Aurora B Kinase Dependent Phosphorylation of Keratin 8 is required for Cytokinesis in Mammalian Cells of Epithelial Origin

Abstract

Keratins assemble into mechanically resilient polymers that physically stabilize epithelial cells. When epithelial cells divide, keratin polymers must be severed to allow cell separation during cytokinesis. Phosphorylation has been implicated in this process, but how keratins are regulated during cell division is not understood. Aurora-B kinase, which is part of the chromosome passenger complex (CPC) accumulates at the cell center during cytokinesis and has been implicated in regulating intermediate filaments. We mapped six Aurora B kinase sites in Keratin 8. Phosphorylation of Keratin 8 at S34 occurred specifically at the cleavage furrow and persisted at the midzone until the completion of cytokinesis. Inhibition of Aurora B or expression of a non-phosphorylatable Keratin 8 mutant impaired keratin disassembly at the cleavage furrow. We propose that Aurora B-mediated phosphorylation promotes localized keratin filament disassembly at the cleavage furrow, allowing spatially regulated disassembly during cytokinesis. Aurora B binds to keratin filaments, and its localization to midzones was reduced in Keratin 8 knockout cells, showing that Keratin 8 facilitates Aurora B targeting during cytokinesis. This suggests a positive feedback cycle whereby Keratin 8 promotes midzone-localization of Aurora B and in turn, is locally disassembled by its kinase activity. This cycle is required for successful furrow ingression and completion of cell division in cancer cells of epithelial origin and might provide a target for solid tumor treatment.