Intraflagellar transport (IFT) components IFT139A and IFT144A function in the same pathway to regulate retrograde movement and stability of IFT particles

Carlo Iomini1,2, Linya Li2 and Susan K. Dutcher2

1Mount Sinai School of Medicine, New York, NY. 2Washington University School of Medicine, St Louis, MO

The assembly and maintenance of cilia and flagella require a coordinated bidirectional movement of protein particles, which are composed of two multimeric complexes, IFTA and IFTB, along the axoneme referred to as intraflagellar transport (IFT). While anterograde transport delivers axonemal precursors and retrograde motors at the flagellar tip, retrograde transport recycles turnover products and anterograde motors back to the cell body. A set of Chlamydomonas temperature-sensitive mutants that lose flagella at the restrictive temperature, but allow analysis of IFT particle velocity and molecular characterization of the flagella at the permissive temperature have been isolated (FLA loci). We have shown that FLA15 and FLA17 encode IFT144 and IFT139, respectively. fla15 and fla17 mutants share a non-conditional phenotype consisting of the reduction of complex A and the accumulation of complex B polypeptides in the flagella, reduced velocity and frequency of retrograde particles and presence of a flagellar bulge (Iomini et al., 2001, J Cell Biol 153(1):13-24). These mutants also show reduction of both complex A and complex B protein levels in the cell body and around the basal bodies. Using a genetic approach we have shown the existence of a synthetic interaction between fla15 and fla17 in both haploid and diploid strains and the rescue of fla17 or fla15 by the presence of two copies of the wild-type IFT144 (FLA15) or IFT139 (FLA17), respectively. Our data suggest that IFT144 and IFT139 act in the same functional pathway to regulate retrograde transport and stabilize IFT particles at the basal body.

e-mail address of presenting author: Carlo.Iomini@mssm.edu