Differential Signaling by Protease-Activated Receptors: Implications for Therapeutic Targeting

Sidhu, Tejminder; French, Shauna L.; Hamilton, Justin Raymond

doi:10.3390/ijms15046169

Cited by 36 publications

(36 citation statements)

References 79 publications

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“…We also showed that LPS failed to induce lung injury in PAR1-null mice. PAR1 and PAR2 are known to play opposing roles in thrombin-induced signaling in several cell types (Kahn et al, 1999; Sidhu et al, 2014; Soh et al, 2010). We therefore speculate from these findings that thrombin-mediated activation of PAR1 in AM-induced Ca 2+ entry through the plasmalemmal channel.…”

Section: Discussionmentioning

confidence: 99%

PAR2-Mediated cAMP Generation Suppresses TRPV4-Dependent Ca2+ Signaling in Alveolar Macrophages to Resolve TLR4-Induced Inflammation

et al. 2019

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SUMMARY Alveolar macrophages (AMs), upon sensing pathogens, trigger host defense by activating toll-like receptor 4 (TLR4), but the counterbalancing mechanisms that deactivate AM inflammatory signaling and prevent lethal edema, the hallmark of acute lung injury (ALI), remain unknown. Here, we demonstrate the essential role of AM protease-activating receptor 2 (PAR2) in rapidly suppressing inflammation to prevent long-lasting injury. We show that thrombin, released during TLR4-induced lung injury, directly activates PAR2 to generate cAMP, which abolishes Ca2+ entry through the TRPV4 channel. Deletion of PAR2 and thus the accompanying cAMP generation augments Ca2+ entry via TRPV4, causing sustained activation of the transcription factor NFAT to produce long-lasting TLR4-mediated inflammatory lung injury. Rescuing thrombin-sensitive PAR2 expression or blocking TRPV4 activity in PAR2-null AMs restores their capacity to resolve inflammation and reverse lung injury. Thus, activation of the thrombin-induced PAR2-cAMP cascade in AMs suppresses TLR4 inflammatory signaling to reinstate tissue integrity.

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Section: Discussionmentioning

confidence: 99%

PAR2-Mediated cAMP Generation Suppresses TRPV4-Dependent Ca2+ Signaling in Alveolar Macrophages to Resolve TLR4-Induced Inflammation

et al. 2019

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“…Because alterations in early outside‐in signaling (such as phosphorylation of c‐Src) are characteristic of thrombin receptor‐promoted integrin outside‐in signaling , the regulation pattern of Shp2 (only influencing late outside‐in signaling) further dissociates Shp2 from the pathways mediated by thrombin receptors. Thus, Shp2 may serve as a signal to distinguish the pathway initiated by TP from that initiated by protease‐activated receptor 4, although both GPCRs share common downstream G‐proteins (Gα q and Gα 12/13 ) to regulate platelet activation .…”

Section: Discussionmentioning

confidence: 99%

Platelet Shp2 negatively regulates thrombus stability under high shear stress

Liu

et al. 2019

Journal of Thrombosis and Haemostasis

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Shp2 negatively regulates thrombus stability under pathological shear rate. Shp2 suppresses TXA2 receptor‐mediated platelet dense granule secretion. Through αIIbβ3 outside‐in signaling, Shp2 targets calmodulin‐dependent activation of Akt. Shp2 may serve to prevent the formation of unwanted occlusive thrombi. Summary BackgroundPerpetuation is the final phase of thrombus formation; however, its mechanisms and regulation are poorly understood. ObjectiveTo investigate the mechanism of Shp2 in platelet function and thrombosis. Methods and resultsWe demonstrate that the platelet‐expressed Src homology region 2 domain‐containing protein tyrosine phosphatase Shp2 is a negative regulator of thrombus stability under high shear stress. In a ferric chloride‐induced mesenteric arteriole thrombosis model, megakaryocyte/platelet‐specific Shp2‐deficient mice showed less thrombi shedding than wild‐type mice, although their occlusion times were comparable. In accordance with this in vivo phenotype, a microfluidic whole‐blood perfusion assay revealed that the thrombi formed on collagen surfaces by Shp2‐deficient platelets were more stable under high shear rates than those produced by wild‐type platelets. Whereas Shp2 deficiency did not alter platelet responsiveness towards thrombin, ADP and collagen stimulation, Shp2‐deficient platelets showed increased dense granule secretion when stimulated by the thromboxane A2 analog U46619. Shp2 appears to act downstream of integrin αIIbβ3 outside‐in signaling, inhibiting the phosphorylation of Akt (Ser473 and Thr308) and dense granule secretion. Calmodulin was also shown to bind both Shp2 and Akt, linking Shp2 to Akt activation. ConclusionsPlatelet Shp2 negatively regulates thrombus perpetuation under high shear stress. This signaling pathway may constitute an important mechanism for the prevention of unwanted occlusive thrombus formation, without dramatically interfering with hemostasis.

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“…5,7 Accordingly, these signaling pathways are essential in the maintenance of vascular homeostasis. [8][9][10][11] Recent advances in the cardiovascular characterization of PAR signaling make them extremely attractive for drug targeting 3 ; however, how PARs regulate the human eNOS/ NO pathway remains unclear. Studies have shown that multiple PARs modulate the production of NO via posttranslational modifications of endothelial nitric oxide synthases (eNOS) via specific phosphorylation of various regulatory sites.…”

Section: Introductionmentioning

confidence: 99%

Featured Article: Differential regulation of endothelial nitric oxide synthase phosphorylation by protease-activated receptors in adult human endothelial cells

Tillery

Epperson

Eguchi

et al. 2016

Exp Biol Med (Maywood)

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Protease-activated receptors have been shown to regulate endothelial nitric oxide synthase through the phosphorylation of specific sites on the enzyme. It has been established that PAR-2 activation phosphorylates eNOS-Ser-1177 and leads to the production of the potent vasodilator nitric oxide, while PAR-1 activation phosphorylates eNOS-Thr-495 and decreases nitric oxide production in human umbilical vein endothelial cells. In this study, we hypothesize a differential coupling of protease-activated receptors to the signaling pathways that regulates endothelial nitric oxide synthase and nitric oxide production in primary adult human coronary artery endothelial cells. Using Western Blot analysis, we showed that thrombin and the PAR-1 activating peptide, TFLLR, lead to the phosphorylation of eNOS-Ser-1177 in human coronary artery endothelial cells, which was blocked by SCH-79797 (SCH), a PAR-1 inhibitor. Using the nitrate/nitrite assay, we also demonstrated that the thrombin- and TFLLR-induced production of nitric oxide was inhibited by SCH and L-NAME, a NOS inhibitor. In addition, we observed that TFLLR, unlike thrombin, significantly phosphorylated eNOS-Thr-495, which may explain the observed delay in nitric oxide production in comparison to that of thrombin. Activation of PAR-2 by SLIGRL, a PAR-2 specific ligand, leads to dual phosphorylation of both catalytic sites but primarily regulated eNOS-Thr-495 phosphorylation with no change in nitric oxide production in human coronary artery endothelial cells. PAR-3, known as the non-signaling receptor, was activated by TFRGAP, a PAR-3 mimicking peptide, and significantly induced the phosphorylation of eNOS-Thr-495 with minimal phosphorylation of eNOS-Ser-1177 with no change in nitric oxide production. In addition, we confirmed that PAR-mediated eNOS-Ser-1177 phosphorylation was Ca(2+)-dependent using the Ca(2+) chelator, BAPTA, while eNOS-Thr-495 phosphorylation was mediated via Rho kinase using the ROCK inhibitor, Y-27632, suggesting protease-activated receptor coupling to Gq and G12/13, respectively. These data suggest a vascular bed specific differential coupling of protease-activated receptors to the signaling pathways that regulate endothelial nitric oxide synthase and nitric oxide production that may be responsible for endothelial dysfunction associated with cardiovascular disease.

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Differential Signaling by Protease-Activated Receptors: Implications for Therapeutic Targeting

Cited by 36 publications

References 79 publications

PAR2-Mediated cAMP Generation Suppresses TRPV4-Dependent Ca2+ Signaling in Alveolar Macrophages to Resolve TLR4-Induced Inflammation

PAR2-Mediated cAMP Generation Suppresses TRPV4-Dependent Ca2+ Signaling in Alveolar Macrophages to Resolve TLR4-Induced Inflammation

Platelet Shp2 negatively regulates thrombus stability under high shear stress

Featured Article: Differential regulation of endothelial nitric oxide synthase phosphorylation by protease-activated receptors in adult human endothelial cells

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