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Description

Proteinase-activated receptor 4 (UniProt Q96RI0, also known as Coagulation factor II receptor-like 3, PAR-4, Thrombin receptor-like 3) is encoded by the F2RL3 (also known as PAR4) gene (Gene ID 9002) in human. Protease-activated receptors (PARs) constitute a unique family of seven-transmembrane, G-protein-coupled receptors (GPCRs) activated by proteolytic cleavage of their N-terminal propeptide sequence. Once cleaved off, the N-terminal propeptide fragment functions as a ligand and activates the receptor by binding the second extracellular loop. The four PAR family members (PAR-1 to PAR-4) are widely expressed and activated by multiple proteases, and utilize different types of G-proteins (Gi, Gq, and G12/13) for signal transdution depending on the activating protease and cellular context. PAR-4 is expressed on platelets and exhibits a low-affinity for thrombin. However, PAR-4 is able to form hetero-oligomers with both PAR-1 and the ADP receptor P2Y12 to mediate thrombin- and ADP-initiated signaling. PAR-4 cleavage is significantly enhanced through hetero-oligomerization with PAR-1, and PAR-4 interaction with P2Y12 is directly linked to arrestin-2 recruitment and AKT signaling. PAR-4 is a 7-transmembrane (a.a. 83-103, 109-129, 152-172, 192-213, 248-268, 284-304, 320-343) GPCR activated by thrombin cleavage between R47 and G48, having 3 extracellular loops and 3 intracellular loops between the extracellular N-terminal end (a.a. 48-82) the cytoplasmic C-terminal tail (a.a. 344-385).