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Mol Biol Cell. 2019 May 22:mbcE19010063. doi: 10.1091/mbc.E19-01-0063. [Epub ahead of print]

PACRG and FAP20 form the inner junction of axonemal doublet microtubules and regulate ciliary motility.

Author information

1
Department of Biological Sciences, Class of 1978 Life Sciences Center Dartmouth College, Hanover NH 03755.
2
Departments of Cell Biology and Biophysics, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390.
3
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455.

Abstract

We previously demonstrated that PACRG plays a role in regulating dynein-driven microtubule sliding in motile cilia. To expand our understanding of the role of PACRG in ciliary assembly and motility we used a combination of functional and structural studies, including newly identified Chlamydomonas pacrg mutants. Using cryo-electron tomography we show that PACRG and FAP20 form the inner junction between the A- and B-tubule along the length of all nine ciliary doublet microtubules. The lack of PACRG and FAP20 also results in reduced assembly of inner arm dynein IDA b and the beak-MIP structures. In addition, our functional studies reveal that loss of PACRG and/or FAP20 causes severe cell motility defects, as well as reduced in vitro microtubule sliding velocities. Interestingly, the addition of exogenous PACRG and/or FAP20 protein to isolated mutant axonemes restores microtubule sliding velocities, but not ciliary beating. Taken together these studies show that PACRG and FAP20 comprise the inner junction bridge that serves as a hub for both directly modulating dynein-driven microtubule sliding, as well as for the assembly of additional ciliary components that play essential roles in generating coordinated ciliary beating. Video S1 Video S1 Supplemental Video 1. Video of a wild-type cell swimming forward with an asymmetric waveform. Cells were captured at 500 fps using a pco.1200HS camera and videos created at 30 fps with Camware (The Cooke Corporation, Londonderry, NH) and ImageJ (Schneider et al., 2012) software. Video S2 Video S2 Supplemental Video 2. Video of a pacrg mutant cell (CLiP 159) with abnormal waveform and motility. Cells were captured at 500 fps using a pco.1200HS camera and videos created at 30 fps with Camware (The Cooke Corporation, Londonderry, NH) and ImageJ (Schneider et al., 2012) software. Video S3 Video S3 Supplemental Video 3. Video of a pacrg mutant cell (pf12-cc1031) with abnormal waveform and motility. Cells were captured at 500 fps using a pco.1200HS camera and videos created at 30 fps with Camware (The Cooke Corporation, Londonderry, NH) and ImageJ (Schneider et al., 2012) software.

PMID:
31116684
DOI:
10.1091/mbc.E19-01-0063

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