Cell surface expression of the McDonough strain of feline sarcoma virus fms gene product (gp 140fms).

The unique oncogene carried by the McDonough strain of feline sarcoma virus (SM-FeSV), called v-fms, directs the synthesis of a set of related glycoproteins, called gP 180gag-fms, gp 140fms, and gp 120fms. We have prepared antibodies to these proteins and used indirect immunofluorescence techniques on viable SM-FeSV transformed cells to demonstrate that fms-specific determinants are expressed on the external surface. The fms-specific fluorescence co-localized with clathrin and was detectable in clathrin-coated pits and endocytotic vesicles. Two cell surface labeling methods indicated that gp140fms was the only fms-related protein on the cell surface. In view of the relationship between the erbB oncogene product and the epidermal growth factor receptor, and the fact that growth factor receptors utilize clathrin-coated pits in endocytosis, we believe the gp140fms transforming protein of SM-FeSV also could function as an analog of a growth factor receptor.