Department of Biology, Special Seminar: Aga Kendrick

Description

Aga Kendrick, a postdoctoral fellow in the Department of Cellular and Molecular Medicine at the University of California, San Diego, will give a Special Seminar titled "Time-Resolved Cryo-EM Visualizes Snapshots of Dynein's Activation Pathway" for the Department of Biology.

Professor Trina Schroer will host.

Abstract:

Regulation of cytoplasmic dynein-1 (dynein) is critical for diverse functions of eukaryotic cells, including cell division and longrange intracellular transport. Both dynein and Lis1, an essential dynein regulator, are mutated in patients with neurodevelopmental diseases and are conserved from fungi to mammals. Dynein is a dynamic molecule with activity controlled by an autoinhibited state called "Phi" , in which its two motor domains interact in a way that prevents motility. Lis1 is important for promoting the formation of active dynein complexes; however, how Lis1 performs this function is unknown. Here, we use cryogenic electron microscopy (cryo-EM) and functional assays to determine the structural changes underlying dynein activation by Lis1. We capture an early intermediate step in the activation pathway, suggesting that Lis1 acts as a molecular wedge to activate dynein by breaking the autoinhibitory Phi conformation. To identify other steps in the activation pathway and account for the dynamic nature of dynein, we turn to time-resolved cryo-EM with highly heterogeneous samples. We introduce heterogeneity by adding ATP during our sample preparation, which allows dynein to go through its mechanochemical cycle. Using this approach, we capture numerous distinct dynein and dynein-Lis1 structures from the same sample and show that the presence of these different structures at different time points is regulated by Lis1. Based on our novel dynein-Lis1 structures we propose a new model for dynein activation, in which Lis1 relieves dynein autoinhibition and promotes conformations that are compatible with motility. Taken together, our approach and results highlight the importance of using time-resolved cryo-EM in studying highly dynamic processes.