title: Appearance of the LAT protein at an early stage of B-cell development and its possible role.
abstract: The linker protein LAT is expressed mainly in T and natural killer (NK) cells. LAT-deficient mice have an arrest of intrathymic T-cell development at the CD4+ CD8+ stage and lack mature T cells in the periphery. However, no gross abnormality in development and function of the B and NK cells has been described. Here we report that LAT is expressed in mouse progenitor B (pro-B) and precursor B (pre-B) cells, but not in immature or mature B cells. LAT in pre-B cells becomes tyrosine phosphorylated upon cross-linking of the pre-B-cell receptor (pre-BCR) by anti- micro antibody. Incubation of 1xN/2b (mouse pre-B-cell line) cells or bone marrow cells from microMT/ microMT mice, which lack B cells after the small pre-B-cell stage, with anti-Ig beta antibody resulted in the downregulation of LAT expression. Transgenic mice which expressed LAT protein in B-lineage cells showed an increased proportion of pro- and large pre-B cells in the bone marrow and a remarkable reduction in the numbers of mature B cells in peripheral lymphoid tissues. Collectively, the present results indicate that LAT is expressed in the cells at the early stages of B-lineage development, but is absent in immature and mature B cells. LAT may play a crucial role in the negative regulation of B-cell development at the transition from pre-B to mature B-cell stages, and signal(s) via the pre-BCR may extinguish LAT expression, thus allowing pre-B-cell differentiation towards the mature B-cell stage.
authors.affiliation: Department of Molecular Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Oya
authors.forename: Jiyang
authors.initials: J
authors.lastname: Wang
authors.forename: Yumi
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Koga
authors.forename: Takeshi
authors.initials: T
authors.lastname: Watanabe
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D002454:Cell Differentiation / Q000276:immunology; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D015536:Down-Regulation / Q000276:immunology; D005434:Flow Cytometry; D008213:Lymphocyte Activation / Q000276:immunology; D008221:Lymphoid Tissue / Q000276:immunology; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D013154:Spleen / Q000276:immunology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D011947:Receptors, Antigen, B-Cell; D014443:Tyrosine