Insulin leads to a parallel translocation of PI-3-kinase and protein kinase C zeta.
Protein kinase C consists of a family of at least 12 isoforms which exhibit clear differences in their cofactor dependence and responsiveness to phospholipids. Insulin effects on PKC translocation/activation are now clearly established but responsiveness to this hormone was observed so far only for the classical PKC-isoforms alpha and beta. While activation of the classical PKC's requires Ca2+ and occurs mainly through Diacylglycerol (DAG), stimulation of the atypical isoform PKC-zeta appears to function through a different mechanism involving PI-3-kinase activation. In the present study we used rat-1 fibroblasts stably over-expressing human insulin receptor to investigate whether insulin can activate PKC-zeta and whether such an effect might be related to insulin's effect on PI-3-kinase. After stimulation of the cells with insulin (10(-7) mol/l) for one to ten minutes, a rapid translocation of PKC-zeta to the plasma membrane was detectable, as determined by immunoblotting of plasma membrane proteins with antibodies against PKC-zeta. In parallel immunoblots applying antibodies against the regulatory subunit of PI-3-kinase (p85), an insulin-induced translocation of p85 was detectable within one minute after stimulation. The translocation of p85 was associated with an increase in PI-3-kinase activity at the plasma membrane. The data show that insulin stimulates translocation of PKC-zeta in rat-1 fibroblasts. The parallel kinetics of PI-3-kinase translocation/activation and PKC-zeta translocation are compatible with the idea that the insulin effect on PKC-zeta is transduced through PI-3-kinase activation.
Mosthaf
L
L
Hagedorn Research Institute, Gentofte, Denmark.
Kellerer
M
M
Mühlhöfer
A
A
Mushack
J
J
Seffer
E
E
Häring
H U
HU
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005347:Fibroblasts; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000096:biosynthesis / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
D007328:Insulin; D007527:Isoenzymes; D011994:Recombinant Proteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011972:Receptor, Insulin; D011493:Protein Kinase C