Protease-activated receptor 2 (PAR2) is a unique G protein-coupled receptor for which there is no known endogenous ligand. Instead, PAR2 is cleaved by proteases to reveal a new N-terminal receptor sequence (SLIGKV-). This activates intracellular signal transduction pathways that mediate physiology but also diseases, such as cancers, obesity, metabolic, respiratory and gastrointestinal disorders. Short synthetic peptides that mimic the tethered ligand receptor sequence (e.g., SLIGRL-NH2, SLIGKV-NH2, and 2-furoyl-LIGRLO-NH2) can bind to PAR2 and activate cell signalling in the absence of a protease.
Here, we demonstrate that two PAR2 agonists, namely an endogenous protease (trypsin) and a selective synthetic peptide (2-furoyl-LIGRLO-NH2), induce PAR2-MEK-ERK1/2 signalling and gene expression of transcription factors and inflammatory cytokines that promote motility of ovarian OV90 cancer cells. We use peptides to identify a novel mechanism in which PAR2 has to first activate a combination of coupled G proteins (specifically both Gαq/11, Gα12/13) as well as β-arrestin1/2, which leads to Src activation then transactivation of epidermal growth factor receptor (EGFR). This signalling sequence induces migration and invasion of OV90 ovarian cancer cells. Gene deletion of PAR2 or the above G proteins or β-arrestin1/2, or a PAR2 antagonist (I-191), or inhibitors of downstream proteins in this signalling pathway, each attenuates human ovarian cancer cell responses to PAR2 agonists. This study highlights a novel shared signalling cascade, requiring each of Gαq/11, Gα12/13 and β-arrestin1/2, for PAR2-induced ovarian cancer cell migration and invasion. Peptide (e.g. 2-furoyl-LIGRLO-NH2) activated PAR2 thus has an unusual control mechanism that is not linked to a specific G protein or β-arrestin, but rather requires parallel involvement of two G proteins and β-arrestin1/2 in order to effect the signalling pathway resulting in ovarian cancer cell migration.