Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 728 Clinical Research Building, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
Nat Commun. 2013;4:2523. doi: 10.1038/ncomms3523.
CARMIL is an approximately 1,370-amino-acid cytoskeletal scaffold that has crucial roles in cell motility and tissue development through interactions with cytoskeletal effectors and regulation of capping protein at the leading edge. However, the mechanism of CARMIL leading edge localization is unknown. Here we show that CARMIL interacts directly with the plasma membrane through its amino-terminal region. The crystal structure of CARMIL1-668 reveals that this region harbours a non-canonical pleckstrin homology (PH) domain connected to a 16-leucine-rich repeat domain. Lipid binding is mediated by the PH domain, but is further enhanced by a central helical domain. Small-angle X-ray scattering reveals that the helical domain mediates antiparallel dimerization, properly positioning the PH domains for simultaneous membrane interaction. In cells, deletion of the PH domain impairs leading edge localization. The results support a direct membrane-binding mechanism for CARMIL localization at the leading edge, where it regulates cytoskeletal effectors and motility.
CARMIL 是一种大约由 1370 个氨基酸组成的细胞骨架支架，通过与细胞骨架效应器相互作用和调节前沿的盖帽蛋白，在细胞运动和组织发育中起着关键作用。然而，CARMIL 前沿定位的机制尚不清楚。在这里，我们表明 CARMIL 通过其氨基末端区域直接与质膜相互作用。CARMIL1-668 的晶体结构表明，该区域包含一个非典型的 PH 结构域，连接到一个 16 个亮氨酸丰富的重复结构域。脂质结合由 PH 结构域介导，但通过中央螺旋结构域进一步增强。小角度 X 射线散射表明，螺旋结构域介导反平行二聚化，正确定位 PH 结构域以同时进行膜相互作用。在细胞中，PH 结构域的缺失会损害前沿定位。结果支持 CARMIL 在前沿的直接膜结合机制，在前沿，它调节细胞骨架效应器和运动。
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