A central role for the Hsp90.Cdc37 molecular chaperone module in interleukin-1 receptor-associated-kinase-dependent signaling by toll-like receptors.
Toll-like receptors (TLRs) serve crucial roles in innate immunity by mediating the activation of macrophages by microbial pathogens. The protein kinase interleukin-1 receptor associated kinase (IRAK-1) is a key component of TLR signaling pathways via its interaction with TRAF6, which subsequently leads to the activation of MAP kinases and various transcription factors. IRAK-1 is degraded following TLR activation, and this has been proposed to contribute to tolerance in macrophages by limiting further TLR-mediated signaling. Using a mass spectrometric-based approach, we have identified a cohort of chaperones and co-chaperones including Hsp90 and Cdc37, which bind to IRAK-1 but not IRAK-4 in 293T cells. Pharmacologic inhibition of Hsp90 led to a rapid decline in the expression level of IRAK-1, whereas overexpression of Cdc37 enhanced the activation and oligomerization of IRAK-1 in 293T cells. Significantly, the inhibition of Hsp90 in macrophages resulted in the destabilization and degradation of IRAK-1 but not IRAK-4. Concomitant with the loss of IRAK-1 expression was a reduction in the activation of p38 MAP kinase and Erk1/2 following stimulation with the bacterially derived TLR ligands, lipopolysaccharide and CpG DNA. Moreover, TLR ligand-induced expression of proinflammatory cytokines was also reduced. Thus we conclude that the level of on-going support provided to IRAK-1 by the Hsp90-Cdc37 chaperone module directly influences the magnitude of TLR-mediated macrophage activation. In addition, because further TLR signaling depends on the synthesis of new IRAK-1, the Hsp90-Cdc37 chaperone module could also contribute to tolerance in macrophages by controlling the rate at which nascent IRAK-1 is folded into a functional conformation.
De Nardo
Dominic
D
Department of Medicine, The University of Melbourne, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
Masendycz
Paul
P
Ho
Sokwei
S
Cross
Maddalena
M
Fleetwood
Andrew J
AJ
Reynolds
Eric C
EC
Hamilton
John A
JA
Scholz
Glen M
GM
D016227:Benzoquinones; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology; D018797:Cell Cycle Proteins / Q000502:physiology*; D002460:Cell Line; D018833:Chaperonins; D002845:Chromatography; D002851:Chromatography, High Pressure Liquid; D018899:CpG Islands; D016207:Cytokines / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D018841:HSP90 Heat-Shock Proteins / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D053592:Interleukin-1 Receptor-Associated Kinases; D047029:Lactams, Macrocyclic; D008024:Ligands; D008070:Lipopolysaccharides / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000166:cytology; D013058:Mass Spectrometry; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013997:Time Factors; D051193:Toll-Like Receptors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D016227:Benzoquinones; C498362:CDC37 protein, human; D018797:Cell Cycle Proteins; D016207:Cytokines; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D008024:Ligands; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D011809:Quinones; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D051193:Toll-Like Receptors; D012313:RNA; D011494:Protein Kinases; D053592:Interleukin-1 Receptor-Associated Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D018833:Chaperonins; C001277:geldanamycin