title: Geldanamycin inhibits tyrosine phosphorylation-dependent NF-kappaB activation.
abstract: Hsp90 is a protein chaperone regulating the stability and activity of many signalling molecules. The requirement of Hsp90 activity in the NF-kappaB pathway has been recently reported by several authors using the Hsp90 ATPase inhibitor geldanamycin (GA), an anti-tumor drug. Hsp90 inhibition blocks the synthesis and activation of the IKK complex, the major kinases complex responsible for IkappaBalpha phosphorylation on serine 32 and 36, a key step for its degradation and the nuclear translocation of NF-kappaB. However, the effect of GA on other IkappaBalpha kinases, including tyrosine kinases, is unknown. In the present study, we investigated the effect of GA on NF-kappaB activation induced by sodium pervanadate (PV), a tyrosine phosphatase inhibitor triggering c-Src-mediated tyrosine phosphorylation of IkappaBalpha. We report for the first time that GA inhibits PV-induced IkappaBalpha tyrosine phosphorylation and degradation. Using an in vitro kinase assay, we demonstrated that GA inhibits the activity of c-Src as an IkappaBalpha tyrosine kinase, but not its cellular expression. As a result, GA blocked PV-induced NF-kappaB DNA-binding activity on an exogenous kappaB element and on the endogenous ikappabalpha promoter, thereby inhibiting ikappabalpha transcription. Finally, we demonstrated that, despite NF-kappaB inhibition, pre-treatment with GA does not potentiate PV-induced apoptosis. We conclude that c-Src requires Hsp90 for its tyrosine kinase activity, and its inhibition by GA blocks c-Src-dependent signalling pathways, such as NF-kappaB activation induced by sodium pervanadate. The effect of GA on PV-induced apoptosis is discussed in the light of recent publications in the literature.
authors.affiliation: GIGA-Research, University of Liège, B-4000 Liège, Belgium.
authors.forename: Julie
authors.initials: J
authors.lastname: Crèvecoeur
authors.forename: Marie-Paule
authors.initials: MP
authors.lastname: Merville
authors.forename: Jacques
authors.initials: J
authors.lastname: Piette
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Gloire
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones / Q000737:chemistry / Q000494:pharmacology*; D004247:DNA / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D016391:Genes, src / Q000502:physiology; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic / Q000737:chemistry / Q000494:pharmacology*; D015394:Molecular Structure; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D014443:Tyrosine / Q000378:metabolism*; D014638:Vanadates / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D016328:NF-kappa B; D012333:RNA, Messenger; C076715:pervanadate; D014638:Vanadates; D014443:Tyrosine; D004247:DNA; D051550:I-kappa B Kinase; C001277:geldanamycin