The Experts below are selected from a list of 14535 Experts worldwide ranked by ideXlab platform
Morley D Hollenberg - One of the best experts on this subject based on the ideXlab platform.
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thrombin mediated direct activation of proteinase activated receptor 2 another target for thrombin signaling
Molecular Pharmacology, 2016Co-Authors: Koichiro Mihara, Mahmoud Saifeddine, Kristina K Hansen, Rithwik Ramachandran, Bernard Renaux, Danny Polley, Stacy Gibson, Christina Vanderboor, Morley D HollenbergAbstract:Thrombin is known to signal to cells by cleaving/activating a G-protein-coupled family of proteinase-activated receptors (PARs). The signaling mechanism involves the proteolytic unmasking of an N-terminal receptor sequence that acts as a tethered receptor-activating ligand. To date, the recognized targets of thrombin cleavage and activation for signaling are PAR1 and PAR4, in which thrombin cleaves at a conserved target arginine to reveal a tethered ligand. PAR2, which like PAR1 is also cleaved at an N-terminal arginine to unmask its tethered ligand, is generally regarded as a target for trypsin but not for thrombin signaling. We now show that thrombin, at concentrations that can be achieved at sites of acute injury or in a tumor microenvironment, can directly activate PAR2 vasorelaxation and signaling, stimulating calcium and mitogen-activated protein kinase responses along with triggeringβ-arrestin recruitment. Thus, PAR2 can be added alongside PAR1 and PAR4 to the targets, whereby thrombin can affect tissue function.
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proteinase activated receptors pars focus on receptor receptor interactions and their physiological and pathophysiological impact
Cell Communication and Signaling, 2013Co-Authors: Frank Gieseler, Morley D Hollenberg, Hendrik Ungefroren, Utz Settmacher, Roland KaufmannAbstract:Proteinase-activated receptors (PARs) are a subfamily of G protein-coupled receptors (GPCRs) with four members, PAR1, PAR2, PAR3 and PAR4, playing critical functions in hemostasis, thrombosis, embryonic development, wound healing, inflammation and cancer progression. PARs are characterized by a unique activation mechanism involving receptor cleavage by different proteinases at specific sites within the extracellular amino-terminus and the exposure of amino-terminal “tethered ligand“ domains that bind to and activate the cleaved receptors. After activation, the PAR family members are able to stimulate complex intracellular signalling networks via classical G protein-mediated pathways and beta-arrestin signalling. In addition, different receptor crosstalk mechanisms critically contribute to a high diversity of PAR signal transduction and receptor-trafficking processes that result in multiple physiological effects.
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proteinase activated receptors pars focus on receptor receptor interactions and their physiological and pathophysiological impact
Cell Communication and Signaling, 2013Co-Authors: Frank Gieseler, Morley D Hollenberg, Hendrik Ungefroren, Utz Settmacher, Roland KaufmannAbstract:Proteinase-activated receptors (PARs) are a subfamily of G protein-coupled receptors (GPCRs) with four members, PAR1, PAR2, PAR3 and PAR4, playing critical functions in hemostasis, thrombosis, embryonic development, wound healing, inflammation and cancer progression. PARs are characterized by a unique activation mechanism involving receptor cleavage by different proteinases at specific sites within the extracellular amino-terminus and the exposure of amino-terminal “tethered ligand“ domains that bind to and activate the cleaved receptors. After activation, the PAR family members are able to stimulate complex intracellular signalling networks via classical G protein-mediated pathways and beta-arrestin signalling. In addition, different receptor crosstalk mechanisms critically contribute to a high diversity of PAR signal transduction and receptor-trafficking processes that result in multiple physiological effects. In this review, we summarize current information about PAR-initiated physical and functional receptor interactions and their physiological and pathological roles. We focus especially on PAR homo- and heterodimerization, transactivation of receptor tyrosine kinases (RTKs) and receptor serine/threonine kinases (RSTKs), communication with other GPCRs, toll-like receptors and NOD-like receptors, ion channel receptors, and on PAR association with cargo receptors. In addition, we discuss the suitability of these receptor interaction mechanisms as targets for modulating PAR signalling in disease.
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cux1 transcription factor is a downstream effector of the proteinase activated receptor 2 par2
Journal of Biological Chemistry, 2009Co-Authors: Brian J Wilson, Morley D Hollenberg, Ryoko Harada, Lam Leduy, Alain NepveuAbstract:Proteinase-activated receptors (PARs) are G-protein-coupled receptors that have been linked to an array of cellular processes, including inflammation, migration, and proliferation. Although signal transduction downstream of PARs has been actively investigated, little is known about the mechanisms that lead to changes in transcriptional programs. Here we show that the CUX1 homeodomain protein is a downstream effector of PAR2. Treatment of epithelial and fibroblastic cells with trypsin or the PAR2-activating peptide (PAR2-AP) caused a rapid increase in CUX1 DNA binding activity. The stimulation of CUX1 was specific to PAR2 because no effect was observed with thrombin or the PAR1-AP. Using a panel of recombinant CUX1 proteins, the regulation was found to involve the cut repeat 3 (CR3) and the cut homeodomain, two DNA binding domains that are present in all CUX1 isoforms. Expression analysis in cux1 / mouse embryo fibroblasts led to the identification of three genes that are regulated downstream of both PAR2 and CUX1 as follows: interleukin-1, matrix metalloproteinase-10, and cyclo-oxygenase-2. p110 CUX1 was able to activate each of these genes, both in reporter assays and following the infection of cells. Moreover, the treatment of Hs578T breast tumor cells with trypsin led to a rapid recruitment of p110 CUX1 to the promoter of these genes and to a concomitant increase in their mRNA steady-state levels. Altogether, these results suggest a model whereby activation of PAR2 triggers a signaling cascade that culminates with the stimulation of p110 CUX1 DNA binding and the transcriptional activation of target genes.
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evaluation of proteinase activated receptor 1 par1 agonists and antagonists using a cultured cell receptor desensitization assay activation of par2 by par1 targeted ligands
Journal of Pharmacology and Experimental Therapeutics, 1999Co-Authors: Atsufumi Kawabata, Mahmoud Saifeddine, Bahjat Alani, Lorraine Leblond, Morley D HollenbergAbstract:We developed a calcium signaling-based assay, using cultured human embryonic kidney cells (HEK), that evaluates simultaneously, the activation/desensitization or blockade of the proteinase-activated receptors, PAR1 and PAR2. Using this assay, we analyzed the actions of a number of previously described putative PAR1-targeted peptide agonists and antagonists. We found that most of the previously described PAR1-targeted agents can also activate/desensitize PAR2, and most of these peptides can also activate a calcium signaling pathway in a target cell that possesses PAR2 along with PAR1. Furthermore, we used this assay to develop a PAR1receptor-activating probe [Ala-parafluoroPhe-Arg-Cha-Cit-Tyr-NH2(Cit-NH2)], which displays a high degree of specificity for PAR1 over PAR2, and we used the assay to quantitate the ability of trypsin to disarm the activation of PAR1 by thrombin. The abilities of the PAR1-targeted agents to desensitize or block PAR1 in the HEK cell assay were compared with their activities in a human platelet aggregation assay. Our data illustrate the usefulness of the HEK cell assay for evaluating the PAR1/PAR2 selectivity of PAR-activating agonists. The PAR1-selective agonist that we developed using the assay should prove useful for studying the effects of selectively activating PAR1 in vivo.
Shaun R. Coughlin - One of the best experts on this subject based on the ideXlab platform.
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cellular localization of membrane type serine protease 1 and identification of protease activated receptor 2 and single chain urokinase type plasminogen activator as substrates
Journal of Biological Chemistry, 2000Co-Authors: Toshihiko Takeuchi, Shaun R. Coughlin, Wei Huang, Jennifer L Harris, Charles S CraikAbstract:Abstract Membrane-type serine protease 1 (MT-SP1) was recently cloned, and we now report its biochemical characterization. MT-SP1 is predicted to be a type II transmembrane protein with an extracellular protease domain. This localization was experimentally verified using immunofluorescent microscopy and a cell-surface biotinylation technique. The substrate specificity of MT-SP1 was determined using a positional scanning-synthetic combinatorial library and substrate phage techniques. The preferred cleavage sequences were found to be (P4-(Arg/Lys)P3-(X)P2-(Ser)P1-(Arg)P1′-(Ala)) and (P4-(X)P3-(Arg/Lys)P2-(Ser)P1(Arg) P1′(Ala)), whereX is a non-basic amino acid. Protease-activated receptor 2 (PAR2) and single-chain urokinase-type plasminogen activator are proteins that are localized to the extracellular surface and contain the preferred MT-SP1 cleavage sequence. The ability of MT-SP1 to activate PARs was assessed by exposing PAR-expressingXenopus oocytes to the soluble MT-SP1 protease domain. The latter triggered calcium signaling in PAR2-expressing oocytes at 10 nm but failed to trigger calcium signaling in oocytes expressing PAR1, PAR3, or PAR4 at 100 nm. Single-chain urokinase-type plasminogen activator was activated using catalytic amounts of MT-SP1 (1 nm), but plasminogen was not cleaved under similar conditions. The membrane localization of MT-SP1 and its affinity for these key extracellular substrates suggests a role of the proteolytic activity in regulatory events.
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tissue factor and factor x dependent activation of protease activated receptor 2 by factor viia
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Eric Camerer, Wei Huang, Shaun R. CoughlinAbstract:Protease-activated receptor 2 (PAR2) is expressed by vascular endothelial cells and other cells in which its function and physiological activator(s) are unknown. Unlike PAR1, PAR3, and PAR4, PAR2 is not activatable by thrombin. Coagulation factors VIIa (FVIIa) and Xa (FXa) are proteases that act upstream of thrombin in the coagulation cascade and require cofactors to interact with their substrates. These proteases elicit cellular responses, but their receptor(s) have not been identified. We asked whether FVIIa and FXa might activate PARs if presented by their cofactors. Co-expression of tissue factor (TF), the cellular cofactor for FVIIa, together with PAR1, PAR2, PAR3, or PAR4 conferred TF-dependent FVIIa activation of PAR2 and, to lesser degree, PAR1. Responses to FXa were also observed but were independent of exogenous cofactor. The TF/FVIIa complex converts the inactive zymogen Factor X (FX) to FXa. Strikingly, when FX was present, low picomolar concentrations of FVIIa caused robust signaling in cells expressing TF and PAR2. Responses in keratinocytes and cytokine-treated endothelial cells suggested that PAR2 may be activated directly by TF/FVIIa and indirectly by TF/FVIIa-generated FXa at naturally occurring expression levels of TF and PAR2. These results suggest that PAR2, although not activatable by thrombin, may nonetheless function as a sensor for coagulation proteases and contribute to endothelial activation in the setting of injury and inflammation. More generally, these findings highlight the potential importance of cofactors in regulating PAR function and specificity.
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par3 is a cofactor for par4 activation by thrombin
Nature, 2000Co-Authors: Mayumi Nakanishimatsui, Yaowu Zheng, David Sulciner, Ethan J Weiss, Matthew J Ludeman, Shaun R. CoughlinAbstract:Identification of the mechanisms by which the coagulation protease thrombin activates platelets is critical for understanding haemostasis and thrombosis. Thrombin activates cells at least in part by cleaving protease-activated G-protein-coupled receptors (PARs)1. PAR3 and PAR4 are thrombin receptors expressed in mouse platelets2,3. Inhibition of thrombin binding to mPAR3 (ref. 4) and knockout of the mPAR3 gene3 inhibited mouse platelet activation at low but not high concentrations of thrombin. Thus PAR3 is important for thrombin signalling in mouse platelets. Expression of human PAR3 in heterologous expression systems reliably resulted in responsiveness to thrombin2. Curiously, despite its importance for the activation of mouse platelets by thrombin3,4, mouse PAR3 (mPAR3) did not lead to thrombin signalling even when overexpressed. We now report that mPAR3 and mPAR4 interact in a novel way: mPAR3 does not itself mediate transmembrane signalling but instead functions as a cofactor for the cleavage and activation of mPAR4 by thrombin. This establishes a paradigm for cofactor-assisted PAR activation and for a G-protein-coupled receptor's acting as an accessory molecule to present ligand to another receptor.
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how the protease thrombin talks to cells
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Shaun R. CoughlinAbstract:Abstract How does a protease act like a hormone to regulate cellular functions? The coagulation protease thrombin (EC 3.4.21.5) activates platelets and regulates the behavior of other cells by means of G protein-coupled protease-activated receptors (PARs). PAR1 is activated when thrombin binds to and cleaves its amino-terminal exodomain to unmask a new receptor amino terminus. This new amino terminus then serves as a tethered peptide ligand, binding intramolecularly to the body of the receptor to effect transmembrane signaling. The irreversibility of PAR1’s proteolytic activation mechanism stands in contrast to the reversible ligand binding that activates classical G protein-coupled receptors and compels special mechanisms for desensitization and resensitization. In endothelial cells and fibroblasts, activated PAR1 rapidly internalizes and then sorts to lysosomes rather than recycling to the plasma membrane as do classical G protein-coupled receptors. This trafficking behavior is critical for termination of thrombin signaling. An intracellular pool of thrombin receptors refreshes the cell surface with naive receptors, thereby maintaining thrombin responsiveness. Thus cells have evolved a trafficking solution to the signaling problem presented by PARs. Four PARs have now been identified. PAR1, PAR3, and PAR4 can all be activated by thrombin. PAR2 is activated by trypsin and by trypsin-like proteases but not by thrombin. Recent studies with knockout mice, receptor-activating peptides, and blocking antibodies are beginning to define the role of these receptors in vivo.
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protease activated receptors 1 and 4 mediate activation of human platelets by thrombin
Journal of Clinical Investigation, 1999Co-Authors: Mark L Kahn, Mayumi Nakanishimatsui, Hiroaki Ishihara, Michael J. Shapiro, Shaun R. CoughlinAbstract:Because of the role of thrombin and platelets in myocardial infarction and other pathological processes, identifying and blocking the receptors by which thrombin activates platelets has been an important goal. Three protease-activated receptors (PARs) for thrombin -- PAR1, PAR3, and PAR4 -- are now known. PAR1 functions in human platelets, and the recent observation that a PAR4-activating peptide activates human platelets suggests that PAR4 also acts in these cells. Whether PAR1 and PAR4 account for activation of human platelets by thrombin, or whether PAR3 or still other receptors contribute, is unknown. We have examined the roles of PAR1, PAR3, and PAR4 in platelets. PAR1 and PAR4 mRNA and protein were detected in human platelets. Activation of either receptor was sufficient to trigger platelet secretion and aggregation. Inhibition of PAR1 alone by antagonist, blocking antibody, or desensitization blocked platelet activation by 1 nM thrombin but only modestly attenuated platelet activation by 30 nM thrombin. Inhibition of PAR4 alone using a blocking antibody had little effect at either thrombin concentration. Strikingly, simultaneous inhibition of both PAR1 and PAR4 virtually ablated platelet secretion and aggregation, even at 30 nM thrombin. These observations suggest that PAR1 and PAR4 account for most, if not all, thrombin signaling in platelets and that antagonists that block these receptors might be useful antithrombotic agents.
Mahmoud Saifeddine - One of the best experts on this subject based on the ideXlab platform.
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thrombin mediated direct activation of proteinase activated receptor 2 another target for thrombin signaling
Molecular Pharmacology, 2016Co-Authors: Koichiro Mihara, Mahmoud Saifeddine, Kristina K Hansen, Rithwik Ramachandran, Bernard Renaux, Danny Polley, Stacy Gibson, Christina Vanderboor, Morley D HollenbergAbstract:Thrombin is known to signal to cells by cleaving/activating a G-protein-coupled family of proteinase-activated receptors (PARs). The signaling mechanism involves the proteolytic unmasking of an N-terminal receptor sequence that acts as a tethered receptor-activating ligand. To date, the recognized targets of thrombin cleavage and activation for signaling are PAR1 and PAR4, in which thrombin cleaves at a conserved target arginine to reveal a tethered ligand. PAR2, which like PAR1 is also cleaved at an N-terminal arginine to unmask its tethered ligand, is generally regarded as a target for trypsin but not for thrombin signaling. We now show that thrombin, at concentrations that can be achieved at sites of acute injury or in a tumor microenvironment, can directly activate PAR2 vasorelaxation and signaling, stimulating calcium and mitogen-activated protein kinase responses along with triggeringβ-arrestin recruitment. Thus, PAR2 can be added alongside PAR1 and PAR4 to the targets, whereby thrombin can affect tissue function.
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proteinase activated receptors 1 and 2 and the regulation of porcine coronary artery contractility a role for distinct tyrosine kinase pathways
British Journal of Pharmacology, 2014Co-Authors: Mahmoud Saifeddine, Koichiro Mihara, Rithwik Ramachandran, Mahmoud Eldaly, Chris R TriggleAbstract:Background and Purpose Because angiotensin-II-mediated porcine coronary artery (PCA) vasoconstriction is blocked by protein tyrosine kinase (PYK) inhibitors, we hypothesized that proteinase-activated receptors (PARs), known to regulate vascular tension, like angiotensin-II, would also cause PCA contractions via PYK-dependent signalling pathways. Experimental Approach Contractions of intact and endothelium-free isolated PCA rings, stimulated by PAR1/PAR2-activating peptides, angiotensin-II, PGF2α, EGF, PDGF and KCl, were monitored with/without multiple signalling pathway inhibitors, including AG-tyrphostins AG18 (non-specific PYKs), AG1478 (EGF-receptor kinase), AG1296 (PDGF receptor kinase), PP1 (Src kinase), U0126 and PD98059 (MEK/MAPKinase kinase), indomethacin/SC-560/NS-398 (COX-1/2) and L-NAME (NOS). Key Results AG18 inhibited the contractions induced by all the agonists except KCl, whereas U0126 attenuated contractions induced by PAR1/PAR2 agonists, EGF and angiotensin-II, but not by PGF2α, the COX-produced metabolites of arachidonate and KCl. PP1 only affected the responses to PAR1/PAR2-activating peptides and angiotensin-II. The EGF-kinase inhibitor, AG1478, attenuated contractions initiated by the PARs (PAR2 >> PAR1) and EGF itself, but not by angiotensin-II, PGF2α or KCl. COX-1/2 inhibitors blocked the contractions induced by all the agonists, except KCl and PGF2α. Conclusion and Implications PAR1/2-mediated contractions of the PCA are dependent on Src and MAPKinase and, in part, involve EGF-receptor-kinase transactivation and the generation of a COX-derived contractile agonist. However, the PYK signalling pathways used by PARs are distinct from each other and from those triggered by angiotensin-II and EGF. These signalling pathways may be therapeutic targets for managing coagulation-proteinase-induced coronary vasospasm.
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proteinase activated receptors targets for kallikrein signaling
Journal of Biological Chemistry, 2006Co-Authors: Katerina Oikonomopoulou, Mahmoud Saifeddine, Nigel W Bunnett, Kristina K Hansen, Michael Blaber, Sachiko I Blaber, Isobel A Scarisbrick, Patricia Andradegordon, Graeme S Cottrell, Eleftherios P DiamandisAbstract:Abstract Serine proteinases like thrombin can signal to cells by the cleavage/activation of proteinase-activated receptors (PARs). Although thrombin is a recognized physiological activator of PAR1 and PAR4, the endogenous enzymes responsible for activating PAR2 in settings other than the gastrointestinal system, where trypsin can activate PAR2, are unknown. We tested the hypothesis that the human tissue kallikrein (hK) family of proteinases regulates PAR signaling by using the following: 1) a high pressure liquid chromatography (HPLC)-mass spectral analysis of the cleavage products yielded upon incubation of hK5, -6, and -14 with synthetic PAR N-terminal peptide sequences representing the cleavage/activation motifs of PAR1, PAR2, and PAR4; 2) PAR-dependent calcium signaling responses in cells expressing PAR1, PAR2, and PAR4 and in human platelets; 3) a vascular ring vasorelaxation assay; and 4) a PAR4-dependent rat and human platelet aggregation assay. We found that hK5, -6, and -14 all yielded PAR peptide cleavage sequences consistent with either receptor activation or inactivation/disarming. Furthermore, hK14 was able to activate PAR1, PAR2, and PAR4 and to disarm/inhibit PAR1. Although hK5 and -6 were also able to activate PAR2, they failed to cause PAR4-dependent aggregation of rat and human platelets, although hK14 did. Furthermore, the relative potencies and maximum effects of hK14 and -6 to activate PAR2-mediated calcium signaling differed. Our data indicate that in physiological settings, hKs may represent important endogenous regulators of the PARs and that different hKs can have differential actions on PAR1, PAR2, and PAR4.
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evaluation of proteinase activated receptor 1 par1 agonists and antagonists using a cultured cell receptor desensitization assay activation of par2 by par1 targeted ligands
Journal of Pharmacology and Experimental Therapeutics, 1999Co-Authors: Atsufumi Kawabata, Mahmoud Saifeddine, Bahjat Alani, Lorraine Leblond, Morley D HollenbergAbstract:We developed a calcium signaling-based assay, using cultured human embryonic kidney cells (HEK), that evaluates simultaneously, the activation/desensitization or blockade of the proteinase-activated receptors, PAR1 and PAR2. Using this assay, we analyzed the actions of a number of previously described putative PAR1-targeted peptide agonists and antagonists. We found that most of the previously described PAR1-targeted agents can also activate/desensitize PAR2, and most of these peptides can also activate a calcium signaling pathway in a target cell that possesses PAR2 along with PAR1. Furthermore, we used this assay to develop a PAR1receptor-activating probe [Ala-parafluoroPhe-Arg-Cha-Cit-Tyr-NH2(Cit-NH2)], which displays a high degree of specificity for PAR1 over PAR2, and we used the assay to quantitate the ability of trypsin to disarm the activation of PAR1 by thrombin. The abilities of the PAR1-targeted agents to desensitize or block PAR1 in the HEK cell assay were compared with their activities in a human platelet aggregation assay. Our data illustrate the usefulness of the HEK cell assay for evaluating the PAR1/PAR2 selectivity of PAR-activating agonists. The PAR1-selective agonist that we developed using the assay should prove useful for studying the effects of selectively activating PAR1 in vivo.
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proteinase activated receptor 2 par2 activating peptides identification of a receptor distinct from par2 that regulates intestinal transport
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: Nathalie Vergnolle, Mahmoud Saifeddine, Bahjat Alani, Wallace K Macnaughton, John L Wallace, Morley D HollenbergAbstract:The effects of PAR2-activating PAR2-activating peptides, SLIGRL (SL)-NH2, and trans-cinnamoyl-LIGRLO (tc)-NH2 were compared with the action of trypsin, thrombin, and the PAR1 selective-activating peptide: Ala-parafluoroPhe-Arg-cyclohexylAla-Citrulline-Tyr (Cit)-NH2 for stimulating intestinal ion transport. These agonists were added to the serosa of stripped rat jejunum segments mounted in Ussing chambers, and short circuit current (Isc) was used to monitor active ion transport. The relative potencies of these agonists also were evaluated in two bioassays specific for the activation of rat PAR2: a cloned rat PAR2 cell calcium-signaling assay (PAR2-KNRK cells) and an aorta ring relaxation (AR) assay. In the Isc assay, all agonists, except thrombin, induced an Isc increase. The SL-NH2-induced Isc changes were blocked by indomethacin but not by tetrodotoxin. The relative potencies of the agonists in the Isc assay (trypsin≫SL-NH2>tc-NH2>Cit-NH2) were strikingly different from their relative potencies in the cloned PAR2-KNRK cell calcium assay (trypsin≫>tc-NH2 ≅ SL-NH2≫>Cit-NH2) and in the AR assay (trypsin≫>tc-NH2 ≅ SL-NH2). Furthermore, all agonists were maximally active in the PAR2-KNRK cell and AR assays at concentrations that were one (PAR2 -activating peptides) or two (trypsin) orders of magnitude lower than those required to activate intestinal transport. Based on the distinct potency profile for these agonists and the considerable differences in the concentration ranges required to induce an Isc effect in the intestinal assay compared with the PAR2-KNRK and AR assays, we conclude that a proteinase-activated receptor, pharmacologically distinct from PAR2 and PAR1, is present in rat jejunum and regulates intestinal transport via a prostanoid-mediated mechanism.
Nigel W Bunnett - One of the best experts on this subject based on the ideXlab platform.
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the transient receptor potential vanilloid 4 trpv4 ion channel mediates protease activated receptor 1 par1 induced vascular hyperpermeability
Laboratory Investigation, 2020Co-Authors: Scott Peng, Megan S Grace, Arisbel B Gondin, Jeffri S Retamal, Larissa Dill, William Darby, Nigel W BunnettAbstract:Endothelial barrier disruption is a hallmark of tissue injury, edema, and inflammation. Vascular endothelial cells express the G protein-coupled receptor (GPCR) protease acctivated receptor 1 (PAR1) and the ion channel transient receptor potential vanilloid 4 (TRPV4), and these signaling proteins are known to respond to inflammatory conditions and promote edema through remodeling of cell–cell junctions and modulation of endothelial barriers. It has previously been established that signaling initiated by the related protease activated receptor 2 (PAR2) is enhanced by TRPV4 in sensory neurons and that this functional interaction plays a critical role in the development of neurogenic inflammation and nociception. Here, we investigated the PAR1–TRPV4 axis, to determine if TRPV4 plays a similar role in the control of edema mediated by thrombin-induced signaling. Using Evans Blue permeation and retention as an indication of increased vascular permeability in vivo, we showed that TRPV4 contributes to PAR1-induced vascular hyperpermeability in the airways and upper gastrointestinal tract of mice. TRPV4 contributes to sustained PAR1-induced Ca2+ signaling in recombinant cell systems and to PAR1-dependent endothelial junction remodeling in vitro. This study supports the role of GPCR–TRP channel functional interactions in inflammatory-associated changes to vascular function and indicates that TRPV4 is a signaling effector for multiple PAR family members.
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proteinase activated receptors targets for kallikrein signaling
Journal of Biological Chemistry, 2006Co-Authors: Katerina Oikonomopoulou, Mahmoud Saifeddine, Nigel W Bunnett, Kristina K Hansen, Michael Blaber, Sachiko I Blaber, Isobel A Scarisbrick, Patricia Andradegordon, Graeme S Cottrell, Eleftherios P DiamandisAbstract:Abstract Serine proteinases like thrombin can signal to cells by the cleavage/activation of proteinase-activated receptors (PARs). Although thrombin is a recognized physiological activator of PAR1 and PAR4, the endogenous enzymes responsible for activating PAR2 in settings other than the gastrointestinal system, where trypsin can activate PAR2, are unknown. We tested the hypothesis that the human tissue kallikrein (hK) family of proteinases regulates PAR signaling by using the following: 1) a high pressure liquid chromatography (HPLC)-mass spectral analysis of the cleavage products yielded upon incubation of hK5, -6, and -14 with synthetic PAR N-terminal peptide sequences representing the cleavage/activation motifs of PAR1, PAR2, and PAR4; 2) PAR-dependent calcium signaling responses in cells expressing PAR1, PAR2, and PAR4 and in human platelets; 3) a vascular ring vasorelaxation assay; and 4) a PAR4-dependent rat and human platelet aggregation assay. We found that hK5, -6, and -14 all yielded PAR peptide cleavage sequences consistent with either receptor activation or inactivation/disarming. Furthermore, hK14 was able to activate PAR1, PAR2, and PAR4 and to disarm/inhibit PAR1. Although hK5 and -6 were also able to activate PAR2, they failed to cause PAR4-dependent aggregation of rat and human platelets, although hK14 did. Furthermore, the relative potencies and maximum effects of hK14 and -6 to activate PAR2-mediated calcium signaling differed. Our data indicate that in physiological settings, hKs may represent important endogenous regulators of the PARs and that different hKs can have differential actions on PAR1, PAR2, and PAR4.
Roland Kaufmann - One of the best experts on this subject based on the ideXlab platform.
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Signaling Crosstalk of TGF-β/ALK5 and PAR2/PAR1: A Complex Regulatory Network Controlling Fibrosis and Cancer
MDPI AG, 2018Co-Authors: Hendrik Ungefroren, Frank Gieseler, Roland Kaufmann, Utz Settmacher, Hendrik Lehnert, Bernhard H. RauchAbstract:Both signaling by transforming growth factor-β (TGF-β) and agonists of the G Protein-coupled receptors proteinase-activated receptor-1 (PAR1) and -2 (PAR2) have been linked to tissue fibrosis and cancer. Intriguingly, TGF-β and PAR signaling either converge on the regulation of certain matrix genes overexpressed in these pathologies or display mutual regulation of their signaling components, which is mediated in part through sphingosine kinases and sphingosine-1-phosphate and indicative of an intimate signaling crosstalk between the two pathways. In the first part of this review, we summarize the various regulatory interactions that have been discovered so far according to the organ/tissue in which they were described. In the second part, we highlight the types of signaling crosstalk between TGF-β on the one hand and PAR2/PAR1 on the other hand. Both ligand–receptor systems interact at various levels and by several mechanisms including mutual regulation of ligand–ligand, ligand–receptor, and receptor–receptor at the transcriptional, post-transcriptional, and receptor transactivation levels. These mutual interactions between PAR2/PAR1 and TGF-β signaling components eventually result in feed-forward loops/vicious cycles of matrix deposition and malignant traits that exacerbate fibrosis and oncogenesis, respectively. Given the crucial role of PAR2 and PAR1 in controlling TGF-β receptor activation, signaling, TGF-β synthesis and bioactivation, combining PAR inhibitors with TGF-β blocking agents may turn out to be more efficient than targeting TGF-β alone in alleviating unwanted TGF-β-dependent responses but retaining the beneficial ones
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proteinase activated receptors pars focus on receptor receptor interactions and their physiological and pathophysiological impact
Cell Communication and Signaling, 2013Co-Authors: Frank Gieseler, Morley D Hollenberg, Hendrik Ungefroren, Utz Settmacher, Roland KaufmannAbstract:Proteinase-activated receptors (PARs) are a subfamily of G protein-coupled receptors (GPCRs) with four members, PAR1, PAR2, PAR3 and PAR4, playing critical functions in hemostasis, thrombosis, embryonic development, wound healing, inflammation and cancer progression. PARs are characterized by a unique activation mechanism involving receptor cleavage by different proteinases at specific sites within the extracellular amino-terminus and the exposure of amino-terminal “tethered ligand“ domains that bind to and activate the cleaved receptors. After activation, the PAR family members are able to stimulate complex intracellular signalling networks via classical G protein-mediated pathways and beta-arrestin signalling. In addition, different receptor crosstalk mechanisms critically contribute to a high diversity of PAR signal transduction and receptor-trafficking processes that result in multiple physiological effects.
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proteinase activated receptors pars focus on receptor receptor interactions and their physiological and pathophysiological impact
Cell Communication and Signaling, 2013Co-Authors: Frank Gieseler, Morley D Hollenberg, Hendrik Ungefroren, Utz Settmacher, Roland KaufmannAbstract:Proteinase-activated receptors (PARs) are a subfamily of G protein-coupled receptors (GPCRs) with four members, PAR1, PAR2, PAR3 and PAR4, playing critical functions in hemostasis, thrombosis, embryonic development, wound healing, inflammation and cancer progression. PARs are characterized by a unique activation mechanism involving receptor cleavage by different proteinases at specific sites within the extracellular amino-terminus and the exposure of amino-terminal “tethered ligand“ domains that bind to and activate the cleaved receptors. After activation, the PAR family members are able to stimulate complex intracellular signalling networks via classical G protein-mediated pathways and beta-arrestin signalling. In addition, different receptor crosstalk mechanisms critically contribute to a high diversity of PAR signal transduction and receptor-trafficking processes that result in multiple physiological effects. In this review, we summarize current information about PAR-initiated physical and functional receptor interactions and their physiological and pathological roles. We focus especially on PAR homo- and heterodimerization, transactivation of receptor tyrosine kinases (RTKs) and receptor serine/threonine kinases (RSTKs), communication with other GPCRs, toll-like receptors and NOD-like receptors, ion channel receptors, and on PAR association with cargo receptors. In addition, we discuss the suitability of these receptor interaction mechanisms as targets for modulating PAR signalling in disease.
