title: A trs20 mutation that mimics an SEDT-causing mutation blocks selective and non-selective autophagy: a model for TRAPP III organization.
abstract: TRAPP is a multisubunit complex that functions in membrane traffic. Mutations in the mammalian TRAPP protein C2 are linked to the skeletal disorder spondyloepiphyseal dysplasia tarda (SEDT) that is thought to arise from an inability to secrete procollagen from the endoplasmic reticulum. Here, we show that C2 binds to the SNARE protein Syntaxin 5 and this interaction is weakened by an SEDT-causing missense mutation (D47Y). Interestingly, the equivalent mutation (D46Y) in the yeast C2 homolog Trs20p does not block anterograde traffic but did affect endocytosis. The trs20D46Y mutation interfered with the interaction between Trs20p and Trs85p (TRAPP III-specific subunit), Trs120p and Trs130p (TRAPP II-specific subunits). Size exclusion chromatography suggested that this yeast mutation destabilized the TRAPP III complex that is involved in autophagy. We further show that this mutation blocks both the selective cytosol-to-vacuole (cvt) pathway as well as non-selective autophagy. We demonstrate that the apparent molecular size of the TRAPP III complex is dependent upon membranes, and that the presence of TRAPP III is dependent upon Atg9p. Finally, we demonstrate that lipidated Bet3p is enriched in TRAPP III and that lipidation increases the efficiency of autophagy. Our study suggests that Trs20p acts as an adaptor for Trs85p and Trs120p and reveals complexities in TRAPP III assembly and function. The implications of C2D47Y in SEDT are discussed.
authors.affiliation: Department of Biology, Concordia University, Montreal, Quebec, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Brunet
authors.forename: Nassim
authors.initials: N
authors.lastname: Shahrzad
authors.forename: Djenann
authors.initials: D
authors.lastname: Saint-Dic
authors.forename: Hartley
authors.initials: H
authors.lastname: Dutczak
authors.forename: Michael
authors.initials: M
authors.lastname: Sacher
mesh_terms: D001343:Autophagy / Q000235:genetics*; D002460:Cell Line; D045744:Cell Line, Tumor; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D040181:Genetic Diseases, X-Linked / Q000235:genetics* / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense / Q000235:genetics*; D010009:Osteochondrodysplasias / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; C120759:TRAPPC2 protein, human; D014157:Transcription Factors; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP
keywords: Atg9p; Bet3p; SEDT; TRAPP; Trs20p; Trs85p; autophagy