Oligomeric assemblies of intraflagellar transport (IFT) particles build cilia through sequential recruitment and transport of ciliary cargo proteins within cilia. Here we present the 1.8Å resolution crystal structure of the Chlamydomonas IFT-B protein IFT80, which reveals the architecture of two N-terminal b-propellers followed by an a-helical extension. The N-terminal b-propeller tethers IFT80 to the IFT-B complex via IFT38 whereas the second b-propeller and the C-terminal a-helical extension result in IFT80 homo-dimerization. Using CRISPR/Cas to create biallelic Ift80 frameshift mutations in IMCD3 mouse cells, we demonstrate that IFT80 is absolutely required for ciliogenesis. Structural mapping and rescue experiments reveal that human disease-causing missense mutations do not cluster within IFT80 and form functional IFT particles. Unlike missense mutant forms of IFT80, deletion of the C-terminal dimerization domain prevented rescue of ciliogenesis. Taken together our results may provide a first insight into higher order IFT complex formation likely required for IFT train formation.
The structural coordinates for IFT80 and diffraction data have been uploaded to the protein data bank (PDB).Macros used for data analysis are available for download through links provided in the material and methods part of the manuscript.
- Esben Lorentzen
- Dagan Jenkins
- Dagan Jenkins
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Andrew P Carter, MRC Laboratory of Molecular Biology, United Kingdom
© 2018, Taschner et al.
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