The effects of insulin and phorbol 12-myristate 13-acetate (PMA) on the levels of cellular phosphoinositides were investigated in 3T3-L1 adipocytes. Stimulation for 4 min with PMA (1 µM) or insulin (10 nM) increased levels of PtdIns(3,4,5)P3 approx. 2-fold and 6-fold respectively. PMA also had a small effect on the cellular levels of PtdIns4P, whereas insulin had no effect on PtdIns4P levels; levels of PtdIns(4,5)P2 and PtdIns3P were not significantly affected by either agent. Insulin increased the levels of the p85α subunit of phosphoinositide (PI) 3-kinase associated with membranes, whereas PMA decreased levels of membrane-associated p85α. PMA did not increase PI 3-kinase activity in anti-phosphotyrosine or anti-p85 immunoprecipitates. The stimulation of glucose transport by insulin or PMA was blocked by 100 nM wortmannin or 10 ng/ml LY294002, indicating that PI 3-kinase is essential for stimulation by both agents. In summary, these results demonstrate: (1) that PMA and insulin stimulate PtdIns(3,4,5)P3 production by distinct mechanisms in 3T3-L1 adipocytes, and (2) that stimulation of PtdIns(3,4,5)P3 production by PMA is likely to be important in signalling pathways leading from PMA stimulation to end-point responses such as glucose transport.
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Research Article|
August 15 1996
Phorbol esters stimulate phosphatidylinositol 3,4,5-trisphosphate production in 3T3-L1 adipocytes: implications for stimulation of glucose transport
Barbara T. NAVÉ;
Barbara T. NAVÉ
1Department of Clinical Biochemistry, University of Cambridge, Cambridge, U.K.
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Kenneth SIDDLE;
Kenneth SIDDLE
1Department of Clinical Biochemistry, University of Cambridge, Cambridge, U.K.
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Peter R SHEPHERD
Peter R SHEPHERD
*
1Department of Clinical Biochemistry, University of Cambridge, Cambridge, U.K.
*To whom correspondence should be sent, at present address: Department of Biochemistry and Molecular Biology, University College London, Gower St., London WC1E 6BT, U.K.
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Publisher: Portland Press Ltd
Received:
February 13 1996
Revision Received:
May 03 1996
Accepted:
May 14 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 318 (1): 203–205.
Article history
Received:
February 13 1996
Revision Received:
May 03 1996
Accepted:
May 14 1996
Citation
Barbara T. NAVÉ, Kenneth SIDDLE, Peter R SHEPHERD; Phorbol esters stimulate phosphatidylinositol 3,4,5-trisphosphate production in 3T3-L1 adipocytes: implications for stimulation of glucose transport. Biochem J 15 August 1996; 318 (1): 203–205. doi: https://doi.org/10.1042/bj3180203
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