MPL1, a Novel Phosphatase with Leucine-Rich Repeats, Is Essential for Proper ERK2 Phosphorylation and Cell Motility

The novelDictyostelium phosphataseMPL1 contains six leucine-rich repeats at the amino-terminal end and a phosphatase domain at the carboxyl end. Similarly architectured phosphatases exist among other protozoa, such asEntamoeba histolytica ,Leishmania major , andTrypanosoma cruzi .MPL1 was strongly induced after 5 h of development; ablation by homologous recombination led to defective streaming and aggregation during development. In addition, cyclic AMP (cAMP)-pulsedmpl1 − cells showed reduced random and directional motility. At the molecular level,mpl1 − cells displayed higher prestimulus and persistent poststimulus ERK2 phosphorylation in response to cAMP stimulation. Consistent with their phenotype of persistent ERK2 phosphorylation,mpl1 − cells also displayed an aberrant pattern of cAMP production, resembling that of theregA − cells. Reintroduction of a full-lengthMPL1 intompl1 − cells restored aggregation, ERK2 regulation, random and directional motility, and cAMP production similar to wild-type cells. We propose that MPL1 is a novel phosphatase essential for proper regulation of ERK2 phosphorylation and optimal motility during development.