Abstract：
The abLIM1 is a nonerythroid actin-binding protein critical for stable plasma membrane-cortex interactions under mechanical tension. Its depletion by RNA interference results in sparse, poorly interconnected cortical actin networks and severe blebbing of migrating cells. Its isoforms, abLIM-L, abLIM-M, and abLIM-S, contain, respectively four, three, and no LIM domains, followed by a C terminus entirely homologous to erythroid cortex protein dematin. How abLIM1 functions, however, remains unclear. Here we show that abLIM1 is a liquid-liquid phase separation (LLPS)-dependent self-organizer of actin networks. Phase-separated condensates of abLIM-S-mimicking ΔLIM or the major isoform abLIM-M nucleated, flew along, and cross-linked together actin filaments (F-actin) to produce unique aster-like radial arrays and interconnected webs of F-actin bundles. Interestingly, ΔLIM condensates facilitated actin nucleation and network formation even in the absence of Mg2+. Our results suggest that abLIM1 functions as an LLPS-dependent actin nucleator and cross-linker and provide insights into how LLPS-induced condensates could self-construct intracellular architectures of high connectivity and plasticity.
摘要：
abLIM1是一种非红系肌动蛋白结合蛋白，对于在机械张力下稳定的质膜-皮质相互作用至关重要。它通过RNA干扰的消耗导致稀疏，皮质肌动蛋白网络连接不良，迁移细胞严重起泡。它的同工型，abLIM-L,abLIM-M,和abLIM-S,包含,分别为四,三,没有LIM域,随后是与红系皮质蛋白dematin完全同源的C末端。abLIM1的功能，然而,尚不清楚。在这里，我们表明abLIM1是肌动蛋白网络的液-液相分离（LLPS）依赖性自组织。abLIM-S模拟ΔLIM或主要同工型abLIM-M成核的相分离冷凝物，飞过,并将肌动蛋白丝（F-actin）交联在一起，以产生独特的aster状放射状阵列和互连的F-actin束网。有趣的是,即使在不存在Mg2的情况下，ΔLIM冷凝物也促进了肌动蛋白成核和网络形成。我们的结果表明，abLIM1作为LLPS依赖性肌动蛋白成核剂和交联剂，并提供了有关LLPS诱导的缩合物如何自我构建高连通性和可塑性的细胞内结构的见解。
