Src Kinase Activity Is Regulated by the SHP-1 Protein-tyrosine Phosphatase

doi:10.1074/jbc.272.34.21113

Src Kinase Activity Is Regulated by the SHP-1 Protein-tyrosine Phosphatase*

From the ^‡Departments of Medicine, Immunology and Medical Genetics and Microbiology, University of Toronto and the Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada, the ^‖Department of Molecular Oncology, M.D. Anderson Cancer Center, Houston, Texas 77030, and the ^‡Toronto Hospital Research Institute and the Canadian Red Cross Society, Toronto, Ontario M5G 2M1, Canada

Abstract

Activation of the cellular Src tyrosine kinase depends upon dephosphorylation of the carboxyl-terminal inhibitory tyrosine phosphorylation site. Herein we show that Src isolated from human platelets and Jurkat T cells is preferentially dephosphorylated at its inhibitory phosphotyrosine site by the SHP-1 tyrosine phosphatase. The data also revealed association of Src with SHP-1 in both platelets and lymphocytes and the capacity of Src to phosphorylate SHP-1 and interact with the SHP-1 NH₂-terminal SH2 domain in vitro. Analysis of Src activity in thymocytes from SHP-1-deficient motheaten and viable motheaten mice revealed this kinase activity to be substantially lower than that detected in wild-type thymocytes, but to be enhanced by in vitroexposure to SHP-1. Similarly, immunoblotting analysis of thymocyte Src expression before and after selective depletion of active Src protein indicated that the proportion of active relative to inactive Src protein is markedly reduced in motheaten compared with wild-type cells. These observations, together with the finding of reduced Src activity in HEY cells expressing a dominant negative form of SHP-1, provide compelling evidence that SHP-1 functions include the positive regulation of Src activation.

Footnotes

↵* This work was supported in part by grants from the Medical Research Council of Canada, National Cancer Institute of Canada (NCIC), and the Canadian Red Cross Society and Blood Services Research and Development Project Grant.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.
↵§ Recipient of an NCIC Steve Fonyo Studentship Award.
↵¶ The first two authors contributed equally to this work and share first authorship.
↵** An Arthritis Society of Canada Research Scientist. To whom correspondence should be addressed: Mount Sinai Hospital, Rm. 656A, 600 University Ave., Toronto, Ontario M5G 1X5, Canada.
↵1 The abbreviations used are: PTK, protein-tyrosine kinase; PTP, protein-tyrosine phosphatase; SH, Src homology domain; PAGE, polyacrylamide gel electrophoresis; PBL, peripheral blood lymphocytes; GST, glutathioneS-transferase; Tricine,N-tris(hydroxymethyl)methylglycine.
- Received May 27, 1997.