12 - Flagellar Motility and the Dynein Regulatory Complex

Abstract

Eukaryotic cilia and flagella are highly conserved, microtubule-based structures that play fundamental roles in sensory transduction and cell motility. This chapter focuses on the dynein regulatory complex (DRC), about which very little is known so far. It begins with a brief review of the work on the central-pair microtubules and radial spokes, which are required for flagellar motility in Chlamydomonas under physiological conditions. Following this, it deals with the identification and characterization of two groups of extragenic suppressor mutations that can restore motility to paralyzed central pair/radial spoke defective mutants. The first group of suppressor mutations has demonstrated that specific changes in both the outer and inner dynein arms can override defects in the central-pair/radial-spoke complex to restore motility. Characterization of the second group of suppressors, the DRC mutants, has revealed that the DRC serves both as an adaptor for the binding of specific inner-arm dynein isoforms and as part of the nexin link that resists microtubule sliding. It also reviews the recent efforts to identify nexine DRC subunits and localizes them within the substructure of the DRC. Finally, it presents the proposed functions of the DRC and nexin links and discusses possible future directions for research.