Dynein

Dynein is a family of motor proteins that move along microtubules toward the minus end, using energy from ATP hydrolysis. It plays essential roles in intracellular transport, organelle positioning, cell division, and the beating of cilia and flagella. The dynein family comprises two main types: cytoplasmic dyneins, which power retrograde transport and various cytoplasmic movements, and axonemal dyneins, which generate the sliding forces that produce ciliary and flagellar bending.

Cytoplasmic dyneins include dynein-1, the major minus-end–directed motor responsible for transporting vesicles, organelles, and protein complexes toward the cell center, and dynein-2, which participates in retrograde intraflagellar transport within cilia. Axonemal dyneins are arranged as outer dynein arms and inner dynein arms along the axoneme of cilia and flagella, where they drive coordinated bending rather than cargo transport.

Structure is that of a large multi-subunit complex. The motor domain is formed by two or more AAA+ ATPase rings connected to a microtubule-binding stalk. A separate tail region binds light chains and intermediate chains, linking cargo via the dynactin complex and adaptor proteins in cytoplasmic dynein. The motor’s activity is regulated by cofactors such as dynactin, Lis1, NudE/NudEL, and various cargo adapters like BICD proteins.

Biological significance includes retrograde transport in neurons, mitotic spindle orientation, organelle positioning, and ciliary motility. Clinically, mutations in dynein genes (notably DYNC1H1) have been associated with neurodevelopmental disorders and congenital anomalies, while defects in axonemal dyneins can cause ciliopathies such as primary ciliary dyskinesia.