title: Actin is required for IFT regulation in Chlamydomonas reinhardtii.
abstract: Assembly of cilia and flagella requires intraflagellar transport (IFT), a highly regulated kinesin-based transport system that moves cargo from the basal body to the tip of flagella [1]. The recruitment of IFT components to basal bodies is a function of flagellar length, with increased recruitment in rapidly growing short flagella [2]. The molecular pathways regulating IFT are largely a mystery. Because actin network disruption leads to changes in ciliary length and number, actin has been proposed to have a role in ciliary assembly. However, the mechanisms involved are unknown. In Chlamydomonas reinhardtii, conventional actin is found in both the cell body and the inner dynein arm complexes within flagella [3, 4]. Previous work showed that treating Chlamydomonas cells with the actin-depolymerizing compound cytochalasin D resulted in reversible flagellar shortening [5], but how actin is related to flagellar length or assembly remains unknown. Here we utilize small-molecule inhibitors and genetic mutants to analyze the role of actin dynamics in flagellar assembly in Chlamydomonas reinhardtii. We demonstrate that actin plays a role in IFT recruitment to basal bodies during flagellar elongation and that when actin is perturbed, the normal dependence of IFT recruitment on flagellar length is lost. We also find that actin is required for sufficient entry of IFT material into flagella during assembly. These same effects are recapitulated with a myosin inhibitor, suggesting that actin may act via myosin in a pathway by which flagellar assembly is regulated by flagellar length.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address: pacrofts@gmail.com.
authors.forename: Prachee
authors.initials: P
authors.lastname: Avasthi
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Onishi
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Karpiak
authors.affiliation: Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Yamamoto
authors.affiliation: Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA.
authors.forename: Luke
authors.initials: L
authors.lastname: Mackinder
authors.affiliation: Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA.
authors.forename: Martin C
authors.initials: MC
authors.lastname: Jonikas
authors.affiliation: Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Winfield S
authors.initials: WS
authors.lastname: Sale
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Shoichet
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Pringle
authors.affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address: wallace.marshall@ucsf.edu.
authors.forename: Wallace F
authors.initials: WF
authors.lastname: Marshall
mesh_terms: D000199:Actins / Q000378:metabolism*; D054468:Axoneme / Q000378:metabolism; D001692:Biological Transport; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D055503:Protein Multimerization / Q000502:physiology
chemical_list: D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins