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Proc Natl Acad Sci U S A. 2019 Nov 12;116(46):23152-23162. doi: 10.1073/pnas.1910960116. Epub 2019 Oct 28.

Scaffold subunits support associated subunit assembly in the Chlamydomonas ciliary nexin-dynein regulatory complex.

Author information

1
Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390.
2
Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390.
3
Department of Genetics, Cell Biology, and Development, University of Minnesota Medical School, Minneapolis, MN 55455.
4
Department of Genetics, Cell Biology, and Development, University of Minnesota Medical School, Minneapolis, MN 55455 porte001@umn.edu daniela.nicastro@utsouthwestern.edu.
5
Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390; porte001@umn.edu daniela.nicastro@utsouthwestern.edu.

Abstract

The nexin-dynein regulatory complex (N-DRC) in motile cilia and flagella functions as a linker between neighboring doublet microtubules, acts to stabilize the axonemal core structure, and serves as a central hub for the regulation of ciliary motility. Although the N-DRC has been studied extensively using genetic, biochemical, and structural approaches, the precise arrangement of the 11 (or more) N-DRC subunits remains unknown. Here, using cryo-electron tomography, we have compared the structure of Chlamydomonas wild-type flagella to that of strains with specific DRC subunit deletions or rescued strains with tagged DRC subunits. Our results show that DRC7 is a central linker subunit that helps connect the N-DRC to the outer dynein arms. DRC11 is required for the assembly of DRC8, and DRC8/11 form a subcomplex in the proximal lobe of the linker domain that is required to form stable contacts to the neighboring B-tubule. Gold labeling of tagged subunits determines the precise locations of the previously ambiguous N terminus of DRC4 and C terminus of DRC5. DRC4 is now shown to contribute to the core scaffold of the N-DRC. Our results reveal the overall architecture of N-DRC, with the 3 subunits DRC1/2/4 forming a core complex that serves as the scaffold for the assembly of the "functional subunits," namely DRC3/5-8/11. These findings shed light on N-DRC assembly and its role in regulating flagellar beating.

KEYWORDS:

N-DRC; axoneme; cilia; cryo-electron tomography; flagella

PMID:
31659045
PMCID:
PMC6859327
[Available on 2020-04-28]
DOI:
10.1073/pnas.1910960116

Conflict of interest statement

The authors declare no competing interest.

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