title: Intrinsic tethering activity of endosomal Rab proteins.
abstract: Rab small G proteins control membrane trafficking events required for many processes including secretion, lipid metabolism, antigen presentation and growth factor signaling. Rabs recruit effectors that mediate diverse functions including vesicle tethering and fusion. However, many mechanistic questions about Rab-regulated vesicle tethering are unresolved. Using chemically defined reaction systems, we discovered that Vps21, a Saccharomyces cerevisiae ortholog of mammalian endosomal Rab5, functions in trans with itself and with at least two other endosomal Rabs to directly mediate GTP-dependent tethering. Vps21-mediated tethering was stringently and reversibly regulated by an upstream activator, Vps9, and an inhibitor, Gyp1, which were sufficient to drive dynamic cycles of tethering and detethering. These experiments reveal a previously undescribed mode of tethering by endocytic Rabs. In our working model, the intrinsic tethering capacity Vps21 operates in concert with conventional effectors and SNAREs to drive efficient docking and fusion.
authors.affiliation: Department of Biochemistry, University of Washington School of Medicine, Seattle, Washington, USA.
authors.forename: Sheng-Ying
authors.initials: SY
authors.lastname: Lo
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Brett
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Plemel
authors.forename: Marissa
authors.initials: M
authors.lastname: Vignali
authors.forename: Stanley
authors.initials: S
authors.lastname: Fields
authors.forename: Tamir
authors.initials: T
authors.lastname: Gonen
authors.forename: Alexey J
authors.initials: AJ
authors.lastname: Merz
mesh_terms: D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D011485:Protein Binding; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; C416529:GYP1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D008081:Liposomes; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C099285:VPS9 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C120216:Ypt10 protein, S cerevisiae; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; C086866:VPS21 protein, S cerevisiae; C086868:YPT53 protein, S cerevisiae; D020691:rab GTP-Binding Proteins