Lymphocyte lineage-restricted tyrosine-phosphorylated proteins that bind PLC gamma 1 SH2 domains.
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.
Gilliland
L K
LK
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, Washington 98121.
Schieven
G L
GL
Norris
N A
NA
Kanner
S B
SB
Aruffo
A
A
Ledbetter
J A
JA
D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D008214:Lymphocytes / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011233:Precipitin Tests; D011956:Receptors, Cell Surface / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
D001798:Blood Proteins; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D014443:Tyrosine; D066246:ErbB Receptors; D017479:Receptors, Platelet-Derived Growth Factor; D010738:Type C Phospholipases