Thrombin receptor cleavage

Ishii, K., Hein, L., Kobilka, B. and Coughlin, S.R. (1993) Kinetics of thrombin receptor cleavage in intact cells. Relation to signaling. J. Biol. Chem. 268 9780-9786. 

In some cases, receptor inactivation, e.g., of the V2 vasopressin receptor, is mediated by agonist-induced enzymatic cleavage of the GPCR. This nonendocytic proteolysis is promoted by a plasma membrane-associated metalloprotease. Proteinase-activated receptors (PARs) such as the thrombin receptor also follow a distinctly different pathway. PARs require the enzymatic cleavage of their N terminus, and the newly generated N terminus activates the receptor. Once... 

The protease-activated receptors (PARs), a subclass of GPCRs that function in the coagulation cascade, suggest that a comprehensive survey of the GPCR portion of the proteome provides information about the structure and function of this receptor class. The PAR factor II (thrombin) receptor-like 2 (F2RL2) is inactive in the cascade until proteolytic cleavage of its extracellular amino terminus. A Phe240Ser variant that is located in the second intracellular loop, found at a frequency of approx. 8%, disrupts receptor activation by proteolysis. 

Figure 1. Diagram of the human thrombin receptor, viewed edge-on, showing the sequence around the proteolytic cleavage site (LDPR-SFLLRN) in the long extracellular amino-terminus and the seven transmembrane domains (TM1-TM7).

Yin A thrombin-receptor is fashioned by virtue of the duplication of a gene for a [protein region that will stick in a cell membrane]. Cleavage by the TF-activated prothrombin effects cell contractility or clumping. 

Cleavage of the thrombin receptor provokes several events in the platelet, includ-ing ... 

Thrombin initially acts by binding to the thrombin receptor, a membrane-boxmd protein in the plasma membrane of the platelet. Thrombin binds to the thrombin receptor, and then catalyzes the cleavage of its N-terminal region. Thrombin cleaves in between the residues of arginine and serine (Arg-Ser), as indicated herein. The following diagram depicts the first 18 amino acid residues of the thrombin receptor. The various features of the drawing are not to scale ... 

Fig. 28.16 The thrombin receptor, a member of the PA family of receptors, expresses an endogenous ligand — tethered ligand — at the extracellular AZ-terminc subsequent to proteolytic cleavage.

Thrombin, a serine protease, cleaves fibrinogen into fibrin to create a fibrous plug and also amplifies its own production through the activation of factor XI and cofactors V and Vlll. Thrombin also plays a crucial role in the activation of platelets through the cleavage of the protease-activated receptors on the platelet surface. Antagonists of G-protein-coupled protease-activated receptor PARi have been synthesised to study the role of thrombin PARi receptor in thrombosis and vascular injury. Thrombosis is the most common cause of death in the industrialised world and, whether through venous thromboembolism, myocardial infarction or stroke, ultimately involves the inappropriate activity of... 

Activation of receptors can also be mediated by proteolytic cleavage of the extracellular domain of the receptor by proteases like thrombin. For these protease activated receptors, a proteolytically produced peptide functions as the activating ligand. 

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