Direct identification of a major autophosphorylation site on vascular endothelial growth factor receptor Flt-1 that mediates phosphatidylinositol 3'-kinase binding.

Progress has been made in our understanding of the mechanism by which the binding of vascular endothelial growth factor (VEGF) to cognate receptors induces a range of biological responses, but it is far from complete. Identification of receptor autophosphorylation sites will allow us to determine how activated VEGF receptors are coupled to specific downstream signalling proteins. In the present study, we have expressed human VEGF receptors in insect cells using the baculovirus expression system, identified a major autophosphorylation site on the VEGF receptor fms-like tyrosine kinase-1 (Flt-1) by HPLC-electrospray ionization (ESI)-MS, and characterized in vitro interactions between Flt-1 and phosphatidylinositol 3'-kinase (PI3-kinase).

Fv2 encodes a truncated form of the Stk receptor tyrosine kinase.

The Friend virus susceptibility 2 (Fv2) locus encodes a dominant host factor that confers susceptibility to Friend virus-induced erythroleukaemia in mice. We mapped Fv2 to a 1.0-Mb interval that also contained the gene (Ron) encoding the stem cell kinase receptor (Stk).

Characterization of the VEGF binding site on the Flt-1 receptor.

The angiogenic growth factor VEGF binds to the receptor tyrosine kinases Flt-1 and KDR/Flk-1. Immunoglobulin (Ig)-like loop-2 of Flt-1 is involved in binding VEGF, but the contribution of other Flt-1 Ig-loops to VEGF binding remains unclear. We tested the ability of membrane-bound chimeras between the extracellular domain of Flt-1 and the cell adhesion molecule embigin to bind VEGF.

Embigin, a developmentally expressed member of the immunoglobulin super family, is also expressed during regression of prostate and mammary gland.

Cell adhesion molecules (CAMs) are intimately involved in a variety of cellular processes, including development, cell growth, apoptosis, and differentiation. Interaction of CAMs with components of the extracellular matrix (ECM) growth factors, and other CAMs provides an intricate regulatory mechanism for a diverse range of cellular responses. Embigin is a developmentally expressed protein that is a member of the immunoglobulin superfamily (IgSF) class of CAMs.

Stable and temperature-sensitive transformation of rat kidney epithelial cells suppresses expression of acidic fibroblast growth factor 1 but activates secretion of fibroblast growth factor 3 (int-2) and vascular endothelial growth factor.

Rat kidney proximal tubule epithelial cells (RPTE) in primary culture express acidic fibroblast growth factor 1 (FGF-1). Transformation of RPTE by SV40 (SV-RPTE) suppressed FGF-1 expression but activated secretion of FGF-like factor(s). SV-RPTE conditioned medium contained growth-promoting activity for SV-RPTE and human umbilical vein endothelial cells, indicating that both autocrine and angiogenic factors were secreted.