Sánchez-Mateos P, Arroyo A G, Balboa M A, Sánchez-Madrid F
Hospital de la Princesa, Universidad Autónoma de Madrid, Spain.
Eur J Immunol. 1993 Oct;23(10):2642-8. doi: 10.1002/eji.1830231038.
Leukocyte adhesion to and subsequent spreading on the endothelium are the initial steps in the migration of these cells to the surrounding tissues. We have investigated the participation of different VLA heterodimers in cell spreading by using the anti-beta 1 TS2/16 monoclonal antibody (mAb) which induces a conformational change of different VLA integrin receptors, enabling a high-affinity interaction with their ligands. Both VLA-4 and VLA-5 fibronectin (FN), as well as VLA-2 collagen (COL) receptors mediated cell spreading and morphological changes. The spreading of U-937 and alpha 4-transfected K-562 cells was induced in both FN and VCAM-1, suggesting that the morphological changes may be induced by cell-cell as well as cell-extracellular matrix (ECM) interactions. Furthermore, the beta 1-regulated cell spreading on VCAM-1 and COL took place independently of the VLA-5 FN receptor function. The enhancing effect on cell attachment induced by anti-beta 1 TS2/16 mAb was observed in the presence of different doses of cytochalasin D, whereas cell spreading was abolished. Signal transduction during beta 1-stimulated integrin-ligand interaction was also investigated. We have found the co-localization of beta 1 integrins and tyrosine-phosphorylated proteins during the spreading of U-937 and alpha 2- and alpha 4-transfected K-562 cells on both ECM (FN and COL) and cellular (VCAM-1) ligands. Kinetic studies showed that tyrosine phosphorylation was almost coincident with cellular spreading. The tyrosine phosphorylation of polypeptides of 130 kDa and 77 kDa was triggered in U-937 cells by the interaction of FN with the VLA-5 receptor in a high-affinity conformation. However, no signaling was observed by inducing the high-affinity state of receptor in the absence of appropriate ligand. These data suggest that tyrosine kinase activation is a post-receptor occupancy event that might be critical in regulating the adhesive properties of integrins.
白细胞黏附于内皮细胞并随后在内皮细胞上铺展是这些细胞迁移至周围组织的起始步骤。我们通过使用抗β1 TS2/16单克隆抗体（mAb）研究了不同VLA异二聚体在细胞铺展中的作用，该抗体可诱导不同VLA整合素受体发生构象变化，从而使其与配体进行高亲和力相互作用。VLA-4和VLA-5纤连蛋白（FN）受体以及VLA-2胶原蛋白（COL）受体均介导细胞铺展和形态变化。U-937细胞和α4转染的K-562细胞在FN和血管细胞黏附分子-1（VCAM-1）上均发生铺展，这表明形态变化可能由细胞-细胞以及细胞-细胞外基质（ECM）相互作用所诱导。此外，β1调节的细胞在VCAM-1和COL上的铺展独立于VLA-5 FN受体功能。在存在不同剂量细胞松弛素D的情况下，观察到抗β1 TS2/16 mAb对细胞黏附的增强作用，而细胞铺展则被消除。我们还研究了β1刺激的整合素-配体相互作用过程中的信号转导。我们发现，在U-937细胞以及α2和α4转染的K-562细胞在ECM（FN和COL）和细胞（VCAM-1）配体上的铺展过程中，β1整合素与酪氨酸磷酸化蛋白共定位。动力学研究表明，酪氨酸磷酸化几乎与细胞铺展同时发生。在U-937细胞中，FN与处于高亲和力构象状态的VLA-5受体相互作用可触发130 kDa和77 kDa多肽的酪氨酸磷酸化。然而，在没有合适配体的情况下诱导受体处于高亲和力状态时未观察到信号传导。这些数据表明，酪氨酸激酶激活是受体占据后的一个事件，可能在调节整合素的黏附特性中起关键作用。
