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Comparative Analysis of Ciliary Membranes and Ectosomes. Curr Biol 2016; 26:3327-3335. [PMID: 27866888 DOI: 10.1016/j.cub.2016.09.055] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 06/20/2016] [Accepted: 09/27/2016] [Indexed: 01/06/2023]
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.
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Hilton LK, Meili F, Buckoll PD, Rodriguez-Pike JC, Choutka CP, Kirschner JA, Warner F, Lethan M, Garces FA, Qi J, Quarmby LM. A Forward Genetic Screen and Whole Genome Sequencing Identify Deflagellation Defective Mutants in Chlamydomonas, Including Assignment of ADF1 as a TRP Channel. G3 (BETHESDA, MD.) 2016; 6:3409-3418. [PMID: 27520959 PMCID: PMC5068960 DOI: 10.1534/g3.116.034264] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 08/09/2016] [Indexed: 01/21/2023]
Abstract
With rare exception, ciliated cells entering mitosis lose their cilia, thereby freeing basal bodies to serve as centrosomes in the formation of high-fidelity mitotic spindles. Cilia can be lost by shedding or disassembly, but either way, it appears that the final release may be via a coordinated severing of the nine axonemal outer doublet microtubules linking the basal body to the ciliary transition zone. Little is known about the mechanism or regulation of this important process. The stress-induced deflagellation response of Chlamydomonas provides a basis to identifying key players in axonemal severing. In an earlier screen we uncovered multiple alleles for each of three deflagellation genes, ADF1, FA1, and FA2 Products of the two FA genes localize to the site of axonemal severing and encode a scaffolding protein and a member of the NIMA-related family of ciliary-cell cycle kinases. The identity of the ADF1 gene remained elusive. Here, we report a new screen using a mutagenesis that yields point mutations in Chlamydomonas, an enhanced screening methodology, and whole genome sequencing. We isolated numerous new alleles of the three known genes, and one or two alleles each of at least four new genes. We identify ADF1 as a TRP ion channel, which we suggest may reside at the flagellar transition zone.
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Affiliation(s)
- Laura K Hilton
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Fabian Meili
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Paul D Buckoll
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Julie C Rodriguez-Pike
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Courtney P Choutka
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Jaime A Kirschner
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Freda Warner
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Mette Lethan
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Fabian A Garces
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Jingnan Qi
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Lynne M Quarmby
- Department of Molecular Biology & Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
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