title: p125A exists as part of the mammalian Sec13/Sec31 COPII subcomplex to facilitate ER-Golgi transport.
abstract: Coat protein II (COPII)-mediated export from the endoplasmic reticulum (ER) involves sequential recruitment of COPII complex components, including the Sar1 GTPase, the Sec23/Sec24 subcomplex, and the Sec13/Sec31 subcomplex. p125A was originally identified as a Sec23A-interacting protein. Here we demonstrate that p125A also interacts with the C-terminal region of Sec31A. The Sec31A-interacting domain of p125A is between residues 260-600, and is therefore a distinct domain from that required for interaction with Sec23A. Gel filtration and immunodepletion studies suggest that the majority of cytosolic p125A exists as a ternary complex with the Sec13/Sec31A subcomplex, suggesting that Sec 13, Sec31A, and p125A exist in the cytosol primarily as preassembled Sec13/Sec31A/p125A heterohexamers. Golgi morphology and protein export from the ER were affected in p125A-silenced cells. Our results suggest that p125A is part of the Sec13/Sec31A subcomplex and facilitates ER export in mammalian cells.
authors.affiliation: Cancer and Developmental Cell Biology Division, Institute of Molecular and Cell Biology, Singapore 138673, Singapore.
authors.forename: Yan Shan
authors.initials: YS
authors.lastname: Ong
authors.forename: Bor Luen
authors.initials: BL
authors.lastname: Tang
authors.forename: Li Shen
authors.initials: LS
authors.lastname: Loo
authors.forename: Wanjin
authors.initials: W
authors.lastname: Hong
mesh_terms: D022181:COP-Coated Vesicles / Q000737:chemistry* / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016601:RNA-Binding Proteins; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D016601:RNA-Binding Proteins; C120603:SEC23IP protein, human; D033921:Vesicular Transport Proteins