Disassembly of F-actin filaments in human endothelial cells cultured on type V collagen.

We examined the inhibitory activity of type V collagen on cell attachment and cell growth and the role of stress fibers and beta 1 integrin in cultured human endothelial cells. Human endothelial cells cultured on type V collagen attached temporarily to the substrate and formed stress fibers. However, the cells failed to proliferate and gradually detached from the substrate. After 24 h, the cells on type V collagen lacked discernible stress fibers (F-actin filaments) and exhibited dots in small aggregates of F-actin. In addition, the cells expressed little or no proteins as focal adhesions, including vinculin and beta 1 integrin. In contrast, the cells on fibronectin and type I collagen formed complete F-actin filaments, exhibited sufficient vinculin and beta 1 integrin, and grew logarithmically from 2 days. On the other hand, human smooth muscle cells formed complete F-actin filaments, revealed typical focal adhesions, and started to proliferate rapidly after 24 h on type V collagen as well as on fibronectin and type I collagen. Thus, the disassembly of F-actin filaments was observed as a specific phenomenon in human endothelial cells cultured on type V collagen. Moreover, the F-actin filaments disappeared from endothelial cells treated with cytochalasin D after 24 h and the cells detached from fibronectin and type I collagen with time, a result consistent with the observations on type V collagen. Accordingly, the disassembly of F-actin filaments in focal adhesions may result in the detachment of endothelial cells from type V collagen.