title: Class I and IIa HDACs Mediate HIF-1α Stability Through PHD2-Dependent Mechanism, While HDAC6, a Class IIb Member, Promotes HIF-1α Transcriptional Activity in Nucleus Pulposus Cells of the Intervertebral Disc.
abstract: The objective of this study was to determine the role of histone deacetylases (HDACs) in regulating HIF-1α protein stability and activity in nucleus pulposus (NP) cells. Treatment of NP cells with pan-HDAC inhibitor TSA resulted in decreased HIF-1α levels under both normoxia and hypoxia in a dose-dependent fashion. TSA-mediated HIF-1α degradation was rescued by concomitant inhibition of not only the 26S proteasome but also PHD2 function. Moreover, TSA treatment of PHD2(-/-) cells had little effect on HIF-1α levels, supporting the notion that inhibition of PHD2 function by HDACs contributed to HIF-1α stabilization. Surprisingly, class-specific HDAC inhibitors did not affect HIF-1α protein stability, indicating that multiple HDACs controlled HIF-1α stability by regulating HIF-1α-PHD2 interaction in NP cells. Interestingly, lower-dose TSA that did not affect HIF-1α stability decreased its activity and target gene expression. Likewise, rescue of TSA-mediated HIF-1α protein degradation by blocking proteasomal or PHD activity did not restore HIF-1 activity, suggesting that HDACs independently regulate HIF-1α stability and activity. Noteworthy, selective inhibition of HDAC6 and not of class I and IIa HDACs decreased HIF-1-mediated transcription under hypoxia to a similar extent as lower-dose TSA, contrasting the reported role of HDAC6 as a transcriptional repressor in other cell types. Moreover, HDAC6 inhibition completely blocked TSA effects on HIF-1 activity. HDAC6 associated with and deacetylated HSP90, an important cofactor for HIF-1 function in NP cells, and HDAC6 inhibition decreased p300 transactivation in NP cells. Taken together, these results suggest that although multiple class I and class IIa HDACs control HIF-1 stability, HDAC6, a class IIb HDAC, is a novel mediator of HIF-1 activity in NP cells possibly through promoting action of critical HIF-1 cofactors. © 2016 American Society for Bone and Mineral Research.
authors.affiliation: Department of Orthopaedic Surgery and Graduate Program in Cell and Developmental Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Zachary R
authors.initials: ZR
authors.lastname: Schoepflin
authors.affiliation: Department of Orthopaedic Surgery and Graduate Program in Cell and Developmental Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Irving M
authors.initials: IM
authors.lastname: Shapiro
authors.affiliation: Department of Orthopaedic Surgery and Graduate Program in Cell and Developmental Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Makarand V
authors.initials: MV
authors.lastname: Risbud
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000073864:Histone Deacetylase 6 / Q000235:genetics / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D007403:Intervertebral Disc / Q000166:cytology / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D051381:Rats; D014158:Transcription, Genetic / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*; D050880:p300-CBP Transcription Factors / Q000235:genetics / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D000073864:Histone Deacetylase 6; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D011393:Procollagen-Proline Dioxygenase; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C497444:Hif1a protein, rat; C580731:Egln1 protein, rat; C545556:HDAC6 protein, rat
keywords: HDAC6; HIF-1α; HYPOXIA; INTERVERTEBRAL DISC; NUCLEUS PULPOSUS; TRANSCRIPTION FACTOR