Moesin and myosin phosphatase confine neutrophil orientation in a chemotactic gradient.
Bottom Line: Neutrophils respond to invading bacteria by adopting a polarized morphology, migrating in the correct direction, and engulfing the bacteria.Attractant-induced activation of myosin phosphatase deactivated moesin at the prospective leading edge to break symmetry and establish polarity.Subsequent translocation of moesin to the trailing edge confined the formation of a prominent pseudopod directed toward pathogens and prevented secondary pseudopod formation in other directions.
Affiliation: Department of Pharmacology and Department of Medicine, University of Illinois, Chicago, IL 60612.Show MeSH
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Mentions: Next, we addressed the potential regulatory relationship between moesin and MLC by coexpressing YFP-tagged moesin and CFP-tagged MLC in HL60 cells. We again demonstrated that both moesin-YFP and MLC-CFP were localized to the trailing edges of polarized cells stimulated with fMLF (Fig. 3 A, left). To inhibit MLC activity, we treated cells with either the myosin inhibitor blebbistatin (100 µM, 30 min) or the Rho kinase inhibitor Y27632 (10 µM, 30 min). Upon uniform stimulation of fMLF, these inhibitor-treated cells formed multiple pseudopods in the earlier stage and gradually formed a single prominent pseudopod and a long tail, as reported previously (Xu et al., 2003). As expected, MLC-CFP showed reduced membrane localization and was more uniformly distributed in cells treated with either of the inhibitors (Fig. 3 A, middle and right panels in the third row). However, moesin-YFP remained associated with the cell membrane in these long tails (Fig. 3 A, middle and right panels in the second row; the distributions of both MLC and moesin over time are shown in Table S3). Thus, inhibiting MLC activity caused MLC to be uniformly distributed but did not alter the attractant-induced localization of moesin at the trailing edge.
Affiliation: Department of Pharmacology and Department of Medicine, University of Illinois, Chicago, IL 60612.