Non-muscle Myosin-II Is Required for the Generation of a Constriction Site for Subsequent Abscission

Abstract

Summary It remains unknown when, where, and how the site of abscission is generated during cytokinesis. Here, we show that the sites of constriction, i.e., the sites of future abscission, are initially formed at the ends of the intercellular bridge during early midbody stage, and that these sites are associated with the non-muscle myosin-IIB (not myosin-IIA), actin filaments, and septin 9 until abscission. The ESCRT-III component CHMP4B localizes to the midbody and “spreads” to the site of abscission only during late midbody stage. Strikingly, inhibition of myosin-II motor activity by a low dose of Blebbistatin completely abolishes the formation of the constriction sites, resulting in the localization of all the above-mentioned components to the midbody region. These data strongly suggest that a secondary actomyosin ring provides the primary driving force for the thinning of the intercellular bridge to allow ESCRT-mediated membrane fission.

Precise tuning of cortical contractility regulates cell shape during cytokinesis

“…On the other hand, MIIB depleted cells showed a marked increase in binucleation even though the rate of cleavage furrow ingression was not different from controls. This data supports previous suggestions that MIIB is important for the completion of abscission (Lordier et al, 2012) and a recent study has provided strong evidence that this is the case (Wang et al, 2019). In further support of this hypothesis, MIIB stayed enriched in the cleavage furrow at late stages of ingression whereas MIIA localization was reduced ( Figure 5).…”

The postmitotic midbody: Regulating polarity, stemness, and proliferation

“…III filaments are able to slide to the abscission site (Wang et al, 2019). Anillin, a major component of the cytokinetic ring, and septins, cytoskeletal filaments sensitive to membrane curvature, have also been implicated in the regulation of secondary ingression sites.…”

Actin and Actin-Associated Proteins in Extracellular Vesicles Shed by Osteoclasts

“…Crawling motility is powered by force generated by actin polymerization to push against membranes [46], so the notion of actin polymerization pushing against membranes to facilitate bud formation is plausible. Likewise, myosins for delivering materials [47] and for the scission of membranes, as in cytokinesis where myosin II works in conjunction with elements of ESCRT [48], is well established. In addition, myosin contraction, downstream of ADP-ribosylation factor 6 (ARF6) signaling, has been implicated in the formation of microvesicles [49].…”