahon
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK
| | - Peter J. Cullen
- Henry Wellcome Integrated Signalling Laboratories, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
- Author for correspondence (e-mail: )
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196
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Itoh T, Erdmann KS, Roux A, Habermann B, Werner H, De Camilli P. Dynamin and the actin cytoskeleton cooperatively regulate plasma membrane invagination by BAR and F-BAR proteins. Dev Cell 2006; 9:791-804. [PMID: 16326391 DOI: 10.1016/j.devcel.2005.11.005] [Citation(s) in RCA: 478] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Revised: 09/17/2005] [Accepted: 11/09/2005] [Indexed: 11/19/2022]
Abstract
Cell membranes undergo continuous curvature changes as a result of membrane trafficking and cell motility. Deformations are achieved both by forces extrinsic to the membrane as well as by structural modifications in the bilayer or at the bilayer surface that favor the acquisition of curvature. We report here that a family of proteins previously implicated in the regulation of the actin cytoskeleton also have powerful lipid bilayer-deforming properties via an N-terminal module (F-BAR) similar to the BAR domain. Several such proteins, like a subset of BAR domain proteins, bind to dynamin, a GTPase implicated in endocytosis and actin dynamics, via SH3 domains. The ability of BAR and F-BAR domain proteins to induce tubular invaginations of the plasma membrane is enhanced by disruption of the actin cytoskeleton and is antagonized by dynamin. These results suggest a close interplay between the mechanisms that control actin dynamics and those that mediate plasma membrane invagination and fission.
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Affiliation(s)
- Toshiki Itoh
- Department of Cell Biology and Howard Hughes Medical Institute, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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197
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Sossa KG, Court BL, Carroll RC. NMDA receptors mediate calcium-dependent, bidirectional changes in dendritic PICK1 clustering. Mol Cell Neurosci 2006; 31:574-85. [PMID: 16406232 DOI: 10.1016/j.mcn.2005.11.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 11/07/2005] [Accepted: 11/22/2005] [Indexed: 02/03/2023] Open
Abstract
AMPA receptor (AMPAR) trafficking at CNS synapses is regulated by several receptor-binding proteins. One model of AMPAR endocytosis entails the cotargeting of the GluR2-interacting protein PICK1 and activated PKC to synapses. We demonstrate that NMDA receptor (NMDAR) activation mediates bidirectional changes in surface AMPARs through two additional forms of PICK1 redistribution. In neurons, NMDAR activation, which induces AMPAR endocytosis, increases endosomal PICK1 clustering. In contrast, stronger NMDAR activation rapidly reduces PICK1 clustering accompanied by decreases in PICK1/GluR2 association and increases in surface AMPAR levels. PICK1-siRNA similarly increases surface AMPARs and occludes the NMDAR-mediated effect, demonstrating the role of PICK1 in this process. Bidirectional NMDAR-mediated changes in PICK1 localization are determined by the magnitude of receptor-activated dendritic calcium signals. Our results show that PICK1 localization in dendrites is subject to multiple forms of regulation that contribute to surface AMPAR expression, likely by modulating the numbers of AMPARs maintained in intracellular compartments.
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Affiliation(s)
- K G Sossa
- Department of Neuroscience, Rose Kennedy Center for Mental Retardation, 1410 Pelham Parkway, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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198
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Icking A, Schilling K, Wiesenthal A, Opitz N, Müller-Esterl W. FCH/Cdc15 domain determines distinct subcellular localization of NOSTRIN. FEBS Lett 2005; 580:223-8. [PMID: 16376344 DOI: 10.1016/j.febslet.2005.11.078] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Accepted: 11/30/2005] [Indexed: 12/17/2022]
Abstract
NOSTRIN, an NO synthase binding protein, belongs to the PCH family of proteins, exposing a typical domain structure. While its SH3 domain and the C-terminal coiled-coil region cc2 have been studied earlier, the function of the N-terminal half comprising a Cdc15 domain with an FCH (Fes/CIP homology) region followed by a coiled-coil stretch cc1 is unknown. Here, we show that the FCH region is necessary and sufficient for membrane association of NOSTRIN, whereas the Cdc15 domain further specifies subcellular distribution of the protein. Thus, the FCH region and the Cdc15 domain fulfill complementary functions in subcellular targeting of NOSTRIN.
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Affiliation(s)
- Ann Icking
- Institute of Biochemistry II, University of Frankfurt Medical School, Theodor-Stern-Kai 7, D-60590 Frankfurt, Germany
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199
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Abstract
A motile cell, when stimulated, shows a dramatic increase in the activity of its membrane, manifested by the appearance of dynamic membrane structures such as lamellipodia, filopodia, and membrane ruffles. The external stimulus turns on membrane bound activators, like Cdc42 and PIP2, which cause increased branching and polymerization of the actin cytoskeleton in their vicinity leading to a local protrusive force on the membrane. The emergence of the complex membrane structures is a result of the coupling between the dynamics of the membrane, the activators, and the protrusive forces. We present a simple model that treats the dynamics of a membrane under the action of actin polymerization forces that depend on the local density of freely diffusing activators on the membrane. We show that, depending on the spontaneous membrane curvature associated with the activators, the resulting membrane motion can be wavelike, corresponding to membrane ruffling and actin waves, or unstable, indicating the tendency of filopodia to form. Our model also quantitatively explains a variety of related experimental observations and makes several testable predictions.
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Affiliation(s)
- Nir S Gov
- Department of Chemical Physics, The Weizmann Institute of Science, Rehovot, Israel 76100.
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200
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Nakada-Tsukui K, Saito-Nakano Y, Ali V, Nozaki T. A retromerlike complex is a novel Rab7 effector that is involved in the transport of the virulence factor cysteine protease in the enteric protozoan parasite Entamoeba histolytica. Mol Biol Cell 2005; 16:5294-303. [PMID: 16120649 PMCID: PMC1266427 DOI: 10.1091/mbc.e05-04-0283] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Vesicular trafficking plays an important role in a virulence mechanism of the enteric protozoan parasite Entamoeba histolytica as secreted and lysosomal cysteine protease (CP) contributes to both cytolysis of tissues and degradation of internalized host cells. Despite the primary importance of intracellular sorting in pathogenesis, the molecular mechanism of CP trafficking remains largely unknown. In this report we demonstrate that transport of CP is regulated through a specific interaction of Rab7A small GTPase (EhRab7A) with the retromerlike complex. The amoebic retromerlike complex composed of Vps26, Vps29, and Vps35 was identified as EhRab7A-binding proteins. The amoebic retromerlike complex specifically bound to GTP-EhRab7A, but not GDP-EhRab7A through the direct binding via the carboxy terminus of EhVps26. In erythrophagocytosis the retromerlike complex was recruited to prephagosomal vacuoles, the unique preparatory vacuole of digestive enzymes, and later to phagosomes. This dynamism was indistinguishable from that of EhRab7A, and consistent with the premise that the retromerlike complex is involved in the retrograde transport of putative hydrolase receptor(s) from preparatory vacuoles and phagosomes to the Golgi apparatus. EhRab7A overexpression caused enlargement of lysosomes and decrease of the cellular CP activity. The reduced CP activity was restored by the coexpression of EhVps26, implying that the EhRab7A-mediated transport of CP to phagosomes is regulated by the retromerlike complex.
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Affiliation(s)
- Kumiko Nakada-Tsukui
- Department of Parasitology, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
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