FAP206 is a microtubule-docking adapter for ciliary radial spoke 2 and dynein c.
Bottom Line: A knockout of the conserved ciliary protein FAP206 in the ciliate Tetrahymena resulted in slow cell motility.Cryo-electron tomography showed that in the absence of FAP206, the 96-nm repeats lacked RS2 and dynein c.Overexpressed GFP-FAP206 decorated nonciliary microtubules in vivo.
Affiliation: Department of Cellular Biology, University of Georgia, Athens, GA 30602.Show MeSH
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Mentions: To investigate further the organization of dynein arms, we analyzed the structure of ODAs and IDAs within the 96-nm axonemal repeat. The ODAs are homogeneous in shape and repeat every 24 nm, whereas the row of IDAs is more complex, with multiple subtypes of arms repeating every 96 nm (Bui et al., 2009; Barber et al., 2012; Heuser et al., 2012a). In the subtomogram averages, the structure of the ODAs appeared unaffected by the loss of FAP206 (Figure 2, A and B, and Supplemental Movies S4 and S5). In agreement with previous studies (Nicastro et al., 2006; Pigino et al., 2011; Barber et al., 2012; Bui et al., 2012; Lin et al., 2012) the wild-type repeat shows the ring-shaped AAA motor domains of all IDAs, including the most proximally located, two-headed dynein f (I1), followed by six single-headed dyneins: a (attached to the base of RS1), b (which is doublet specific in Chlamydomonas but seems generally present in Tetrahymena), c (attached to the base of RS2), e (attached to the N-DRC distal of RS2), and g and d (attached near the base of RS3/RS3S; Figure 5A). In the averaged axonemal repeat of FAP206-KO, the IDA array had a single gap that corresponds precisely to the position of dynein c (Figure 5D), whereas assembly of the remaining IDAs was unaffected. Both the head and tail of dynein c were missing in all (100% after classification) 96-nm repeats of FAP206-KO axonemes (Figure 5E). Note that a relatively small fraction of wild-type repeats (11%) also lacked dynein c (Figure 5, B and C). These repeats were randomly distributed along the axoneme length and among the nine doublets (unpublished data). Thus, in the wild type, dynein c is either naturally missing or lost during the axoneme preparation in a small subset of the 96-nm repeats.
Affiliation: Department of Cellular Biology, University of Georgia, Athens, GA 30602.