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  • cytoskeleton club

    • Mardi 14 janvier 11:30-12:30 - Guillaume Romet-Lemonne - Institut Jacques Monod, Paris

      Cytoskeleton club - Association of SPIN90, Arp2/3 complex, and formin mDia1 controls cortical actin organization

      Résumé : Cellular shape is controlled by the submembranous cortex, an actomyosin network mainly generated by two actin nucleators : the Arp2/3 complex and the formin mDia1. Changes in relative nucleator activity may allow cells to rapidly alter their cortical organization, mechanics and shape but how this is controlled is unknown. Here, we investigate how nucleation-promoting factors (NPFs) mediate interaction between nucleators. In vitro, the NPF SPIN90 (also known as DIP/WISH/NCKIPSD) promotes formation of unbranched filaments by Arp2/3, a process thought to provide the initial filament for the generation of dendritic networks. Paradoxically, in cells, we find that SPIN90 appears to favor a formin-dominated cortex. Our experiments in vitro reveal this feature stems mainly from two mechanisms : efficient recruitment of mDia1 to SPIN90-Arp2/3 nucleated filaments and formation of a ternary SPIN90-Arp2/3-mDia1 complex that greatly enhances filament nucleation. Both mechanisms yield rapidly elongating filaments with mDia1 at their barbed ends and SPIN90-Arp2/3 at their pointed ends. Thus, in networks, SPIN90 lowers branching densities and increases the proportion of long filaments elongated by mDia1. This synergistic interplay between Arp2/3 and mDia1 may regulate the diverse actin structures present in cells.

      Lieu : Bibliothèque - bât. 34


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