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A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole

Protein transport in eukaryotic cells requires the selective docking and fusion of transport intermediates with the appropriate target membrane. t-SNARE molecules that are associated with distinct intracellular compartments may serve as receptors for transport vesicle docking and membrane fusion thr...

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Detalles Bibliográficos
Autores principales: Darsow, Tamara, Rieder, Stephanie E., Emr, Scott D.
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1997
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2141632/
https://www.ncbi.nlm.nih.gov/pubmed/9245783
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author Darsow, Tamara
Rieder, Stephanie E.
Emr, Scott D.
author_facet Darsow, Tamara
Rieder, Stephanie E.
Emr, Scott D.
author_sort Darsow, Tamara
collection PubMed
description Protein transport in eukaryotic cells requires the selective docking and fusion of transport intermediates with the appropriate target membrane. t-SNARE molecules that are associated with distinct intracellular compartments may serve as receptors for transport vesicle docking and membrane fusion through interactions with specific v-SNARE molecules on vesicle membranes, providing the inherent specificity of these reactions. VAM3 encodes a 283–amino acid protein that shares homology with the syntaxin family of t-SNARE molecules. Polyclonal antiserum raised against Vam3p recognized a 35-kD protein that was associated with vacuolar membranes by subcellular fractionation. Null mutants of vam3 exhibited defects in the maturation of multiple vacuolar proteins and contained numerous aberrant membrane-enclosed compartments. To study the primary function of Vam3p, a temperature-sensitive allele of vam3 was generated (vam3(tsf)). Upon shifting the vam3(tsf) mutant cells to nonpermissive temperature, an immediate block in protein transport through two distinct biosynthetic routes to the vacuole was observed: transport via both the carboxypeptidase Y pathway and the alkaline phosphatase pathway was inhibited. In addition, vam3(tsf) cells also exhibited defects in autophagy. Both the delivery of aminopeptidase I and the docking/ fusion of autophagosomes with the vacuole were defective at high temperature. Upon temperature shift, vam3(tsf) cells accumulated novel membrane compartments, including multivesicular bodies, which may represent blocked transport intermediates. Genetic interactions between VAM3 and a SEC1 family member, VPS33, suggest the two proteins may act together to direct the docking and/or fusion of multiple transport intermediates with the vacuole. Thus, Vam3p appears to function as a multispecificity receptor in heterotypic membrane docking and fusion reactions with the vacuole. Surprisingly, we also found that overexpression of the endosomal t-SNARE, Pep12p, suppressed vam3Δ mutant phenotypes and, likewise, overexpression of Vam3p suppressed the pep12Δ mutant phenotypes. This result indicated that SNAREs alone do not define the specificity of vesicle docking reactions.
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spelling pubmed-21416322008-05-01 A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole Darsow, Tamara Rieder, Stephanie E. Emr, Scott D. J Cell Biol Article Protein transport in eukaryotic cells requires the selective docking and fusion of transport intermediates with the appropriate target membrane. t-SNARE molecules that are associated with distinct intracellular compartments may serve as receptors for transport vesicle docking and membrane fusion through interactions with specific v-SNARE molecules on vesicle membranes, providing the inherent specificity of these reactions. VAM3 encodes a 283–amino acid protein that shares homology with the syntaxin family of t-SNARE molecules. Polyclonal antiserum raised against Vam3p recognized a 35-kD protein that was associated with vacuolar membranes by subcellular fractionation. Null mutants of vam3 exhibited defects in the maturation of multiple vacuolar proteins and contained numerous aberrant membrane-enclosed compartments. To study the primary function of Vam3p, a temperature-sensitive allele of vam3 was generated (vam3(tsf)). Upon shifting the vam3(tsf) mutant cells to nonpermissive temperature, an immediate block in protein transport through two distinct biosynthetic routes to the vacuole was observed: transport via both the carboxypeptidase Y pathway and the alkaline phosphatase pathway was inhibited. In addition, vam3(tsf) cells also exhibited defects in autophagy. Both the delivery of aminopeptidase I and the docking/ fusion of autophagosomes with the vacuole were defective at high temperature. Upon temperature shift, vam3(tsf) cells accumulated novel membrane compartments, including multivesicular bodies, which may represent blocked transport intermediates. Genetic interactions between VAM3 and a SEC1 family member, VPS33, suggest the two proteins may act together to direct the docking and/or fusion of multiple transport intermediates with the vacuole. Thus, Vam3p appears to function as a multispecificity receptor in heterotypic membrane docking and fusion reactions with the vacuole. Surprisingly, we also found that overexpression of the endosomal t-SNARE, Pep12p, suppressed vam3Δ mutant phenotypes and, likewise, overexpression of Vam3p suppressed the pep12Δ mutant phenotypes. This result indicated that SNAREs alone do not define the specificity of vesicle docking reactions. The Rockefeller University Press 1997-08-11 /pmc/articles/PMC2141632/ /pubmed/9245783 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Article
Darsow, Tamara
Rieder, Stephanie E.
Emr, Scott D.
A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole
title A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole
title_full A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole
title_fullStr A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole
title_full_unstemmed A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole
title_short A Multispecificity Syntaxin Homologue, Vam3p, Essential for Autophagic and Biosynthetic Protein Transport to the Vacuole
title_sort multispecificity syntaxin homologue, vam3p, essential for autophagic and biosynthetic protein transport to the vacuole
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2141632/
https://www.ncbi.nlm.nih.gov/pubmed/9245783
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