Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
Cell Architecture Research Institute, Huazhong University of Science and Technology, Wuhan, Hubei, China.
J Cell Biol. 2021 May 3;220(5). doi: 10.1083/jcb.202007149.
Cargo sorting and the subsequent membrane carrier formation require a properly organized endosomal actin network. To better understand the actin dynamics during endocytic recycling, we performed a genetic screen in C. elegans and identified RTKN-1/Rhotekin as a requisite to sustain endosome-associated actin integrity. Loss of RTKN-1 led to a prominent decrease in actin structures and basolateral recycling defects. Furthermore, we showed that the presence of RTKN-1 thwarts the actin disassembly competence of UNC-60A/cofilin. Consistently, in RTKN-1-deficient cells, UNC-60A knockdown replenished actin structures and alleviated the recycling defects. Notably, an intramolecular interaction within RTKN-1 could mediate the formation of oligomers. Overexpression of an RTKN-1 mutant form that lacks self-binding capacity failed to restore actin structures and recycling flow in rtkn-1 mutants. Finally, we demonstrated that SDPN-1/Syndapin acts to direct the recycling endosomal dwelling of RTKN-1 and promotes actin integrity there. Taken together, these findings consolidated the role of SDPN-1 in organizing the endosomal actin network architecture and introduced RTKN-1 as a novel regulatory protein involved in this process.
货物分拣和随后的膜载体形成需要一个组织良好的内体肌动蛋白网络。为了更好地理解内吞体再循环过程中的肌动蛋白动力学，我们在秀丽隐杆线虫中进行了基因筛选，并鉴定 RTKN-1/Rhotekin 是维持内体相关肌动蛋白完整性所必需的。RTKN-1 的缺失导致肌动蛋白结构明显减少和基底外侧再循环缺陷。此外，我们表明 RTKN-1 的存在阻止了 UNC-60A/cofilin 的肌动蛋白解聚能力。一致地，在 RTKN-1 缺陷细胞中，UNC-60A 的敲低补充了肌动蛋白结构并缓解了再循环缺陷。值得注意的是，RTKN-1 内的分子间相互作用可以介导寡聚体的形成。过量表达缺乏自我结合能力的 RTKN-1 突变体形式未能恢复 rtkn-1 突变体中的肌动蛋白结构和再循环流。最后，我们证明了 SDPN-1/Syndapin 作用于指导 RTKN-1 的再循环内体居住并促进那里的肌动蛋白完整性。总之，这些发现巩固了 SDPN-1 在组织内体肌动蛋白网络架构中的作用，并引入了 RTKN-1 作为参与该过程的新型调节蛋白。
