Cell Biology

The intraflagellar transport train

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Science  09 Nov 2018:
Vol. 362, Issue 6415, pp. 652
DOI: 10.1126/science.362.6415.652-c

Assembly of the cilium requires bidirectional intraflagellar transport (IFT) of building blocks along microtubules to and from the site of assembly at its tip. Dynein-1b motors are required to power retrograde transport and are believed to reach the ciliary tip by kinesin-2–driven anterograde IFT. It is unclear which mechanism prevents a tug-of-war between these oppositely directed microtubule motors. Jordan et al. used cryo–electron tomography to examine the architecture of IFT trains in Chlamydomonas cilia in situ. Their findings revealed the relative positions of IFT motors on anterograde versus retrograde trains. Dynein-1b in its autoinhibited form was an integral part of anterograde trains but is positioned to prevent premature engagement with the microtubules. Once at the cilia tip, the dynein converted into its activated form, engaged the microtubules, and then powered retrograde transport.

Nat. Cell Biol. 20, 1250 (2018).

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