title: Comparative Analysis of Ciliary Membranes and Ectosomes.
abstract: Primary and motile cilia/flagella function as cellular antennae, receiving signals from the environment and subsequently activating signaling pathways that are critical for cellular homeostasis and differentiation [1-3]. Recent work with the green alga Chlamydomonas and the nematode C. elegans demonstrated that ectosomes can be released from the cilium and can mediate the intercellular communication [4-9]. To better understand the function of flagellar ectosomes, we have compared their protein composition to that of the flagellar membrane from which they are derived. Ectosomes released from flagella have a unique protein composition, being enriched in a subset of flagellar membrane proteins, proteases, proteins from the endosomal sorting complex required for transport (ESCRT) [10-12], small GTPases, and ubiquitinated proteins. Live imaging showed that an ESCRT-related protein (PDCD6) was enriched in ectosomes released from flagella during gamete activation. We devised a sensitive and rapid assay to monitor ectosome release using luciferase fused to PDCD6 and a mutated ubiquitin. Ectosome release increased when cells underwent flagellar resorption. Knockdown of two ESCRT-related proteins, PDCD6 and VPS4, attenuated ectosome release during flagellar shortening and shortening was slowed. These data suggest that the ESCRT proteins mediate ectosome release and thereby influence flagellar shortening in Chlamydomonas. In addition, the prevalence of receptors such as agglutinin and ubiquitinated proteins in ciliary ectosomes suggests that they are involved in cell signaling and turnover of ciliary proteins.
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China.
authors.forename: Huan
authors.initials: H
authors.lastname: Long
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Nannan
authors.initials: N
authors.lastname: Xu
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China.
authors.forename: Gai
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA.
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Diener
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA.
authors.forename: Joel L
authors.initials: JL
authors.lastname: Rosenbaum
authors.affiliation: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province 430072, China. Electronic address: huangky@ihb.ac.cn.
authors.forename: Kaiyao
authors.initials: K
authors.lastname: Huang
mesh_terms: D002450:Cell Communication; D002462:Cell Membrane / Q000502:physiology*; D055252:Cell-Derived Microparticles / Q000502:physiology; D002696:Chlamydomonas / Q000166:cytology / Q000502:physiology*; D002923:Cilia / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D055785:Gene Knockdown Techniques; D008565:Membrane Proteins
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D008565:Membrane Proteins
keywords: Chlamydomonas; ESCRT; cilia; ectosome; flagella; ubiquitin