Analysis of the effects of Gla-containing proteins and their receptors on the proliferation of vascular smooth muscle cells.

新的受体酪氨酸激酶包括Sky，我们已经从Hep G2 cDNA文库中克隆，Axl/Ufo和Mer/Eyk形成基于独特胞外结构域的亚家族。最近，已报道含有γ-羧基谷氨酸（Gla）的蛋白质，蛋白S和Gas 6是受体酪氨酸激酶Axl/Sky亚家族的生理配体。在本研究中，我们试图阐明这种配体-受体系统介导的新信号通路在血管平滑肌细胞增殖中的生理重要性。人蛋白S和大鼠Gas 6均未能诱导大鼠动脉血管平滑肌细胞增殖，然而，中野等人报道，大鼠Gas 6增强凝血酶的促有丝分裂活性。Gas 6和Axl/Sky受体亚家族的研究表明，人蛋白S与Axl、Sky和Mer的可溶性受体结合能力较强，而与Axl、Sky和Mer的结合能力较弱。Gas 6的C-末端性激素结合球蛋白样结构域是Gas 6与Axl结合所必需的，而N-末端Gla结构域对Gas 6与Axl的相互作用具有调节作用。为了了解由结合蛋白S和Gas 6介导的Axl/Sky受体家族的新信号通路是否与血管痉挛性病变的形成有关，我们继续确定这些分子在血管平滑肌细胞增殖的病变中的表达。

Novel receptor tyrosine kinases including Sky, which we have cloned from a Hep G2 cDNA library, Axl/Ufo and Mer/Eyk form a subfamily based on a unique extracellular domain. Recently gamma-carboxyglutamic acid (Gla)-containing proteins, protein S and Gas6, have been reported to be physiological ligands for the Axl/Sky subfamily of receptor tyrosine kinases. In this study, we tried to elucidate the physiological importance of the novel signaling pathway mediated by this ligand-receptor system in the proliferation of vascular smooth muscle cells.Both human protein S and rat Gas6 failed to induce proliferation of rat arterial vascular smooth muscle cells, however, rat Gas6 potentiated the mitogenic activity of thrombin as reported by Nakano et al. Species specificity has been reported to exist in the interaction between protein S or Gas6 and Axl/Sky receptor subfamily, we are now analyzing the effect of human protein S on the proliferation of bovine and human vascular smooth muscle cells.Analysis of the binding ability of the soluble receptors of human Axl, human Sky and mouse Mer composed of the extracellular domain of receptors fused to the Fc domain of immunoglobulin G1 showed that rat Gas6, but not human protein S,bound to Axl, Sky and Mer. The C-terminal sex hormone-binding globulin-like domain of Gas6 was indispensable for the binding of Gas6 to Axl and the N-terminal Gla domain had a regulatory role on the interaction.We developed a swine model of coronary spasms with intimal thickening by chronically treating the outside of the coronary arteries with a inflammatory cytokine, IL-1beta. In order to know whether the novel signaling pathway mediated by binding protein S and Gas6 to Axl/Sky receptor family is implicated in formation of the vasospastic lesions, we proceed to determine the expression of these molecules in the lesions with proliferation of vascular smooth muscle cells.