This peptide is one of the four PAR sub-types, and is acted upon by thrombin; not trypsin. It is a high-affinity thrombin receptor. PAR-3 mRNA is expressed in the cutaneous mast cells of humans. PARs have been studied for their roles in itch and, their itch-associated response through histamine-dependent/independent pathways have been reported. PAR-3 has been shown not to induce itching alone but possibly in conjunction with PAR4. Co-expression of PAR3 and PAR4 enhances thrombin action suggesting that PAR3 alone does not mediate transmembrane signaling but instead functions as a cofactor to activate PAR4.
1, Tsujii, K. et al. J Pharmacol Sci. 108:385-388 (2008). 2, Leger, AJ. et al. Circ, 114:1070-1077 (2006).