ABSTRACT
Intraflagellar transport (IFT) is a motor-driven motility of large proteins arrays called IFT trains along the microtubules of the ciliary axoneme. This chapter reviews the composition of IFT dynein and its role in cilia assembly, maintenance, and function. IFT is a specialized form of intracellular transport, which moves proteins from the cell body into cilia and vice versa. IFT was first observed by DIC video microcopy as birefringent particles moving up and down inside cilia. Active transport by IFT allows proteins to be moved against cellular concentration gradients. Thus, IFT, selective protein entry, and ciliary self-assembly establish and maintain the highly selective protein make-up of cilia. Loss of function mutations in many IFT particle and motor proteins result in a failure to assemble cilia; in mammals, the complete loss of cilia is embryonic lethal. The IFT particles function as cargo adaptors that bind many ciliary proteins and enable them to move in and out of cilia by IFT.
