title: Regulation of Lck and Fyn tyrosine kinase activities by transmembrane protein tyrosine phosphatase leukocyte common antigen-related molecule.
abstract: Leukocyte common antigen-related molecule (LAR) is a receptor-like protein tyrosine phosphatase (PTPase) with two PTPase domains. In the present study, we detected the expression of LAR in the brain, kidney, and thymus of mice using anti-LAR PTPase domain subunit monoclonal antibody (mAb) YU1. In the thymus, LAR was expressed on CD4(-)CD8(-) and CD4(-)CD8(low) thymocytes. The development of thymocytes in CD45 knockout mice is blocked partially in the maturation of CD4(-)CD8(-) to CD4(+)CD8(+). We postulated that LAR regulates Lck and Fyn in the immature thymocytes. Transfection of wild-type LAR activated extracellular signal-regulated kinase signal transduction pathway in CD45-deficient Jurkat cells stimulated with anti-CD3 mAb. LAR mutants, with Cys to Ser mutation in the catalytic center of PTPase D1, bound to tyrosine-phosphorylated Lck and Fyn, and LAR PTPase domain 2 was tyrosine phosphorylated by Fyn tyrosine kinase. The phosphorylated LAR was associated with Fyn Src homology 2 domain. Moreover, LAR dephosphorylated phosphorylated tyrosine residues in both the COOH terminus and kinase domain of Fyn in vitro. Our results indicate that Lck and Fyn would be substrates of LAR in immature thymocytes and that each LAR PTPase domain plays distinct functional roles in phosphorylation and dephosphorylation.
authors.affiliation: Department of Immunology, Graduate School of Pharmaceutical Sciences, Osaka University, Yamadaoka, Suita, Osaka, Japan. tujikawa@phs.osaka-u.ac.jp
authors.forename: Kazutake
authors.initials: K
authors.lastname: Tsujikawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ichijo
authors.forename: Kazuki
authors.initials: K
authors.lastname: Moriyama
authors.forename: Noriko
authors.initials: N
authors.lastname: Tadotsu
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Naoki
authors.initials: N
authors.lastname: Sakane
authors.forename: So-ichiro
authors.initials: S
authors.lastname: Fukada
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Furukawa
authors.forename: Haruo
authors.initials: H
authors.lastname: Saito
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015704:CD4 Antigens / Q000096:biosynthesis; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D016827:CD8 Antigens / Q000096:biosynthesis; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D019169:Jurkat Cells; D017493:Leukocyte Common Antigens / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008156:Luciferases / Q000378:metabolism; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D051379:Mice; D008957:Models, Genetic; D009154:Mutation; D010766:Phosphorylation; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D015398:Signal Transduction; D013950:Thymus Gland / Q000166:cytology; D014018:Tissue Distribution; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D000911:Antibodies, Monoclonal; D015704:CD4 Antigens; D016827:CD8 Antigens; D018076:DNA, Complementary; D011518:Proto-Oncogene Proteins; D014443:Tyrosine; D008156:Luciferases; D005982:Glutathione Transferase; C494957:FYN protein, human; C494960:Fyn protein, mouse; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051076:Proto-Oncogene Proteins c-fyn; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases