IRG Meetings


Each month the MRSEC holds Active Matter and Membrane talks. Everyone is invited to attend. The research goal of the MRSEC is to understand the emergence of biomimetic functionalities that are highly sought-after in materials science and to synergistically engineer life-like materials.

Greg Hoeprich, Goode Lab Postdoc, Organizer


Thursday, April 26, 2018
IRG Talk: A Novel Actin Filament Sliding and Compaction Mechanism Jointly Catalyzed by Srv2/CAP and its Interacting Partner Abp1

Sean Guo, Goode Lab
Abstract: Dynamic remodeling of filamentous actin networks is a critical step in cell migration, cell adhesion, and many other actin-based processes. However, we are only beginning to understand the mechanisms used by cells to reorganize actin network architecture. Here, we describe a new remodeling activity, jointly catalyzed by two conserved actin binding proteins that interact: Abp1 (Actin binding protein 1) and Srv2/CAP (Cyclase-associated protein). In TIRF microscopy assays, these two proteins together induce dynamic crosslinking and sliding of filaments, resulting in filament coalescence and compaction into thick bundles as well as overall coarsening of the actin network. Remodeling depended on direct interactions between Abp1 and Srv2/CAP, and on interactions between Abp1 and F-actin. Structurally, Srv2/CAP self-assembles into a hexameric wheel-shaped hub with six Abp1-binding sites, making the combination of the two proteins a robust actin crosslinker. Using multi-wavelength TIRF microscopy with labeled Abp1 and Srv2/CAP molecules, we directly visualized Abp1-Srv2/CAP complexes gliding diffusively along filaments and accumulating in regions of highest filament overlap, in turn leading to further coalescence. These observations define a new mode of actin network reorganization, driven by the unique molecular architecture of Srv2/CAP hexamers and their interactions with Abp1. We further recapitulated this ATP-free, contractile system into oil-water interface and 3D emulsion system. The prospect of combining a contractile polymer system with an extensile system (microtubule and kinesin) raises exciting new possibilities for observing emergent properties.
4:00PM
Abelson 229

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