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The Microtubule Plus End-Tracking Protein EB1 Is Localized to the Flagellar Tip and Basal Bodies in Chlamydomonas reinhardtii

2003; Elsevier BV; Volume: 13; Issue: 22 Linguagem: Inglês

10.1016/j.cub.2003.10.058

1879-0445

Lotte B. Pedersen, Stefan Geimer, Roger D. Sloboda, Joel L. Rosenbaum,

Microtubule and mitosis dynamics

Flagellar axonemes assemble and continuously turn over at the flagellar tip. The supply and removal of axonemal subunits at the tip are mediated by intraflagellar transport (IFT) [1Marshall W.F. Rosenbaum J.L. Intraflagellar transport balances continuous turnover of outer doublet microtubules implications for flagellar length control.J. Cell Biol. 2001; 153: 405-414Crossref Scopus (258) Google Scholar, 2Rosenbaum J.L. Witman G.B. Intraflagellar transport.Nat. Rev. Mol. Cell Biol. 2002; 3: 813-825Crossref PubMed Scopus (1128) Google Scholar], a motility process essential for the assembly and maintenance of all eukaryotic flagella and cilia. IFT is characterized by the movement of large protein complexes (IFT particles) from the basal bodies to the flagellar tip by kinesin-II and from the tip back to the basal bodies by cytoplasmic dynein 1b. The IFT particles consist of ∼16 polypeptides partitioned into two complexes, A and B [2Rosenbaum J.L. Witman G.B. Intraflagellar transport.Nat. Rev. Mol. Cell Biol. 2002; 3: 813-825Crossref PubMed Scopus (1128) Google Scholar, 3Cole D.G. The intraflagellar transport machinery of Chlamydomonas reinhardtii.Traffic. 2003; 4: 1-8Crossref PubMed Scopus (187) Google Scholar], and associate with axonemal precursors/turn over products. The mechanisms by which IFT motor regulation and cargo loading/unloading occur at the flagellar tip are unknown. We identified a Chlamydomonas reinhardtii ortholog of the microtubule (MT) plus end-tracking protein EB1 [4Tirnauer J.S. Bierer B.E. EB1 proteins regulate microtubule dynamics, cell polarity, and chromosome stability.J. Cell Biol. 2000; 149: 761-766Crossref PubMed Scopus (211) Google Scholar] (CrEB1) and show here that CrEB1 localizes to the tip of flagella and to the proximal part of the basal bodies. Furthermore, we found that CrEB1 is depleted from flagella of the temperature-sensitive (ts) flagellar assembly-defective (fla) mutant fla11ts at the restrictive temperature. This depletion of CrEB1 is accompanied by a dramatic accumulation of IFT particle polypeptides near the flagellar tip.