The Rho1 GTPase controls anillo-septin assembly to facilitate contractile ring closure during cytokinesis

Sabrya C Carim; Gilles R X Hickson

doi:10.1016/j.isci.2023.106903

The Rho1 GTPase controls anillo-septin assembly to facilitate contractile ring closure during cytokinesis

iScience. 2023 May 19;26(6):106903. doi: 10.1016/j.isci.2023.106903. eCollection 2023 Jun 16.

Authors

Sabrya C Carim¹, Gilles R X Hickson^{1

2}

Affiliations

¹ CHU Sainte-Justine Research Center, 3175 Chemin de la Côte Ste-Catherine, Montréal, QC H3T 1C5, Canada.
² Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC H3C 3J7, Canada.

Abstract

Animal cell cytokinesis requires activation of the GTPase RhoA (Rho1 in Drosophila), which assembles an F-actin- and myosin II-dependent contractile ring (CR) at the equatorial plasma membrane. CR closure is poorly understood, but involves the multidomain scaffold protein, Anillin. Anillin binds many CR components including F-actin and myosin II (collectively actomyosin), RhoA and the septins. Anillin recruits septins to the CR but the mechanism is unclear. Live imaging of Drosophila S2 cells and HeLa cells revealed that the Anillin N-terminus, which scaffolds actomyosin, cannot recruit septins to the CR. Rather, septin recruitment required the ability of the Anillin C-terminus to bind Rho1-GTP and the presence of the Anillin PH domain, in a sequential mechanism occurring at the plasma membrane, independently of F-actin. Anillin mutations that blocked septin recruitment, but not actomyosin scaffolding, slowed CR closure and disrupted cytokinesis. Thus, CR closure requires coordination of two Rho1-dependent networks: actomyosin and anillo-septin.

Keywords: Cell biology; Molecular biology.