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Direct observation of cortactin protecting Arp2/3-actin filament branch junctions from GMF-mediated destabilization
Journal article   Open access   Peer reviewed

Direct observation of cortactin protecting Arp2/3-actin filament branch junctions from GMF-mediated destabilization

Emma R McGuirk, Neha Koundinya, Priyashree Nagarajan, Shae B Padrick and Bruce L Goode
European journal of cell biology, v 103(1), pp 151378-151378
01 Mar 2024
DOI: https://doi.org/10.1016/j.ejcb.2023.151378
PMID: 38071835
Featured in Collection :   UN Sustainable Development Goals @ Drexel
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https://doi.org/10.1016/j.ejcb.2023.151378View
Published, Version of Record (VoR) Open

Abstract

Cortactin GMF Glia maturation factor Actin Branch TIRF microscopy
How cells tightly control the formation and turnover of branched actin filament arrays to drive cell motility, endocytosis, and other cellular processes is still not well understood. Here, we investigated the mechanistic relationship between two binding partners of the Arp2/3 complex, glia maturation factor (GMF) and cortactin. Individually, GMF and cortactin have opposite effects on the stability of actin filament branches, but it is unknown how they work in concert with each other to govern branch turnover. Using TIRF microscopy, we observe that GMF's branch destabilizing activities are potently blocked by cortactin (IC = 1.3 nM) and that this inhibition requires direct interactions of cortactin with Arp2/3 complex. The simplest model that would explain these results is competition for binding Arp2/3 complex. However, we find that cortactin and GMF do not compete for free Arp2/3 complex in solution. Further, we use single molecule analysis to show that cortactin's on-rate (3 ×10 s M ) and off-rate (0.03 s ) at branch junctions are minimally affected by excess GMF. Together, these results show that cortactin binds with high affinity to branch junctions, where it blocks the destabilizing effects of GMF, possibly by a mechanism that is allosteric in nature. In addition, the affinities we measure for cortactin at actin filament branch junctions (K = 0.9 nM) and filament sides (K = 206 nM) are approximately 20-fold stronger than previously reported. These observations contribute to an emerging view of molecular complexity in how Arp2/3 complex is regulated through the integration of multiple inputs.

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Collaboration types
Domestic collaboration
Web of Science research areas
Cell Biology
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