3 research outputs found
A FAP46 Mutant Provides New Insights into the Function and Assembly of the C1d Complex of the Ciliary Central Apparatus
Virtually all motile eukaryotic cilia and flagella have a \u279+2\u27 axoneme in which nine doublet microtubules surround two singlet microtubules. Associated with the central pair of microtubules are protein complexes that form at least seven biochemically and structurally distinct central pair projections. Analysis of mutants lacking specific projections has indicated that each may play a unique role in the control of flagellar motility. One of these is the C1d projection previously shown to contain the proteins FAP54, FAP46, FAP74 and FAP221/Pcdp1, which exhibits Ca(2+)-sensitive calmodulin binding. Here we report the isolation and characterization of a Chlamydomonas reinhardtii null mutant for FAP46. This mutant, fap46-1, lacks the C1d projection and has impaired motility, confirming the importance of this projection for normal flagellar movement. Those cells that are motile have severe defects in phototaxis and the photoshock response, underscoring a role for the C1d projection in Ca(2+)-mediated flagellar behavior. The data also reveal for the first time that the C1d projection is involved in the control of interdoublet sliding velocity. Our studies further identify a novel C1d subunit that we term C1d-87, give new insight into relationships between the C1d subunits, and provide evidence for multiple sites of calmodulin interaction within the C1d projection. These results represent significant advances in our understanding of an important but little studied axonemal structure
Pcdp1 is a central apparatus protein that binds Ca2+-calmodulin and regulates ciliary motility
A complex that localizes to the C1d central pair projection of cilia controls flagellar waveform and beat frequency in response to calcium
The Pcdp1 complex coordinates the activity of dynein isoforms to produce wild-type ciliary motility
The C1d projection of the central apparatus includes Pcdp1 and is required for ciliary motility. A combination of structural and functional studies shows that C1d is required for coordination of dynein activity on specific doublets and differentially affects the activity of both the outer and inner dynein arms