An Unconventional Myosin Required For Cell Polarization and Chemotaxis. (PDF Link)
Breshears LM, Wessels D, Soll DR, Titus MA (2010). PNAS. 107(15):6918-23.

MyTH/FERM (myosin tail homology 4/band 4.1, ezrin, radixin, and moesin) myosins have roles in cellular adhesion, extension of actin-filled projections such as filopodia and stereocilia, and directional migration. The amoeba Dictyostelium discoideum expresses a simple complement of MyTH/FERM myosins, a class VII (M7) myosin required for cell-substrate adhesion and a unique myosin named MyoG. Mutants lacking MyoG exhibit a wide range of normal actin-based behaviors, including chemotaxis to folic acid, but have a striking defect in polarization and chemotaxis to cAMP. Although the myoG mutants respond to cAMP stimulation by increasing persistence and weakly increasing levels of cortical F-actin, they do not polarize; instead, they maintain a round shape and move slowly and randomly when exposed to a chemotactic gradient. The mutants also fail to activate and localize PI3K to the membrane closest to the source of chemoattractant. These data reveal a role for a MyTH/FERM myosin in mediating early chemotactic signaling and suggest that MyTH/FERM proteins have conserved roles in signaling and the generation of cell polarity.

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Figure 4 from paper: Chemotactic signaling is impaired in myoG null cells. (A) Actin pol- ymerization in response to cAMP is dampened in myoG- cells. Analysis of changes in cytoskeletal F-actin levels in both control () and myoG mutant () cells after a 100-nM cAMP pulse (administered at time = 0). Data shown from three independent experiments represent the mean ± SD of control (n = 8) and myoG null cells (n = 14). (B) Localization of CRAC-GFP and N-PI3K1-GFP in a cAMP gradient. Aggregation competent cells were exposed to a cAMP gradient in a Zigmond chamber and photographed after 15 min. The cAMP source is at the right in all panels. (Scale bar, 10 μm.) 

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