title: The RhoGAP activity of CYK-4/MgcRacGAP functions non-canonically by promoting RhoA activation during cytokinesis.
abstract: Cytokinesis requires activation of the GTPase RhoA. ECT-2, the exchange factor responsible for RhoA activation, is regulated to ensure spatiotemporal control of contractile ring assembly. Centralspindlin, composed of the Rho family GTPase-activating protein (RhoGAP) MgcRacGAP/CYK-4 and the kinesin MKLP1/ZEN-4, is known to activate ECT-2, but the underlying mechanism is not understood. We report that ECT-2-mediated RhoA activation depends on the ability of CYK-4 to localize to the plasma membrane, bind RhoA, and promote GTP hydrolysis by RhoA. Defects resulting from loss of CYK-4 RhoGAP activity can be rescued by activating mutations in ECT-2 or depletion of RGA-3/4, which functions as a conventional RhoGAP for RhoA. Consistent with CYK-4 RhoGAP activity contributing to GEF activation, the catalytic domains of CYK-4 and ECT-2 directly interact. Thus, counterintuitively, CYK-4 RhoGAP activity promotes RhoA activation. We propose that the most active form of the cytokinetic RhoGEF involves complex formation between ECT-2, centralspindlin and RhoA.
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, United States.
authors.forename: Donglei
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, United States.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-8723-7232
authors.initials: M
authors.lastname: Glotzer
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D048749:Cytokinesis; D020690:GTPase-Activating Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: C513388:CYK-4 protein, C elegans; D029742:Caenorhabditis elegans Proteins; C507872:Ect-2 protein, C elegans; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C085379:rho GTPase-activating protein; D020742:rhoA GTP-Binding Protein
keywords: C. elegans; Rac; Rho GTPase; RhoGAP; RhoGEF; cell biology; centralspindlin; cytokinesis