title: GERp95 belongs to a family of signal-transducing proteins and requires Hsp90 activity for stability and Golgi localization.
abstract: GERp95 (Golgi-endoplasmic reticulum protein 95 kDa) is part of a large family of highly conserved proteins found in all metazoans and the fission yeast Schizosaccharomyces pombe. Genetic studies suggest that homologs of GERp95 are components of signaling pathways that regulate cellular differentiation, development, and RNA interference. However, the precise molecular functions of these proteins remain unknown. Genetic analysis of GERp95 homologs has been complicated by the presence of multiple genes with overlapping functions in most organisms. Binding partners for members of this protein family have not been identified. The purpose of this study was to identify proteins that associate with GERp95. Glutathione S-transferase-GERp95 fusions were expressed in transfected cells, and proteins that bound to GERp95 were co-purified using glutathione-agarose beads. The amino-terminal region of GERp95 was found to interact with the specialized chaperone Hsp90 and a number of its cognate binding proteins. Inhibition of Hsp90 activity with geldanamycin or radicicol resulted in rapid degradation of newly synthesized GERp95. The membrane-associated pool of GERp95 was not bound to Hsp90, although activity of this chaperone was required for stable association of GERp95 with the Golgi in normal rat kidney cells. These results indicate that GERp95 engages an Hsp90 chaperone complex prior to association with intracellular membranes.
authors.affiliation: Department of Cell Biology, University of Alberta, Edmonton T6G 2H7, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Tahbaz
authors.forename: J B
authors.initials: JB
authors.lastname: Carmichael
authors.forename: T C
authors.initials: TC
authors.lastname: Hobman
mesh_terms: D000818:Animals; D060565:Argonaute Proteins; D016227:Benzoquinones; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015852:Eukaryotic Initiation Factor-2; D005786:Gene Expression Regulation; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000166:cytology; D047029:Lactams, Macrocyclic; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011809:Quinones / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012156:Reticulocytes / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: C582332:Ago2 protein, rat; D060565:Argonaute Proteins; D016227:Benzoquinones; D015852:Eukaryotic Initiation Factor-2; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D008565:Membrane Proteins; D011809:Quinones; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; C001277:geldanamycin