Permissive action of protein kinase C-zeta in insulin-induced CD36- and GLUT4 translocation in cardiac myocytes.
Insulin stimulates cardiac long-chain fatty acid (LCFA) and glucose uptake via translocation of human homolog of rat fatty acid translocase (CD36) and GLUT4 respectively, from intracellular membrane compartments to the sarcolemma, a process dependent on the activation of phosphatidylinositol-3 kinase. To identify downstream kinases of insulin signaling involved in translocation of CD36 and GLUT4 in the heart, we tested i) which cardiac protein kinase C (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.
Luiken
Joost J F P
JJ
Department of Molecular Genetics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, PO Box 616, NL-6200 MD Maastricht, The Netherlands. j.luiken@gen.unimaas.nl
Ouwens
D Margriet
DM
Habets
Daphna D J
DD
van der Zon
Gerard C M
GC
Coumans
Will A
WA
Schwenk
Robert W
RW
Bonen
Arend
A
Glatz
Jan F C
JF
D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D005227:Fatty Acids / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D011917:Rats, Inbred Lew; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000099221:Protein Kinase C zeta
D018955:CD36 Antigens; D005227:Fatty Acids; D051275:Glucose Transporter Type 4; D007328:Insulin; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D013755:Tetradecanoylphorbol Acetate; D000099221:Protein Kinase C zeta; C008132:Cd36 protein, rat; C495694:Slc2a4 protein, rat