ABSTRACT
Cilia are organelles important for signaling and motility. They are composed of microtubules ensheathed in plasma membrane. The mechanisms related to ciliogenesis also require another cytoskeletal element, actin, which has been shown to be important for organizing the basal bodies and transition zone at the base of cilia and for short- and long-range trafficking. However, most studies of actin’s role in ciliogenesis have taken a broad approach by knocking out all filamentous actin until now. Here, we more delicately dissect the interplay between actin and cilia by specifically focusing on actin networks nucleated by the Arp2/3 complex in Chlamydomonas. We find that knocking out Arp2/3-mediated actin networks dramatically impairs ciliary assembly and maintenance in these cells, and these defects are due to a problem with incorporation and gating of existing ciliary proteins, particularly in the early stages of assembly. We also show that cells lacking the Arp2/3 complex have more dramatic defects in ciliary maintenance using material from non-Golgi sources. Finally, we find relocalization of a ciliary membrane protein from the cell periphery to the cilia by internalization is dependent on actin and the Arp2/3 complex. Based on these results, we propose a new model of ciliary protein targeting during early ciliogenesis in which proteins previously targeted from the Golgi to the plasma membrane are reclaimed from this reservoir by Arp2/3-mediated networks.
Competing Interest Statement
The authors have declared no competing interest.
