Genomes and Genes
CELL SURFACE RECOGNITION AND CELL INTERACTIONS
Principal Investigator: William Snell
Affiliation: University of Texas Southwestern Medical Center
Abstract: The long-term goals of my research are to understand the cellular and molecular properties of cilia/flagella that underlie their functions. My laboratory uses the biflagellated green alga Chlamydomonas reinhardtii as a model system to study cilium-generated signaling and ciliary/flagellar shortening. During the Chlamydomonas mating reaction, adhesion receptors (agglutinins) on the flagella of minus gametes bind to their cognate agglutinins on the flagella of plus gametes, thereby activating a cilium-generated signaling pathway in both cells that activates the gametes for cell-cell fusion to form a zygote. Immediately after zygote formation (and also during experimentally-imposed stress), Chlamydomonas cells shorten and completely resorb their flagella. We propose to use Chlamydomonas to dissect novel functions and mechanisms of regulation of the intraflagellar transport (IFT) machinery. Because almost every mammalian cell possesses a primary cilium that is used for signal transduction and also must be resorbed during cell cycle entry, our studies will provide novel insights into fundamental cellular mechanisms essential for human development and homeostasis. In previous studies of flagellar adhesion-induced signaling, we had shown that a regulatory protein, a flagellar protein tyrosine kinase (PTK), was activated early in the pathway. Moreover, using mutant gametes conditionally defective in IFT, we presented evidence that IFT is required for signal transduction in an intact cilium/flagellum. In the current funding period we discovered that a second regulatory protein in the pathway, a cGMP-dependent protein kinase, becomes associated with large assemblies within flagella whose formation requires IFT. To our surprise, the large, newly formed assemblies also contain IFT particles. Here, in our studies on signaling, we propose experiments to test the model that, in addition to its roles in flagellar assembly and disassembly, the IFT machinery participates directly in cilium-generated signaling and links membrane receptor interactions to gamete activation. Our previous studies on flagellar shortening showed that an aurora-like protein kinase (CALK) was essential for regulated shortening. In the current funding period, we made the surprising discovery that IFT trafficking within flagella and cargo loading onto IFT particles in the cell body are regulated during shortening. Moreover, we found that a protein that disassembles microtubules, a depolymerizing kinesin, in the cell body is phosphorylated and transported into flagella as microtubule disassembly is triggered during shortening. Our specific aims are to dissect the function of the intraflagellar transport machinery in flagellar adhesion-induced signaling, investigate the molecules that couple flagellar adhesion to gamete activation, and study the cellular and molecular mechanisms of flagellar shortening. PUBLIC HEALTH RELEVANCE: Primary cilia carry out key signaling roles in development and homeostasis and they are resorbed before cell cycle entry. Yet, we know little about the cellular and molecular mechanisms of cilium-generated signaling or ciliary disassembly. Studying flagellar adhesion and flagellar shortening in Chlamydomonas will continue to uncover novel and fundamental properties of these remarkable organelles.
Funding Period: ----------------1978 - ---------------2013-
more information: NIH RePORT
- Intraflagellar transport particles participate directly in cilium-generated signaling in ChlamydomonasQian Wang
Department of Cell Biology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
Cell 125:549-62. 2006..Our results lead to a model in which the IFT machinery is required not only for assembling cilia and flagella but also for organizing a signaling pathway within the organelles during cilium-generated signaling...
- Evolutionarily conserved Delta(25(27))-olefin ergosterol biosynthesis pathway in the alga Chlamydomonas reinhardtiiMatthew B Miller
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409, USA
J Lipid Res 53:1636-45. 2012..Thus, our findings demonstrate that two separate isoprenoid-24-alkyl sterol pathways evolved in fungi and green algae, both of which converge to yield a common membrane insert ergosterol...
- Comparative genomics in Chlamydomonas and Plasmodium identifies an ancient nuclear envelope protein family essential for sexual reproduction in protists, fungi, plants, and vertebratesJue Ning
Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, Texas 75390, USA
Genes Dev 27:1198-215. 2013..Our comparative transcriptomics approach provides a new resource for studying sexual development and demonstrates that exploiting the data can lead to the discovery of novel biology that is conserved across distant taxa...
- Activation loop phosphorylation of a protein kinase is a molecular marker of organelle size that dynamically reports flagellar lengthMuqing Cao
Ministry of Education Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing 100084, China
Proc Natl Acad Sci U S A 110:12337-42. 2013..Thus, phosphorylation of CALK in its activation loop is implicated in the disassembly arm of a length feedback mechanism and is a continuous and dynamic molecular marker of flagellar length during both assembly and disassembly. ..
- Regulated membrane protein entry into flagella is facilitated by cytoplasmic microtubules and does not require IFTOlivier Belzile
Department of Cell Biology, University of Texas Southwestern Medical School, 6000 Harry Hines Boulevard, Dallas, TX 75390 9039, USA
Curr Biol 23:1460-5. 2013..Thus, integral membrane proteins can negotiate passage through the ciliary diffusion barrier without the need for a motor. ..
- A microtubule depolymerizing kinesin functions during both flagellar disassembly and flagellar assembly in ChlamydomonasTian Piao
Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China
Proc Natl Acad Sci U S A 106:4713-8. 2009..Furthermore, they are inhibited in flagellar shortening. Thus, CrKinesin-13 is dynamically regulated during flagellar assembly and disassembly in Chlamydomonas and functions in each...
- The ciliary membraneRajat Rohatgi
Department of Medicine, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305, USA
Curr Opin Cell Biol 22:541-6. 2010..The regulated movement of membrane proteins and lipids across this barrier is central to the sensory function of these organelles...
- The phosphorylation state of an aurora-like kinase marks the length of growing flagella in ChlamydomonasMinna Luo
Protein Science Laboratory of the Ministry of Education, School of Life Sciences, Tsinghua University, Beijing 100084, China
Curr Biol 21:586-91. 2011..Our results demonstrate that cells possess a mechanism for translating flagellar length into a posttranslational modification of a known flagellar regulatory protein...