Structure of a microtubule-bound axonemal dynein

Travis Walton,Alan Brown,Hao Wu

doi:10.1038/s41467-020-20735-7

Travis Walton, Alan Brown + Show 1 more

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https://doi.org/10.1038/s41467-020-20735-7

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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.

Highlights

Axonemal dyneins are tethered to doublet microtubules inside cilia to drive ciliary beating, a process critical for cellular motility and extracellular fluid flow
This core is expanded by an additional heavy chain (α-HC) appended to the tail of β-HC and the calcium-responsive light chain LC4 bound to the tail of γ-HC
We show that neighboring dyneins overlap, with the motor domains of β-HC and γ-HC interacting with the IC–LC block and N-terminal tails of the equivalent proteins in the preceding dynein

Summary

Introduction

Axonemal dyneins are tethered to doublet microtubules inside cilia to drive ciliary beating, a process critical for cellular motility and extracellular fluid flow. 1234567890():,; Dyneins are a eukaryotic family of ATP-dependent microtubule motor[1] They are categorized by their two major roles inside cells; cytoplasmic dyneins travel along microtubules and are responsible for both intracellular and intraflagellar transport[2], whereas axonemal dyneins are docked onto doublet microtubules inside cilia and power ciliary beating[3]. The axonemal dyneins are attached to the doublet microtubules in two continuous rows known as the outer dynein arm (ODA) and the inner dynein arm (IDA) The dyneins within these arms have distinct molecular compositions, periodicities, and roles in ciliary waveform generation[9,10], each generates force by pushing against their neighboring doublet microtubule[11]. To understand the unique subunit organization of axonemal dyneins and molecular mechanisms that regulate their function, we have determined a structure of the ODA complex in its microtubulebound post-powerstroke state using single-particle cryo-EM

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