β-Arrestins Scaffold Cofilin with Chronophin to Direct Localized Actin Filament Severing and Membrane Protrusions Downstream of Protease-activated Receptor-2*

Protease-activated receptor-2 (PAR-2) mediates pro-inflammatory signals in a number of organs, including enhancing leukocyte recruitment to sites of injury and infection. At the cellular level, PAR-2 promotes activation of the actin filament-severing protein cofilin, which is crucial for the reorganization of the actin cytoskeleton and chemotaxis. These responses require the scaffolding functions of β-arrestins; however, the mechanism by which β-arrestins spatially regulate cofilin activity and the role of this pathway in primary cells has not been investigated. Here, using size-exclusion chromatography and co-immunoprecipitation, we demonstrate that PAR-2 promotes the formation of a complex containing β-arrestins, cofilin, and chronophin (CIN) in primary leukocytes and cultured cells. Both association of cofilin with CIN and cell migration are inhibited in leukocytes from β-arrestin-2−/− mice. We show that, in response to PAR-2 activation, β-arrestins scaffold cofilin with its upstream activator CIN, to facilitate the localized generation of free actin barbed ends, leading to membrane protrusion. These studies suggest that a major role of β-arrestins in chemotaxis is to spatially regulate cofilin activity to facilitate the formation of a leading edge, and that this pathway may be important for PAR-2-stimulated immune cell migration.