dyneïnes

Dyneïnes are a family of minus-end–directed motor proteins that move along microtubules in eukaryotic cells. They convert the energy of ATP hydrolysis into mechanical work, enabling directed transport of diverse cargo and, in some contexts, the motility of cilia and flagella. Two broad classes are recognized: cytoplasmic dyneins and axonemal dyneins.

Cytoplasmic dyneins, primarily dynein-1, move most cargo toward the microtubule minus ends, typically toward the cell center. They often rely on a multiprotein activator complex called dynactin and various cargo adaptors to attach vesicles, organelles, and protein assemblies. A second cytoplasmic dynein, dynein-2, functions in retrograde intraflagellar transport within cilia.

Axonemal dyneins are specialized for the beating of cilia and flagella. They exist as outer dynein arms and inner dynein arms, which generate sliding forces between adjacent microtubule doublets, producing bending waves that drive motility. These dyneins are structurally distinct from cytoplasmic dyneins and are encoded by separate gene families.

Structure and mechanism: each dynein motor is a large, multi-subunit complex. The heavy chain contains the motor domain with an AAA+ ATPase ring that binds and hydrolyzes ATP, generating conformational changes that power the movement of a linker domain. Intermediate and light chains regulate cargo binding and complex stability. In cells, cytoplasmic dyneins cooperate with dynactin and other cofactors to achieve processive transport; regulation is aided by LIS1 and related proteins.

Clinical and biological significance: dyneins are essential for proper neuronal transport, spindle organization during cell division, and the assembly and function of cilia. Defects can cause ciliopathies, laterality defects, and neurodevelopmental disorders in humans and model organisms.