A GAP that Divides [version 1; peer review: 3 approved]

• Published in: F1000 research Vol. 6; p. 1788
• Main Authors: Basant, Angika, Glotzer, Michael
• Format: Journal Article
• Language: English
• Published: England F1000Research 2017; F1000 Research Ltd
• Subjects: Cell Adhesion; Cell Growth & Division; Cell Signaling; Cytoskeleton; Review; cytokinesis; RhoA; GAP proteins
• ISSN: 2046-1402; 2046-1402
• DOI: 10.12688/f1000research.12064.1

Cytokinesis in metazoan cells is mediated by an actomyosin-based contractile ring that assembles in response to activation of the small GTPase RhoA. The guanine nucleotide exchange factor that activates RhoA during cytokinesis, ECT-2, is highly regulated. In most metazoan cells, with the notable exception of the early
Caenorhabditis elegans embryo, RhoA activation and furrow ingression require the centralspindlin complex. This exception is due to the existence of a parallel pathway for RhoA activation in
C. elegans. Centralspindlin contains CYK-4 which contains a predicted Rho family GTPase-activating protein (GAP) domain. The function of this domain has been the subject of considerable debate. Some publications suggest that the GAP domain promotes RhoA activation (for example, Zhang and Glotzer, 2015; Loria, Longhini and Glotzer, 2012), whereas others suggest that it functions to inactivate the GTPase Rac1 (for example, Zhuravlev
et al., 2017). Here, we review the mechanisms underlying RhoA activation during cytokinesis, primarily focusing on data in
C. elegans. We highlight the importance of considering the parallel pathway for RhoA activation and detailed analyses of 
cyk-4 mutant phenotypes when evaluating the role of the GAP domain of CYK-4.