Evidence for functionally active protease-activated receptor-4 (PAR-4) in human vascular smooth muscle cells

Br J Pharmacol. 2001 Apr;132(7):1441-6. doi: 10.1038/sj.bjp.0703947.


1. This study investigates, whether in addition to the protease-activated receptor-1 (PAR-1), PAR-4 is present in vascular smooth muscle cells (SMC) of the human saphenous vein and whether this receptor is functionally active. PAR-1 and PAR-4 are stimulated by thrombin and by the synthetic peptides SFLLRN and GYPGQV, respectively. 2. mRNAs for both, PAR-1 and PAR-4, were detected in the SMC by using reverse transcriptase polymerase chain reaction (RT - PCR). 3. Treatment of the SMC with GYPGQV (200 microM) resulted in a transient increase in free intracellular calcium. This calcium signal was completely abolished after a preceding challenge with thrombin (10 nM), indicating homologous receptor desensitization. 4. Stimulation of the SMC with 10 nM thrombin or 200 microM SFLLRN caused a time-dependent activation of the extracellular signal-regulated kinases-1/2 (ERK-1/2) with a maximum at 5 min. In contrast, 100 nM thrombin as well as 200 microM of GYPGQV induced a prolonged phosphorylation of ERK-1/2 with a maximum at 60 min. These data suggest that PAR-1 and PAR-4 are activated by thrombin at distinct concentrations and with distinct kinetics. 5. GYPGQV stimulated [(3)H]-thymidine incorporation in SMC. At 500 microM, the peptide increased DNA synthesis 2.5 fold above controls. A comparable mitogenic effect was obtained after stimulation of the SMC by 10 nM thrombin or 100 microM SFLLRN, respectively. 6. These data indicate that a functionally active PAR-4 is present in SMC and, in addition to PAR-1, might contribute to thrombin-induced mitogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Calcium / metabolism
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Enzyme Activation / drug effects
  • Humans
  • Mitogen-Activated Protein Kinase 1 / drug effects
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / drug effects
  • Mitogen-Activated Protein Kinases / metabolism
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism*
  • Oligopeptides / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Thrombin / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Thrombin / pharmacology
  • Thymidine / metabolism
  • Time Factors


  • Oligopeptides
  • RNA, Messenger
  • Receptors, Thrombin
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases
  • Thrombin
  • protease-activated receptor 4
  • Calcium
  • Thymidine