title: A membrane protein enriched in endoplasmic reticulum exit sites interacts with COPII.
abstract: Although all mammalian COPII components have now been cloned, little is known of their interactions with other regulatory proteins involved in exit from the endoplasmic reticulum (ER). We report here that a mammalian protein (Yip1A) that is about 31% identical to S. cerevisiae and which interacts with and modulates COPII-mediated ER-Golgi transport. Yip1A transcripts are ubiquitously expressed. Transcripts of a related mammalian homologue, Yip1B, are found specifically in the heart. Indirect immunofluorescence microscopy revealed that Yip1A is localized to vesicular structures that are concentrated at the perinuclear region. The structures marked by Yip1A co-localized with Sec31A and Sec13, components of the COPII coat protein complex. Immunoelectron microscopy also showed that Yip1A co-localizes with Sec13 at ER exit sites. Overexpression of the hydrophilic N terminus of Yip1A arrests ER-Golgi transport of the vesicular stomatitis G protein and causes fragmentation and dispersion of the Golgi apparatus. A glutathione S-transferase fusion protein with the hydrophilic N terminus of Yip1A (GST-Yip1A) is able to bind to and deplete vital components from rat liver cytosol that is essential for in vitro vesicular stomatitis G transport. Peptide sequence analysis of cytosolic proteins that are specifically bound to GST-Yip1A revealed, among other proteins, mammalian COPII components Sec23 and Sec24. A highly conserved domain at the N terminus of Yip1A is required for Sec23/Sec24 interaction. Our results suggest that Yip1A is involved in the regulation of ER-Golgi traffic at the level of ER exit sites.
authors.affiliation: Membrane Biology Laboratory, Central Imaging and Histology Facility, Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Republic of Singapore. mcbtbl@imcb.nus.edu.sg
authors.forename: B L
authors.initials: BL
authors.lastname: Tang
authors.forename: Y S
authors.initials: YS
authors.lastname: Ong
authors.forename: B
authors.initials: B
authors.lastname: Huang
authors.forename: S
authors.initials: S
authors.lastname: Wei
authors.forename: E T
authors.initials: ET
authors.lastname: Wong
authors.forename: R
authors.initials: R
authors.lastname: Qi
authors.forename: H
authors.initials: H
authors.lastname: Horstmann
authors.forename: W
authors.initials: W
authors.lastname: Hong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D022181:COP-Coated Vesicles / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002451:Cell Compartmentation; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000737:chemistry*; D006056:Golgi Apparatus; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism; D018000:Receptors, Peptide / Q000302:isolation & purification; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014709:Vero Cells; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; C064459:KDEL receptor; D008565:Membrane Proteins; D010750:Phosphoproteins; D011506:Proteins; D018000:Receptors, Peptide; C512739:SEC23A protein, human; C106113:SEC31 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C079038:Sec23a protein, mouse; C512740:Sec23a protein, rat; D033921:Vesicular Transport Proteins; C414462:Yip1 protein, S cerevisiae