| Research Abstract |
1.We examined the F-actin filaments and the expression of integrin in human vascular endothelial cells cultured on type I and type V collagens.The cells attached to type V collagen, formed complete F-actin filaments, and expressed alpha2, alpha3, and beta1 integrins 0.5-1 h after inoculation.These phenomena are referred to as the first ECM-integrin-cytoskeleton system.After 24h, the cells on type V collagen failed to form the second system, and gradually detached from the substrate.In contrast, the cells on type I collagen developed both the first and second systems, and acclimatized themselves to the environment.The cell detachment from type V collagen is not attributed to endogenously produced TSP with anti-adhesive properties, but resulted from the failure to reconstitute the second ECM-integrin-cytoskeleton system in focal adhesion.
We next attempted to identify the cell surface integrins for native and heat-denatured type I collagens in primary and secondary cultures of rabbit aort
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ic smooth muscle cells (SMC).The cells in the contractile state adhered to native type I collagen through the alpha1beta1 and alpha1beta1 integrins, but the relative amount of alpha3 integrin decreased.The initial adhesion of cells in secondary culture to native type I collagen was mediated only by the alpha1beta1 and alpha3beta1 integrin.The cell-binding sequences did not contain DGEA or RGD.In contrast, cell adhesion to denatured type I collagen was mediated only by the alpha1beta1 integrin in the contractile state and by the alpha1beta1、alpha2beta1, and alpha3beta1 integrins in the synthetic state.In denatured type I collagen, the sequences DGEA and RGD served as a recognition site for the alpha2beta1 integrins.Our results suggest that rabbit SMC can recognize the native and denatured type I collagens throgh interactions with triple helix-binding receptors and alpha3 chain-binding receptors and that the expression pattem of integrins changes in conjunction with the phenotypic properties of vascular SMC. Less
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