Eukaryotic cells use microtubule tracks to move cargo over long distances. There are two types of molecular motors that move on microtubules: dyneins and kinesins. Dyneins move cargo towards the minus ends of microtubules, typically towards the cell interior. Most kinesins move cargo in the opposite direction, generally towards the cell surface. Our lab is tackling broad questions about how the transport system works.

 How does the dynein motor work and how is it regulated?

Cytoplasmic dynein-1 is the only motor used for long-distance minus-end-directed microtubule-based trafficking in eukaryotic cells ranging from human neurons to the hyphae of filamentous fungi. Yet, it transports dozens, if not hundreds of different cargos. One of our lab’s goals is to understand how this large, multi-subunit, motor is regulated. A key regulator of dynein is Lis1 and its binding partners Nde1 and Ndel1. Mutations in Lis1 cause the brain neurodevelopment disease lissencephaly. Current experiments in the lab are focused on determining how these regulators work in yeast, filamentous fungi and in human cells. We use quantitative approaches to do this, including single-molecule imaging and in vitro reconstitution experiments, cryo-electron microscopy (in collaboration with the lab of Andres Leschziner), proteomics, and live-cell imaging.

How does the transport system work?

In addition to cytoplasmic dynein-1, about 40 kinesin motors (in humans) are responsible for functions that oppose cytoplasmic dynein-1. Dynein and these kinesins are responsible for nearly all long distance transport in eukaryotic cells. What is the full list of dynein and kinesin cargos? How are the motors linked to their cargos? How does a single dynein transport so many distinct cargos? We are addressing these questions using two different discovery-based approaches:

1. We use the filamentous fungus, Aspergillus nidulans, as a powerful genetic system to dissect microtubule-based transport. We have conducted screens to identify genes required for the transport of endosomes, peroxisomes, and nuclei. Through these screens we discovered a gene, PxdA, which is required for peroxisome motility. Our current data suggest that PxdA may be a tether that links peroxisomes to early endosomes and that peroxisomes move by "hitchhiking" on early endosomes. 

2. We also use proteomic approaches to identify the dynein and kinesin protein interactomes. We used proximity-dependent biotinylation in living human cells to identify the dynein/ dynactin interactome as well as the interactome of distinct dynein activating adaptors, coiled-coil containing proteins that are required for the motility of dynein from many species. In our proteomic studies we identified two new dynein activating adaptors: NIN and NINL. We also identified many new candidate cargos and cargo adaptors.