PT - JOURNAL ARTICLE AU - Bigge, Brae M AU - Rosenthal, Nicholas E AU - Avasthi, Prachee TI - Initial ciliary assembly in <em>Chlamydomonas</em> requires Arp2/3 complex-dependent endocytosis AID - 10.1101/2020.11.24.396002 DP - 2021 Jan 01 TA - bioRxiv PG - 2020.11.24.396002 4099 - http://biorxiv.org/content/early/2021/12/15/2020.11.24.396002.short 4100 - http://biorxiv.org/content/early/2021/12/15/2020.11.24.396002.full 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 StatementPA is a paid consultant for Arcadia Science