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Background: Bioinformatic analysis revealed that PAR4 possesses an ER retention motif. Results: PAR2 both abrogates and facilitates chaperone protein interaction with PAR4 to allow PAR4 to evade ER retention and be delivered to the plasma membrane. Conclusion: PAR2 regulates PAR4 localization and cell signaling through heterodimerization. Significance: Impact upon understanding PAR2 and PAR4 in inflammation where clear roles are defined., Proteinase-activated receptors 4 (PAR4) is a class A G protein-coupled receptor (GPCR) recognized through the ability of serine proteases such as thrombin and trypsin to mediate receptor activation. Due to the irreversible nature of activation, a fresh supply of receptor is required to be mobilized to the cell surface for responsiveness to agonist to be sustained. Unlike other PAR subtypes, the mechanisms regulating receptor trafficking of PAR4 remain unknown. Here, we report novel features of the intracellular trafficking of PAR4 to the plasma membrane. PAR4 was poorly expressed at the plasma membrane and largely retained in the endoplasmic reticulum (ER) in a complex with the COPI protein subunit β-COP1. Analysis of the PAR4 protein sequence identified an arginine-based (RXR) ER retention sequence located within intracellular loop-2 (R183AR → A183AA), mutation of which allowed efficient membrane delivery of PAR4. Interestingly, co-expression with PAR2 facilitated plasma membrane delivery of PAR4, an effect produced through disruption of β-COP1 binding and facilitation of interaction with the chaperone protein 14-3-3ζ. Intermolecular FRET studies confirmed heterodimerization between PAR2 and PAR4. PAR2 also enhanced glycosylation of PAR4 and activation of PAR4 signaling. Our results identify a novel regulatory role for PAR2 in the anterograde traffic of PAR4. PAR2 was shown to both facilitate and abrogate protein interactions with PAR4, impacting upon receptor localization and cell signal transduction. This work is likely to impact markedly upon the understanding of the receptor pharmacology of PAR4 in normal physiology and disease.

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.

The mechanisms underpinning the coupling of GPCRs, such as PAR-2, to the phosphorylation of p65 NFkappaB have not been investigated. In the current study we found that trypsin and the selective PAR-2 activating peptide, 2f-LIGKV-OH, stimulated large and sustained increases in the serine 536 phosphorylation of p65/RelA in a transfected skin epithelial cell line and primary keratinocytes. Parallel experiments showed that in both cell types, p65 NFkappaB phosphorylation is mediated through the selective activation of IKK2. Treatment with PKC inhibitor GF109203X or PKCalpha siRNA reduced phosphorylation at 15 min but not 30 min, whilst rottlerin, a selective PKCdelta inhibitor and PKCdelta siRNA reduced the response at both time points. Pre-treatment of cells with the novel Gq/11 inhibitor YM-254890 and Gq/11 siRNA caused a similar pattern of inhibition and also reduced PAR-2-mediated NFkappaB transcriptional activity. Furthermore, stimulation of cells through a novel PAR-2 mutant PAR-2(34-43), delayed p65 phosphorylation but was without effect on the kinetics of ERK activation. Inhibition of Gi or G12/13 pathways by pertussis toxin pre-treatment or over-expression of the RGS mutant Lsc, also did not effect NFkappaB phosphorylation. Taken together these data indicate dependency for Gq/11 in early phosphorylation of p65 NFkappaB and this subsequently affects initial NFkappaB-dependent gene transcriptional activity, however later regulation of p65 is unaffected. Overall these novel data demonstrate an IKK2-dependent, predominantly G-protein-independent pathway involved in PAR-2 regulation of NFkappaB phosphorylation in keratinocytes.

Mood disorders are often associated with poor glycemic control, and antidepressant treatments for mood and pain disorders can alter plasma glucose levels in patients with diabetes. A previous meta-analysis from three studies showed that duloxetine modestly increased fasting plasma glucose (FPG) and HbA(1c) levels in patients with diabetic peripheral neuropathic pain (DPNP). This meta-analysis examined whether there were any short- and long-term effects of duloxetine (20-120 mg/day) on glycemic control in patients with diagnoses other than DPNP.Short-term data (9-27 weeks): seven studies of duloxetine in general anxiety disorder, fibromyalgia, and chronic lower back pain (CLBP). Long-term data: 41-week, uncontrolled extension of the short-term CLBP study and 52-week study in patients with recurrence of major depressive disorder.Baseline-to-endpoint changes in FPG and HbA(1c) levels.In short-term studies, patients were randomly assigned to placebo (n = 1098) or duloxetine (n = 1563). Mean baseline-to-endpoint changes in FPG and HbA(1c) did not significantly differ in duloxetine-treated patients compared with placebo-treated patients. In the 41-week study (n = 181), duloxetine-treated patients experienced a small but significant within-group baseline-to-endpoint increase in HbA(1c) (mean change = 0.1%; p0.001). This result was in contrast to absence of effect on mean baseline-to-endpoint within-group changes in FPG (p = 0.326) in that study, and to absence of between-treatment changes in FPG (p = 0.744) and HbA(1c) (p = 0.180) in the 52-week placebo-controlled study.Duloxetine treatment did not significantly alter FPG and HbA(1c) levels compared with placebo treatment in the short-term studies. A small but statistically significant within-group increase in HbA(1c) was found in the 41-week study, but not in between-treatment group differences in the 52-week study. Neither of the long-term studies showed significant changes in the FPG levels. The small, non-reproducible HbA(1c) increase in one study of patients without DPNP may have resulted from patients with unrecognized diabetes in these trials.

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 PAR(2), we assessed the effects of K-14585 on PAR(2)-mediated [(3)H] inositol phosphate accumulation, MAP kinase activation, p65 NFkappaB phosphorylation and DNA binding and IL-8 production.Pretreatment with K-14585 (5 microM) inhibited [(3)H] inositol phosphate levels stimulated by PAR(2)-activating peptide Ser-Leu-Ile-Gly-Lys-Val (SLIGKV-OH) in PAR(2)-expressing NCTC2544 cells. K-14585 pretreatment did not influence PAR(2)-mediated extracellular regulated kinase activation but inhibited p38 MAP kinase phosphorylation. At a higher concentration (30 microM), K-14585 alone stimulated p38 MAP kinase activation. These effects were replicated in EAhy926 cells, endogenously expressing PAR(2), but not in parental or PAR(4)-expressing NCTC2544 cells, suggesting these effects were PAR(2)-dependent. SLIGKV-mediated stimulation of p38 MAP kinase phosphorylation was substantially reduced by the G(q/11) inhibitor YM-254890, without affecting K-14585-mediated phosphorylation. Pretreatment with K-14585 inhibited PAR(2)-mediated p65 NFkappaB phosphorylation and NFkappaB-DNA binding. K-14585 (30 microM) alone stimulated comparable NFkappaB 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 PAR(2), one G(q/11)-dependent and the other G(q/11)-independent.