School of Pharmaceutical Science and Technology, Life Science Platform, Tianjin University, 92 Weijin Road, Nankai District, Tianjin, 300072, China.
J Cell Sci. 2023 Mar 15;136(6). doi: 10.1242/jcs.260684. Epub 2023 Mar 20.
Filamin A (FLNA) is an actin crosslinking protein that mediates mechanotransduction. External and internal mechanical forces, through the actin cytoskeleton, can induce conformational changes of the FLNA molecule to expose cryptic binding sites for its binding partners. Here, we identified Ras GTPase-activating protein SH3 domain-binding protein 1 (G3BP1) as a new FLNA mechanobinding partner. Unlike other FLNA binding partners to the mechanosensing domain repeat 21 (R21), G3BP1 requires an additional neighboring repeat R22 to interact. We demonstrated that their interaction occurs in the cytosol of living cells in an actin polymerization-dependent manner. We also mapped the FLNA-binding site on G3BP1 and found that a F360A point mutation in the RNA recognition motif disrupts the interaction. RNA interfered with the FLNA-G3BP1 interaction, and FLNA did not localize in RNA-rich stress granules (SGs). Disruption of the interaction was sufficient to promote phase-separated SG formation, and arsenite treatment further stimulated the formation of SGs. Taken together, these data identify G3BP1 as a new mechanobinding protein that interacts with the FLNA mechanosensing domain R21 and suggest that SG formation is partially regulated by mechanical force.
细丝蛋白 A（FLNA）是一种肌动蛋白交联蛋白，可介导机械转导。外部和内部机械力通过肌动蛋白细胞骨架，可以诱导 FLNA 分子的构象变化，暴露出其结合伴侣的隐藏结合位点。在这里，我们确定 Ras GTP 酶激活蛋白 SH3 结构域结合蛋白 1（G3BP1）为 FLNA 的新机械结合伴侣。与其他机械传感域重复 21（R21）的 FLNA 结合伴侣不同，G3BP1 需要额外的相邻重复 R22 才能相互作用。我们证明它们的相互作用发生在活细胞的细胞质中，依赖于肌动蛋白聚合。我们还绘制了 G3BP1 上的 FLNA 结合位点，并发现 RNA 识别基序中的 F360A 点突变会破坏相互作用。RNA 干扰了 FLNA-G3BP1 相互作用，FLNA 不在富含 RNA 的应激颗粒（SGs）中定位。相互作用的破坏足以促进相分离的 SG 形成，并且亚砷酸盐处理进一步刺激了 SG 的形成。总之，这些数据将 G3BP1 鉴定为与 FLNA 机械传感域 R21 相互作用的新机械结合蛋白，并表明 SG 形成部分受机械力调节。
