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11 décembre 2018: 1 événement

  • Cytoskeleton club

    Mardi 11 décembre 11:30-13:00 - Alexis Gautreau - Ecole Polytechnique, CNRS UMR7654, Palaiseau

    Cytoskeleton club - Assembly of an actin polymerising machine : The WASH - Dynactin - Arp2/3 supercomplex

    Résumé : The Arp2/3 complex contains two Actin-related proteins (Arp), Arp2 and Arp3. At the surface of endosomes, the WASH complex activates the Arp2/3 complex and generates branched actin networks, which have been shown to be critical for endosomal sorting and recycling. The WASH complex is a stable multiprotein complex, which needs first to be assembled to perform its function. Here we report the identification of the first assembly factor of the WASH complex (Visweshwaran et al., EMBO J 2018). This assembly factor allows the assembly at centrosomes of a previously unrecognized trimeric WASH complex that carries most WASH functions. Up-regulation of the assembly factor enhances WASH complex assembly in invasive cancer cells and is associated with a poor survival prognosis of breast cancer patients. The WASH complex also recruits a pre-existing heterodimeric complex called the Capping Protein. We will present unpublished data showing that the WASH complex binds to and colocalizes with Dynactin. Dynactin is the major activator of the microtubule motor Dynein. Dynactin is a large multiprotein complex, which is organized along a capped minifilament containing Arp1 and 11. We were able to show that WASH appropriates CP from Dynactin and can thus elongate a primer filament that initiates the autocatalytic branched nucleation of actin filaments. These data thus ascribe a function to the Arp minifilament of Dynactin, show for the first time a role of Dynactin in polymerizing actin and illustrate how two Arp containing molecular machines perform endosomal membrane fission through the coordination of microtubule motors and actin polymerization.

    Lieu : Bibliothèque - bât. 34

    En savoir plus : Cytoskeleton club