Activation of Phospholipase C-γ by Phosphatidylinositol 3,4,5-Trisphosphate*
- Yun Soo Bae‡,
- Lloyd G. Cantley§,
- Ching-Shih Chen¶,
- Seung-Ryul Kim‡‖,
- Ki-Sun Kwon‡ and
- Sue Goo Rhee‡**
- From the ‡Laboratory of Cell Signaling, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, the§Department of Medicine, Beth Israel Hospital, Harvard Medical School, Boston, Massachusetts 02115, and the ¶Division of Medicinal Chemistry and Pharmaceutics, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40506
Abstract
Signal transduction across cell membranes often involves the activation of both phosphatidylinositol (PI)-specific phospholipase C (PLC) and phosphoinositide 3-kinase (PI 3-kinase). Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), a substrate for both enzymes, is converted to phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) by the action of PI 3-kinase. Here, we show that PI(3,4,5)P3 activates purified PLC-γ isozymes by interacting with their Src homology 2 domains. Furthermore, the expression of an activated catalytic subunit of PI 3-kinase in COS-7 cells resulted in an increase in inositol phosphate formation, whereas platelet-derived growth factor-induced PLC activation in NIH 3T3 cells was markedly inhibited by the specific PI 3-kinase inhibitor LY294002. These results suggest that receptors coupled to PI 3-kinase may activate PLC-γ isozymes indirectly, in the absence of PLC-γ tyrosine phosphorylation, through the generation of PI(3,4,5)P3.
Footnotes
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↵* This work was supported in part by National Institutes of Health Grants DK48871 (to L. G. C.) and GM53448 (to C.-S. C.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‖ Present address: Dept. of Biochemistry, Chungbuk National University Medical School, Chongju 361-763, Korea.
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↵** To whom correspondence should be addressed: National Institutes of Health, Bldg. 3, Rm. 122, 3 Center Dr., MSC 0320, Bethesda, MD 20892-0320. Tel.: 301-496-9646; Fax: 301-480-0357.
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↵1 The abbreviations used are: PLC, phosphatidylinositol-specific phospholipase C; PI 3-kinase, phosphoinositide 3-kinase; PI(4,5)P2, phosphatidylinositol 4,5-bisphosphate; PI(3,4)P2, phosphatidylinositol 3,4-bisphosphate; PI(3,4,5)P3, phosphatidylinositol 3,4,5-trisphosphate; I(1,4,5)P3, inositol 1,4,5-trisphosphate; SH2, Src homology 2; PH, pleckstrin homology; p85, the 85-kDa regulatory subunit of PI 3-kinase; p110, the 110-kDa catalytic subunit of PI 3-kinase; GST, glutathioneS-transferase; fMLP, formylmethionyl-leucyl-phenylalanine; PDGF, platelet-derived growth factor; MLCK, myosin light chain kinase; PTK, protein-tyrosine kinase; DMEM, Dulbecco’s modified Eagle’s medium.
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- Received October 14, 1997.
- Revision received December 11, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
