Heterodimeric Phosphoinositide 3-Kinase Consisting of p85 and p110β Is Synergistically Activated by the βγ Subunits of G Proteins and Phosphotyrosyl Peptide

doi:10.1074/jbc.272.39.24252

Heterodimeric Phosphoinositide 3-Kinase Consisting of p85 and p110β Is Synergistically Activated by the βγ Subunits of G Proteins and Phosphotyrosyl Peptide*

From the ^‡Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, the ^§Laboratory of Biochemistry, Department of Agricultural Chemistry, Faculty of Agriculture, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, and the ^¶Ui Laboratory, Institute of Physical and Chemical Research, Hirosawa 2-1, Wako-shi 351-01, Japan

Abstract

Phosphoinositide 3-kinase (PI 3-kinase) is a key signaling enzyme implicated in variety of receptor-stimulated cell responses. Receptors with intrinsic or associated tyrosine kinase activity recruit heterodimeric PI 3-kinases consisting of a 110-kDa catalytic subunit (p110) and an 85-kDa regulatory subunit (p85). We separated a PI 3-kinase that could be stimulated by the βγ subunits of G protein (Gβγ) from rat liver. The Gβγ-sensitive PI 3-kinase appeared to be a heterodimer consisting of p110β and p85 (or their related subunits). The stimulation by Gβγ was inhibited by the GDP-bound α subunit of the inhibitory GTP-binding protein. Moreover, the stimulatory action of Gβγ was markedly enhanced by the simultaneous addition of a phosphotyrosyl peptide synthesized according to the amino acid sequence of the insulin receptor substrate-1. Such enzymic properties could be observed with a recombinant p110β/p85α expressed in COS-7 cells with their cDNAs. In contrast, another heterodimeric PI 3-kinase consisting of p110α and p85 in the same rat liver, together with a recombinant p110α/p85α, was not activated by Gβγ, although their activities were stimulated by the phosphotyrosyl peptide. These results indicate that p110β/p85 PI 3-kinase may be regulated in a cooperative manner by two different types of membrane receptors, one possessing tyrosine kinase activity and the other activating GTP-binding proteins.

Footnotes

↵* This work was supported in part by research grants from the Scientific Research Fund of the Ministry of Education, Science, Sports, and Culture of Japan and by Grant JSPS-RFTF 96L00505 from the “Research for the Future” Program of the Japan Society for the Promotion of Science.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.
↵‖ To whom correspondence should be addressed. Tel.: 81-3-3812-2111 (ext. 4753); Fax: 81-3-3815-9604; E-mail:hazeki{at}mol.f.u-tokyo.ac.jp.
↵1 The abbreviations used are: PI, phosphoinositide; PtdIns(3)P, phosphatidylinositol 3-monophosphate; PtdIns(3,4)P ₂, phosphatidylinositol 3,4-bisphosphate; PtdIns(4,5)P ₂, phosphatidylinositol 4,5-bisphosphate; PtdIns(3,4,5)P ₃, phosphatidylinositol 3,4,5-triphosphate; SH2, Src homology 2; SH3, Src homology 3; Gα, α subunits of GTP-binding proteins; Gβγ, βγ subunits of GTP-binding proteins; p85, 85-kDa regulatory subunit of PI 3-kinase; p110, 110-kDa catalytic subunit of PI 3-kinase; PAGE, polyacrylamide gel electrophoresis; DTT, dithiothreitol; MES, 4-morpholineethanesulfonic acid; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid.
↵2 H. Kurosu, O. Hazeki, and T. Katada, unpublished results.
↵3 T. Suzuki, O. Hazeki, and T. Katada, manuscript in preparation.
- Received June 9, 1997.
- Revision received July 29, 1997.