The Experts below are selected from a list of 99 Experts worldwide ranked by ideXlab platform
Nia J Bryant - One of the best experts on this subject based on the ideXlab platform.
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sorting of glut4 into its insulin sensitive store requires the sec1 Munc18 Protein mvps45
Molecular Biology of the Cell, 2013Co-Authors: Jennifer Roccisana, Nia J Bryant, Jessica B A Sadler, Gwyn W. GouldAbstract:Insulin stimulates glucose transport in fat and muscle cells by regulating delivery of the facilitative glucose transporter, glucose transporter isoform 4 (GLUT4), to the plasma membrane. In the absence of insulin, GLUT4 is sequestered away from the general recycling endosomal pathway into specialized vesicles, referred to as GLUT4-storage vesicles. Understanding the sorting of GLUT4 into this store is a major challenge. Here we examine the role of the Sec1/Munc18 Protein mVps45 in GLUT4 trafficking. We show that mVps45 is up-regulated upon differentiation of 3T3-L1 fibroblasts into adipocytes and is expressed at stoichiometric levels with its cognate target–soluble N-ethylmaleimide–sensitive factor attachment Protein receptor, syntaxin 16. Depletion of mVps45 in 3T3-L1 adipocytes results in decreased GLUT4 levels and impaired insulin-stimulated glucose transport. Using subcellular fractionation and an in vitro assay for GLUT4-storage vesicle formation, we show that mVps45 is required to correctly traffic GLUT4 into this compartment. Collectively our data reveal a crucial role for mVps45 in the delivery of GLUT4 into its specialized, insulin-regulated compartment.
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arabidopsis sec1 Munc18 Protein sec11 is a competitive and dynamic modulator of snare binding and syp121 dependent vesicle traffic
The Plant Cell, 2013Co-Authors: Rucha Karnik, Nia J Bryant, Christopher Grefen, Robert Bayne, Annegret Honsbein, Tim Kohler, Dimitrios Kioumourtzoglou, Mary Williams, Michael R BlattAbstract:The Arabidopsis thaliana Qa-SNARE SYP121 (=SYR1/PEN1) drives vesicle traffic at the plasma membrane of cells throughout the vegetative plant. It facilitates responses to drought, to the water stress hormone abscisic acid, and to pathogen attack, and it is essential for recovery from so-called programmed stomatal closure. How SYP121-mediated traffic is regulated is largely unknown, although it is thought to depend on formation of a fusion-competent SNARE core complex with the cognate partners VAMP721 and SNAP33. Like SYP121, the Arabidopsis Sec1/Munc18 Protein SEC11 (=KEULE) is expressed throughout the vegetative plant. We find that SEC11 binds directly with SYP121 both in vitro and in vivo to affect secretory traffic. Binding occurs through two distinct modes, one requiring only SEC11 and SYP121 and the second dependent on assembly of a complex with VAMP721 and SNAP33. SEC11 competes dynamically for SYP121 binding with SNAP33 and VAMP721, and this competition is predicated by SEC11 association with the N terminus of SYP121. These and additional data are consistent with a model in which SYP121-mediated vesicle fusion is regulated by an unusual “handshaking” mechanism of concerted SEC11 debinding and rebinding. They also implicate one or more factors that alter or disrupt SEC11 association with the SYP121 N terminus as an early step initiating SNARE complex formation.
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the sec1 Munc18 Protein vps45 regulates cellular levels of its snare binding partners tlg2 and snc2 in saccharomyces cerevisiae
PLOS ONE, 2012Co-Authors: Scott G Shanks, Lindsay N Carpp, Marion S Struthers, Rebecca K Mccann, Nia J BryantAbstract:Intracellular membrane trafficking pathways must be tightly regulated to ensure proper functioning of all eukaryotic cells. Central to membrane trafficking is the formation of specific SNARE (soluble N-ethylmeleimide-sensitive factor attachment Protein receptor) complexes between Proteins on opposing lipid bilayers. The Sec1/Munc18 (SM) family of Proteins play an essential role in SNARE-mediated membrane fusion, and like the SNAREs are conserved through evolution from yeast to humans. The SM Protein Vps45 is required for the formation of yeast endosomal SNARE complexes and is thus essential for traffic through the endosomal system. Here we report that, in addition to its role in regulating SNARE complex assembly, Vps45 regulates cellular levels of its SNARE binding partners: the syntaxin Tlg2 and the v-SNARE Snc2: Cells lacking Vps45 have reduced cellular levels of Tlg2 and Snc2; and elevation of Vps45 levels results in concomitant increases in the levels of both Tlg2 and Snc2. As well as regulating traffic through the endosomal system, the Snc v-SNAREs are also required for exocytosis. Unlike most vps mutants, cells lacking Vps45 display multiple growth phenotypes. Here we report that these can be reversed by selectively restoring Snc2 levels in vps45 mutant cells. Our data indicate that as well as functioning as part of the machinery that controls SNARE complex assembly, Vps45 also plays a key role in determining the levels of its cognate SNARE Proteins; another key factor in regulation of membrane traffic.
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tyrosine phosphorylation of Munc18c on residue 521 abrogates binding to syntaxin 4
BMC Biochemistry, 2011Co-Authors: Nia J Bryant, Veronica Aran, Gwyn W. GouldAbstract:Background Insulin stimulates exocytosis of GLUT4 from an intracellular store to the cell surface of fat and muscle cells. Fusion of GLUT4-containing vesicles with the plasma membrane requires the SNARE Proteins Syntaxin 4, VAMP2 and the regulatory Sec1/Munc18 Protein, Munc18c. Syntaxin 4 and Munc18c form a complex that is disrupted upon insulin treatment of adipocytes. Munc18c is tyrosine phosphorylated in response to insulin in these cells. Here, we directly test the hypothesis that tyrosine phosphorylation of Munc18c is responsible for the observed insulin-dependent abrogation of binding between Munc18c and Syntaxin 4.
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the sec1p Munc18 Protein vps45p binds its cognate snare Proteins via two distinct modes
Journal of Cell Biology, 2006Co-Authors: Lindsay N Carpp, Leonora F Ciufo, Scott G Shanks, Alan Boyd, Nia J BryantAbstract:Sec1p/Munc18 (SM) Proteins are essential for SNARE-mediated membrane trafficking. The formulation of unifying hypotheses for the function of the SM Protein family has been hampered by the observation that two of its members bind their cognate syntaxins (Sxs) in strikingly different ways. The SM Protein Vps45p binds its Sx Tlg2p in a manner analogous to that captured by the Sly1p–Sed5p crystal structure, whereby the NH2-terminal peptide of the Sx inserts into a hydrophobic pocket on the outer face of domain I of the SM Protein. In this study, we report that although this mode of interaction is critical for the binding of Vps45p to Tlg2p, the SM Protein also binds Tlg2p-containing SNARE complexes via a second mode that involves neither the NH2 terminus of Tlg2p nor the region of Vps45p that facilitates this interaction. Our findings point to the possibility that SM Proteins interact with their cognate SNARE Proteins through distinct mechanisms at different stages in the SNARE assembly/disassembly cycle.
Frederick M Hughson - One of the best experts on this subject based on the ideXlab platform.
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the sec1 Munc18 Protein vps45 holds the qa snare tlg2 in an open conformation
eLife, 2020Co-Authors: Travis J Eisemann, Frederick Allen, Kelly Lau, Gregory R Shimamura, Philip D Jeffrey, Frederick M HughsonAbstract:Fusion of intracellular trafficking vesicles is mediated by the assembly of SNARE Proteins into membrane-bridging complexes. SNARE-mediated membrane fusion requires Sec1/Munc18-family (SM) Proteins, SNARE chaperones that can function as templates to catalyze SNARE complex assembly. Paradoxically, the SM Protein Munc18-1 traps the Qa-SNARE Protein syntaxin-1 in an autoinhibited closed conformation. Here we present the structure of a second SM-Qa-SNARE complex, Vps45-Tlg2. Strikingly, Vps45 holds Tlg2 in an open conformation, with its SNARE motif disengaged from its Habc domain and its linker region unfolded. The domain 3a helical hairpin of Vps45 is unfurled, exposing the presumptive R-SNARE binding site to allow template complex formation. Although Tlg2 has a pronounced tendency to form homo-tetramers, Vps45 can rescue Tlg2 tetramers into stoichiometric Vps45-Tlg2 complexes. Our findings demonstrate that SM Proteins can engage Qa-SNAREs using at least two different modes, one in which the SNARE is closed and one in which it is open.
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the sec1 Munc18 Protein vps45 holds the qa snare tlg2 in an open conformation
bioRxiv, 2020Co-Authors: Travis J Eisemann, Frederick Allen, Kelly Lau, Gregory R Shimamura, Philip D Jeffrey, Frederick M HughsonAbstract:Fusion of intracellular trafficking vesicles is mediated by the assembly of soluble N-ethylmaleimide-sensitive fusion Protein receptors (SNAREs) to form membrane-bridging complexes. Also required for SNARE-mediated membrane fusion are Sec1/Munc18-family (SM) Proteins, SNARE chaperones that can function as templates to catalyze SNARE complex assembly. In the paradigmatic structure of an SM−SNARE complex, Munc18-1 bound to the Qa-SNARE syntaxin 1, the SNARE Protein is trapped in an autoinhibited closed conformation that prevents it from entering into SNARE complexes. Here, we present the structure of a second SM−Qa-SNARE complex, Vps45−Tlg2. Strikingly, Vps45 holds Tlg2 in an open conformation, with its SNARE motif disengaged from its three-helical Habc domain and its linker region unfolded. The domain 3a helical hairpin of Vps45 is unfurled, exposing the presumptive R-SNARE binding site to allow template complex formation. Tlg2 has a pronounced tendency to self-associate via its SNARE motif, and we demonstrate that Vps45 can rescue Tlg2 oligomers into stoichiometric Vps45−Tlg2 complexes. Our findings demonstrate that SM Proteins can engage Qa-SNAREs using at least two different modes, one in which the SNARE is closed and one in which it is open.
Scott G Shanks - One of the best experts on this subject based on the ideXlab platform.
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the sec1 Munc18 Protein vps45 regulates cellular levels of its snare binding partners tlg2 and snc2 in saccharomyces cerevisiae
PLOS ONE, 2012Co-Authors: Scott G Shanks, Lindsay N Carpp, Marion S Struthers, Rebecca K Mccann, Nia J BryantAbstract:Intracellular membrane trafficking pathways must be tightly regulated to ensure proper functioning of all eukaryotic cells. Central to membrane trafficking is the formation of specific SNARE (soluble N-ethylmeleimide-sensitive factor attachment Protein receptor) complexes between Proteins on opposing lipid bilayers. The Sec1/Munc18 (SM) family of Proteins play an essential role in SNARE-mediated membrane fusion, and like the SNAREs are conserved through evolution from yeast to humans. The SM Protein Vps45 is required for the formation of yeast endosomal SNARE complexes and is thus essential for traffic through the endosomal system. Here we report that, in addition to its role in regulating SNARE complex assembly, Vps45 regulates cellular levels of its SNARE binding partners: the syntaxin Tlg2 and the v-SNARE Snc2: Cells lacking Vps45 have reduced cellular levels of Tlg2 and Snc2; and elevation of Vps45 levels results in concomitant increases in the levels of both Tlg2 and Snc2. As well as regulating traffic through the endosomal system, the Snc v-SNAREs are also required for exocytosis. Unlike most vps mutants, cells lacking Vps45 display multiple growth phenotypes. Here we report that these can be reversed by selectively restoring Snc2 levels in vps45 mutant cells. Our data indicate that as well as functioning as part of the machinery that controls SNARE complex assembly, Vps45 also plays a key role in determining the levels of its cognate SNARE Proteins; another key factor in regulation of membrane traffic.
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the sec1p Munc18 Protein vps45p binds its cognate snare Proteins via two distinct modes
Journal of Cell Biology, 2006Co-Authors: Lindsay N Carpp, Leonora F Ciufo, Scott G Shanks, Alan Boyd, Nia J BryantAbstract:Sec1p/Munc18 (SM) Proteins are essential for SNARE-mediated membrane trafficking. The formulation of unifying hypotheses for the function of the SM Protein family has been hampered by the observation that two of its members bind their cognate syntaxins (Sxs) in strikingly different ways. The SM Protein Vps45p binds its Sx Tlg2p in a manner analogous to that captured by the Sly1p–Sed5p crystal structure, whereby the NH2-terminal peptide of the Sx inserts into a hydrophobic pocket on the outer face of domain I of the SM Protein. In this study, we report that although this mode of interaction is critical for the binding of Vps45p to Tlg2p, the SM Protein also binds Tlg2p-containing SNARE complexes via a second mode that involves neither the NH2 terminus of Tlg2p nor the region of Vps45p that facilitates this interaction. Our findings point to the possibility that SM Proteins interact with their cognate SNARE Proteins through distinct mechanisms at different stages in the SNARE assembly/disassembly cycle.
Travis J Eisemann - One of the best experts on this subject based on the ideXlab platform.
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the sec1 Munc18 Protein vps45 holds the qa snare tlg2 in an open conformation
eLife, 2020Co-Authors: Travis J Eisemann, Frederick Allen, Kelly Lau, Gregory R Shimamura, Philip D Jeffrey, Frederick M HughsonAbstract:Fusion of intracellular trafficking vesicles is mediated by the assembly of SNARE Proteins into membrane-bridging complexes. SNARE-mediated membrane fusion requires Sec1/Munc18-family (SM) Proteins, SNARE chaperones that can function as templates to catalyze SNARE complex assembly. Paradoxically, the SM Protein Munc18-1 traps the Qa-SNARE Protein syntaxin-1 in an autoinhibited closed conformation. Here we present the structure of a second SM-Qa-SNARE complex, Vps45-Tlg2. Strikingly, Vps45 holds Tlg2 in an open conformation, with its SNARE motif disengaged from its Habc domain and its linker region unfolded. The domain 3a helical hairpin of Vps45 is unfurled, exposing the presumptive R-SNARE binding site to allow template complex formation. Although Tlg2 has a pronounced tendency to form homo-tetramers, Vps45 can rescue Tlg2 tetramers into stoichiometric Vps45-Tlg2 complexes. Our findings demonstrate that SM Proteins can engage Qa-SNAREs using at least two different modes, one in which the SNARE is closed and one in which it is open.
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the sec1 Munc18 Protein vps45 holds the qa snare tlg2 in an open conformation
bioRxiv, 2020Co-Authors: Travis J Eisemann, Frederick Allen, Kelly Lau, Gregory R Shimamura, Philip D Jeffrey, Frederick M HughsonAbstract:Fusion of intracellular trafficking vesicles is mediated by the assembly of soluble N-ethylmaleimide-sensitive fusion Protein receptors (SNAREs) to form membrane-bridging complexes. Also required for SNARE-mediated membrane fusion are Sec1/Munc18-family (SM) Proteins, SNARE chaperones that can function as templates to catalyze SNARE complex assembly. In the paradigmatic structure of an SM−SNARE complex, Munc18-1 bound to the Qa-SNARE syntaxin 1, the SNARE Protein is trapped in an autoinhibited closed conformation that prevents it from entering into SNARE complexes. Here, we present the structure of a second SM−Qa-SNARE complex, Vps45−Tlg2. Strikingly, Vps45 holds Tlg2 in an open conformation, with its SNARE motif disengaged from its three-helical Habc domain and its linker region unfolded. The domain 3a helical hairpin of Vps45 is unfurled, exposing the presumptive R-SNARE binding site to allow template complex formation. Tlg2 has a pronounced tendency to self-associate via its SNARE motif, and we demonstrate that Vps45 can rescue Tlg2 oligomers into stoichiometric Vps45−Tlg2 complexes. Our findings demonstrate that SM Proteins can engage Qa-SNAREs using at least two different modes, one in which the SNARE is closed and one in which it is open.
Kelly Lau - One of the best experts on this subject based on the ideXlab platform.
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the sec1 Munc18 Protein vps45 holds the qa snare tlg2 in an open conformation
eLife, 2020Co-Authors: Travis J Eisemann, Frederick Allen, Kelly Lau, Gregory R Shimamura, Philip D Jeffrey, Frederick M HughsonAbstract:Fusion of intracellular trafficking vesicles is mediated by the assembly of SNARE Proteins into membrane-bridging complexes. SNARE-mediated membrane fusion requires Sec1/Munc18-family (SM) Proteins, SNARE chaperones that can function as templates to catalyze SNARE complex assembly. Paradoxically, the SM Protein Munc18-1 traps the Qa-SNARE Protein syntaxin-1 in an autoinhibited closed conformation. Here we present the structure of a second SM-Qa-SNARE complex, Vps45-Tlg2. Strikingly, Vps45 holds Tlg2 in an open conformation, with its SNARE motif disengaged from its Habc domain and its linker region unfolded. The domain 3a helical hairpin of Vps45 is unfurled, exposing the presumptive R-SNARE binding site to allow template complex formation. Although Tlg2 has a pronounced tendency to form homo-tetramers, Vps45 can rescue Tlg2 tetramers into stoichiometric Vps45-Tlg2 complexes. Our findings demonstrate that SM Proteins can engage Qa-SNAREs using at least two different modes, one in which the SNARE is closed and one in which it is open.
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the sec1 Munc18 Protein vps45 holds the qa snare tlg2 in an open conformation
bioRxiv, 2020Co-Authors: Travis J Eisemann, Frederick Allen, Kelly Lau, Gregory R Shimamura, Philip D Jeffrey, Frederick M HughsonAbstract:Fusion of intracellular trafficking vesicles is mediated by the assembly of soluble N-ethylmaleimide-sensitive fusion Protein receptors (SNAREs) to form membrane-bridging complexes. Also required for SNARE-mediated membrane fusion are Sec1/Munc18-family (SM) Proteins, SNARE chaperones that can function as templates to catalyze SNARE complex assembly. In the paradigmatic structure of an SM−SNARE complex, Munc18-1 bound to the Qa-SNARE syntaxin 1, the SNARE Protein is trapped in an autoinhibited closed conformation that prevents it from entering into SNARE complexes. Here, we present the structure of a second SM−Qa-SNARE complex, Vps45−Tlg2. Strikingly, Vps45 holds Tlg2 in an open conformation, with its SNARE motif disengaged from its three-helical Habc domain and its linker region unfolded. The domain 3a helical hairpin of Vps45 is unfurled, exposing the presumptive R-SNARE binding site to allow template complex formation. Tlg2 has a pronounced tendency to self-associate via its SNARE motif, and we demonstrate that Vps45 can rescue Tlg2 oligomers into stoichiometric Vps45−Tlg2 complexes. Our findings demonstrate that SM Proteins can engage Qa-SNAREs using at least two different modes, one in which the SNARE is closed and one in which it is open.
