title: Trs65p, a subunit of the Ypt1p GEF TRAPPII, interacts with the Arf1p exchange factor Gea2p to facilitate COPI-mediated vesicle traffic.
abstract: The TRAPP complexes are multimeric guanine exchange factors (GEFs) for the Rab GTPase Ypt1p. The three complexes (TRAPPI, TRAPPII, and TRAPPIII) share a core of common subunits required for GEF activity, as well as unique subunits (Trs130p, Trs120p, Trs85p, and Trs65p) that redirect the GEF from the endoplasmic reticulum-Golgi pathway to different cellular locations where TRAPP mediates distinct membrane trafficking events. Roles for three of the four unique TRAPP subunits have been described before; however, the role of the TRAPPII-specific subunit Trs65p has remained elusive. Here we demonstrate that Trs65p directly binds to the C-terminus of the Arf1p exchange factor Gea2p and provide in vivo evidence that this interaction is physiologically relevant. Gea2p and TRAPPII also bind to the yeast orthologue of the γ subunit of the COPI coat complex (Sec21p), a known Arf1p effector. These and previous findings reveal that TRAPPII is part of an Arf1p GEF-effector loop that appears to play a role in recruiting or stabilizing TRAPPII to membranes. In support of this proposal, we show that TRAPPII is more soluble in an arf1Δ mutant.
authors.affiliation: Department of Cellular and Molecular Medicine, Howard Hughes Medical Institute, University of California at San Diego, La Jolla, CA 92093-0668, USA.
authors.forename: Shuliang
authors.initials: S
authors.lastname: Chen
authors.forename: Huaqing
authors.initials: H
authors.lastname: Cai
authors.forename: Sei-Kyoung
authors.initials: SK
authors.lastname: Park
authors.forename: Shekar
authors.initials: S
authors.lastname: Menon
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Jackson
authors.forename: Susan
authors.initials: S
authors.lastname: Ferro-Novick
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000235:genetics / Q000378:metabolism*; D022181:COP-Coated Vesicles / Q000235:genetics* / Q000378:metabolism; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012995:Solubility; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018118:Chloride Channels; C121632:GEA2 protein, S cerevisiae; C089713:GEF1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D029701:Saccharomyces cerevisiae Proteins; C080595:TRS65 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C406327:transport protein particle, TRAPP; C060755:YPT1 protein, S cerevisiae; D020823:ADP-Ribosylation Factor 1; D020691:rab GTP-Binding Proteins