Autocrine Proteinase Activated Receptor (PAR) mediated signaling in prostate cancer cells.

Proteinase activated receptors (PARs) are G protein-coupled receptors (GPCRs) activated by limited N-terminal proteolysis. A variety of proteolytic enzymes derived from the coagulation cascade and inflammatory milieu activate PARs, however specific activators in different physiological and pathophysiological contexts remain poorly defined. PARs are highly expressed in many cancer cells and regulate various aspects of tumor growth and metastasis. Endogenous proteinases that regulate PARs in the setting of various tumors however remains unresolved. Prostate cancer (PCa) remains a major cause of mortality in men despite advances in early detection and clinical intervention. PAR expression has been reported in PCa, however, their role here remains poorly defined. In androgen independent PC3 cells, we find functional expression of PAR1 and PAR2 but not PAR4. Using genetically encoded PAR cleavage biosensors, we find that PCa cells secrete proteolytic enzymes that cleave PARs and trigger autocrine signaling. Deletion of PAR1 and PAR2 using CRISPR/Cas9 combined with microarray analysis revealed genes that are differentially regulated by this autocrine signalling mechanism. Interestingly, several genes that are known PCa prognostic factors or biomarker were differentially expressed in PAR1-KO and PAR2-KO PC3 cells. We also examined PAR1 and PAR2 regulation of PCa cell proliferation and migration using PAR1 and PAR2-KO PC3 cells, as well as PAR1 and PAR2 specific agonists and antagonists. We find that PAR1 and PAR2 have opposite effects on PC3 cell proliferation and migration. In summary, we have identified an autocrine signaling mechanism through PARs as a regulator of PCa cell function.