Science Direct paper for the Baum Group

PP1-Mediated Moesin Dephosphorylation Couples Polar Relaxation to Mitotic Exit

Authors: Patricia Kunda*, Nelio Rodrigues*, Emadaldin Moeendarbary, Tao Liu, Aleksander Ivetic, Guillaume Charras, Buzz Baum (* joint first authors)

Abstract

Animal cells undergo dramatic actin-dependent changes in shape as they progress through mitosis; they round up upon mitotic entry, and elongate during chromosome segregation, before dividing into two. Moesin, the sole Drosophila ERM-family protein, plays a critical role in this process, through the construction of a stiff, rounded metaphase cortex. At mitotic exit, this rigid cortex must be dismantled to allow for anaphase elongation and cytokinesis through the loss of the active pool of phospho-Thr559Moesin from cell poles. Here, in an RNAi screen for phosphatases involved in the temporal and spatial control of Moesin, we identify PP1-87B RNAi as having elevated p-Moesin levels and reduced cortical compliance. In mitosis, RNAi-induced depletion of PP1-87B or depletion of a conserved non-catalytic PP1 phosphatase subunit Sds22 leads to defects in p-Moesin clearance from cell poles at anaphase, a delay in anaphase elongation, together with defects in bipolar anaphase relaxation and cytokinesis. Importantly, similar cortical defects are seen at anaphase following the expression of a constitutively active, phospho-mimetic version of Moesin. These data reveal a new role for the PP1-87B/Sds22 phosphatase, and important regulator of the metaphase-anaphase transition, in coupling Moesin-dependent cell shape changes to mitotic exit.<!--
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