title: Smy2p participates in COPII vesicle formation through the interaction with Sec23p/Sec24p subcomplex.
abstract: The coat protein complex II (COPII) is essential for vesicle formation from the endoplasmic reticulum (ER) and is composed of two heterodimeric subcomplexes, Sec23p/Sec24p and Sec13p/Sec31p, and the small guanosine triphosphatase Sar1p. In an effort to identify novel factors that may participate in COPII vesicle formation, we isolated SMY2, a yeast gene encoding a protein of unknown function, as a multicopy suppressor of the temperature-sensitive sec24-20 mutant. We found that even a low-copy expression of SMY2 was sufficient for the suppression of the sec24-20 phenotypes, and the chromosomal deletion of SMY2 led to a severe growth defect in the sec24-20 background. In addition, SMY2 exhibited genetic interactions with several other genes involved in the ER-to-Golgi transport. Subcellular fractionation analysis showed that Smy2p was a peripheral membrane protein fractionating together with COPII components. However, Smy2p was not loaded onto COPII vesicles generated in vitro. Interestingly, coimmunoprecipitation between Smy2p and the Sec23p/Sec24p subcomplex was specifically observed in sec23-1 and sec24-20 backgrounds, suggesting that this interaction was a prerequisite for the suppression of the sec24-20 phenotypes by overexpression of SMY2. We propose that Smy2p is located on the surface of the ER and facilitates COPII vesicle formation through the interaction with Sec23p/Sec24p subcomplex.
authors.affiliation: Molecular Membrane Biology Laboratory, RIKEN Discovery Research Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Higashio
authors.forename: Ken
authors.initials: K
authors.lastname: Sato
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
mesh_terms: D022181:COP-Coated Vesicles / Q000378:metabolism*; D015825:Chromosomes, Fungal; D004721:Endoplasmic Reticulum / Q000378:metabolism; D020690:GTPase-Activating Proteins; D005800:Genes, Fungal; D006056:Golgi Apparatus / Q000378:metabolism; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D021381:Protein Transport; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins
chemical_list: D020690:GTPase-Activating Proteins; D008565:Membrane Proteins; D012097:Repressor Proteins; C079037:SEC23 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; C083574:SMY2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins