Phosphoinositide-3-kinase-independent contractile activities associated with Fcγ-receptor-mediated phagocytosis and macropinocytosis in macrophages
Phosphoinositide-3-kinase-independent contractile activities associated with Fcγ-receptor-mediated phagocytosis and macropinocytosis in macrophages
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DOI：
10.1242/jcs.00235
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发表时间：
2003-01-15
影响因子：
4
通讯作者：
Swanson, JA
中科院分区：
文献类型：
--
作者：
Araki, N;Hatae, T;Swanson, JA
以往的研究表明，Fc γ受体（FcR）介导的巨噬细胞的吞噬和巨胞饮作用包括两个分离的活动：磷酸肌醇3-激酶（PI3K）独立的吞噬杯的延伸和PI3K依赖的收缩机制，关闭吞噬体和皱褶到细胞内的细胞器。在这里，我们确定了一个额外的收缩活动，持续存在的PI3K抑制剂渥曼青霉素。ML-7是肌球蛋白轻链激酶（MLCK）的抑制剂，可抑制FcR介导的吞噬作用、巨胞饮作用和与皱褶相关的细胞运动。扫描电子显微镜检查表明，在不同的抑制剂的吞噬杯之间的形态有显着差异：而吞噬杯的控制细胞和渥曼青霉素处理的细胞符合密切的颗粒，并出现了收缩，ML-7处理的细胞中的吞噬杯更开放。表达绿色荧光蛋白（GFP）-肌动蛋白融合的巨噬细胞的视频显微镜显示，结合IgG调理红细胞在吞噬体形成和关闭过程中被挤压。在ML-7中，富含GFP-肌动蛋白的突起向外延伸，但未能挤压颗粒。此外，与PI 3 K抑制剂的作用相反，ML-7显着减少了褶边运动，并扰乱了圆形褶边的形成。因此，这些基于PI3K非依赖性肌球蛋白-II的收缩活动挤压吞噬杯和弯曲皱褶，代表了吞噬作用和巨胞饮作用期间肌动蛋白细胞骨架的第三组分活性。
Previous studies have shown that Fcgamma receptor (FcR)-mediated phagocytosis and macropinocytosis in macrophages consist of two dissociable activities: a phosphoinositide 3-kinase (PI3K)-independent extension of phagocytic cups and a PI3K-dependent contractile mechanism that closes phagosomes and ruffles into intracellular organelles. Here, we identify an additional contractile activity that persists in the presence of the PI3K inhibitor wortmannin. ML-7, an inhibitor of myosin-light-chain kinase (MLCK), inhibited FcR-mediated phagocytosis, macropinocytosis and cell movements associated with ruffling. Scanning electron microscopy demonstrated a striking difference in morphology between phagocytic cups in the different inhibitors: whereas phagocytic cups of control cells and wortmannin-treated cells conformed closely to particles and appeared to have constricted them, the phagocytic cups in cells treated with ML-7 were more open. Video microscopy of macrophages expressing green-fluorescent-protein (GFP)-actin fusions revealed that bound IgG-opsonized erythrocytes were squeezed during phagosome formation and closure. In ML-7, GFP-actin-rich protrusions extended outward but failed to squeeze particles. Moreover, in contrast to the effects of PI3K inhibitors, ML-7 markedly reduced ruffle movement, and perturbed circular ruffle formation. These PI3K-independent myosin-II-based contractile activities that squeeze phagocytic cups and curve ruffles therefore represent a third component activity of the actin cytoskeleton during phagocytosis and macropinocytosis.