Dual effect of the novel peptide antagonist K-14585 on Proteinase-Activated Receptor-2 (PAR2)-mediated signalling

Here we have examined the effects of the novel peptide antagonist N-[1-(2,6-dichlorophenyl)methyl]-3-(1-pyrrolidinylmethyl)-1H-indol-5-yl]aminocarbonyl}-glycinyl-L-lysinyl-L-phenylalanyl-N-benzhydrylamide (K-14585) on proteinase-activated receptor (PAR)2-mediated intracellular signalling events. Using NCTC2544 cells expressing PAR2, we assessed the effects of K-14585 on PAR2-mediated [3H] inositol phosphate accumulation, MAP kinase activation, p65 NFκB phosphorylation and DNA binding and IL-8 production. Pretreatment with K-14585 (5 µM) inhibited [3H] inositol phosphate levels stimulated by PAR2-activating peptide Ser-Leu-Ile-Gly-Lys-Val (SLIGKV-OH) in PAR2-expressing NCTC2544 cells. K-14585 pretreatment did not influence PAR2-mediated extracellular regulated kinase activation but inhibited p38 MAP kinase phosphorylation. At a higher concentration (30 µM), K-14585 alone stimulated p38 MAP kinase activation. These effects were replicated in EAhy926 cells, endogenously expressing PAR2, but not in parental or PAR4-expressing NCTC2544 cells, suggesting these effects were PAR2-dependent. SLIGKV-mediated stimulation of p38 MAP kinase phosphorylation was substantially reduced by the Gq/11 inhibitor YM-254890, without affecting K-14585-mediated phosphorylation. Pretreatment with K-14585 inhibited PAR2-mediated p65 NFκB phosphorylation and NFκB-DNA binding. K-14585 (30 µM) alone stimulated comparable NFκB reporter activity to SLIGKV-OH. K-14585 inhibited SLIGKV-stimulated IL-8 production, but given alone increased IL-8. While SLIGKV-induced IL-8 formation was reduced by both SB203580 and YM-254890, the response to K-14585 was sensitive to SB203580 but not YM-254890. These data reveal that K-14585 has a duality of action functioning both as an antagonist and agonist due to either partial agonist actions or possible agonist-directed signalling. The data also suggest two modes of p38 MAP kinase activation emanating from PAR2, one Gq/11-dependent and the other Gq/11-independent.