Tarui Takehiko, Andronicos Nicholas, Czekay Ralf-Peter, Mazar Andrew P, Bdeir Khalil, Parry Graham C, Kuo Alice, Loskutoff David J, Cines Douglas B, Takada Yoshikazu
Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
J Biol Chem. 2003 Aug 8;278(32):29863-72. doi: 10.1074/jbc.M304694200. Epub 2003 May 15.
Urokinase-type plasminogen activator (uPA) induces cell adhesion and chemotactic movement. uPA signaling requires its binding to uPA receptor (uPAR/CD87), but how glycosylphosphatidylinositol-anchored uPAR mediates signaling is unclear. uPAR is a ligand for several integrins (e.g. alpha 5 beta 1) and supports cell-cell interaction by binding to integrins on apposing cells (in trans). We studied whether binding of uPAR to alpha 5 beta 1 in cis is involved in adhesion and migration of Chinese hamster ovary cells in response to immobilized uPA. This process was temperature-sensitive and required mitogen-activated protein kinase activation. Anti-uPAR antibody or depletion of uPAR blocked, whereas overexpression of uPAR enhanced, cell adhesion to uPA. Adhesion to uPA was also blocked by deletion of the growth factor domain (GFD) of uPA and by anti-GFD antibody, whereas neither the isolated uPA kringle nor serine protease domain supported adhesion directly. Interestingly, anti-alpha 5 antibody, RGD peptide, and function-blocking mutations in alpha 5 beta 1 blocked adhesion to uPA. uPA-induced cell migration also required GFD, uPAR, and alpha 5 beta 1, but alpha 5 beta 1 alone did not support uPA-induced adhesion and migration. Thus, binding of uPA causes uPAR to act as a ligand for alpha 5 beta 1 to induce cell adhesion, intracellular signaling, and cell migration. We demonstrated that uPA induced RGD-dependent binding of uPAR to alpha 5 beta 1 in solution. These results suggest that uPA-induced adhesion and migration of Chinese hamster ovary cells occurs as a consequence of (a) uPA binding to uPAR through GFD, (b) the subsequent binding of a uPA.uPAR complex to alpha 5 beta 1 via uPAR, and (c) signal transduction through alpha 5 beta 1.
尿激酶型纤溶酶原激活剂（uPA）可诱导细胞黏附和趋化运动。uPA信号传导需要其与uPA受体（uPAR/CD87）结合，但糖基磷脂酰肌醇锚定的uPAR如何介导信号传导尚不清楚。uPAR是几种整合素（如α5β1）的配体，并通过与相邻细胞上的整合素（反式）结合来支持细胞间相互作用。我们研究了uPAR与α5β1顺式结合是否参与中国仓鼠卵巢细胞对固定化uPA的黏附和迁移。这个过程对温度敏感，并且需要丝裂原活化蛋白激酶激活。抗uPAR抗体或uPAR的缺失会阻断细胞对uPA的黏附，而uPAR的过表达则会增强这种黏附。uPA生长因子结构域（GFD）的缺失和抗GFD抗体也会阻断对uPA的黏附，而单独的uPA kringle或丝氨酸蛋白酶结构域都不能直接支持黏附。有趣地是，可以阻断对uPA的黏附。uPA诱导的细胞迁移也需要GFD、uPAR和α5β1，但单独的α5β1并不支持uPA诱导的黏附和迁移。因此，uPA的结合导致uPAR作为α5β1的配体，从而诱导细胞黏附、细胞内信号传导和细胞迁移。我们证明，uPA在溶液中诱导uPAR与α5β1的RGD依赖性结合。这些结果表明，uPA诱导中国仓鼠卵巢细胞的黏附和迁移是以下结果：（a）uPA通过GFD与uPAR结合；（b）随后uPA.uPAR复合物通过uPAR与α5β1结合；（c）通过α5β1进行信号转导。
