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

The integrin-mediated interaction of cells with components of the extracellular matrix (ECM) regulates many cellular processes including cell division. Cytokinesis is the last step of cell division and is critical for normal development and tissue homeostasis as it ensures the proper segregation of genetic and cytoplasmic material between daughter cells. Cytokinesis failure leads to defects in development and tissue differentiation, as well as tumorigenesis. Abscission of intercellular bridge that connects presumptive daughter cells is the last step of cell division. The mitotic kinesin-like protein 1 (MKLP1) plays a central role in positioning the abscission machinery. Here, we show that α6 integrins promote successful cytokinesis in salivary gland epithelial cells by regulating the expression of MKLP1. RNAi-mediated depletion of α6 integrins inhibits cytokinesis and the expression of MKLP1 and p90 ribosomal-S6-kinase 2 (RSK2). Depletion of RSK2 results in similar defects in cytokinesis and also inhibits the expression of MKLP1, suggesting that the expression of RSK2 is required downstream of integrins to promote MKLP1 expression and successful cytokinesis. RNAi-mediated depletion of RSK2 in embryonic salivary glands in organ culture also results in the inhibition of cytokinesis and MKLP1 expression, indicating the physiological significance of this pathway.