To understand how the stimulation of phosphoinositide 3-kinase (PI 3-kinase) by different growth factors can activate different subsets of downstream responses, growth-factor regulation of PI 3-kinase activity at different intracellular locations was investigated in 3T3-L1 adipocytes. Insulin caused a large stimulation of glucose transport and stimulated recruitment of transferrin receptors to the plasma membrane (PM) in these cells, whereas platelet-derived growth factor (PDGF)-bb was virtually without effect on these responses. Subcellular fractionation studies after stimulation with PDGF-bb or insulin revealed a differential effect of these growth factors on subcellular localization of PI 3-kinase activity. PDGF was more effective than insulin in stimulating PI 3-kinase activity and recruiting the p85α PI 3-kinase adaptor subunit in the fraction containing the PM. However, in the microsomal fraction insulin significantly increased PI 3-kinase activity and p85α levels, whereas PDGF was almost without effect. In the microsomal membrane fraction the insulin-stimulated recruitment of p85α closely matched the increase PI 3-kinase activity, indicating that insulin stimulation of PI 3-kinase in this fraction is largely due to recruitment of PI 3-kinase enzyme rather than alterations in specific activity. Insulin-stimulated recruitment of p85α to the microsomal membranes was not inhibited by wortmannin, indicating that PI 3-kinase activity was not required for this process. A further level of compartment-specific regulation of PI 3-kinase in response to PDGF was revealed by the finding that tyrosine phosphorylation of the p85α adaptor was restricted to the PM-containing fraction. Insulin had no effect on p85 tyrosine phosphorylation in either fraction. In summary, these results suggest a basis by which insulin and PDGF could both use PI 3-kinase signalling cascades but achieve different signalling outcomes.
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Research Article|
August 15 1996
Compartment-specific regulation of phosphoinositide 3-kinase by platelet-derived growth factor and insulin in 3T3-L1 adipocytes
Barbara T. NAVÉ;
Barbara T. NAVÉ
1Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QR, U.K.
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RichardHAIGH J;
RichardHAIGH J
1Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QR, U.K.
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Amanda C HAYWARD;
Amanda C HAYWARD
1Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QR, U.K.
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Kenneth SIDDLE;
Kenneth SIDDLE
1Department of Clinical Biochemistry, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 2QR, U.K.
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Peter R. SHEPHERD
†To whom correspondence should be addressed.
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Publisher: Portland Press Ltd
Received:
January 19 1996
Revision Received:
April 12 1996
Accepted:
April 22 1996
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1996
1996
Biochem J (1996) 318 (1): 55–60.
Article history
Received:
January 19 1996
Revision Received:
April 12 1996
Accepted:
April 22 1996
Citation
Barbara T. NAVÉ, RichardHAIGH J, Amanda C HAYWARD, Kenneth SIDDLE, Peter R. SHEPHERD; Compartment-specific regulation of phosphoinositide 3-kinase by platelet-derived growth factor and insulin in 3T3-L1 adipocytes. Biochem J 15 August 1996; 318 (1): 55–60. doi: https://doi.org/10.1042/bj3180055
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