How Microtubules And Motor Proteins Enable The Maintenance And Functioning Of Cilia


Cilia are highly conserved, microtubule-based organelles present on the vast majority of human cells.1 The two major types are primary cilia, also known as sensory or nonmotile cilia, and motile cilia (Figure 1a). Most cells have a single primary cilium2 that serves sensory and signaling functions, whereas motile cilia are a particular feature of specialized multiciliated cells and beat in a coordinated fashion to drive extracellular fluid flow.1,3 Ciliary beating enables mucus clearance by the respiratory epithelium, cerebrospinal fluid circulation via the ependyma, and egg transportation in fallopian tubes.4

Regardless of type, all cilia are anchored intracellularly by a modified centriolar structure known as the basal body.4 The extracellular protrusion is referred to as the axoneme5 and is supported by a cylindrical bundle of nine microtubule doublets (Figure 1b). In motile cilia, an additional central doublet is present and the combined axonemal microtubules act as a scaffold for other structural components,3,5 most notably the axonemal dynein assemblies that power ciliary beating.6

In this newsletter, we will briefly review the unique roles of key ciliary motor proteins including kinesin-2, dynein-2, and axonemal dynein arms, and also consider the pathological consequences of mutations that affect their normal functioning.7

Also included in this newsletter:

  • Motor and Microtubule Tools
  • Related Publications