Lymphocyte lineage-restricted tyrosine-phosphorylated proteins that bind PLC gamma 1 SH2 domains

• Published in: The Journal of biological chemistry 1992-07, Vol.267 (19), p.13610-13616
• Main Authors: Gilliland, L K, Schieven, G L, Norris, N A, Kanner, S B, Aruffo, A, Ledbetter, J A
• Format: Article
• Language: English
• Subjects: Binding Sites; Blood Proteins - metabolism; Blotting, Western; Cells, Cultured; ErbB Receptors - metabolism; Humans; Lymphocytes - enzymology; Lymphocytes - metabolism; Phosphorylation; Platelet-Derived Growth Factor - metabolism; Precipitin Tests; Receptors, Cell Surface - metabolism; Receptors, Platelet-Derived Growth Factor; Tumor Cells, Cultured; Type C Phospholipases - metabolism; Tyrosine - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)42256-9

Epidermal growth factor (EGF) or platelet-derived growth factor binding to their receptor on fibroblasts induces tyrosine phosphorylation of PLC gamma 1 and stable association of PLC gamma 1 with the receptor protein tyrosine kinase. Similarly in lymphocytes, cross-linking of antigen receptors induces the formation of molecular complexes incorporating PLC gamma 1; however, associated kinase activity is thought to be mediated through cytoplasmic protein tyrosine kinase(s). In this report, we generated a fusion protein containing the SH2 domains of human PLC gamma 1 and human IgG1 heavy chain constant region to identify lymphocyte phosphoprotein-binding PLC gamma 1 SH2 domains following cellular activation. As in EGF- or platelet-derived growth factor-stimulated fibroblasts, PLC gamma 1 is coprecipitated in activated lymphocytes, complexed with associated tyrosine-phosphorylated proteins. One of these, a 35/36-kDa protein found prominently in T cells and at lower levels in B cells, bound to the fusion protein in immunoprecipitation experiments. The fusion protein showed lineage restricted association with a 74-kDa phosphoprotein in T cells and a 93-kDa phosphoprotein in B cells. It bound to activated EGF receptor in fibroblasts as expected, and protein tyrosine kinase activity was precipitated from EGF-stimulated cells. However, PLC gamma 1-associated protein tyrosine kinase activity was not detected in activated lymphocytes. These data suggest that lymphocyte PLC gamma 1 SH2-binding proteins are cell lineage specific and may be transiently associated with activated PLC gamma 1.