Dynein, an ancient microtubule-based motor protein, performs diverse cellular functions in nearly all eukaryotic cells, with the exception of land plants. It has evolved into three subfamilies-cytoplasmic dynein-1, cytoplasmic dynein-2, and axonemal dyneins-each differentiated by their cellular functions. These megadalton complexes consist of multiple subunits, with the heavy chain being the largest subunit that generates motion and force along microtubules by converting the chemical energy of ATP hydrolysis into mechanical work. Beyond this catalytic core, the functionality of dynein is significantly enhanced by numerous non-catalytic subunits. These subunits are integral to the complex, contributing to its stability, regulating its enzymatic activities, targeting it to specific cellular locations, and mediating its interactions with other cofactors. The diversity of non-catalytic subunits expands dynein\'s cellular roles, enabling it to perform critical tasks despite the conservation of its heavy chains. In this review, we discuss recent findings and insights regarding these non-catalytic subunits.

Cytoplasmic dynein-2 powers retrograde intraflagellar transport that is essential for cilium formation and maintenance. Inactivation of dynein-2 by mutations in DYNC2H1 causes skeletal dysplasias, and it remains unclear how the dynein-2 heavy chain moves in cilia. Here, using the genome-editing technique to produce fluorescent dynein-2 heavy chain in Caenorhabditis elegans, we show by high-resolution live microscopy that dynein-2 moves in a surprising way along distinct ciliary domains. Dynein-2 shows triphasic movement in the retrograde direction: dynein-2 accelerates in the ciliary distal region and then moves at maximum velocity and finally decelerates adjacent to the base, which may represent a physical obstacle due to transition zone barriers. By knocking the conserved ciliopathy-related mutations into the C. elegans dynein-2 heavy chain, we find that these mutations reduce its transport speed and frequency. Disruption of the dynein-2 tail domain, light intermediate chain, or intraflagellar transport (IFT)-B complex abolishes dynein-2\'s ciliary localization, revealing their important roles in ciliary entry of dynein-2. Furthermore, our affinity purification and genetic analyses show that IFT-A subunits IFT-139 and IFT-43 function redundantly to promote dynein-2 motility. These results reveal the molecular regulation of dynein-2 movement in sensory cilia.