Thrombin receptor activating peptide (TRAP) stimulates mitogenesis, c-fos and PDGF-A gene expression in human vascular smooth muscle cells.
The synthetic peptide SFLLRNPNDKYEPF, identical in sequence to the new amino-terminus of the thrombin receptor generated following cleavage of thrombin, acts a thrombin receptor agonist/activating peptide (TRAP). In this study, Northern blot analysis showed that cultured human vascular smooth muscle cells (HVSMC) express a thrombin receptor transcript. TRAP, in contrast to thrombin was shown to be a weak mitogen for HVSMC. A combination of TRAP and enzymatically-inactivated thrombin (PPACK-thrombin) which provides receptor occupancy, did not potentiate TRAP-induced mitogenesis, indicating that TRAP and PPACK-thrombin do not reproduce the mitogenic effect of enzymatically-active thrombin. Both thrombin and TRAP, induced the expression of c-fos and the PDGF-A gene in a pertussis toxin (PTX)-insensitive manner. Examination of thrombin and TRAP-treated cells by immunofluorescence staining followed by computer assisted image analysis revealed that thrombin and to a lesser extent TRAP induced PDGF-AA protein expression. Antibodies to PDGF-AA partially inhibited thrombin but not TRAP-induced mitogenesis in HVSMC. This study indicates that in addition to the common signalling pathways utilised by thrombin and TRAP, enzymatically-active thrombin activates other signalling pathways and hence TRAP does not mimic fully the biological effect of thrombin on HVSMC.
Kanthou
C
C
Vascular Biology Laboratory, Thrombosis Research Institute, Chelsea, London, UK.
Benzakour
O
O
Patel
G
G
Deadman
J
J
Kakkar
V V
VV
Lupu
F
F
D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D006801:Humans; D008938:Mitosis / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology*; D010982:Platelet-Derived Growth Factor / Q000096:biosynthesis / Q000235:genetics*
D010446:Peptide Fragments; D010982:Platelet-Derived Growth Factor; C075278:platelet-derived growth factor A; C072032:thrombin receptor peptide (42-55)