Protease-activated receptor 1 (PAR1) signalling desensitization is counteracted via PAR4 signalling in human platelets
2011 (English)In: Biochemical Journal, ISSN 0264-6021, E-ISSN 1470-8728, Vol. 436, 469-480 p.Article in journal (Refereed) Published
FARs (protease-activated receptors) 1 and 4 belong to the family of G-protein-coupled receptors which induce both G(alpha 12/13) and G(alpha q) signalling. By applying the specific PAR1- and PAR4-activating hexapeptides, SFLLRN and AYPGKF respectively, we found that aggregation of isolated human platelets mediated via PAR1, but not via PAR4, is abolished upon homologous receptor activation in a concentration- and time-dependent fashion. This effect was not due to receptor internalization, but to a decrease in Ca(2+) mobilization, PKC (protein kinase C) signalling and alpha-granule secretion, as well as to a complete lack of dense granule secretion. Interestingly, subthreshold PAR4 activation rapidly abrogated PAR1 signalling desensitization by differentially reconstituting these affected signalling events and functional responses, which was sufficient to re-establish aggregation. The lack of ADP release and P2Y(12) receptor-induced G(alpha i) signalling accounted for the loss of the aggregation response, as mimicking G(alpha i/z) signalling with 2-MeS-ADP (2-methylthioadenosine-5-O-diphosphate) or epinephrine (adrenaline) could substitute for intermediate PAR4 activation. Finally, we found that the re-sensitization of PAR1 signalling-induced aggregation via PAR4 relied on PKC-mediated release of both ADP from dense granules and fibrinogen from alpha-granules. The present study elucidates further differences in human platelet PAR signalling regulation and provides evidence for a cross-talk in which PAR4 signalling counteracts mechanisms involved in PAR1 signalling down-regulation.
Place, publisher, year, edition, pages
Portland Press -- London , 2011. Vol. 436, 469-480 p.
ADP; desensitization; P2Y(12) receptor; platelet; protease-activated receptor (PAR); protein kinase C (PKC)
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-69897DOI: 10.1042/BJ20101360ISI: 000291413200027OAI: oai:DiVA.org:liu-69897DiVA: diva2:433293