Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, MO 63110.
Mol Biol Cell. 2013 Oct;24(19):3047-55. doi: 10.1091/mbc.E13-05-0270. Epub 2013 Jul 31.
The regulation of free barbed ends is central to the control of dynamic actin assembly and actin-based motility in cells. Capping protein (CP) is known to regulate barbed ends and control actin assembly in cells. The CARMIL family of proteins can bind and inhibit CP in vitro, but the physiological significance of the interaction of CARMIL with CP in cells is poorly understood. Mammalian cells lacking CARMIL1 have defects in lamellipodia, macropinocytosis, cell migration, and Rac1 activation. Here we investigate the physiological significance of the CARMIL1-CP interaction, using a point mutant with a well-defined biochemical defect. We find that the CARMIL1-CP interaction is essential for the assembly of lamellipodia, the formation of ruffles, and the process of macropinocytosis. In contrast, the interaction of CARMIL1 with CP shows little to no importance for other functions of CARMIL1, including localization of CARMIL1 to the membrane, activation of Rac1, and cell migration. One implication is that lamellipodia are only marginally important for cell migration in a wound-healing model. The results also suggest that the ability of CARMIL1 to inhibit CP in cells may be regulated.
游离的带刺末端的调节对于控制细胞中动态肌动蛋白组装和基于肌动蛋白的运动至关重要。众所周知，盖帽蛋白 (CP) 可以调节带刺末端并控制细胞中的肌动蛋白组装。CARMIL 蛋白家族可以在体外结合并抑制 CP，但 CARMIL 与 CP 在细胞中的相互作用的生理意义知之甚少。缺乏 CARMIL1 的哺乳动物细胞在片状伪足、巨胞饮、细胞迁移和 Rac1 激活方面存在缺陷。在这里，我们使用具有明确生化缺陷的点突变体来研究 CARMIL1-CP 相互作用的生理意义。我们发现，CARMIL1-CP 相互作用对于片状伪足的组装、皱襞的形成和巨胞饮作用的过程是必不可少的。相比之下，CARMIL1 与 CP 的相互作用对于 CARMIL1 的其他功能（包括 CARMIL1 向膜的定位、Rac1 的激活和细胞迁移）几乎没有重要性。一种含义是，在划痕愈合模型中，片状伪足对细胞迁移的重要性很小。结果还表明，CARMIL1 抑制细胞中 CP 的能力可能受到调节。
