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Agonist Peptide (agonist + peptide)
Selected AbstractsEfficient help for autoreactive B-cell activation requires CD4+ T-cell recognition of an agonist peptide at the effector stageEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2009Brian D. Hondowicz Abstract T-cell recognition of peptide/MHC complexes is flexible and can lead to differential activation, but how interactions with agonist (full activation) or partial agonist (suboptimal activation) peptides can shape immune responses in vivo is not well characterized. We investigated the effect of stimulation by agonist or partial agonist ligands during initial CD4+ T-cell priming, and subsequent T-B-cell cognate interactions, on antibody production by anti-chromatin B cells. We found that autoantibody production required TCR recognition of an agonist peptide at the effector stage of B-cell activation. However, interaction with a weak agonist ligand at this effector stage failed to promote efficient autoantibody production, even if the CD4+ T cells were fully primed by an agonist peptide. These studies suggest that the reactivity of the TCR for a target self-peptide during CD4+ T-B-cell interaction can be a critical determinant in restraining anti-chromatin autoantibody production. [source] Vav1 transduces TCR signals required for LFA-1 function and cell polarization at the immunological synapseEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 3 2003Laurence Ardouin Abstract Activation of T lineage cells through the TCR by peptide,MHC complexes on APC is critically dependent on rearrangement of the actin cytoskeleton. Vav1 is a guanine nucleotide exchange factor for members of the Rho/Rac family of GTPases which is activated following TCR stimulation, suggesting that it may transduce TCR signals to the activation of some or all actin-controlled processes. Weshow that Vav1-deficient double-positive thymocytes are less efficient at forming conjugates with APC presenting agonist peptide than wild-type cells are. Furthermore we demonstrate that Vav1 is required for TCR-induced activation of the integrin LFA-1, which is likely to explain the defect in conjugate formation. However, once Vav1-deficient cells form a conjugate, the assembly of proteins into an immunological synapse at the conjugate interface is normal. In contrast, thymocyte polarization is defective in the absence of Vav1, as judged by the relocalization of the microtubule-organizing center. These data demonstrate that Vav1 transduces signals to only a subset of cytoskeleton-dependent events at the immunological synapse. [source] Human airway trypsin-like protease induces amphiregulin release through a mechanism involving protease-activated receptor-2-mediated ERK activation and TNF ,-converting enzyme activity in airway epithelial cellsFEBS JOURNAL, Issue 24 2005Manabu Chokki Human airway trypsin-like protease (HAT), a serine protease found in the sputum of patients with chronic airway diseases, is an agonist of protease-activated receptor-2 (PAR-2). Previous results have shown that HAT enhances the release of amphiregulin (AR); further, it causes MUC5AC gene expression through the AR-epidermal growth factor receptor pathway in the airway epithelial cell line NCI-H292. In this study, the mechanisms by which HAT-induced AR release can occur were investigated. HAT-induced AR gene expression was mediated by extracellular signal-regulated kinase (ERK) pathway, as pretreatment of cells with ERK pathway inhibitor eliminated the effect of HAT on AR mRNA. Both HAT and PAR-2 agonist peptide (PAR-2 AP) induced ERK phosphorylation; further, desensitization of PAR-2 with a brief exposure of cells to PAR-2 AP resulted in inhibition of HAT-induced ERK phosphorylation, suggesting that HAT activates ERK through PAR-2. Moreover, PAR-2 AP induced AR gene expression subsequent to protein production in the cellular fraction through the ERK pathway indicating that PAR-2-mediated activation of ERK is essential for HAT-induced AR production. However, in contrast to HAT, PAR-2 AP could not cause AR release into extracellular space; it appears that activation of PAR-2 is not sufficient for HAT-induced AR release. Finally, HAT-induced AR release was eliminated by blockade of tumour necrosis factor ,-converting enzyme (TACE) by the TAPI-1 and RNA interference, suggesting that TACE activity is necessary for HAT-induced AR release. These observations show that HAT induces AR production through the PAR-2 mediated ERK pathway, and then causes AR release by a TACE-dependent mechanism. [source] Mite serine protease activates protease-activated receptor-2 and induces cytokine release in human keratinocytesALLERGY, Issue 9 2009T. Kato Background:, House dust mites produce serine and cysteine proteases. Mite-derived proteases have been suggested to be involved in the pathogenesis of allergies; however, whether mite-derived serine protease activity can stimulate keratinocytes remains unknown. Methods:, We examined the activation of primary human keratinocytes by serine protease-rich extract of whole mite culture and compared with that by recombinant group 1 allergens (rDer f 1 and rDer p 1), which exclusively exhibit cysteine protease activity. Results:, Protease activity of whole mite culture extract (WCE), rDer f 1 and rDer p 1 induced the release of IL-8 and granulocyte-macrophage colony-stimulating factor. Protease activity of WCEs induced a significant upregulation of their mRNA expression but rDer f 1 had much less effect. Protease activity of the WCE stimulated intracellular Ca2+ mobilization but rDer f 1 and rDer p 1 did not. The mobilization induced by agonists for the human protease-activated receptor (PAR)-2, an agonist peptide or trypsin, was diminished by pre-incubation of keratinocytes with WCE. rDer f 1 inefficiently cleaved a synthetic N-terminal peptide of PAR-2 at different sites from trypsin, but the resultant peptides did not stimulate the release of interleukin-8. Conclusions:, The results suggest that mite-derived serine protease activity may contribute to the pathogenesis of atopic dermatitis by activating keratinocytes via PAR-2 activation but cysteine protease activity of Der f 1 and Der p 1 acts via another mechanism. [source] Functional protease-activated receptors in the dorsal motor nucleus of the vagusNEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2010H. Wang Abstract Background, Protease-activated receptors (PARs), a family member of G-protein coupled receptors, are present and functionally active in a wide variety of cells. The object of this study was to demonstrate the presence and function of PAR-1 and PAR-2 in the dorsal motor nucleus of the vagus (DMV). Methods, DMNV neurons were isolated from neonatal rat brainstems using micro-dissection and enzymatic digestion. Neurons were cultured in Neurobasal medium A containing 2% B27 supplement. Intracellular calcium concentration ([Ca2 + ]i) was measured using fura-2 based microspectrometry. Expression of PARs was detected by RT-PCR and immunofluorescent staining. Key Result, Thrombin and PAR-1 agonist peptide activate PAR-1 with a maximum change in [Ca2 + ]i expressed as ,F/F0 of 229 ± 14% and 137 ± 7%, respectively. Trypsin and PAR-2 agonist peptide activate PAR-2 with a maximum ,F/F0 change of 258 ± 12% and 242 ± 10%, respectively. Inhibition of phospholipase C (PLC) by U73312 (1 ,m) decreased the maximal change in ,F/F0 induced by PAR-1 activation from 140 ± 17% to 21 ± 3%, while the PAR-2-mediated maximal change in ,F/F0 decreased from 185 ± 21% to 19 ± 6%. Blockade of IP3 receptor with 2APB inhibited the maximal change in ,F/F0 due to PAR-1 and PAR-2 activation by 72 ± 13% and 71 ± 20% respectively. PAR-1 immnuoreactivity was present in DMV neurons. Increase in transcripts for PAR-1 and PAR-2 were detected in DMV tissues derived from IBD rats relative to control animals. Conclusions & Inferences, Our results indicate that PAR-1 and PAR-2 are present in the DMV neurons, and their activation leads to increases in intracellular calcium via signal transduction mechanism that involves activation of PLC and the production of IP3. [source] Protease-activated receptor-4 (PAR4): a role as inhibitor of visceral pain and hypersensitivityNEUROGASTROENTEROLOGY & MOTILITY, Issue 11 2009C. Augé Abstract, Protease-activated receptor-4 (PAR4) belongs to the family of receptors activated by the proteolytic cleavage of their extracellular N-terminal domain and the subsequent binding of the newly released N-terminus. While largely expressed in the colon, the role of PAR4 in gut functions has not been defined. We have investigated the effects of PAR4 agonist on colonic sensations and sensory neuron signalling, and its role in visceral pain. We observed that a single administration of the PAR4 agonist peptide (AYPGKF-NH2), but not the control peptide (YAPGKF-NH2) into the colon lumen of mice significantly reduced the visceromotor response to colorectal distension at different pressures of distension. Further, intracolonic administration of the PAR4 agonist, but not the control peptide, was able to significantly inhibit PAR2 agonist- and transcient receptor potential vanilloid-4 (TRPV4) agonist-induced allodynia and hyperalgesia in response to colorectal distension. Protease-activated receptor-4 was detected in sensory neurons projecting from the colon, and isolated from the dorsal root ganglia, where it co-expressed with PAR2 and TRPV4. In total sensory neurons, PAR4 agonist exposure inhibited free intracellular calcium mobilization induced by the pro-nociceptive agonists of PAR2 and TRPV4. Finally, PAR4 -deficient mice experienced increased pain behaviour in response to intracolonic administration of mustard oil, compared with wild-type littermates. These results show that PAR4 agonists modulate colonic nociceptive response, inhibit colonic hypersensitivity and primary afferent responses to pro-nociceptive mediators. Endogenous activation of PAR4 also plays a major role in controlling visceral pain. These results identify PAR4 as a previously unknown modulator of visceral nociception. [source] Biological properties of a specific G,q/11 inhibitor, YM-254890, on platelet functions and thrombus formation under high-shear stressBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2006Toshio Uemura 1The effects of YM-254890, a specific G,q/11 inhibitor, on platelet functions, thrombus formation under high-shear rate condition and femoral artery thrombosis in cynomolgus monkeys were investigated. 2YM-254890 concentration dependently inhibited ADP-induced intracellular Ca2+ elevation, with an IC50 value of 0.92±0.28 ,M. 3P-selectin expression induced by ADP or thrombin receptor agonist peptide (TRAP) was strongly inhibited by YM-254890, with IC50 values of 0.51±0.02 and 0.16±0.08 ,M, respectively. 4YM-254890 had no effect on the binding of fibrinogen to purified GPIIb/IIIa, but strongly inhibited binding to TRAP-stimulated washed platelets. 5YM-254890 completely inhibited platelet shape change induced by ADP, but not that induced by collagen, TRAP, arachidonic acid, U46619 or A23187. 6YM-254890 attenuated ADP-, collagen-, TRAP-, arachidonic acid- and U46619-induced platelet aggregation with IC50 values of <1 ,M, whereas it had no effect on phorbol 12-myristate 13-acetate-, ristocetin-, thapsigargin- or A23187-induced platelet aggregation. 7High-shear stress-induced platelet aggregation and platelet-rich thrombus formation on a collagen surface under high-shear flow conditions were concentration dependently inhibited by YM-254890. 8The antithrombotic effect of YM-254890 was evaluated in a model of cyclic flow reductions in the femoral artery of cynomolgus monkeys. The intravenous bolus injection of YM-254890 dose dependently inhibited recurrent thrombosis without affecting systemic blood pressure or prolonging template bleeding time. 9YM-254890 is a useful tool for investigating G,q/11 -coupled receptor signaling and the physiological roles of G,q/11. British Journal of Pharmacology (2006) 148, 61,69. doi:10.1038/sj.bjp.0706711 [source] | ||||||||||