Published online before print November 23, 2005, doi: 10.1161/01.RES.0000197781.20524.b9
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© 2006 American Heart Association, Inc.
Integrative Physiology |
c-Jun N-Terminal Kinases Mediate Reactivation of Akt and Cardiomyocyte Survival After Hypoxic Injury In Vitro and In Vivo
From the Molecular Cardiology (Z.S., K.B., E.H., B.W., J.K., X.C., M.A., S.B., T.F., H.K.) and Molecular Oncology Research Institutes (P.N.T.), Tufts-New England Medical Center and Tufts University School of Medicine, Boston, Mass; Vertex Pharmaceuticals, Inc (L.P., U.G., Y.W., R.M., K.K., M.N., F.S., Y.Y.), Cambridge Mass; and Department of Biochemistry (W.H.), Tufts University, Boston, Mass. Current affiliation for H.K.: Clinic for Internal Medicine III, University of the Saarland, Hamburg/Saar, Germany.
Correspondence to Thomas Force, MD, Center for Translational Medicine, Jefferson Medical College, 1025 Walnut St, Suite 411, Philadelphia, PA 19107. E-mail thomas.force{at}jefferson.edu
Akt is a central regulator of cardiomyocyte survival after ischemic injury in vitro and in vivo, but the mechanisms regulating Akt activity in the postischemic cardiomyocyte are not known. Furthermore, although much is known about the detrimental role that the c-Jun N-terminal kinases (JNKs) play in promoting death of cells exposed to various stresses, little is known of the molecular mechanisms by which JNK activation can be protective. We report that JNKs are necessary for the reactivation of Akt after ischemic injury. We identified Thr450 of Akt as a residue that is phosphorylated by JNKs, and the phosphorylation status of Thr450 regulates reactivation of Akt after hypoxia, apparently by priming Akt for subsequent phosphorylation by 3-phosphoinositide–dependent protein kinase. The reduction in Akt activity that is induced by JNK inhibition may have significant biological consequences, as we find that JNKs, acting via Akt, are critical determinants of survival in posthypoxic cardiomyocytes in culture. Furthermore, in contrast to selective p38–mitogen-activated protein kinase inhibition, which was cardioprotective in vivo, concurrent inhibition of both JNKs and p38–mitogen-activated protein kinases increased ischemia/reperfusion injury in the heart of the intact rat. These studies demonstrate that reactivation of Akt after resolution of hypoxia and ischemia is regulated by JNKs and suggest that this is likely a central mechanism of the myocyte protective effect of JNKs.
Key Words: Akt • apoptosis • c-Jun NH2-terminal kinase • hypoxia • ischemia • signal transduction
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