Protease-activated receptor 4: from structure to function and back again.

Protease-activated receptors are a family of four GPCRs (PAR1-PAR4) with a number of unique attributes. Nearly two and a half decades after the discovery of the first PAR, an antagonist targeting this receptor has been approved for human use. The first-in-class PAR1 antagonist, vorapaxar, was approved for use in the USA in 2014 for the prevention of thrombotic cardiovascular events in patients with a history of myocardial infarction or with peripheral arterial disease. These recent developments indicate the clinical potential of manipulating PAR function. While much work has been aimed at uncovering the function of PAR1 and, to a lesser extent, PAR2, comparatively little is known regarding the pharmacology and physiology of PAR3 and PAR4. Recent studies have begun to develop the pharmacological and genetic tools required to study PAR4 function in detail, and there is now emerging evidence for the function of PAR4 in disease settings. In this review, we detail the discovery, structure, pharmacology, physiological significance and therapeutic potential of PAR4. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.