Protease-activated receptors (PARs) comprise a family of four G protein-coupled (GPCRs) that have broad functions in health and disease. Unlike most GPCRs, PARs are uniquely activated by proteolytic cleavage their extracellular N termini. To fully understand PAR activation function vivo, it is critical to also study the proteases activate them. As heavily regulated at post-translational level, ...