Structure of a microtubule-bound axonemal dynein

Abstract

Axonemal dyneins are tethered to doublet microtubules inside cilia to drive ciliary beating, a process critical for cellular motility and extracellular fluid flow. Axonemal dyneins are evolutionarily and biochemically distinct from cytoplasmic dyneins that transport cargo, and the mechanisms regulating their localization and function are poorly understood. Here, we report a single-particle cryo-EM reconstruction of a three-headed axonemal dynein natively bound to doublet microtubules isolated from cilia. The slanted conformation of the axonemal dynein causes interaction of its motor domains with the neighboring dynein complex. Our structure shows how a heterotrimeric docking complex specifically localizes the linear array of axonemal dyneins to the doublet microtubule by directly interacting with the heavy chains. Our structural analysis establishes the arrangement of conserved heavy, intermediate and light chain subunits, and provides a framework to understand the roles of individual subunits and the interactions between dyneins during ciliary waveform generation.

Remodeling and activation mechanisms of outer arm dyneins revealed by cryo‐EM

“…In our Tetrahymena model, there is more modeled region around the linker region. In contrast, there is more modeled region in DC in the Chlamydomonas model from Walton et al (2021), especially the region connecting the DC1/2 on the doublet surface and the extended coiled‐coil region associated with the ODA complex (red arrowheads). These differences could relate to different properties of the Tetrahymena and Chlamydomonas ODA or different ways of sample preparation.…”

“… A, BThe model of our Tetrahymena ODA complex (A) and Chlamydomonas ODA complex (PDB ID: 7KZM, Walton et al , 2021) (B) viewed from different sides. The Dyh5 head of Tetrahymena ODA is shown as 18‐Å resolution surface rendering.…”

“…Since LC3 was shown to interact with other proteins within the cilia depending on the redox state, LC3 might recruit other regulatory proteins to the Dyh4 AAA+ ring to modulate its motor activity. In the recent Chlamydomonas ODA structure, the linker of the β‐HC, which corresponds to Tetrahymena Dyh4, is in a canonical post‐powerstroke configuration (Walton et al , 2021). Furthermore, the Chlamydomonas γ‐HC (equivalent to Tetrahymena Dyh3) showed the linker configuration similar to that of Tetrahymena Dyh4.…”

Composition and function of ciliary inner‐dynein‐arm subunits studied in Chlamydomonas reinhardtii

“…Presumably the axonemal dyneins will display similar motor structures to cytoplasmic dyneins (Carter, Cho, Jin, & Vale, 2011; Kon et al, 2012), but currently we do not know if this is really the case. Although axonemal dynein structures have been resolved by cryo‐electron tomography at the resolution of ~20 Å (Bui et al, 2012, 2008, 2009; Nicastro et al, 2006; Oda et al, 2014), however, to date only detailed high‐resolution structures of ODAs have been reported (Mali et al, 2021; Walton, Wu, & Brown, 2021). Such structural data of IDAs is essential for further definition of the regulation and mechanism of IDAs.…”

Light chain 2 is a Tctex-type related axonemal dynein light chain that regulates directional ciliary motility in Trypanosoma brucei

“…There is significant additional evidence from multiple species supporting the model of axonemal dynein motors requiring significant regulation [10] to achieve the precise and regular tip-to-base ciliary beat waveforms necessary for persistent directional motility [20]. Inner and outer arm axonemal dynein regulation acts through multiple direct and indirect interactions, including through their ICs and LCs, which respond to various stimuli, including Ca 2+ , phosphorylation, and redox poise [21–23], and in conjunction with the N-DRC, radial spokes, and the central pair complex [11, 12].…”