Protease-activated receptor

Protease - activated receptors ( PARs ) are a subset of G protein- coupled receptors; checking this receptor type based on the action of serine proteases (especially thrombin) which cleave the extracellular N- terminus of the receptor and thereby expose a protein domain, which as bound ligand ( tethered ligand ) acts and remains permanently associated with the ligand binding domain of the receptor. PARs play an important role in platelet activation and in the context of various atherosclerotic processes.

Classification and occurrence

There are four PAR isoforms differed ( PAR1 -4 ), of which PAR1, PAR3 and PAR4 can be activated under physiological conditions by thrombin. PAR2 is not activated by thrombin, but by various other clotting factors and trypsin. Protease -activated receptors have been in various types of cells of the vascular system ( inter alia, platelets, endothelial cells and smooth muscle cells ) discovered and characterized. In addition, PARs were also detected in cells of the nervous system as well as in T lymphocytes.

Biological Function

The functional significance of protease-activated receptors has been mainly studied in vascular cells. The main function of PARs here is the mediation of Thrombinsignalen in the cell interior. Based on the thrombin-activated receptor and on the cytoplasmic side associated with him heterotrimeric G- proteins - different depending on Rezeptorisoform and cell type - intracellular signaling pathways are activated and so certain cellular processes such as cell activation (for platelets), proliferation, migration, cell matrix synthesis ( in vascular smooth muscle cells ), etc. is controlled.