Lien vers Pubmed [PMID] – 30133348
Mol. Biol. Cell 2018 Aug;:mbcE18060405
Doublet and triplet microtubules are essential and highly stable core structures of centrioles, basal bodies, cilia and flagella. In contrast to dynamic cytoplasmic microtubules, their luminal surface is coated with regularly arranged Microtubule Inner Proteins (MIPs). However, the protein composition and biological function(s) of MIPs remain poorly understood. Using genetic, biochemical and imaging techniques we identified Tetrahymena RIB72A and RIB72B proteins as ciliary MIPs. Fluorescence imaging of tagged RIB72A and RIB72B showed that both proteins co-localize to Tetrahymena cilia and basal bodies, but assemble independently. Cryo-electron tomography of RIB72A and/or RIB72B knockout strains revealed major structural defects in the ciliary A-tubule involving MIP1, MIP4 and MIP6 structures. The defects of individual mutants were complementary in the double mutant. All mutants had reduced swimming speed and ciliary beat frequencies, and high-speed video imaging revealed abnormal highly curved cilia during power stroke. Our results show that RIB72A and RIB72B are crucial for the structural assembly of ciliary A-tubule MIPs and are important for proper ciliary motility. Video S1 Video S1 Video S1. A wild-type Tetrahymena cell swimming inside a microfluidic channel, recorded at 2000 frames/sec. (Stills appear in Figure 4 and Figure S3). Video S2 Video S2 Video S2. A Tetrahymena RIB72A-KO cell swimming inside a microfluidic channel, recorded at 2000 frames/sec. (Stills appear in Figure 4). Video S3 Video S3 Video S3. A Tetrahymena RIB72B-KO cell swimming inside a microfluidic channel, recorded at 2000 frames/sec. (Stills appear in Figure 4). Video S4 Video S4 Video S4. A Tetrahymena RIB72A/B-KO cell swimming inside a microfluidic channel, recorded at 2000 frames/sec. (Stills appear in Figure 4 and Figure S3). Video S5 Video S5 Video S5. A Tetrahymena RIB72A/B-KO cell swimming inside a microfluidic channel, recorded at 2000 frames/sec. Red arrow marks a cilium with a kink near the distal region.
https://www.ncbi.nlm.nih.gov/pubmed/30133348