Integrin Signaling Laboratory, Department of Vascular Biology, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
J Cell Sci. 2011 Aug 15;124(Pt 16):2763-76. doi: 10.1242/jcs.080804.
Caveolae are relatively stable membrane invaginations that compartmentalize signaling, regulate lipid metabolism and mediate viral entry. Caveolae are closely associated with actin fibers and internalize in response to diverse stimuli. Loss of cell adhesion is known to induce rapid and robust caveolae internalization and trafficking toward a Rab11-positive recycling endosome; however, pathways governing this process are poorly understood. Here, we report that filamin A is required to maintain the F-actin-dependent linear distribution of caveolin-1. High spatiotemporal resolution particle tracking of caveolin-1-GFP vesicles by total internal reflection fluorescence (TIRF) microscopy revealed that FLNa is required for the F-actin-dependent arrest of caveolin-1 vesicles in a confined area and their stable anchorage to the plasma membrane. The linear distribution and anchorage of caveolin-1 vesicles are both required for proper caveolin-1 inwards trafficking. De-adhesion-triggered caveolae inward trafficking towards a recycling endosome is impaired in FLNa-depleted HeLa and FLNa-deficient M2-melanoma cells. Inwards trafficking of caveolin-1 requires both the ability of FLNa to bind actin and cycling PKCα-dependent phosphorylation of FLNa on Ser2152 after cell detachment.
小窝是相对稳定的质膜内陷，分隔信号转导、调节脂质代谢并介导病毒进入。小窝与肌动蛋白纤维密切相关，并在受到各种刺激时内陷。已知细胞黏附丧失会诱导小窝快速而强烈的内陷，并向 Rab11 阳性的再循环内体转运；然而，调控这一过程的途径还知之甚少。在这里，我们报告肌联蛋白 A 对于维持依赖 F-肌动蛋白的窖蛋白-1 的线性分布是必需的。通过全内反射荧光（TIRF）显微镜对窖蛋白-1-GFP 囊泡进行高时空分辨率的颗粒追踪显示，FLNa 对于依赖 F-肌动蛋白的窖蛋白-1 囊泡在一个受限区域的阻滞以及它们在质膜上的稳定锚定是必需的。窖蛋白-1 囊泡的线性分布和锚定对于窖蛋白-1 的正确向内转运都是必需的。在 FLNa 耗尽的 HeLa 和 FLNa 缺陷的 M2 黑素瘤细胞中，脱黏附触发的小窝向内转运到再循环内体受到损害。向内转运的窖蛋白-1 需要 FLNa 结合肌动蛋白的能力以及细胞分离后 PKCα 依赖性 Ser2152 磷酸化循环的 FLNa。
