Coclustering CD45 with CD4 or CD8 alters the phosphorylation and kinase activity of p56lck.
Antibody-mediated CD4 crosslinking results in increased tyrosine phosphorylation and tyrosine kinase activity of the associated p56lck. Treatment with anti-CD4 and anti-Ig also induced the phosphorylation of p56lck in a CD45- mutant cell line, indicating that the increase in phosphotyrosine content of p56lck is not the result of being sequestered from CD45 protein tyrosine phosphatase (PTPase). Antibody-mediated coclustering of CD45 with CD4 inhibited the anti-CD4-induced phosphorylation of p56lck on tyrosine and the concomitant increase in in vitro kinase activity. Similar results were obtained when CD45 was coclustered with CD8 on cytotoxic T cell lines. These observations provide strong evidence that p56lck is a substrate for CD45 in vivo and provide an assay to study the regulation and specificity of CD45 PTPase activity.
Ostergaard
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HL
Department of Cancer Biology, Salk Institute, San Diego, California 92138.
Trowbridge
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IS
D000937:Antigen-Antibody Reactions; D000943:Antigens, Differentiation / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D015704:CD4 Antigens / Q000276:immunology*; D016827:CD8 Antigens; D002460:Cell Line; D006649:Histocompatibility Antigens / Q000276:immunology*; D015151:Immunoblotting; D066298:In Vitro Techniques; D017493:Leukocyte Common Antigens; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D016827:CD8 Antigens; D006649:Histocompatibility Antigens; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D017493:Leukocyte Common Antigens