The type I TGFß receptor ALK‐1 and it’s ligands promote angiogenesis (544.2)

Abstract

Control of angiogenesis is critical in diseases such as cancer, heart disease, or wound repair. Growth factors such as transforming growth factor beta (TGFß) and fibroblast growth factor 2 (FGF‐2) contribute to angiogenesis. The TGFß family signaling receptor Activin‐Like Kinase 1 Receptor (ALK‐1) is expressed in coronary venular endothelial cells (CVEC) at near confluent cell densities on gelatin, but not collagen but it is induced by TGFß + FGF‐2 during tube formation in collagen. Other genes induced during tube formation were Smad 6 and Fibroblast Growth Factor Receptor 1 (FGFR1). By contrast, ALK‐5, a related TGFß type 1 receptor, and TGFßRII were expressed in these cells in both gelatin and collagen. ALK‐1 is also expressed in other EC types, smooth muscle cells, cardiac fibroblasts, embryonic fibroblasts (3T3) but not epithelial cells. Three ligands: TGFß, activin, and bone morphogenetic protein 9 (BMP‐9), have been shown to bind ALK‐1. We show that endogenous activin binds ALK 1 and can be displaced by exogenous TGFß. It may function to regulate control of ALK 1 activation. The response of endothelial cells to various ALK‐1 ligands may depend on the cell matrix of endothelial cells and which other co‐receptors (type II receptors and endoglin) are expressed. We are: 1) testing expression of various ALK‐1 ligands and co‐receptors in endothelial cells under various conditions; and 2) we are generating mutants of ALK‐1, ALK‐5, and endoglin to further test their roles in angiogenesis.Grant Funding Source: Research support was from AHA‐TX and Dept Veteran’s Affairs grants (JH)