Download MendeleyIntraflagellar transport protein IFT172 contains a C-terminal ubiquitin-binding U-box-like domain involved in ciliary signaling.
Zacharia, N.K., Kuhns, S., Boegholm, N., Christensen, A., Wang, J., Petriman, N.A., Lorentzen, A., Fialova, J.L., Menguy, L., Saunier, S., Christensen, S.T., Andersen, J.S., Bhogaraju, S., Lorentzen, E.(2026) Elife 14
- PubMed: 42334455 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.7554/eLife.104906
- Primary Citation Related Structures:
9H2D - PubMed Abstract:
Intraflagellar transport (IFT) is a fundamental process driving ciliogenesis in most eukaryotic organisms. IFT172, the largest protein of the IFT complex, plays a crucial role in cilium formation, and several disease-causing IFT172 variants have been identified in ciliopathy patients. While IFT172 is tethered to the IFT-B complex via its N-terminal domains, the function of its C-terminal domains has remained elusive. Here, using both human and Chlamydomonas reinhardtii IFT172, we reveal that the C-terminal part of IFT172 interacts with IFT-A complex subunits, providing a molecular basis for the role of IFT172 in bridging IFT-A and IFT-B complexes. We determine the crystal structure of the C-terminal part of IFT172, uncovering a conserved U-box-like domain often found in E3 ubiquitin ligases. This domain exhibits ubiquitin-binding properties, and IFT172 undergoes ubiquitin conjugation in vitro, an activity that is reduced in the C1727R patient ciliopathy variant. We use CRISPR-engineered RPE-1 cells to demonstrate that the U-box-like domain is essential for IFT172 protein stability and proper cilium formation. Notably, RPE-1 cells with heterozygous deletion of the U-box domain show altered TGF-β signaling responses, particularly in SMAD2 phosphorylation levels and AKT activation. Our findings suggest that IFT172, beyond its structural role in bridging IFT-A and IFT-B complexes within IFT trains, harbors a conserved U-box-like domain with potential involvement in ciliary ubiquitination processes and signaling, providing new insights into the molecular mechanisms underlying IFT172-related ciliopathies.
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark.
Organizational Affiliation:
