The RhoGAP domain of CYK-4 has an essential role in RhoA activation.
Cytokinesis in animal cells is mediated by a cortical actomyosin-based contractile ring. The GTPase RhoA is a critical regulator of this process as it activates both nonmuscle myosin and a nucleator of actin filaments [1]. The site at which active RhoA and its effectors accumulate is controlled by the microtubule-based spindle during anaphase [2]. ECT-2, the guanine nucleotide exchange factor (GEF) that activates RhoA during cytokinesis, is regulated by phosphorylation and subcellular localization [3-5]. ECT2 localization depends on interactions with CYK-4/MgcRacGAP, a Rho GTPase-activating protein (GAP) domain containing protein [5, 6]. Here we show that, contrary to expectations, the Rho GTPase-activating protein (GAP) domain of CYK-4 promotes activation of RhoA during cytokinesis. Furthermore, we show that the primary phenotype caused by mutations in the GAP domain of CYK-4 is not caused by ectopic activation of CED-10/Rac1 and ARX-2/Arp2. However, inhibition of CED-10/Rac1 and ARX-2/Arp2 facilitates ingression of weak cleavage furrows. These results demonstrate that a GAP domain can contribute to activation of a small GTPase. Furthermore, cleavage furrow ingression is sensitive to the balance of contractile forces and cortical tension.
Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
Andy
A
Loria
Katrina M
KM
Longhini
Michael
M
Glotzer
D051377:Actin-Related Protein 2 / Q000235:genetics / Q000502:physiology; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D048749:Cytokinesis; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D017434:Protein Structure, Tertiary; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000502:physiology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D051377:Actin-Related Protein 2; C407268:CED-10 protein, C elegans; C513388:CYK-4 protein, C elegans; D029742:Caenorhabditis elegans Proteins; C476568:arx-2 protein, C elegans; D020744:rac GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein