The phosphorylated 1169-tyrosine containing region of Flt-1 kinase (VEGFR-1) is a major binding site for PLC gamma

Flt-1, a tyrosine kinase receptor for vascular endothelial growth factor (VEGF), plays important roles in the ansogenesis required for embryogenesis and in monocyte/macrophage migration. However, the signal transduction of: Flt-1 is poorly understood due to its very weak tyrosine kinase activity. Therefore, we overexpressed Flt-1 in insect cells using the Baculovirus system in order to examine for autophosphorylation sites and association with adapter molecules such as phospholipase C gamma-1 (PLC gamma). Tyr-1169 and Tyr-1213 on Flt-1 were found to be auto-phosphorylated, but only a phenylalanine mutant of Tyr-1169 strongly suppressed its association with PLC gamma. In Flt-1 overexpressing NIH3T3 cells, VEGF induced autophosphorylation of Flt-1, tyrosine-phosphorylation of PLC gamma and protein kinase C-dependent activation of MAP kinase. These results strongly suggest that Tyr-1169 on Flt-1 is a major binding site for PLC gamma and important for Fit-1 signal transduction within the cell. (C) 1997 Academic Press.