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J Biol Chem. 1999 Jan 22;274(4):2303-7.

Definition of the sites of interaction between the protein tyrosine phosphatase SHP-1 and CD22.

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  • 1Howard Hughes Medical Institute, Department of Pathology and Molecular Microbiology, Center for Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.


CD22 phosphorylation is an early event of B cell antigen receptor engagement and results in the recruitment of the negative regulatory tyrosine phosphatase, SHP-1. Peptides representing the potential phosphorylation sites within the cytoplasmic domain of CD22 have been used to stimulate SHP-1 catalytic activity and to inhibit the binding of SHP-1 to CD22 (Doody, G., Justement, L., Delibrias, C., Matthews, R., Lin, J., Thomas, M., and Fearon, D. (1995) Science 269, 242-244). However, the sites of phosphorylation within the cytoplasmic domain of CD22 and the importance of each for the recruitment and activation of SHP-1 remain unknown. Here we demonstrate that there are multiple sites within the cytoplasmic domain of CD22 that interact with the Src homology 2 domains of SHP-1. Nevertheless, a minimum of two tyrosines in CD22 is required for the association with SHP-1. Furthermore, both Src homology 2 domains of SHP-1 are necessary for efficient binding to CD22.

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