PT  - JOURNAL ARTICLE
AU  - Anke C Rosenkranz
AU  - Bernhard H Rauch
AU  - Anke Doller
AU  - Wolfgang Eberhardt Eberhardt
AU  - Andreas Bohm
AU  - Ellen Bretschneider
AU  - Karsten Schror
TI  - REGULATION OF HUMAN VASCULAR PROTEASE-ACTIVATED RECEPTOR-3 THROUGH mRNA STABILISATION AND THE TRANSCRIPTION FACTOR NFAT
AID  - 10.1124/mol.111.072850
DP  - 2011 Jan 01
TA  - Molecular Pharmacology
PG  - mol.111.072850
4099  - http://molpharm.aspetjournals.org/content/early/2011/05/19/mol.111.072850.short
4100  - http://molpharm.aspetjournals.org/content/early/2011/05/19/mol.111.072850.full
AB  - Thrombin promotes vascular smooth muscle cell (SMC) proliferation and inflammation via protease-activated receptor PAR-1. A further thrombin receptor, PAR-3, acts as a PAR-1 cofactor in some cell-types. Unlike PAR-1, PAR-3 is dynamically regulated at the mRNA level in thrombin-stimulated SMC. This study investigated the mechanisms controlling PAR-3 expression. In human vascular SMC, PAR-3 siRNA attenuated thrombin-stimulated interleukin-6 expression and ERK1/2 phosphorylation, indicating PAR-3 contributes to net thrombin responses in these cells. Thrombin slowed decay of PAR-3 but not PAR-1 mRNA in the presence of actinomycin D, and induced cytosolic shuttling and PAR-3 mRNA binding of the mRNA-stabilising protein human antigen R (HuR). HuR siRNA prevented thrombin-induced PAR-3 expression. By contrast forskolin inhibited HuR shuttling and destabilised PAR-3 mRNA, thus reducing PAR-3 mRNA and protein expression. Other cyclic AMP elevating agents including the prostacyclin-mimetic iloprost also downregulated PAR-3, accompanied by decreased HuR/PAR-3 mRNA binding. Iloprost-induced suppression of PAR-3 was reversed with a myristoylated inhibitor of protein kinase A and mimicked by phorbol ester, an inducer of cyclooxygenase-2. In separate studies, iloprost attenuated PAR-3 promoter activity and prevented binding of nuclear factor of activated T-cells (NFAT2) to the human PAR-3 promoter in a chromatin immunoprecipitation assay. Accordingly, PAR-3 expression was suppressed by the NFAT inhibitor cyclosporine A or NFAT2 siRNA. Thus human PAR-3, unlike PAR-1, is regulated post-transcriptionally via the mRNA stabilising factor HuR, while transcriptional control involves NFAT2. Through modulation of PAR-3 expression, prostacyclin and NFAT inhibitors may limit proliferative and inflammatory responses to thrombin after vessel injury.