Samara Reck-Peterson

Research

The contents of eukaryotic cells are highly dynamic, yet organized spatially and temporally. This is achieved primarily by the microtubule cytoskeleton and associated transport machinery, whose fundamental nature is highlighted by the many neurological diseases caused by mutations in them. The overarching goal of the Reck-Peterson lab is to understand how this system works at the molecular, cellular, and organismal scales.

The Reck-Peterson lab is highly interdisciplinary and we use in vitro biochemical reconstitution, protein engineering, single-molecule imaging, proteomics, live-cell imaging, and genetics to achieve our goals. Through collaborative projects with others at UC San Diego we use cryo-electron microscopy (with Andres Leschziner’s lab) and cryo-electron tomography (with Elizabeth Villa’s lab) to incorporate a structure-guided approach to understanding intracellular transport, and we develop testable quantitative physical models of transport (with Elena Koslover’s lab).

The Reck-Peterson lab has made major contributions to determining how the dynein motor works and is regulated, to developing tools and screening strategies to study bi-directional movement of cargos on microtubules, to understanding the regulation of intracellular transport in cells, and most recently to determining how defects in microtubule-based trafficking may impact Parkinson’s Disease.

Major projects in the lab include:

(1) How does the dynein motor work?

Dynein is a large and complicated molecular machine. We have made contributions to developing recombinant systems to express dynein, determining how dynein steps along microtubules, and determining how it is regulated by Lis1. Both the dynein motor encoding gene ( DYNC1H1) and the LIS1 gene are mutated in the neurodevelopmental disease lissencephaly. We have shown that the Lis1 protein binds directly to dynein’s motor domain and impacts its mechanochemical cycle (dynein is a AAA ATPase and its nucleotide cycle controls its interactions with its microtubule track). We also discovered that Lis1 promotes the formation of activated dynein complexes. Activated dynein complexes include 12 dynein subunits, 23 dynactin subunits and a dimeric “activating adaptor”.

Current efforts in the lab are focused on determining how Lis1 promotes the formation of these massive activated dynein complexes.

(2) How is cargo-specificity achieved?

In mammals, the dynein motor transports dozens if not hundreds of distinct cargos. How does it do this with specificity? Our past work used two complementary discovery-based approaches—genetics and proteomics—to identify molecules responsible for specifying dynein’s many functions. One mechanism revealed by our past work was organelle hitchhiking, where cargos link to motors indirectly, by attaching themselves to other cargos that are directly bound to the motors. A second strategy for achieving cargo specificity is the expansion of dynein activating adaptor genes in vertebrates. However, the molecular connections between most activating adaptors and dynein’s cargo are unknown.

A current goal is to determine the mechanisms underlying hitchhiking and the linkages between different activating adaptors and their cargos.

(3) Why do perturbations to the transport machinery cause disease?

Mutations in many components of the transport machinery (the motors, the tracks and regulators of both) are directly linked to a wide variety of neurodevelopmental and neurodegenerative diseases. In addition to our studies on Lis1, we recently began working on LRRK2. The LRRK2 gene is one of the most commonly mutated genes in familial Parkinson’s disease. In collaboration with the Leschziner lab, we showed that LRRK2 binds directly to microtubules in the absence of any other proteins. By doing so it can act as a “roadblock” for dynein and kinesin microtubule-based motors, nearly completely abolishing their movement at low nanomolar concentrations.

Current efforts are focused on determining how LRRK2 binds to microtubules and how pathogenic LRRK2 leads to defects in microtubule-based transport.

(4) Other new directions:

We are also exploring a number of new directions related to transport in a variety of organisms using a wide range of techniques and methods.