Thursday, August 04, 2005

563: Functional coordination of intraflagellar transport motors : Nature

Functional coordination of intraflagellar transport motors : Nature:

Cilia have diverse roles in motility and sensory reception, and defects in cilia function contribute to ciliary diseases such as Bardet−Biedl syndrome (BBS). Intraflagellar transport (IFT) motors assemble and maintain cilia by transporting ciliary precursors, bound to protein complexes called IFT particles, from the base of the cilium to their site of incorporation at the distal tip1, 2, 3. In Caenorhabditis elegans, this is accomplished by two IFT motors, kinesin-II and osmotic avoidance defective (OSM)-3 kinesin, which cooperate to form two sequential anterograde IFT pathways that build distinct parts of cilia4, 5, 6, 7. By observing the movement of fluorescent IFT motors and IFT particles along the cilia of numerous ciliary mutants, we identified three genes whose protein products mediate the functional coordination of these motors. The BBS proteins BBS-7 and BBS-8 are required to stabilize complexes of IFT particles containing both of the IFT motors, because IFT particles in bbs-7 and bbs-8 mutants break down into two subcomplexes, IFT-A and IFT-B, which are moved separately by kinesin-II and OSM-3 kinesin, respectively. A conserved ciliary protein, DYF-1, is specifically required for OSM-3 kinesin to dock onto and move IFT particles, because OSM-3 kinesin is inactive and intact IFT particles are moved by kinesin-II alone in dyf-1 mutants. These findings implicate BBS ciliary disease proteins and an OSM-3 kinesin activator in the formation of two IFT pathways that build functional cilia.
I don't know what all that means, but I do know what this is all about:
Notably, phylogenetic analysis identified 14 homologues of DYF-1 (Supplementary Fig. S1) and revealed that, similar to BBS-7, BBS-8 and the kinesin-2 motors8, 17, it is highly conserved among ciliated organisms but is not found in organisms lacking cilia. The functions of these DYF-1 proteins are unknown.
Common descent lets these researchers test an evolutionary hypothesis.