Modification of Phosphatidylinositol 3-Kinase SH2 Domain Binding Properties by Abl- or Lck-mediated Tyrosine Phosphorylation at Tyr-688*
- Maria von Willebrand,
- Scott Williams,
- Manju Saxena,
- Jennifer Gilman,
- Pankaj Tailor,
- Thomas Jascur,
- Gustavo P. Amarante-Mendes‡,
- Douglas R. Green and
- Tomas Mustelin§
- From the Divisions of Cell Biology and Cellular Immunology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121
Abstract
In cells expressing the oncogenic Bcr-Abl tyrosine kinase, the regulatory p85 subunit of phosphatidylinositol 3-kinase is phosphorylated on tyrosine residues. We report that this phosphorylation event is readily catalyzed by the Abl and Lck protein-tyrosine kinases in vitro, by Bcr-Abl or a catalytically activated Lck-Y505F in co-transfected COS cells, and by endogenous kinases in transfected Jurkat T cells upon triggering of their T cell antigen receptor. Using these systems, we have mapped a major phosphorylation site to Tyr-688 in the C-terminal SH2 domain of p85. Tyrosine phosphorylation of p85 in vitro or in vivo was not associated with detectable change in the enzymatic activity of the phosphatidylinositol 3-kinase heterodimer, but correlated with a strong reduction in the binding of some, but not all, phosphoproteins to the SH2 domains of p85. This provides an additional candidate to the list of SH2 domains regulated by tyrosine phosphorylation and may explain why association of phosphatidylinositol 3-kinase with some cellular ligands is transient or of lower stoichiometry than anticipated.
Footnotes
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↵* This work was supported by Finska Läkaresällskapet, the Finnish Cancer Organizations, National Institutes of Health Grant GM52735 and American Cancer Society Grant CB-82 (to D. R. G.), and National Institutes of Health Grants GM48960 and AI35603 (to T. M.). This is publication 185 from the La Jolla Institute for Allergy and Immunology.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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↵‡ Brazilian Research Council (CNPq) Fellow.
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↵§ To whom correspondence should be addressed. Tel.: 619-558-3547; Fax: 619-558-3526; E-mail: tomas_mustelin{at}liai.org.
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↵1 The abbreviations used are: PI3K, phosphatidylinositol 3-kinase; HA, hemagglutinin; Tyr(P), phosphotyrosine; SH2, Src homology 2 region; SH3, Src homology 3 region; mAb, monoclonal antibody; TPCK,l-1-tosylamido-2-phenylethyl chloromethyl ketone; GST, glutathione S-transferase; PAGE, polyacrylamide gel electrophoresis.
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- Received May 23, 1997.
- Revision received December 1, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
