Spatiotemporal regulation of moesin phosphorylation and rear release by Rho and serine/threonine phosphatase during neutrophil migration

Neutrophil motility is crucial to effective host defenses against microorganisms. While uropod retraction is a critical step in the migration of neutrophils, the underlying molecular mechanism is not well understood. Here, we show that inhibition of the Rho small GTPase with C3 exoenzyme prevented the retraction of trailing uropods, indicating that the process of rear release is mediated by a Rho signaling pathway. C3 exoenzyme caused marked elongation of directionally migrating neutrophils, suggesting an additional role for Rho in the maintenance of functional polarized cell shape. We also show that phosphorylation and dephosphorylation of the plasma membrane-actin filament cross-linker moesin are spatiotemporally controlled in migrating neutrophils. In particular, phosphorylation of moesin at threonine 558 depended on Rho activity. Videomicroscopy showed that dephosphorylation of this carboxy-terminal threonine preceded uropod retraction. Calyculin A, an inhibitor of type 1 and type 2A serine/threonine phosphatases, suppressed the moesin dephosphorylation and impaired uropod retraction in a dose-dependent manner. Cypermethrin, an inhibitor of type 2B serine/threonine phosphatase, had no such effects. The finding that Rho small GTPase and type 1/type 2A phosphatases are involved in rear release yields novel insights into the biochemical mechanisms of neutrophil migration.