Carter, A. P. | bioRxiv Science

bioRxiv2017

Cryo-EM shows how dynactin recruits two dyneins for faster movement

Dynein and its cofactor dynactin form a highly processive microtubule motor in the presence of an activating adaptor, such as BICD2. Different adaptors link dynein/dynactin to distinct cargos. Here we use electron microscopy (EM) and single molecule studies to show that adaptors can recruit a second dynein to dynactin. Whereas BICD2 is biased toward recruiting a single dynein, the adaptors BICDR1 and HOOK3 predominantly recruit two. We find that the shift toward a double dynein complex increases both force and speed. A 3.5 [A] cryo-EM reconstruction of a dynein tail/dynactin/BICDR1 complex reveals how dynactin can act as a scaffold to coordinate two dyneins side by side. Our work provides a structural basis for how diverse adaptors recruit different numbers of dyneins and regulate the motile properties of the dynein/dynactin transport machine.

molecular biology↗

bioRxiv2016

DYNC1H1 mutations associated with neurological diseases compromise processivity of dynein-dynactin-cargo adaptor complexes

Mutations in the human DYNC1H1 gene are associated with neurological diseases. DYNC1H1 encodes the heavy chain of cytoplasmic dynein-1, a 1.4 MDa motor complex that traffics organelles, vesicles and macromolecules towards microtubule minus ends. The effects of the DYNC1H1 mutations on dynein motility, and consequently their links to neuropathology, are not understood. Here, we address this issue using a recombinant expression system for human dynein coupled to single-molecule resolution in vitro motility assays. We functionally characterise 14 DYNC1H1 mutations identified in humans diagnosed with malformations in cortical development (MCD) or spinal muscular atrophy with lower extremity predominance (SMALED), as well as three mutations that cause motor and sensory defects in mice. Two of the human mutations, R1962C and H3822P, strongly interfere with dyneins core mechanochemical properties. The remaining mutations selectively compromise the processive mode of dynein movement that is activated by binding to the accessory complex dynactin and the cargo adaptor BICD2. Mutations with the strongest effects on dynein motility in vitro are associated with MCD. The vast majority of mutations do not affect binding of dynein to dynactin and BICD2, and are therefore expected to result in linkage of cargoes to dynein-dynactin complexes that have defective long-range motility. This observation offers an explanation for the dominant effects of DYNC1H1 mutations in vivo. Collectively, our results suggest that compromised processivity of cargo-motor assemblies contributes to human neurological disease and provide insight into the influence of different regions of the heavy chain on dynein motility.

cell biology↗