Although the actomyosin cytoskeleton has been implicated in clathrin-mediated endocytosis, a clear requirement for actomyosin in clathrin-independent endocytosis (CIE) has not been demonstrated. We discovered that the Rho-associated kinase ROCK2 is required for CIE of MHCI and CD59 through promotion of myosin II activity. Myosin IIA promoted internalization of MHCI and myosin IIB drove CD59 uptake in both HeLa and polarized Caco2 intestinal epithelial cells. In Caco2 cells, myosin IIA localized to the basal cortex and apical brush border and mediated MHCI internalization from the basolateral domain, while myosin IIB localized at the basal cortex and apical cell-cell junctions and promoted CD59 uptake from the apical membrane. Atomic force microscopy demonstrated that myosin IIB mediated apical epithelial tension in Caco2 cells. Thus, specific cargoes are internalized by ROCK2-mediated activation of myosin II isoforms to mediate spatial regulation of CIE, possibly by modulation of local cortical tension.

尽管肌动球蛋白细胞骨架与网格蛋白介导的内吞作用有关，但尚未证明在网格蛋白非依赖性内吞作用 (CIE) 中明确需要肌动球蛋白。我们发现通过促进肌球蛋白 II 活性，MHCI 和 CD59 的 CIE 需要 Rho 相关激酶 ROCK2。肌球蛋白 IIA 促进 MHCI 的内化，肌球蛋白 IIB 驱动 HeLa 和极化的 Caco2 肠上皮细胞中的 CD59 摄取。在 Caco2 细胞中，肌球蛋白 IIA 定位于基底皮层和顶端刷状缘并介导来自基底外侧域的 MHCI 内化，而肌球蛋白 IIB 定位于基底皮层和顶端细胞 - 细胞连接处并促进 CD59 从顶端膜摄取。原子力显微镜表明，肌球蛋白 IIB 介导 Caco2 细胞的顶端上皮张力。因此，