title: Insulin promotes the association of heat shock protein 90 with the inositol 1,4,5-trisphosphate receptor to dampen its Ca2+ release activity.
abstract: The inositol 1,4,5-trisphosphate receptor (IP(3)R) is a Ca(2+) release channel that plays a pivotal role in regulating intracellular Ca(2+) levels in resting cells. Three isoforms of IP(3)Rs have been identified, and they all possess a large regulatory domain that covers about 60% of the protein. This regulation is accomplished by interaction with small molecules, posttranslational modifications, and mostly protein-protein interactions. In our search for new binding partners of the IP(3)R, we found that 90-kDa heat-shock protein (Hsp90) binds to the IP(3)R. This interaction increased on stimulation of HEK293T6.11 cells with insulin but not with G(q) protein-coupled receptor (G(q)PCR) agonists. Moreover, the Hsp90 inhibitor geldanamycin (GA) disrupted the interaction between Hsp90 and the IP(3)R. Pretreatment of HEK293T6.11 cells with GA greatly increased the intracellular Ca(2+) release induced by a G(q)PCR agonist. Insulin alone did not induce any intracellular Ca(2+) release. However, insulin diminished the intracellular Ca(2+) release induced by a G(q)PCR agonist. Interestingly, GA abolished the inhibitory effect of insulin on G(q)PCR-induced intracellular Ca(2+) release. Furthermore, in our search for a mechanistic explanation to this phenomenon, we found that inhibition of kinases activated downstream of the insulin receptor greatly increased the interaction between Hsp90 and the IP(3)R. Of greater interest, we found that the simultaneous inhibition of mammalian target of rapamycin and the Src kinase almost completely disrupted the interaction between Hsp90 and the IP(3)R. These results demonstrate that insulin promotes the interaction of Hsp90 with the IP(3)R to dampen its Ca(2+) release activity by a complex mechanism involving mammalian target of rapamycin and the Src kinase.
authors.affiliation: Department of Pharmacology, Faculty of Medicine and Health Sciences, University of Sherbrooke, 3001 12th Avenue North, Sherbrooke, Québec, Canada J1H 5N4.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Nguyen
authors.forename: Nancy
authors.initials: N
authors.lastname: Francoeur
authors.forename: Valérie
authors.initials: V
authors.lastname: Chartrand
authors.forename: Klaus
authors.initials: K
authors.lastname: Klarskov
authors.forename: Gaétan
authors.initials: G
authors.lastname: Guillemette
authors.forename: Guylain
authors.initials: G
authors.lastname: Boulay
mesh_terms: D016227:Benzoquinones / Q000494:pharmacology; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology; D058570:TOR Serine-Threonine Kinases; D019061:src-Family Kinases
chemical_list: D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007328:Insulin; D047029:Lactams, Macrocyclic; D011518:Proto-Oncogene Proteins; D002217:Carbachol; D011494:Protein Kinases; C546842:MTOR protein, human; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; D058570:TOR Serine-Threonine Kinases; D002118:Calcium; C001277:geldanamycin