title: Requirement of Hsp90 activity for IkappaB kinase (IKK) biosynthesis and for constitutive and inducible IKK and NF-kappaB activation.
abstract: The molecular chaperone Hsp90 affects the function and fate of a number of signaling molecules. We have investigated the Hsp90 requirement for constitutive and inducible activity of the IkappaB kinase (IKK) complex and of NF-kappaB. Inhibition by the Hsp90 ATPase inhibitors, geldanamycin (GA) and radicicol (RC), revealed that Hsp90 controls IKKs at two levels, inducibility of enzymatic activity and biogenesis, which can be discriminated by short- and long-time GA incubation, respectively. Short-time inhibition of Hsp90 resulted in impaired IKK kinase activation by TNFalpha, IL-1beta or phorbolester PMA. Furthermore, GA inhibited constitutive activation of IKK and NF-kappaB in Hodgkin's lymphoma cells. Hsp90 function was also required for trans- and autophosphorylation of transfected IKKbeta. GA exposure for several hours resulted in a downmodulation of IKK complex alpha, beta and gamma subunits to various extent. Proteasome inhibition interfered with GA mediated IKK depletion and Hsp90 inhibition induced polyubiquitination of IKKalpha and beta during protein synthesis. In fact, GA blocked biogenesis of IKKalpha and IKKbeta but did not interfere with post-translational turnover. Together, these results define a dual requirement for Hsp90 as a regulator of NF-kappaB signaling by its general involvement in IKK activation and by its role in IKK homeostasis.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Robert-Rössle Str. 10, 13092 Berlin, Germany.
authors.forename: Meike
authors.initials: M
authors.lastname: Broemer
authors.forename: Daniel
authors.initials: D
authors.lastname: Krappmann
authors.forename: Claus
authors.initials: C
authors.lastname: Scheidereit
mesh_terms: D000818:Animals; D016227:Benzoquinones; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase; D007249:Inflammation; D007375:Interleukin-1 / Q000378:metabolism; D047029:Lactams, Macrocyclic; D007783:Lactones / Q000494:pharmacology; D008223:Lymphoma / Q000378:metabolism; D018942:Macrolides; D018832:Molecular Chaperones; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D004791:Enzyme Inhibitors; D018841:HSP90 Heat-Shock Proteins; D007375:Interleukin-1; D047029:Lactams, Macrocyclic; D007783:Lactones; D018942:Macrolides; D018832:Molecular Chaperones; D016328:NF-kappa B; D011809:Quinones; D014409:Tumor Necrosis Factor-alpha; D025801:Ubiquitin; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C035359:monorden; D013755:Tetradecanoylphorbol Acetate; C001277:geldanamycin