Regulation of flagellar dynein activity by a central pair kinesin

Kinesin-like calmodulin-binding protein, KCBP, is a novel member of the C-kinesin superfamily first discovered in flowering plants. This minus-end-directed kinesin exhibits Ca2+-calmodulin-sensitive motor activity in vitro and has been implicated in trichome morphogenesis and cell division. A homologue of KCBP is also found in the unicellular, biflagellate green alga Chlamydomonas reinhardtii (CrKCBP). Unlike plant cells, Chlamydomonas cells do not form trichomes and do not assemble a phragmoplast before cell division. To test whether CrKCBP is involved in additional microtubule-based processes not observed in plants, we generated antibodies against the putative calmodulin-binding domain and used these antibodies in biochemical and localization studies. In interphase cells CrKCBP primarily localizes near the base of the flagella, although surprisingly, a small fraction also localizes along the length of the flagella. CrKCBP is bound to isolated axonemes in an ATP-dependent fashion and is not a component of the dynein arms, radial spokes or central apparatus. During mitosis, CrKCBP appears concentrated at the centrosomes during prophase and metaphase. However, during telophase and cytokinesis CrKCBP co-localizes with the microtubules associated with the phycoplast. These studies implicate CrKCBP in flagellar functions as well as cell division.

Section: A Fraction Of Crkcbp Localizes To Flagellamentioning

confidence: 85%

Section: Crkcbp Associates With the Phycoplast During Cytokinesismentioning

confidence: 99%

A kinesin-like calmodulin-binding protein inChlamydomonas: evidence for a role in cell division and flagellar functions

Dymek

Goduti

Kramer

et al. 2006

“…Several proteins are specifically associated to the central pair and their inactivation usually drastically reduced flagellum motility in Chlamydomonas (Rupp et al, 2001;Smith and Lefebvre, 1996;Smith and Lefebvre, 1997;Yokoyama et al, 2004) and mice . In addition, patients with ultra-structural defects of the central pair displayed the most severe forms of primary ciliary dyskinesia (Tamalet et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

Conserved and specific functions of axoneme components in trypanosome motility

Branche

Kohl

Toutirais

et al. 2006

151

261

The Trypanosoma brucei flagellum is unusual as it is attached along the cell body and contains, in addition to an apparently conventional axoneme, a structure called the paraflagellar rod, which is essential for cell motility. Here, we investigated flagellum behaviour in normal and mutant trypanosome cell lines where expression of genes encoding various axoneme proteins (PF16, PF20, DNAI1, LC2) had been silenced by RNAi. First, we show that the propulsive wave (normally used for forward motility) is abolished in the absence of outer dynein arms, whereas the reverse wave (normally used for changing direction) still occurs. Second, in contrast to Chlamydomonas - but like metazoa, the central pair adopts a fixed orientation during flagellum beating. This orientation becomes highly variable in central-pair- and outer-dynein-arm-mutants. Third, the paraflagellar rod contributes to motility by facilitating three-dimensional wave propagation and controlling cell shape. Fourth, motility is required to complete the last stage of cell division in both insect and bloodstream stages of the parasite. Finally, our study also reveals the conservation of molecular components of the trypanosome flagellum. Coupled to the ease of reverse genetics, it raises the interest of trypanosomes as model organisms to study cilia and flagella.

“…If an ATPase is involved in these interactions, it is likely to be a component of the central pair complex. One such candidate is Klp1, a kinesin-like protein associated with a projection of one of the central pair microtubules and thus in a position to contact the spoke heads (Bernstein et al, 1994;Yokoyama et al, 2004).…”

Section: Spoke Head Proteinsmentioning

confidence: 99%

Radial spoke proteins ofChlamydomonasflagella

Yang

Diener

Chun

et al. 2006

227

282

The radial spoke is a ubiquitous component of \u279+2\u27 cilia and flagella, and plays an essential role in the control of dynein arm activity by relaying signals from the central pair of microtubules to the arms. The Chlamydomonas reinhardtii radial spoke contains at least 23 proteins, only 8 of which have been characterized at the molecular level. Here, we use mass spectrometry to identify 10 additional radial spoke proteins. Many of the newly identified proteins in the spoke stalk are predicted to contain domains associated with signal transduction, including Ca2+-, AKAP- and nucleotide-binding domains. This suggests that the spoke stalk is both a scaffold for signaling molecules and itself a transducer of signals. Moreover, in addition to the recently described HSP40 family member, a second spoke stalk protein is predicted to be a molecular chaperone, implying that there is a sophisticated mechanism for the assembly of this large complex. Among the 18 spoke proteins identified to date, at least 12 have apparent homologs in humans, indicating that the radial spoke has been conserved throughout evolution. The human genes encoding these proteins are candidates for causing primary ciliary dyskinesia, a severe inherited disease involving missing or defective axonemal structures, including the radial spokes