Kucik D F, Dustin M L, Miller J M, Brown E J
Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA,
J Clin Invest. 1996 May 1;97(9):2139-44. doi: 10.1172/JCI118651.
Lymphocytes activate adhesion to intracellular adhesion mlecule 1 (ICAM-1) via leukocyte function associated antigen 1 (LFA-1), their major beta 2 integrin, in response to PMA (phorbol 12-myristate 13-acetate) without an increase in the number of receptors expressed. The molecular details of the mechanism are unknown. To determine the effect of PMA activation on LFA-1 movement within the plasma membrane, we used the single particle tracking technique to measure the diffusion rate of LFA-1 molecules on EBV-transformed B cells before and after PMA activation. Diffusion of LFA-1 on unactivated cells was restricted compared to CR1 (CD35), another transmembrane protein of equivalent size. PMA caused a 10-fold increase in the diffusion rate of LFA-1 without any effect on CD35. The increased LFA-1 motion induced by PMA was random, not directed, indicating that it was due to a release of constraints rather than the application of forces. The diffusion rates of LFA-1 are consistent with cytoskeletal attachment before and free diffusion after PMA. Cytochalasin D led to an equivalent increase in mobility and, at low doses, stimulated adhesion, implying that the nonadhesive state of LFA-1 is actively maintained by the lymphocyte cytoskeleton.
淋巴细胞通过其主要的β2整合素——白细胞功能相关抗原1（LFA-1），对佛波醇12-肉豆蔻酸酯13-乙酸酯（PMA）作出反应，激活与细胞间黏附分子1（ICAM-1）的黏附，而所表达的受体数量并未增加。该机制的分子细节尚不清楚。为了确定PMA激活对LFA-1在质膜内移动的影响，我们使用单粒子追踪技术来测量PMA激活前后EB病毒转化的B细胞上LFA-1分子的扩散速率。与另一种大小相当的跨膜蛋白补体受体1（CR1，即CD35）相比，LFA-1在未激活细胞上的扩散受到限制。PMA使LFA-1的扩散速率增加了10倍，而对CD35没有任何影响。PMA诱导的LFA-1运动增加是随机的，而非定向的，这表明它是由于限制的解除而非力的施加。LFA-1的扩散速率与PMA处理前细胞骨架附着以及处理后自由扩散的情况一致。细胞松弛素D导致迁移率同等增加，并且在低剂量时刺激黏附，这意味着LFA-1的非黏附状态由淋巴细胞细胞骨架积极维持。
