VAMP-associated protein-A regulates partitioning of oxysterol-binding protein-related protein-9 between the endoplasmic reticulum and Golgi apparatus.
We recently showed that oxysterol-binding protein (OSBP), one of twelve related PH domain containing proteins with lipid and sterol binding activity, interacts with VAMP-associated protein (VAP)-A on the endoplasmic reticulum (ER). In addition to OSBP, seven OSBP-related proteins (ORPs) bind VAP-A via a conserved E-F/Y-F/Y-DA 'FFAT' motif. We focused on this interaction for ORP9, which is expressed as a full-length (ORP9L) or truncated version missing the PH domain (ORP9S). Mutation analysis showed that the interaction required the ORP9 FFAT motif and the N-terminal conserved domain of VAP. Endogenous ORP9L displayed Golgi localization, which was partially mediated by the PH domain based on limited localization of OPR9-PH-GFP with the Golgi apparatus. When inducibly overexpressed, ORP9S and ORP9L colocalized with VAP-A and caused vacuolation of the ER as well as retention of the ER-Golgi intermediate compartment marker ERGIC-53/p58 in the ER. ORP9L mutated in the VAP-A binding domain (ORP9L-FY-->AA) did not localize to the ER but appeared with giantin and Sec31 on large vesicular structures, suggesting the presence of a hybrid Golgi-COPII compartment. Normal Golgi localization was also observed for ORP9L-FY-->AA. Results show that VAP binding and PH domains target ORP9 to the ER and a Golgi-COPII compartment, respectively, and that ORP9L overexpression in these compartments severely perturbed their organization.
Wyles
Jessica P
JP
The Atlantic Research Center, Departments of Pediatrics and Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.
Ridgway
Neale D
ND
D017398:Alternative Splicing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002451:Cell Compartmentation; D002999:Clone Cells; D017124:Conserved Sequence; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005786:Gene Expression Regulation; D014644:Genetic Variation; D006056:Golgi Apparatus / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000032:analysis; D011987:Receptors, Steroid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins; D000098825:Oxysterol Binding Proteins
D002352:Carrier Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D012333:RNA, Messenger; D011987:Receptors, Steroid; D011993:Recombinant Fusion Proteins; C114051:VAPA protein, human; C491920:Vapa protein, mouse; D033921:Vesicular Transport Proteins; D000098825:Oxysterol Binding Proteins; D049452:Green Fluorescent Proteins