PHLPP-1 negatively regulates Akt activity and survival in the heart

Shigeki Miyamoto, Nicole H. Purcell, Jeffrey M. Smith, Tianyan Gao, Ross Whittaker, Katherine Huang, Rene Castillo, Chris C. Glembotski, Mark A. Sussman, Alexandra C. Newton, Joan Heller Brown

Research output: Contribution to journalArticlepeer-review

81 Scopus citations

Abstract

Rationale: The recently discovered PHLPP-1 (PH domain leucine-rich repeat protein phosphatase-1) selectively dephosphorylates Akt at Ser473 and terminates Akt signaling in cancer cells. The regulatory role of PHLPP-1 in the heart has not been considered. Objective: To test the hypothesis that blockade/inhibition of PHLPP-1 could constitute a novel way to enhance Akt signals and provide cardioprotection. Methods and Results: PHLPP-1 is expressed in neonatal rat ventricular myocytes (NRVMs) and in adult mouse ventricular myocytes (AMVMs). PHLPP-1 knockdown by small interfering RNA significantly enhances phosphorylation of Akt (p-Akt) at Ser473, but not at Thr308, in NRVMs stimulated with leukemia inhibitory factor (LIF). The increased phosphorylation is accompanied by greater Akt catalytic activity. PHLPP-1 knockdown enhances LIF-mediated cardioprotection against doxorubicin and also protects cardiomyocytes against H2O2. Direct Akt effects at mitochondria have been implicated in cardioprotection and mitochondria/cytosol fractionation revealed a significant enrichment of PHLPP-1 at mitochondria. The ability of PHLPP-1 knockdown to potentiate LIF-mediated increases in p-Akt at mitochondria and an accompanying increase in mitochondrial hexokinase-II was demonstrated. We generated PHLPP-1 knockout (KO) mice and demonstrate that AMVMs isolated from KO mice show potentiated p-Akt at Ser473 in response to agonists. When isolated perfused hearts are subjected to ischemia/reperfusion, p-Akt in whole-heart homogenates and in the mitochondrial fraction is significantly increased. Additionally in PHLPP-1 KO hearts, the increase in p-Akt elicited by ischemia/reperfusion is potentiated and, concomitantly, infarct size is significantly reduced. Conclusions: These results implicate PHLPP-1 as an endogenous negative regulator of Akt activity and cell survival in the heart.

Original languageEnglish (US)
Pages (from-to)476-484
Number of pages9
JournalCirculation research
Volume107
Issue number4
DOIs
StatePublished - Aug 20 2010
Externally publishedYes

Keywords

  • Akt
  • PHLPP
  • heart
  • phosphatase
  • protection

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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