Beta-arrestin-dependent regulation of the cofilin pathway downstream of protease-activated receptor-2.

Beta-arrestins are pleiotropic molecules that mediate signal desensitization, G-protein-independent signaling, scaffolding of signaling molecules, and chemotaxis. Protease-activated receptor-2 (PAR-2), a Galpha(q/11)-coupled receptor, which has been proposed as a therapeutic target for inflammation and cancer, requires the scaffolding function of beta-arrestins for chemotaxis. We hypothesized that PAR-2 can trigger specific responses by differential activation of two pathways, one through classic Galpha(q)/Ca(2+) signaling and one through beta-arrestins, and we proposed that the latter involves scaffolding of proteins involved in cell migration and actin assembly. Here we demonstrate the following. (a) PAR-2 promotes beta-arrestin-dependent dephosphorylation and activation of the actin filament-severing protein (cofilin) independently of Galpha(q)/Ca(2+) signaling. (b) PAR-2-evoked cofilin dephosphorylation requires both the activity of a recently identified cofilin-specific phosphatase (chronophin) and inhibition of LIM kinase (LIMK) activity. (c) Beta-arrestins can interact with cofilin, LIMK, and chronophin and colocalize with them in membrane protrusions, suggesting that beta-arrestins may spatially regulate their activities. These findings identify cofilin as a novel target of beta-arrestin-dependent scaffolding and suggest that many PAR-2-induced processes may be independent of Galpha(q/11) protein coupling.