Citron-kinase mediates transition from constriction to abscission through its coiled-coil domain

Abstract

SummaryCytokinesis is initiated by constriction of the cleavage furrow, and completed with separation of the two daughter cells by abscission. Control of transition from constriction to abscission is therefore crucial for cytokinesis. However, the underlying mechanism is largely unknown. Here, we analyze the role of Citron kinase (Citron-K) that localizes at the cleavage furrow and the midbody, and dissect its action mechanisms during this transition. Citron-K forms a stable ring-like structure at the midbody and its depletion affects the maintenance of the intercellular bridge, resulting in fusion of two daughter cells after the cleavage furrow ingression. RNA interference (RNAi) targeting Citron-K reduced accumulation of RhoA, Anillin, and septins at the intercellular bridge in mid telophase, and impaired concentration and maintenance of KIF14 and PRC1 at the midbody in late telophase. RNAi rescue experiments revealed that these functions of Citron-K are mediated by its coiled-coil (CC) domain, and not by its kinase domain. The C-terminal part of CC contains a Rho-binding domain and a cluster-forming region and is important for concentrating Citron-K from the cleavage furrow to the midbody. The N-terminal part of CC directly binds to KIF14, and this interaction is required for timely transfer of Citron-K to the midbody after furrow ingression. We propose that the CC-domain-mediated translocation and actions of Citron-K ensure proper stabilization of the midbody structure during the transition from constriction to abscission.

Tissue-specific control of midbody microtubule stability by Citron kinase through modulation of TUBB3 phosphorylation

“…Indeed, we showed that CIT-K loss alters midbody microtubule stability in sensitive cells, whereas the stability of microtubules affects the sensitivity of cytokinesis to CIT-K loss (Figure 2). In addition to the previous studies implicating CIT-K in actindependent midbody stabilization, 23,25,53 these results add strong support the notion that CIT-K plays a crucial role in the crosstalk between actin and microtubules responsible for the maturation of midbody that precedes abscission. [23][24][25]54 The activity of CIT-K on microtubule stability is most likely independent from the reported interaction between CIT-K and KIF14.…”

Defining the Protein–Protein Interaction Network of the Human Hippo Pathway

“…4A). CIT has been found to localize at midbody and control RhoA localization and activity during cytokinesis (61)(62)(63)(64)(65). We found that CIT specifically interacted with WWC1, but not with a series of other Hippo pathway components or regulators (Fig.…”

“…As an effector of Rho GTPase, CIT is known to play critical roles in cell proliferation and cell cycle progress, mostly from its functions in cytokinesis (61)(62)(63)(64)(65). In this study, we identified CIT as a negative regulator of the Hippo pathway, which indicates that CIT may function as an oncogene.…”

Citron kinase – renaissance of a neglected mitotic kinase

“…abscission -of the two daughter cells (Fig. 2B and C) (D' Avino and Capalbo, 2016;Eda et al, 2001;Gai et al, 2011;Hu et al, 2012;Watanabe et al, 2013). A pool of CIT-K also accumulates at the central spindle, an array of antiparallel and interdigitating microtubules that assemble between the segregating chromosomes during anaphase (Fig.…”

“…It was later proposed to promote the constriction of the actomyosin contractile ring that drives cleavage furrow ingression during cytokinesis by phosphorylating the myosin regulatory light chain (MRLC) (Madaule et al, 1998(Madaule et al, , 2000Yamashiro et al, 2003). Subsequent studies, however, have revealed that, instead, CIT-K has an evolutionarily conserved role in later stages of cytokinesis, after completion of furrow ingression (Bassi et al, 2011(Bassi et al, , 2013D'Avino et al, 2004;Echard et al, 2004;Gai et al, 2011;Gruneberg et al, 2006;Naim et al, 2004;Shandala et al, 2004;Watanabe et al, 2013), and recent evidence indicates that CIT-K is also important in early mitosis . Furthermore, mutations in CIT-K have been recently found to cause human primary microcephaly, and this kinase has been proposed as a target in anti-cancer therapy (Basit et al, 2016;Fu et al, 2011;Harding et al, 2016;Li et al, 2016;Shaheen et al, 2016).…”