Novel cytokinetic ring components drive negative feedback in cortical contractility

Abstract

Actomyosin-driven cortical contractility is a hallmark of many biological processes. While most attention has been given to the positive regulation of contractility, it is becoming increasingly appreciated that contractility is also limited by negative regulation and mechanical brakes. The cytokinetic ring is an actomyosin contractile structure whose assembly and constriction are activated by the small GTPase RhoA. Here we describe the role of two novel cytokinetic ring components GCK-1 and CCM-3 in inhibiting contractility in the cytokinetic ring. GCK-1 and CCM-3 co-localize with essential cytokinetic ring proteins such as active RhoA, the scaffold protein anillin and non-muscle myosin II (NMM-II) during anaphase. GCK-1 and CCM-3 are interdependent for their localization and require active RhoA and anillin but not NMM-II for their recruitment to the cytokinetic furrow. Partial depletion of either GCK-1 or CCM-3 leads to an increase of active RhoA, anillin and NMM-II in the cytokinetic furrow and increased rates of furrow ingression. Furthermore, GCK-1 and CCM-3 localize to actomyosin foci during pulsed contractility of the cortical cytoskeleton during zygote polarization. Depletion of GCK-1 or CCM-3 leads to an increase in both cortical contractility and baseline active RhoA levels. Together, our findings suggest that GCK-1 and CCM-3 limit contractility during zygote polarization and

CYK-1/Formin activation in cortical RhoA signaling centers promotes organismal left–right symmetry breaking

“…The shape of this gradient, as well as the localization in foci, is similar to what was observed for other RhoA effectors (Movie S10 and SI Appendix, Fig. S5 C and D) (59)(60)(61)(62)(63). We next tested whether the CYK-1/Formin foci are indeed regions of high RhoA activity.…”

CYK-1/Formin activation in cortical RhoA signaling centers promotes organismal left-right symmetry breaking

“…This sets up a gradient of CYK-1/Formin::GFP along the anteroposterior axis (Movie 8, Figure 4A, B). The shape of this gradient, as well as the localization in foci, is similar to what is observed for other RhoA effectors (Movie 10, Supplementary figure 4C, D) [67,68,69,70,71]. We next tested whether the CYK-1/Formin foci are indeed regions of high RhoA activity.…”

“…CC-BY-NC-ND 4.0 International license made available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is The copyright holder for this preprint this version posted January 8, 2021. ; https://doi.org/10.1101/2021.01.08.425924 doi: bioRxiv preprint to what is observed for other RhoA effectors (Movie 10, Supplementary figure 4C, D) [67,68,69,70,71]. We next tested whether the CYK-1/Formin foci are indeed regions of high RhoA activity.…”

Cortical excitability and cell division

“…Similarly, the basis of negative feedback between F-actin and Rho is unknown. A promising candidate is ARHGAP11a (also known as RGA3/4 and MPGAP), which negatively regulates Rho during Caenorhabditis elegans and HeLa cytokinesis 34,43 , and which is associated with delayed, F-actin-dependent negative feedback during pulsed contractions in C. elegans 44 .…”