Ni Na, Kevil Christopher G, Bullard Daniel C, Kucik Dennis F
Department of Genomics and Pathobiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Biophys J. 2003 Dec;85(6):4122-33. doi: 10.1016/S0006-3495(03)74824-3.
An early step in activation of leukocyte adhesion is a release of integrins from cytoskeletal constraints on their diffusion, leading to rearrangement and, consequently, increased avidity. Static adhesion assays using purified ligand as a substrate have demonstrated that very low doses of cytochalasin D disconnect beta2-integrins from their cytoskeletal links, allowing rearrangement and activating adhesion. The adhesion process in blood vessels is poorly simulated by these assays, however, for two reasons: leukocyte adhesion to endothelium 1), occurs in the presence of blood flow and 2), involves the simultaneous interactions of multiple sets of adhesion molecules. We investigated the effect of cytochalasin D, at concentrations that increase integrin diffusion but do not alter leukocyte shape and surface features, on adhesion of leukocytes to endothelial cells under flow. Cytochalasin D increased the number of rolling cells, the number of firmly adherent cells, and the duration of both rolling and firm adhesion. These effects required endothelial cell expression of ICAM-1, the ligand for leukocyte beta2-integrins. The beta2-integrin-ICAM-1 interaction alone was not sufficient, however. Experiments using purified substrates demonstrated that avidity effects on activation of adhesion under flow require functional cooperativity between integrins and other adhesion receptors.
白细胞黏附激活的早期步骤是整合素从细胞骨架对其扩散的限制中释放出来，导致重排，从而增加亲和力。使用纯化配体作为底物的静态黏附试验表明，极低剂量的细胞松弛素D可使β2整合素与其细胞骨架连接断开，从而允许重排并激活黏附。然而，这些试验对血管中的黏附过程模拟得很差，原因有两个：白细胞与内皮细胞的黏附1）发生在血流存在的情况下，2）涉及多组黏附分子的同时相互作用。我们研究了细胞松弛素D在增加整合素扩散但不改变白细胞形状和表面特征的浓度下，对流动状态下白细胞与内皮细胞黏附的影响。细胞松弛素D增加了滚动细胞的数量、牢固黏附细胞的数量以及滚动和牢固黏附的持续时间。这些效应需要内皮细胞表达ICAM-1，即白细胞β2整合素的配体。然而，仅β2整合素-ICAM-1相互作用是不够的。使用纯化底物的实验表明，在流动状态下，亲和力对黏附激活的影响需要整合素与其他黏附受体之间的功能协同作用。
