L’équipe Romet-Lemonne/Jégou a contribué à la publication d’un nouvel article dans Nature structural & molecular biology :
Arp2/3-mediated bidirectional actin assembly by SPIN90 dimers
Résumé :
Branched actin networks nucleated by the Arp2/3 complex have critical roles in various cellular processes, from cell migration to intracellular transport. However, when activated by WISH/DIP/SPIN90-family proteins, Arp2/3 nucleates linear actin filaments. Here we found that human SPIN90 is a dimer that can nucleate bidirectional actin filaments. To understand the basis for this, we determined a 3-Å-resolution structure of human SPIN90–Arp2/3 complex nucleating actin filaments. Our structure shows that SPIN90 dimerizes through a three-helix bundle and interacts with two Arp2/3 complexes. Each SPIN90 molecule binds both Arp2/3 complexes to promote their activation. Our analysis demonstrates that single-filament nucleation by Arp2/3 is mechanistically more like branch formation than previously appreciated. The dimerization domain in SPIN90 orthologs is conserved in metazoans, suggesting that this mode of bidirectional nucleation is a common strategy to generate antiparallel actin filaments.
Figure credit : Liu T, Cao L, Mladenov M, Romet-Lemonne G, Way M, Moores CA. Arp2/3-mediated bidirectional actin assembly by SPIN90 dimers. Nat Struct Mol Biol. 2025 Sep 15. doi: 10.1038/s41594-025-01665-8. Epub ahead of print. PMID: 40954369.