Selective regulation of Lyn tyrosine kinase by CD45 in immature B cells.
It has been well established that protein-tyrosine phosphatase CD45 is critically involved in the regulation of initial tyrosine phosphorylation and effector functions of T and B cells. However, the signaling pathway governed by CD45 is not completely understood. In B cells, it has not been unequivocally resolved as to which protein-tyrosine kinases (PTKs) associated with B cell antigen receptor are regulated by CD45 in intact cells. As a first step toward the elucidation of CD45-initiated signaling events, we have tried to identify physiological substrates for CD45 by analyzing PTK activity in CD45-deficient clones recently generated from the immature B cell line WEHI-231. The results clearly demonstrated that among PTKs examined (Lyn, Lck, and Syk), only Lyn kinase is dysregulated in the absence of CD45 such that without B cell antigen receptor ligation, Lyn is hyperphosphorylated and activated in CD45-negative clones. Thus, Lyn seems to be a selective in vivo substrate for CD45 in immature B cells.
D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology*; D002460:Cell Line; D004792:Enzyme Precursors / Q000302:isolation & purification / Q000378:metabolism; D015870:Gene Expression; D006706:Homeostasis; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D051379:Mice; D011505:Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D013379:Substrate Specificity; D000072377:Syk Kinase; D019061:src-Family Kinases / Q000302:isolation & purification / Q000378:metabolism*
D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D011947:Receptors, Antigen, B-Cell; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D017493:Leukocyte Common Antigens