The Kinetic Landscape and Interplay of Protein Networks in Cytokinesis

Cytokinesis is a complex process accomplished by strict spatiotemporal coordination of distinct functional modules, including assembly and constriction of a cortical actomyosin ring (AMR), targeted vesicle fusion, and localized extracellular matrix remodeling. Each module consists of multiple proteins whose individual roles have been characterized in different model systems. However, the collective behaviors and interplay of the modules under normal and stressed conditions remain poorly understood. In this study, we conducted quantitative time-lapse imaging to analyze the accumulation kinetics of more than 20 proteins from different modules of cytokinesis in budding yeast. This analysis has provided the first picture of the kinetic landscape of cytokinesis, from AMR assembly to cell separation or abscission. This analysis has also revealed that the AMR undergoes biphasic constriction, akin to other model systems, and the switch between the constriction phases is likely triggered by the AMR maturation and primary septum formation. This microscopy-based kinetic analysis, when combined with chemical or genetic perturbations, has provided us with significant mechanistic insights into the functions of actin filaments and the transglutaminase-like protein Cyk3 in cytokinesis.  Importantly, using the kinetic signature, i.e. the peaking time of each cytokinetic module, as a predictive parameter, coupled with functional analysis, we have found that the type-II membrane protein Kre6 catalyzes β-1,6-glucan synthesis and may also coordinate its function with the Fks1-mediated β-1,3-glucan synthesis to drive cell wall maturation before cell separation.