13 - Regulation of Dynein in Ciliary and Flagellar Movement

Abstract

This chapter provides an overview of the regulation of dynein motile activity underlying the oscillatory bending movement of cilia and flagella. It mainly describes the knowledge obtained from studies on sea urchin sperm flagella, referring to other species, as the basic mechanism of dynein regulation is thought to be common to flagella and cilia of many species, barring few differences in some of its features. It begins with discussing the basic features of the components of cilia and flagella, which include dynein arms, microtubules, and beat plane and the central-pair microtubules. Following this, it deals with the regulation of microtubule sliding in the axoneme, discussing microtubule sliding in trypsin-treated axonemes, microtubule sliding in elastase-treated axonemes, and patterns of splitting in elastase-treated axonemes. It also discusses the sliding microtubule theory and bend formation. The sliding microtubule theory, first put forward in the 1950s following morphological observations of dynein arms, postulated that sliding between microtubules within the axonemes is the motive force of flagellar (or ciliary) beating. Finally, it examines the mechanism regulating the coordinated activity of dynein that produces the difference in the amount of microtubule sliding during flagellar oscillation, using mathematical analysis and experiments using elastase-treated axonemes. One of the difficulties that remain concerns how to analyze microtubule sliding in a flagellum that can oscillate. Much more experimental studies are required in this regard.