Mcl-1 degradation during hepatocyte lipoapoptosis

Howard Masuoka, Justin Mott, Steven F. Bronk, Nathan W. Werneburg, Yuko Akazawa, Scott H. Kaufmann, Gregory J. Gores

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

The mechanisms of free fatty acid-induced lipoapoptosis are incompletely understood. Here we demonstrate that Mcl-1, an anti-apoptotic member of the Bcl-2 family, was rapidly degraded in hepatocytes in response to palmitate and stearate by a proteasome-dependent pathway. Overexpression of a ubiquitin-resistant Mcl-1 mutant in Huh-7 cells attenuated palmitate-mediated Mcl-1 loss and lipoapoptosis; conversely, short hairpin RNA-targeted knockdown of Mcl-1 sensitized these cells to lipoapoptosis. Palmitate-induced Mcl-1 degradation was attenuated by the novel protein kinase C (PKC) inhibitor rottlerin. Of the two human novel PKC isozymes, PKCδ and PKCθ, only activation of PKCθ was observed by phospho-immunoblot analysis. As compared with Jurkat cells, a smaller PKCθ polypeptide and mRNA were expressed in hepatocytes consistent with an alternative splice variant. Short hairpin RNA-mediated knockdown of PKCθ reduced Mcl-1 degradation and lipoapoptosis. Likewise, genetic deletion of Pkcθ also attenuated Mcl-1 degradation and cytotoxicity by palmitate in primary hepatocytes. During treatment with palmitate, rottlerin inhibited phosphorylation of Mcl-1 at Ser159, a phosphorylation site previously implicated in Mcl-1 turnover. Consistent with these results, an Mcl-1 S159A mutant was resistant to degradation and improved cell survival during palmitate treatment. Collectively, these results implicate PKCθ-dependent destabilization of Mcl-1 as a mechanism contributing to hepatocyte lipoapoptosis.

Original languageEnglish (US)
Pages (from-to)30039-30048
Number of pages10
JournalJournal of Biological Chemistry
Volume284
Issue number44
DOIs
StatePublished - Oct 30 2009
Externally publishedYes

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Palmitates
Protein Kinase C
Hepatocytes
Degradation
Phosphorylation
Small Interfering RNA
Stearates
Jurkat Cells
Protein C Inhibitor
Proteasome Endopeptidase Complex
Protein Kinase Inhibitors
Cytotoxicity
Ubiquitin
Nonesterified Fatty Acids
Isoenzymes
Cell Survival
Chemical activation
Cells
Messenger RNA
Peptides

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Masuoka, H., Mott, J., Bronk, S. F., Werneburg, N. W., Akazawa, Y., Kaufmann, S. H., & Gores, G. J. (2009). Mcl-1 degradation during hepatocyte lipoapoptosis. Journal of Biological Chemistry, 284(44), 30039-30048. https://doi.org/10.1074/jbc.M109.039545

Mcl-1 degradation during hepatocyte lipoapoptosis. / Masuoka, Howard; Mott, Justin; Bronk, Steven F.; Werneburg, Nathan W.; Akazawa, Yuko; Kaufmann, Scott H.; Gores, Gregory J.

In: Journal of Biological Chemistry, Vol. 284, No. 44, 30.10.2009, p. 30039-30048.

Research output: Contribution to journalArticle

Masuoka, H, Mott, J, Bronk, SF, Werneburg, NW, Akazawa, Y, Kaufmann, SH & Gores, GJ 2009, 'Mcl-1 degradation during hepatocyte lipoapoptosis', Journal of Biological Chemistry, vol. 284, no. 44, pp. 30039-30048. https://doi.org/10.1074/jbc.M109.039545
Masuoka H, Mott J, Bronk SF, Werneburg NW, Akazawa Y, Kaufmann SH et al. Mcl-1 degradation during hepatocyte lipoapoptosis. Journal of Biological Chemistry. 2009 Oct 30;284(44):30039-30048. https://doi.org/10.1074/jbc.M109.039545
Masuoka, Howard ; Mott, Justin ; Bronk, Steven F. ; Werneburg, Nathan W. ; Akazawa, Yuko ; Kaufmann, Scott H. ; Gores, Gregory J. / Mcl-1 degradation during hepatocyte lipoapoptosis. In: Journal of Biological Chemistry. 2009 ; Vol. 284, No. 44. pp. 30039-30048.
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