title: Adenosine nucleotides and the regulation of GRP94-client protein interactions.
abstract: The molecular chaperone heat shock protein 90 (Hsp90) serves essential roles in the regulation of signaling protein function, trafficking, and turnover. Hsp90 function is intimately linked to intrinsic ATP binding and hydrolysis activities, the latter of which is under the regulatory control of accessory factors. Glucose-regulated protein of 94 kDa (GRP94), the endoplasmic reticulum Hsp90, is highly homologous to cytosolic Hsp90. However, neither accessory factors nor adenosine nucleotides have been clearly implicated in the regulation of GRP94-client protein interactions. In the current study, the structural and regulatory consequences of adenosine nucleotide binding to GRP94 were investigated. We report that apo-GRP94 undergoes a time- and temperature-dependent tertiary conformational change that exposes a site(s) of protein-protein interaction; ATP, ADP, and radicicol markedly suppress this conformational change. In concert with these findings, ATP and ADP act identically to suppress GRP94 homooligomerization, as well as both local and global conformational activity. To identify a role(s) for ATP or ADP in the regulation of GRP94-client protein interactions, immunoglobulin (Ig) heavy chain folding intermediates containing bound GRP94 and immunoglobulin binding protein (BiP) were isolated from myeloma cells, and the effects of adenosine nucleotides on chaperone-Ig heavy chain interactions were examined. Whereas ATP elicited efficient release of BiP from both wild-type and mutant Ig heavy chain intermediates, GRP94 remained in stable association with Ig heavy chains in the presence of ATP or ADP. On the basis of these data, we propose that structural maturation of the client protein substrate, rather than ATP binding or hydrolysis, serves as the primary signal for dissociation of GRP94-client protein complexes.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Meredith F N
authors.initials: MF
authors.lastname: Rosser
authors.forename: Brian M
authors.initials: BM
authors.lastname: Trotta
authors.forename: Megan R
authors.initials: MR
authors.lastname: Marshall
authors.forename: Brent
authors.initials: B
authors.lastname: Berwin
authors.forename: Christopher V
authors.initials: CV
authors.lastname: Nicchitta
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D004285:Dogs; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006868:Hydrolysis; D007136:Immunoglobulins / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013050:Spectrometry, Fluorescence; D013552:Swine; D013696:Temperature; D013997:Time Factors
chemical_list: D001059:Apoproteins; D018840:HSP70 Heat-Shock Proteins; D007136:Immunoglobulins; D008024:Ligands; D008565:Membrane Proteins; C018551:glucose-regulated proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate