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

Abstract

Cilia are thin microtubule-based protrusions of eukaryotic cells, beating at high frequency to propel the cell in sperms or clear mucus in the respiratory tract. The ciliary beating is driven by the outer arm dynein arms (ODAs) which anchor on the doublet microtubules. Here, we report the ODA complex structure from the native doublet microtubules by cryo-electron microscopy. Our structure reveals how the ODA complex is attached to the doublet microtubule via the docking complex in its native state. Combined with molecular dynamics simulations, we present a model of how the attachment of the ODA complex to the doublet microtubule induces rearrangements and activation mechanisms within the ODA complex.

Structural organization of the intermediate and light chain complex of Chlamydomonas ciliary I1 dynein

“…63 Cryo-EM single particle reconstruction revealed the highresolution structures of recombinantly expressed human cytoplasmic 64 and IFT 65 dynein complexes, as well as axonemal ODAs docked to isolated doublet microtubules. [66][67][68] These dynein complexes share common organizational features of the tail-bound IC-LC complex, which is important for dynein heavy chain dimerization and cargo-binding, or microtubuledocking in case of axonemal ODAs. Specifically, the IC C-terminal WD40 domain binds to the dynein heavy chain and the extended N-terminus binds to dimers of light chains (LC7, LC8 and TCTEX).…”

Shulin packages axonemal outer dynein arms for ciliary targeting

“…S15, C and D). This clustered conformation is distinct from the one ODAs adopt upon docking onto ciliary doublets, where their motor domains are stacked parallel to each other and free to undergo their catalytic cycle (19,20). Thus, the closed conformation may represent an inactive state of ODAs before their final incorporation into cilia.…”

“…During IFT of ODAs, Shulin may prevent aberrant interactions with axonemal microtubules, which would hinder their transport. At their final location, ODAs interact with the A-tubule via their tail domains and with the B-tubule via their motor domains (20). Shulin's inhibition could be important to allow the ODA tails to correctly dock before the motors can engage the B-tubule.…”