The phosphatidylinositol 3-kinase inhibitor, wortmannin, inhibits insulin-induced activation of phosphatidylcholine hydrolysis and associated protein kinase C translocation in rat adipocytes.
We questioned whether phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase C (PKC) function as interrelated signalling mechanisms during insulin action in rat adipocytes. Insulin rapidly activated a phospholipase D that hydrolyses phosphatidylcholine (PC), and this activation was accompanied by increases in diacylglycerol and translocative activation of PKC-alpha and PKC-beta in the plasma membrane. Wortmannin, an apparently specific PI 3-kinase inhibitor, inhibited insulin-stimulated, phospholipase D-dependent PC hydrolysis and subsequent translocation of PKC-alpha and PKC-beta to the plasma membrane. Wortmannin did not inhibit PKC directly in vitro, or the PKC-dependent effects of phorbol esters on glucose transport in intact adipocytes. The PKC inhibitor RO 31-8220 did not inhibit PI 3-kinase directly or its activation in situ by insulin, but inhibited both insulin-stimulated and phorbol ester-stimulated glucose transport. Our findings suggest that insulin acts through PI 3-kinase to activate a PC-specific phospholipase D and causes the translocative activation of PKC-alpha and PKC-beta in plasma membranes of rat adipocytes.
Standaert
M L
ML
J.A. Haley Veterans' Hospital, Tampa, FL, USA.
Avignon
A
A
Yamada
K
K
Bandyopadhyay
G
G
Farese
R V
RV
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism*; D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006868:Hydrolysis; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D010713:Phosphatidylcholines / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D007211:Indoles; D007328:Insulin; D007527:Isoenzymes; D010713:Phosphatidylcholines; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011493:Protein Kinase C; C064758:Ro 31-8220; D000077191:Wortmannin