Molecular Basis of Ciliogenesis Control by Actin Remodeling Factors

Abstract

Objective: Ciliogenic activity is an important determinant of cellular behavior because the presence or absence of primary cilia exerts a profound impact on cell signaling. Actin cytoskeletal destabilization has been recognized as a dominant inducer of ciliogenesis in cultured mammalian cells. However, underlying molecular mechanisms are poorly understood. Moreover, actin remodeling factors that are involved in ciliogenesis control remain to be identified. Here we demonstrate roles of transcriptional coactivators YAP and TAZ in actin-dependent ciliogenesis control, and identify actin cytoskeleton remodeling factors that mediate the connection between the actin cytoskeleton and YAP/TAZ. Methods: We examined the correlation between ciliogenesis induction and YAP/TAZ activity in RPE1 cells. Ciliogenesis and cytoplasmic relocalization of YAP/TAZ, which inactivates them, were monitored by immunofluorescence. The involvement of YAP/TAZ in ciliogenesis was assessed by RNAi-mediated loss-of-function studies. In addition, we performed an siRNA screen for actin remodeling factors that play a role in ciliogenesis control. Results: Active ciliogenesis either in spatially confined cells or in cells treated with an actin filament destabilizer cytochalasin D coincided with cytoplasmic sequestration of YAP/TAZ. Moreover, knockdown of YAP/TAZ was sufficient to induce ciliogenesis, whereas LPA, which promotes both actin polymerization and YAP/TAZ nuclear accumulation, suppressed serum starvation-mediated ciliogenesis. Moreover, we identified actin cytoskeleton remodeling factors LIMK2 and TESK1 as key players in the actin-dependent control network in which YAP/TAZ are integral components. Conclusion: These findings suggest that actin cytoskeleton