Characteristics of the Four Protease-Activated Receptors
| Receptor | Tethered ligand | Activating proteases | Signaling effectors | Shut-off mechanisms |
|---|---|---|---|---|
| 1 Synthetic peptides that represent the newly formed N terminus can activate PARs independent of protease and cleavage with the exception of PAR3. 2 Shut-off mechanisms are best understood for PAR1 and PAR2, whereas activated PAR4 is not phosphorylated and its shut-off appears to mediated predominantly by internalization. Nothing is known about signal regulation of PAR3. | ||||
| PAR1 | SFLLRN | Thrombin | Gq | Phosphorylation |
| TF-VIIa-Xa or Xa | Gi | β-Arrestins | ||
| APC-EPCR | G12/13 | Internalization | ||
| Trypsin | Degradation | |||
| Plasmin | ||||
| MMP1 | ||||
| Granzyme A | ||||
| PAR2 | SLIGKV | Trypsin | Gq | Phosphorylation |
| Tryptase | Gi | β-Arrestins | ||
| TF-VIIa or TF-VIIa-Xa | G12/13 | |||
| Matriptase (MT-SP1) | β-Arrestins | |||
| Der P3 D9 | ||||
| Bacterial gingipains-R | ||||
| Kallikreins | ||||
| Granzyme A | ||||
| PAR3 | TFRGAP1 | Thrombin | Gq | ?2 |
| PAR4 | GYPGQV | Thrombin | Gq | Internalization |
| Trypsin | G12/13 | |||
| TF-VIIa-Xa | ||||
| Plasmin | ||||
| Cathepsin G | ||||
| Bacterial gingipains-R | ||||
| Kallikreins | ||||