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Evidence for functionally active protease‐activated receptor‐4 (PAR‐4) in human vascular smooth muscle cells
Author(s) -
Bretschneider E,
Kaufmann R,
Braun M,
Nowak G,
Glusa E,
Schrör K
Publication year - 2001
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703947
Subject(s) - thrombin , thrombin receptor , receptor , stimulation , vascular smooth muscle , protease activated receptor , biology , extracellular , dna synthesis , microbiology and biotechnology , protease activated receptor 2 , biochemistry , endocrinology , dna , platelet , immunology , smooth muscle , enzyme linked receptor
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. mRNAs for both, PAR‐1 and PAR‐4, were detected in the SMC by using reverse transcriptase polymerase chain reaction (RT – PCR). Treatment of the SMC with GYPGQV (200 μ M ) resulted in a transient increase in free intracellular calcium. This calcium signal was completely abolished after a preceding challenge with thrombin (10 n M ), indicating homologous receptor desensitization. Stimulation of the SMC with 10 n M thrombin or 200 μ M 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 n M thrombin as well as 200 μ M 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. GYPGQV stimulated [ 3 H]‐thymidine incorporation in SMC. At 500 μ M , the peptide increased DNA synthesis 2.5 fold above controls. A comparable mitogenic effect was obtained after stimulation of the SMC by 10 n M thrombin or 100 μ M SFLLRN, respectively. 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.British Journal of Pharmacology (2001) 132 , 1441–1446; doi: 10.1038/sj.bjp.0703947