TRAPPI tethers COPII vesicles by binding the coat subunit Sec23.
The budding of endoplasmic reticulum (ER)-derived vesicles is dependent on the COPII coat complex. Coat assembly is initiated when Sar1-GTP recruits the cargo adaptor complex, Sec23/Sec24, by binding to its GTPase-activating protein (GAP) Sec23 (ref. 2). This leads to the capture of transmembrane cargo by Sec24 (refs 3, 4) before the coat is polymerized by the Sec13/Sec31 complex. The initial interaction of a vesicle with its target membrane is mediated by tethers. We report here that in yeast and mammalian cells the tethering complex TRAPPI (ref. 7) binds to the coat subunit Sec23. This event requires the Bet3 subunit. In vitro studies demonstrate that the interaction between Sec23 and Bet3 targets TRAPPI to COPII vesicles to mediate vesicle tethering. We propose that the binding of TRAPPI to Sec23 marks a coated vesicle for fusion with another COPII vesicle or the Golgi apparatus. An implication of these findings is that the intracellular destination of a transport vesicle may be determined in part by its coat and its associated cargo.
Cai
Huaqing
H
Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06519, USA.
Yu
Sidney
S
Menon
Shekar
S
Cai
Yiying
Y
Lazarova
Darina
D
Fu
Chunmei
C
Reinisch
Karin
K
Hay
Jesse C
JC
Ferro-Novick
Susan
S
D000818:Animals; D022181:COP-Coated Vesicles / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D020690:GTPase-Activating Proteins; D006056:Golgi Apparatus / Q000378:metabolism; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
C098389:BET3 protein, S cerevisiae; D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; C079037:SEC23 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins