Endothelial Cell Spreading on Type IV Collagen and Spreading-Induced FAK Phosphorylation Is Regulated by Ca2+Influx

The interaction of endothelial cells with their basement membrane and local stroma is highly regulated. The observation that CAI, an inhibitor of Ca++influx, inhibited human umbilical vein endothelial cell (HUVEC) adhesion suggested that Ca++influx was a regulator of HUVEC–matrix interaction. Exposure of HUVEC cells to CAI or SK&F 96365, another Ca++influx inhibitor, selectively blocked spreading but not attachment on type IV collagen but not type I collagen. Ca++influx blockade also prevented spreading-induced FAK phosphorylation and kinase activity and secondary paxillin phosphorylation. No inhibitory effect was observed when the cells spread on type I collagen. The inhibitory effect of CAI on spreading and spreading-associated FAK phosphorylation and kinase activity was reversible. These data indicate that HUVEC cells have a selective requirement for Ca++influx for spreading and downstream signaling on basement membrane type IV collagen.