Abp1 promotes Arp2/3 complex-dependent actin nucleation and stabilizes branch junctions by antagonizing GMF.
Formation and turnover of branched actin networks underlies cell migration and other essential force-driven processes. Type I nucleation-promoting factors (NPFs) such as WASP recruit actin monomers to Arp2/3 complex to stimulate nucleation. In contrast, mechanisms of type II NPFs such as Abp1 (also known as HIP55 and Drebrin-like protein) are ... less well understood. Here, we use single-molecule analysis to investigate yeast Abp1 effects on Arp2/3 complex, and find that Abp1 strongly enhances Arp2/3-dependent branch nucleation by stabilizing Arp2/3 on sides of mother filaments. Abp1 binds dynamically to filament sides, with sub-second lifetimes, yet associates stably with branch junctions. Further, we uncover a role for Abp1 in protecting filament junctions from GMF-induced debranching by competing with GMF for Arp2/3 binding. These data, combined with EM structures of Abp1 dimers bound to Arp2/3 complex in two different conformations, expand our mechanistic understanding of type II NPFs.
Mesh Terms:
Actin Cytoskeleton, Actin-Related Protein 2-3 Complex, Actins, Glia Maturation Factor, Microfilament Proteins, Microscopy, Electron, Transmission, Models, Molecular, Multiprotein Complexes, Protein Binding, Protein Conformation, Protein Multimerization, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Actin Cytoskeleton, Actin-Related Protein 2-3 Complex, Actins, Glia Maturation Factor, Microfilament Proteins, Microscopy, Electron, Transmission, Models, Molecular, Multiprotein Complexes, Protein Binding, Protein Conformation, Protein Multimerization, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Nat Commun
Date: Dec. 24, 2017
PubMed ID: 30042427
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