p90 ribosomal S6 kinase 1 (RSK1) isoenzyme specifically regulates cytokinesis progression

• Published in: Cellular signalling 2014-02, Vol.26 (2), p.208-219
• Main Authors: Nam, Hyun-Ja, Lee, In Jeong, Jang, SeungHoon, Bae, Chang-Dae, Kwak, Sahng-June, Lee, Jae-Ho
• Format: Article
• Language: English
• Subjects: Anaphase; Astral microtubule; Cascades; Cellular; Cleavage; Cleavage furrow; Contractile Proteins - metabolism; Cytokinesis; Cytokinesis - genetics; Failure; Furrows; HeLa Cells; Humans; Kinases; Microtubules - metabolism; Polyploidy; Position (location); rhoA GTP-Binding Protein - metabolism; Ribosomal Protein S6 Kinases, 90-kDa - antagonists & inhibitors; Ribosomal Protein S6 Kinases, 90-kDa - genetics; Ribosomal Protein S6 Kinases, 90-kDa - metabolism; RNA Interference; RNA, Small Interfering - metabolism; RSK1; Signalling; Spindle midzone; Time-Lapse Imaging
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2013.11.014

The p90 ribosomal S6 kinase family (RSK1–4) of Ser/Thr kinases is a downstream component of the Ras-MAPK cascade responsible for regulating various cellular processes. Here, we examined the potential involvement of RSKs in regulating mitosis by transfecting HeLa cells with siRNAs targeting RSK1 and -2, which are the major isoforms. Depletion of RSK1 but not RSK2 triggered a significant accumulation of binucleated cells compared to control cells (0.5% vs. 10.5%, respectively); this was rescued by expression of exogenous RSK1 but not a kinase-defective mutant. Monitoring of cell division by time-lapse imaging revealed that the observed binucleation mainly stemmed from a failure to form and ingress the cleavage furrow during early cytokinesis. Immunocytochemical analysis of RhoA and anillin, the two principal regulators of cleavage furrow formation and ingression, showed that these proteins were abnormally localized during anaphase in RSK1-depleted cells. Furthermore, RSK1-depleted cells seemed to have impairments in midzone microtubule formation, as suggested by morphological changes and lengthening of the midzone (15.2±1.7μm vs. 17.4±1.7μm in control cells). We also observed shortening of the pole-to-polar-cortex distance in RSK1-depleted cells (4.30±1.37μm vs. 2.80±0.84μm in control cells) and scanty distribution of microtubules at the periphery of the equatorial region during anaphase, suggesting an aberrant distribution of astral microtubules. Taken together, these results suggest that RSK1 is specifically required for cleavage furrow formation and ingression during cytokinesis. This may occur via the involvement of RSK1 in proper midzone and astral microtubule structure formation during anaphase, which is essential for the correct localization of anillin and RhoA. •Depletion of RSK1, but not RSK2, induced binucleate cells via cytokinesis failure.•Enzyme activity of RSK1 was required for the cytokinesis progression.•RSK1 affects cleavage furrow ingression via proper localization of anillin and RhoA.•RSK also affects formation of spindle midzone and astral microtubules.