Cells transformed by the McDonough strain of feline sarcoma virus express at their surface a v-fms-specific transmembrane glycoprotein designated gp140v-fms. By labeling with 32Pi, gp140v-fms was shown to be phosphorylated 30-fold more in serine residues than were the cytosolic v-fms polypeptides gp180gag-fms and gp120v-fms. By using the phosphotyrosine phosphatase-specific inhibitor sodium orthovanadate, an additional tyrosine phosphorylation was observed in vivo, again involving predominantly gp140v-fms. In vitro studies showed that the v-fms proteins were phosphorylated by protein kinase C in a calcium- and phosphatidylserine-dependent manner.

Tamura, T., Simon, E., Niemann, H., Snoek, G. T., & Bauer, H. (1986). gp140v-fms molecules expressed at the surface of cells transformed by the McDonough strain of feline sarcoma virus are phosphorylated in tyrosine and serine. Molecular and Cellular Biology, 6(12), 4745–4748.