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

Autor: McGuirk ER; Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, 415 South Street, Waltham, MA 02454, USA., Koundinya N; Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, 415 South Street, Waltham, MA 02454, USA., Nagarajan P; Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, PA 19104, USA., Padrick SB; Department of Biochemistry and Molecular Biology, Drexel University, Philadelphia, PA 19104, USA., Goode BL; Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, 415 South Street, Waltham, MA 02454, USA. Electronic address: goode@brandeis.edu.
Jazyk: angličtina
Zdroj: European journal of cell biology [Eur J Cell Biol] 2024 Mar; Vol. 103 (1), pp. 151378. Date of Electronic Publication: 2023 Dec 05.
DOI: 10.1016/j.ejcb.2023.151378
Abstrakt: 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 50 = 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 7 s -1 M -1 ) and off-rate (0.03 s -1 ) 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 d = 0.9 nM) and filament sides (K d = 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.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)
Databáze: MEDLINE
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