RT Journal Article SR Electronic T1 Initial ciliary assembly in Chlamydomonas requires Arp2/3 complex-dependent endocytosis JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.11.24.396002 DO 10.1101/2020.11.24.396002 A1 Brae M Bigge A1 Nicholas E Rosenthal A1 Prachee Avasthi YR 2021 UL http://biorxiv.org/content/early/2021/04/01/2020.11.24.396002.abstract AB Ciliary assembly, trafficking, and regulation are dependent on microtubules, but the mechanisms of ciliary assembly also require the actin cytoskeleton. Here, we dissect subcellular roles of actin in ciliogenesis by focusing on actin networks nucleated by the Arp2/3 complex in the powerful ciliary model, Chlamydomonas. We find the Arp2/3 complex is required for the initial stages of ciliary assembly when protein and membrane are in high demand, but cannot yet be supplied from the Golgi complex. We provide evidence for Arp2/3 complex-dependent clathrin-mediated endocytosis of ciliary proteins, an increase in endocytic activity upon induction of ciliary growth, and relocalization of plasma membrane proteins to newly formed cilia. Our data support a new model of ciliary protein and membrane trafficking during early ciliogenesis whereby proteins previously targeted to the plasma membrane are reclaimed by Arp2/3 complex-dependent clathrin-mediated endocytosis for initial ciliary assembly.Competing Interest StatementThe authors have declared no competing interest.