Integrins Promote Cytokinesis through the RSK Signaling Axis

Abstract

Cytokinesis is the final stage in cell division. Although integrins can regulate cytokinesis, the mechanisms involved are not fully understood. In this study, we demonstrate that integrin-regulated ERK (extracellular signal-related kinase) and RSK (p90 ribosomal S6 kinase) signaling promotes successful cytokinesis. Inhibiting the activation of ERK and RSK in CHO cells by a mutation in the integrin b1 cytoplasmic tail or with pharmacological inhibitors results in the accumulation of cells with midbodies and the formation of binucleated cells. Activation of ERK and RSK signaling by the expression of constitutively active RAF1 suppresses the mutant phenotype in a RSK-dependent manner. Constitutively active RSK2 also restores cytokinesis inhibited by the mutant integrin. Importantly, the regulatory role of the RSK pathway is not specific to CHO cells. MCF-10A human mammary epithelial cells and HPNE human pancreatic ductal epithelial cells exhibit a similar dependence on RSK for successful cytokinesis. In addition, depriving mitotic MCF10A cells of integrin-mediated adhesion by incubating them in suspension suppressed ERK and RSK activation and resulted in a failure of cytokinesis. Furthermore, inhibition of RSK or integrins within the 3D context of a developing salivary gland organ explant also leads to an accumulation of epithelial cells with midbodies, suggesting a similar defect in cytokinesis. Interestingly, neither ERK nor RSK regulates cytokinesis in human fibroblasts, suggesting cell-type specificity. Taken together, our results identify the integrin-RSK signaling axis as an important regulator of cytokinesis in epithelial cells. We propose that the proper interaction of cells with their microenvironment through integrins contributes to the maintenance of genomic stability by promoting the successful completion of cytokinesis.

FAK inhibitors induce cell multinucleation and dramatically increase pro‐tumoral cytokine expression in RAW 264.7 macrophages

“…They used BJ fibroblast cells and, in this study, we used RAW 264.7 macrophages. The difference may be a result of the cell type-specific response to FAK inhibitors or cell type specificity in the regulation of cytokinesis that has been suggested in previous studies [11,22]. There are two possible reasons for the difference.…”

Alpha 6 integrins promote cytokinesis by regulating the expression of RSK2 and MKLP1

“…Although our previous studies demonstrated that both RSK1 and RSK2 regulated cytokinesis in MCF10A cells (14), these studies did not determine whether both isoforms functioned downstream of integrins or whether they regulated cytokinesis by similar mechanisms. To begin, we confirmed that both RSK1 and RSK2 regulated cytokinesis in SIMS cells.…”

“…However, since integrin signaling can be strongly influenced by substrate compliance (23), and our previous studies demonstrated that cytokinesis is regulated by matrix compliance in a cell typedependent manner (24), it is important to demonstrate that pathways that regulate cytokinesis in cell culture similarly regulate cytokinesis in a more physiological complex context. Since we previously demonstrated that α6 integrins promote successful cytokinesis in embryonic salivary glands in ex vivo organ culture (14), we again used this model to test whether RSK2 regulates cytokinesis and MKLP1 expression in this context. To this end, submandibular salivary glands were isolated from mouse embryos at embryonic day 12.5 -13 (E12.5-E13) and treated for 3 days with either nontargeting or RSK2-targeting siRNA (Fig.…”

“…RSKs are a family of serine/threonine kinases that phosphorylate many cytoplasmic and nuclear targets (15)(16)(17). We previously demonstrated that depletion of either RSK1 or RSK2 in mammary epithelial cells inhibited cytokinesis (14), but did not determine whether both RSK isoforms were activated downstream of integrins or whether RSK1 and RSK2 regulated cytokinesis by similar or distinct mechanisms. Our current study addresses these gaps in knowledge and further explores the important role of RSK2 in the successful completion of cytokinesis.…”

“…Much of what is known about the mechanisms that link integrins and cytokinesis have been identified using cell culture models. Our published studies identified a role for integrins in the regulation of abscission (14) and have defined a role for ERK and its downstream target the ribosomal S6 kinase (RSK) (14). RSKs are a family of serine/threonine kinases that phosphorylate many cytoplasmic and nuclear targets (15)(16)(17).…”