Cassimeris L, McNeill H, Zigmond S H
Biology Department, University of Pennsylvania, Philadelphia 19104-6018.
J Cell Biol. 1990 Apr;110(4):1067-75. doi: 10.1083/jcb.110.4.1067.
Chemoattractants stimulate actin polymerization in lamellipodia of polymorphonuclear leukocytes. We find that removal of chemoattractant results in rapid (within 10 s at 37 degrees C) and selective depolymerization of the F-actin located in lamellipodia. Addition of 10 microM cytochalasin B, in the presence of chemoattractant, also resulted in rapid and selective depolymerization of lamellar F-actin. The elevated F-actin level induced by chemoattractant rapidly returns to the level present in unstimulated cells after (a) a 10-fold decrease in chemoattractant concentration; (b) the addition of 10 microM cytochalasin B; or (c) cooling to 4 degrees C. The F-actin levels of unstimulated cells are only slightly affected by these treatments. Based on the similar effects of cytochalasin addition and chemoattractant dilution, it is likely that both treatments result in actin depolymerization from the pointed ends of filaments. Based on our results we propose that chemoattractant-stimulated polymorphonuclear leukocytes contain two distinct populations of actin filaments. The actin filaments within the lamellipodia are highly labile and in the continued presence of chemoattractant these filaments are rapidly turning over, continually polymerizing at their plus (barbed) ends, and depolymerizing at their minus ends. In contrast, the cortical F-actin filaments of both stimulated and unstimulated cells are differentially stable.
趋化因子刺激多形核白细胞片足中的肌动蛋白聚合。我们发现去除趋化因子会导致片足中F-肌动蛋白迅速（在37℃下10秒内）且选择性地解聚。在存在趋化因子的情况下添加10微摩尔细胞松弛素B，也会导致片状F-肌动蛋白迅速且选择性地解聚。趋化因子诱导的F-肌动蛋白水平升高在以下情况后迅速恢复到未刺激细胞中的水平：（a）趋化因子浓度降低10倍；（b）添加10微摩尔细胞松弛素B；或（c）冷却至4℃。这些处理对未刺激细胞的F-肌动蛋白水平影响很小。基于添加细胞松弛素和稀释趋化因子的相似作用，两种处理可能都导致肌动蛋白从细丝的尖端解聚。根据我们的结果，我们提出趋化因子刺激的多形核白细胞含有两种不同的肌动蛋白丝群体。片足内的肌动蛋白丝高度不稳定，在持续存在趋化因子的情况下，这些丝迅速周转，在其正（带刺）端持续聚合，并在其负端解聚。相比之下，刺激和未刺激细胞的皮质F-肌动蛋白丝具有不同的稳定性。
