Dynein

The Cellular Roles of Dynein Microtubule Motors

Dyneins are molecular motors that direct motion towards the minus end of a microtubule in an ATP-dependent manner. In cytoplasm, dyneins are involved in a wide variety of motile activities including mitosis, nuclear migration, vesicular trafficking, nuclear envelope breakdown, maintenance of the Golgi apparatus, organization and functioning of the endoplasmic reticulum and retrograde axonal transport. In cilia/flagella dyneins play two general roles.

First, an additional “cytoplasmic” dynein isoform (termed 1b or 2) is involved in intraflagellar transport (IFT) which is required for the assembly of both motile cilia/flagella and of immotile sensory cilia at their distal tip. This dynein powers retrograde trafficking of IFT particles from the ciliary tip to the cell body.

Second, at least sixteen other dynein motors form the inner and outer arms that project from the A-tubules of ciliary/flagellar doublet microtubules and transiently interact with the B tubule of the adjacent doublet to generate force. These dyneins are required for formation and propagation of a ciliary/flagellar beat.