title: Inhibition of histone deacetylase 6 acetylates and disrupts the chaperone function of heat shock protein 90: a novel basis for antileukemia activity of histone deacetylase inhibitors.
abstract: The hydroxamic acid (HAA) analogue pan-histone deacetylase (HDAC) inhibitors (HDIs) LAQ824 and LBH589 have been shown to induce acetylation and inhibit the ATP binding and chaperone function of heat shock protein (HSP) 90. This promotes the polyubiquitylation and degradation of the pro-growth and pro-survival client proteins Bcr-Abl, mutant FLT-3, c-Raf, and AKT in human leukemia cells. HDAC6 is a member of the class IIB HDACs. It is predominantly cytosolic, microtubule-associated alpha-tubulin deacetylase that is also known to promote aggresome inclusion of the misfolded polyubiquitylated proteins. Here we demonstrate that in the Bcr-abl oncogene expressing human leukemia K562 cells, HDAC6 can be co-immunoprecipitated with HSP90, and the knock-down of HDAC6 by its siRNA induced the acetylation of HSP90 and alpha-tubulin. Depletion of HDAC6 levels also inhibited the binding of HSP90 to ATP, reduced the chaperone association of HSP90 with its client proteins, e.g. Bcr-Abl, and induced polyubiquitylation and partial depletion of Bcr-Abl. Conversely, the ectopic overexpression of HDAC6 inhibited LAQ824-induced acetylation of HSP90 and alpha-tubulin and reduced LAQ824-mediated depletion of Bcr-Abl, AKT, and c-Raf. Collectively, these findings indicate that HDAC6 is also an HSP90 deacetylase. Targeted inhibition of HDAC6 leads to acetylation of HSP90 and disruption of its chaperone function, resulting in polyubiquitylation and depletion of pro-growth and pro-survival HSP90 client proteins including Bcr-Abl. Depletion of HDAC6 sensitized human leukemia cells to HAA-HDIs and proteasome inhibitors.
authors.affiliation: Department of Interdisciplinary Oncology, H. Lee Moffitt Cancer Center, Tampa, Florida 33612, USA.
authors.forename: Purva
authors.initials: P
authors.lastname: Bali
authors.forename: Michael
authors.initials: M
authors.lastname: Pranpat
authors.forename: James
authors.initials: J
authors.lastname: Bradner
authors.forename: Maria
authors.initials: M
authors.lastname: Balasis
authors.forename: Warren
authors.initials: W
authors.lastname: Fiskus
authors.forename: Fei
authors.initials: F
authors.lastname: Guo
authors.forename: Kathy
authors.initials: K
authors.lastname: Rocha
authors.forename: Sandhya
authors.initials: S
authors.lastname: Kumaraswamy
authors.forename: Sandhya
authors.initials: S
authors.lastname: Boyapalle
authors.forename: Peter
authors.initials: P
authors.lastname: Atadja
authors.forename: Edward
authors.initials: E
authors.lastname: Seto
authors.forename: Kapil
authors.initials: K
authors.lastname: Bhalla
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000970:Antineoplastic Agents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000187:drug effects* / Q000378:metabolism; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000502:physiology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D007211:Indoles; D020014:K562 Cells; D007938:Leukemia / Q000188:drug therapy / Q000473:pathology*; D018832:Molecular Chaperones / Q000187:drug effects; D009363:Neoplasm Proteins / Q000032:analysis / Q000187:drug effects; D000077767:Panobinostat; D011485:Protein Binding; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D018841:HSP90 Heat-Shock Proteins; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D007211:Indoles; C477361:LAQ824; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D025801:Ubiquitin; D000077767:Panobinostat; C433811:HDAC6 protein, human; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases