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This Article Accepted manuscript (PDF) All Versions of this Article: JOE-09-0046v1 201/2/199    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Luiken, J. Articles by Glatz, J. Search for Related Content PubMed PubMed Citation Articles by Luiken, J. Articles by Glatz, J.

J Luiken, Molecular Genetics, Maastricht University, Maastricht, 6200 MD, Netherlands
D Ouwens, Leiden, Netherlands
D Habets, Maastricht, Netherlands
G van der Zon, Leiden, Netherlands
W Coumans, Maastricht, Netherlands
R Schwenk, Maastricht, Netherlands
A Bonen, Guelph, Canada
J Glatz, Maastricht, Netherlands

Correspondence: Joost Luiken, Email: J.Luiken{at}GEN.unimaas.nl

Abstract

Insulin stimulates cardiac long-chain fatty acid (LCFA) and glucose uptake via translocation of CD36 and GLUT4, respectively, from intracellular membrane compartments to the sarcolemma, a process dependent on activation of phosphatidylinositol-3 kinase (PI3K). To identify downstream kinases of insulin signaling involved in translocation of CD36 and GLUT4 in the heart, we tested (i) which cardiac PKC isoforms (alpha, delta, epsilon or zeta) are activated by insulin, and (ii) whether PKC isoform-specific inhibition affects insulin-stimulated substrate uptake in the heart. Insulin-stimulated LCFA and glucose uptake were completely blunted by inhibition of PKC-zeta, but not by inhibition of conventional or novel PKCs. Concomitantly, translocation of CD36 and GLUT4 to the sarcolemma was completely blunted upon inhibition of PKC-zeta. However, insulin, in contrast to the diacylglycerol-analog phorbol-12-myristate-13-acetate (PMA), did not induce membrane-attachment of the conventional and novel PKCs-alpha, -delta and -epsilon. PKC-zeta, was already entirely membrane-bound in non-stimulated cells, and neither insulin nor PMA treatment had any effect on the subcellular localization of PKC-zeta. Furthermore, insulin treatment did not change phosphorylation of PKC-alpha, -delta and -zeta, or enzymatic activity of PKC-zeta towards a PKC-zeta substrate peptide. It is concluded that PKC-zeta, but not any other PKC isoform, is necessary for insulin-induced translocation of GLUT4 and CD36. However, PKC-zeta is already fully active under basal conditions and not further activated by insulin, indicating that its role in insulin-stimulated uptake of both glucose and LCFA is permissive rather than regulatory.