Microtubule binding protein PACRG plays a role in regulating specific ciliary dyneins during microtubule sliding.

The complex waveforms characteristic of motile eukaryotic cilia and flagella are produced by the temporally and spatially regulated action of multiple dynein subforms generating sliding between subsets of axonemal microtubules. Multiple protein complexes have been identified that are associated with the doublet microtubules and that mediate regulatory signals between key axonemal structures, such as the radial spokes and central apparatus, and the dynein arm motors; these complexes include the N-DRC, MIA, and CSC complexes. Previous studies have shown that PACRG (parkin co-regulated gene) forms a complex that is anchored to the axonemal doublet microtubules. Loss of PACRG causes defects in ciliary motility and cilia related diseases. Here, we use an in vitro microtubule sliding assay to demonstrate that PACRG and its interactors are part of a signaling pathway that includes the central apparatus, radial spokes and specific inner dynein arm subforms to control dynein-driven microtubule sliding. Using a biochemical approach, our studies also indicate that PACRG interacts with the radial spokes.