Evidence for involvement of glycoprotein-CD45 phosphatase in reversing glycoprotein-CD3-induced microtubule-associated protein-2 kinase activity in Jurkat T-cells
Department of Molecular Genetics and Microbiology
Medical Subject Headings
Antigens, CD; Antigens, CD3; Antigens, CD45; Antigens, Differentiation; Antigens, Differentiation, T-Lymphocyte; Calcium; Calcium-Calmodulin-Dependent Protein Kinases; Cell Line; Enzyme Activation; Histocompatibility Antigens; Humans; Kinetics; Microtubules; Phosphoprotein Phosphatases; Phosphorylation; Phosphotyrosine; Protein Kinases; Receptors, Antigen, T-Cell; T-Lymphocytes; Tyrosine
Microbiology | Molecular genetics
Ligation of CD3/TCR on T-cells induces transient activation of lymphoid MAP-2 kinase (MAP-2K), a 43 kDa serine kinase which itself is a substrate of an unidentified tyrosine kinase (pp43). The reversibility of the MAP-2K response agrees with removal of tyrosine phosphates from pp43. Since both activity as well as tyrosine phosphorylation of MAP-2K could be prolonged by Na3VO4, a phosphotyrosine phosphatase inhibitor, we studied the effect of the common CD45 isoform, which is a member of the CD45 phosphatase family, on MAP-2K activity in vivo and in vitro. We demonstrate the ability of purified CD45 phosphatase to remove tyrosine phosphates from partially purified lymphoid MAP-2K. Utilizing the approach of heterologous receptor aggregation, we also showed that CD45 could inhibit the induction of MAP-2K activity in intact Jurkat cells during CD3 or CD3 + CD4 stimulation. We therefore suggest that this phosphatase may control the activity of lymphoid MAP-2K in vivo.
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Citation: Biochem J. 1991 Jun 1;276 ( Pt 2):481-5.