3'phosphoinositide‐dependent kinase‐1 is essential for ischemic preconditioning of the myocardium

Abstract

Brief periods of ischemia and reperfusion that precede sustained ischemia lead to a reduction in myocardial infarct size. This phenomenon, known as ischemic preconditioning, is mediated by signaling pathway(s) that are yet to be fully defined. 3′-phosphoinositide-dependent kinase-1 (PDK1) has been implicated in numerous cellular processes. However, the involvement of PDK1 in preconditioning has yet to be elucidated. Studying PDK1 is not as straightforward as it is for the majority of kinases, due to the lack of a specific inhibitor of PDK1. Therefore, we have taken advantage of PDK1 hypomorphic mutant mice with reduced expression of PDK1 to study the role of PDK1 in preconditioning. Whole heart and single cell models of preconditioning demonstrated that the hearts and cardiac cells from PDK1 hypomorphic mice could not be preconditioned. The cardioprotective effect of PDK1 was not related to the effect that preconditioning has on sarcolemmal membrane action potential as revealed by di-8-ANEPPS, a sarcolemmal-potential sensitive dye, and laser confocal microscopy. In contrast, experiments with JC-1, a mitochondrial membrane potentialsensitive dye, has demonstrated that intact PDK1 levels were required for preconditioning-mediated regulation of mitochondrial membrane potential. Western blotting combined with functional experiments have shown that intact PDK1 levels were required for preconditioning-induced phosphorylation of protein kinase B (PKB), glycogen synthase kinase-3β (GSK-3β), and cardioprotection. We conclude that PDK1 mediates preconditioning in the heart by regulating activating PKB-GSK-3β to regulate mitochondrial but not sarcolemmal membrane potential. 3′ phosphoinositide-dependent kinase-1 (PDK1) is essential for ischemic preconditioning of the myocardium. Keywords GSK-3; hypoxia; ischemia; mitochondria; cardioprotectionThe recently discovered 3′-phosphoinositide-dependent kinase-1 (PDK1) is a serine/threonine protein kinase that phosphorylates several members of the automatic gain control (AGC) family of protein kinases, including isoforms of protein kinase B (PKB)/Akt, p70 ribosomal S6 kinase (S6K), serum-and glucocorticoid-induced protein kinase (SGK), and protein kinase C (PKC) (1). So far, it has been shown that the PDK1/automatic gain control kinase-signaling pathway regulates diverse cellular processes, including those relevant to cell survival, proliferation, and metabolic responses to insulin (2). Inadequate regulation of AGC kinase members could contribute to many diseases. A deficiency in the activation of AGC kinases may be a primary cause of the insulin-resistant form of diabetes (3), neuronal cell death following a stroke (4), 1Correspondence: Maternal and Child Health Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK. E-mail: a.jovanovic@dundee.ac.uk. UKPMC Funders Group UKPMC Funders Group Author Manuscript UKPMC Funders Group Author Manuscriptand heart failure (5). However, hyperactivation of this pathway has been implicated ...

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PDK1 coordinates survival pathways and β-adrenergic response in the heart

“…Interestingly, PDK1-MCKCre mice showed attenuation of cardimyocyte cell growth and impairment of left ventricular (LV) contraction. It was reported that cardiomyocytes deficient for Pdk1 were sensitive to hypoxia (5), and that ischemic preconditioning failed to protect Pdk1-hypomorphic mutant mice against myocardial infarction (MI) (6). However, the mechanisms of how PDK1 deficiency induces these cardiac abnormalities remain to be resolved.…”

Parstatin(1-26): The Putative Signal Peptide of Protease-Activated Receptor 1 Confers Potent Protection from Myocardial Ischemia-Reperfusion Injury

“…K ATP channels are opened in a cGMP-dependent manner (Oldenburg et al, 2002(Oldenburg et al, , 2004Qin et al, 2004). Activation of sarcolemmal K ATP channels shortens action membrane potential duration and decreases intracellular Ca 2ϩ loading (Budas et al, 2004(Budas et al, , 2006, and mito-K ATP channel opening attenuates mitochondrial calcium accumulation, prevents Ca 2ϩ -promoted oxidative stress, maintains mitochondrial membrane integrity, and inhibits opening of the mPTP (Facundo et al, 2005). Therefore, PI3K/ Akt signaling may recruit multiple cardioprotective pathways to reduce myocardial damage after ischemia and reperfusion.…”