title: Hsp90 inhibition accelerates cell lysis. Anti-Hsp90 ribozyme reveals a complex mechanism of Hsp90 inhibitors involving both superoxide- and Hsp90-dependent events.
abstract: The 90 kDa heat shock protein, Hsp90, is an abundant molecular chaperone participating in the cytoprotection of eukaryotic cells. Here we analyzed the involvement of Hsp90 in the maintenance of cellular integrity using partial cell lysis as a measure. Inhibition of Hsp90 by geldanamycin, radicicol, cisplatin, and novobiocin induced a significant acceleration of detergent- and hypotonic shock-induced cell lysis. The concentration and time dependence of cell lysis acceleration was in agreement with the Hsp90 inhibition characteristics of the N-terminal inhibitors, geldanamycin and radicicol. Glutathione and other reducing agents partially blocked geldanamycin-induced acceleration of cell lysis but were largely ineffective with other inhibitors. Indeed, geldanamycin treatment led to superoxide production and a change in membrane fluidity. When Hsp90 content was diminished using anti-Hsp90 hammerhead ribozymes, an accelerated cell lysis was also observed. Hsp90 inhibition-induced cell lysis was more pronounced in eukaryotic (yeast, mouse red blood, and human T-lymphoma) cells than in bacteria. Our results indicate that besides the geldanamycin-induced superoxide production, and a consequent increase in cell lysis, inhibition or lack of Hsp90 alone can also compromise cellular integrity. Moreover, cell lysis after hypoxia and complement attack was also enhanced by any type of Hsp90 inhibition used, which shows that the maintenance of cellular integrity by Hsp90 is important in physiologically relevant lytic conditions of tumor cells.
authors.affiliation: Department of Medical Chemistry, Semmelweis University, H-1088 Budapest, Hungary.
authors.forename: Amere Subbarao
authors.initials: AS
authors.lastname: Sreedhar
authors.forename: Katalin
authors.initials: K
authors.lastname: Mihály
authors.forename: Bálint
authors.initials: B
authors.lastname: Pató
authors.forename: Tamás
authors.initials: T
authors.lastname: Schnaider
authors.forename: Attila
authors.initials: A
authors.lastname: Steták
authors.forename: Katalin
authors.initials: K
authors.lastname: Kis-Petik
authors.forename: Judit
authors.initials: J
authors.lastname: Fidy
authors.forename: Tibor
authors.initials: T
authors.lastname: Simonics
authors.forename: Anna
authors.initials: A
authors.lastname: Maraz
authors.forename: Péter
authors.initials: P
authors.lastname: Csermely
mesh_terms: D000818:Animals; D001483:Base Sequence; D016227:Benzoquinones; D020134:Catalytic Domain; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects*; D002945:Cisplatin / Q000494:pharmacology; D016384:Consensus Sequence; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D047029:Lactams, Macrocyclic; D007783:Lactones / Q000494:pharmacology; D018942:Macrolides; D008560:Membrane Fluidity / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008969:Molecular Sequence Data; D009675:Novobiocin / Q000494:pharmacology; D009690:Nucleic Acid Conformation; D011809:Quinones / Q000494:pharmacology; D051381:Rats; D013481:Superoxides / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D007783:Lactones; D018942:Macrolides; D011809:Quinones; D013481:Superoxides; D009675:Novobiocin; C035359:monorden; D002945:Cisplatin; C001277:geldanamycin