Calpain-mediated regulation of WAVE tyrosine dephosphorylation by PTP61F promotes lamellipodia formation

Abstract

WAVE is a major driver of lamellipodial protrusions. Previous studies suggested that Abelson (Abl)-dependent tyrosine phosphorylation of WAVE promotes actin polymerization and lamellipodia formation. Here, we provide evidence that Abl tyrosine kinase rather restricts lamellipodial localization of WAVE and inhibits lamellipodial cell spreading. Additionally, overexpression of a cytoplasmic PTP61F phosphatase increases WAVE localization at lamellipodia tips. PTP61F overexpression or pharmacological inhibition of Abl/Src kinases even protects cells from lamellipodia disruption induced by pervanadate, a potent protein tyrosine phosphatase inhibitor. By contrast, overexpression of a phosphatase-deficient PTP61F trapping mutant phenocopies loss of wave function. We identify the tyrosine Y234 as a prominent phosphorylation site in WAVE. Rescue experiments using CRISPR/Cas9-based KO wave mutant cells confirmed an important role of PTP61F-mediated WAVE dephosphorylation in lamellipodia formation. Our data suggest a model in which calpain-mediated proteolytic release of ER-bound PTP61F antagonizes Abl/Src-dependent WAVE phosphorylation and acts as a mechanism promoting re-localization of WAVE to lamellipodial tips.