WTS-1/LATS regulates endocytic recycling by restraining F-actin assembly in a synergistic manner

The disruption of endosomal actin architecture negatively affects endocytic recycling. However, the underlying homeostatic mechanisms that regulate actin organization during recycling remain unclear. In this study, we identified a synergistic endosomal actin assembly restricting mechanism in C. elegans involving WTS-1, the homolog of LATS kinases, which is a core component of the Hippo pathway. WTS-1 resides on the sorting endosomes and colocalizes with the actin polymerization regulator PTRN-1 [the homolog of the calmodulin-regulated spectrin-associated proteins (CAMSAPs)]. We observed an increase in PTRN-1-labeled structures in WTS-1-deficient cells, indicating that WTS-1 can limit the endosomal localization of PTRN-1. Accordingly, the actin overaccumulation phenotype in WTS-1-depleted cells was mitigated by the associated PTRN-1 loss. We further demonstrated that recycling defects and actin overaccumulation in WTS-1-deficient cells were reduced by the overexpression of constitutively active UNC-60A(S3A) (a cofilin protein homolog), which aligns with the role of LATS as a positive regulator of cofilin activity. Altogether, our data confirmed previous findings, and we propose an additional model, that WTS-1 acts alongside the UNC-60A-mediated actin disassembly to restrict the assembly of endosomal F-actin by curbing PTRN-1 dwelling on endosomes, preserving recycling transport.