title: The Sec1/Munc18 protein Vps45 regulates cellular levels of its SNARE binding partners Tlg2 and Snc2 in Saccharomyces cerevisiae.
abstract: 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.
authors.affiliation: Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell & Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Scott G
authors.initials: SG
authors.lastname: Shanks
authors.forename: Lindsay N
authors.initials: LN
authors.lastname: Carpp
authors.forename: Marion S
authors.initials: MS
authors.lastname: Struthers
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: McCann
authors.forename: Nia J
authors.initials: NJ
authors.lastname: Bryant
mesh_terms: D042541:Intracellular Space / Q000378:metabolism; D051938:Munc18 Proteins / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D011485:Protein Binding; D055550:Protein Stability; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D050683:R-SNARE Proteins / Q000378:metabolism*; D050600:SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051938:Munc18 Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; C497931:SEC1 protein, S cerevisiae; D050600:SNARE Proteins; C083242:SNC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C112252:TLG2 protein, S cerevisiae; C092934:VPS45 protein, S cerevisiae; D033921:Vesicular Transport Proteins