Within the hemopoietic system, LAR phosphatase is a T cell lineage-specific adhesion receptor-like protein whose phosphatase activity appears dispensable for T cell development, repertoire selection and function.
Expression of the receptor-type tyrosine phosphatase LAR was studied in cells of the murine hemopoietic system. The gene is expressed in all cells of the T cell lineage but not in cells of any other hemopoietic lineage and the level of expression in T cells is developmentally regulated. The CD4(-)8(-)44(+) early thymic immigrants and mature (CD4(+)8(-)/CD4(-)8(+)) thymocytes and T cells express low levels, whereas immature (CD4(-)8(-)44(-) and CD4(+)8(+)) thymocytes express high levels of LAR. Among bone marrow cells only uncommitted c-kit(+)B220(+)CD19(-) precursors, but not B cell lineage committed c-kit(+)B220(+)CD19(+) precursors, express low levels of LAR. In contrast to the c-kit(+)B220(+)CD19(+) pre-BI cells from normal mice, counterparts of pre-BI cells from PAX-5-deficient mice express LAR, indicating that PAX-5-mediated commitment to the B cell lineage results in suppression of LAR. During differentiation of PAX-5-deficient pre-BI cell line into non-T cell lineages, expression of LAR is switched off, but it is up-regulated during differentiation into thymocytes. Thus, within the hemopoietic system, LAR appears to be a T cell lineage-specific receptor-type phosphatase. However, surprisingly, truncation of its phosphatase domains has no obvious effect on T cell development, repertoire selection or function.
Basel Institute for Immunology, Basel, Switzerland.
G
G
Terszowski
A
A
Jankowski
W J
WJ
Hendriks
A G
AG
Rolink
P
P
Kisielow
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001854:Bone Marrow Cells / Q000276:immunology; D019070:Cell Lineage; D002478:Cells, Cultured; D002999:Clone Cells; D003001:Cloning, Molecular; D051379:Mice; D008817:Mice, Mutant Strains; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology
D000911:Antibodies, Monoclonal; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D016693:Receptors, Antigen, T-Cell, alpha-beta; D011956:Receptors, Cell Surface; D017027:Protein Tyrosine Phosphatases; C000709129:Ptprf protein, mouse; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2