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  • Utilization of two seven-transmembrane, G protein-coupled receptors, formyl peptide receptor-like 1 and formyl peptide receptor, by the synthetic hexapeptide WKYMVm for h ... 10586077

    Trp-Lys-Tyr-Val-D-Met (WKYMVm) is a synthetic leukocyte-activating peptide postulated to use seven-transmembrane, G protein-coupled receptor(s). In the study to characterize the receptor(s) for WKYMVm, we found that this peptide induced marked chemotaxis and calcium flux in human phagocytes. The signaling induced by WKYMVm in phagocytes was attenuated by high concentrations of the bacterial chemotactic peptide fMLP, suggesting that WKYMVm might use receptor(s) for fMLP. This hypothesis was tested by using cells over expressing genes encoding two seven-transmembrane receptors, formyl peptide receptor (FPR) and formyl peptide receptor-like 1 (FPRL1), which are with high and low affinity for fMLP, respectively. Both FPR- and FPRL1-expressing cells mobilized calcium in response to picomolar concentrations of WKYMVm. While FPRL1-expressing cells migrated to picomolar concentrations of WKYMVm, nanomolar concentrations of the peptide were required to induce migration of FPR-expressing cells. In contrast, fMLP elicited both calcium flux and chemotaxis only in FPR-expressing cells with an efficacy comparable with WKYMVm. Thus, WKYMVm uses both FPR and FPRL1 to stimulate phagocytes with a markedly higher efficacy for FPRL1. Our study suggests that FPR and FPRL1 in phagocytes react to a broad spectrum of agonists and WKYMVm as a remarkably potent agonist provides a valuable tool for studying leukocyte signaling via these receptors.
    Document Type:
    Reference
    Product Catalog Number:
    HTS056M
    Product Catalog Name:
    ChemiScreen™ Membrane Preparation
    Recombinant Human FPRL1 (Formyl Peptide Receptor-Like 1)

  • C-terminal tail phosphorylation of N-formyl peptide receptor: differential recognition of two neutrophil chemoattractant receptors by monoclonal antibodies NFPR1 and NFPR ... 17675514

    The N-formyl peptide receptor (FPR), a G protein-coupled receptor that binds proinflammatory chemoattractant peptides, serves as a model receptor for leukocyte chemotaxis. Recombinant histidine-tagged FPR (rHis-FPR) was purified in lysophosphatidyl glycerol (LPG) by Ni(2+)-NTA agarose chromatography to >95% purity with high yield. MALDI-TOF mass analysis (>36% sequence coverage) and immunoblotting confirmed the identity as FPR. The rHis-FPR served as an immunogen for the production of 2 mAbs, NFPR1 and NFPR2, that epitope map to the FPR C-terminal tail sequences, 305-GQDFRERLI-313 and 337-NSTLPSAEVE-346, respectively. Both mAbs specifically immunoblotted rHis-FPR and recombinant FPR (rFPR) expressed in Chinese hamster ovary cells. NFPR1 also recognized recombinant FPRL1, specifically expressed in mouse L fibroblasts. In human neutrophil membranes, both Abs labeled a 45-75 kDa species (peak M(r) approximately 60 kDa) localized primarily in the plasma membrane with a minor component in the lactoferrin-enriched intracellular fractions, consistent with FPR size and localization. NFPR1 also recognized a band of M(r) approximately 40 kDa localized, in equal proportions to the plasma membrane and lactoferrin-enriched fractions, consistent with FPRL1 size and localization. Only NFPR2 was capable of immunoprecipitation of rFPR in detergent extracts. The recognition of rFPR by NFPR2 is lost after exposure of cellular rFPR to f-Met-Leu-Phe (fMLF) and regained after alkaline phosphatase treatment of rFPR-bearing membranes. In neutrophils, NFPR2 immunofluorescence was lost upon fMLF stimulation. Immunoblotting approximately 60 kDa species, after phosphatase treatment of fMLF-stimulated neutrophil membranes, was also enhanced. We conclude that the region 337-346 of FPR becomes phosphorylated after fMLF activation of rFPR-expressing Chinese hamster ovary cells and neutrophils.
    Document Type:
    Reference
    Product Catalog Number:
    MABF287
    Product Catalog Name:
    Anti-FPR1, C-Term Dephospho Antibody, clone NFPRb

  • Identification of C-terminal phosphorylation sites of N-formyl peptide receptor-1 (FPR1) in human blood neutrophils. 23873933

    Accumulation, activation, and control of neutrophils at inflammation sites is partly driven by N-formyl peptide chemoattractant receptors (FPRs). Occupancy of these G-protein-coupled receptors by formyl peptides has been shown to induce regulatory phosphorylation of cytoplasmic serine/threonine amino acid residues in heterologously expressed recombinant receptors, but the biochemistry of these modifications in primary human neutrophils remains relatively unstudied. FPR1 and FPR2 were partially immunopurified using antibodies that recognize both receptors (NFPRa) or unphosphorylated FPR1 (NFPRb) in dodecylmaltoside extracts of unstimulated and N-formyl-Met-Leu-Phe (fMLF) + cytochalasin B-stimulated neutrophils or their membrane fractions. After deglycosylation and separation by SDS-PAGE, excised Coomassie Blue-staining bands (∼34,000 Mr) were tryptically digested, and FPR1, phospho-FPR1, and FPR2 content was confirmed by peptide mass spectrometry. C-terminal FPR1 peptides (Leu(312)-Arg(322) and Arg(323)-Lys(350)) and extracellular FPR1 peptide (Ile(191)-Arg(201)) as well as three similarly placed FPR2 peptides were identified in unstimulated and fMLF + cytochalasin B-stimulated samples. LC/MS/MS identified seven isoforms of Ala(323)-Lys(350) only in the fMLF + cytochalasin B-stimulated sample. These were individually phosphorylated at Thr(325), Ser(328), Thr(329), Thr(331), Ser(332), Thr(334), and Thr(339). No phospho-FPR2 peptides were detected. Cytochalasin B treatment of neutrophils decreased the sensitivity of fMLF-dependent NFPRb recognition 2-fold, from EC50 = 33 ± 8 to 74 ± 21 nM. Our results suggest that 1) partial immunopurification, deglycosylation, and SDS-PAGE separation of FPRs is sufficient to identify C-terminal FPR1 Ser/Thr phosphorylations by LC/MS/MS; 2) kinases/phosphatases activated in fMLF/cytochalasin B-stimulated neutrophils produce multiple C-terminal tail FPR1 Ser/Thr phosphorylations but have little effect on corresponding FPR2 sites; and 3) the extent of FPR1 phosphorylation can be monitored with C-terminal tail FPR1-phosphospecific antibodies.
    Document Type:
    Reference
    Product Catalog Number:
    MABF287
    Product Catalog Name:
    Anti-FPR1, C-Term Dephospho Antibody, clone NFPRb

  • Primary granule exocytosis in human neutrophils is regulated by Rac-dependent actin remodeling. 18799653

    The actin cytoskeleton regulates exocytosis in all secretory cells. In neutrophils, Rac2 GTPase has been shown to control primary (azurophilic) granule exocytosis. In this report, we propose that Rac2 is required for actin cytoskeletal remodeling to promote primary granule exocytosis. Treatment of neutrophils with low doses (less than or = 10 microM) of the actin-depolymerizing drugs latrunculin B (Lat B) or cytochalasin B (CB) enhanced both formyl peptide receptor- and Ca(2+) ionophore-stimulated exocytosis. Higher concentrations of CB or Lat B, or stabilization of F-actin with jasplakinolide (JP), inhibited primary granule exocytosis measured as myeloperoxidase release but did not affect secondary granule exocytosis determined by lactoferrin release. These results suggest an obligatory role for F-actin disassembly before primary granule exocytosis. However, lysates from secretagogue-stimulated neutrophils showed enhanced actin polymerization activity in vitro. Microscopic analysis showed that resting neutrophils contain significant cortical F-actin, which was redistributed to sites of primary granule translocation when stimulated. Exocytosis and actin remodeling was highly polarized when cells were primed with CB; however, polarization was reduced by Lat B preincubation, and both polarization and exocytosis were blocked when F-actin was stabilized with JP. Treatment of cells with the small molecule Rac inhibitor NSC23766 also inhibited actin remodeling and primary granule exocytosis induced by Lat B/fMLF or CB/fMLF, but not by Ca(2+) ionophore. Therefore, we propose a role for F-actin depolymerization at the cell cortex coupled with Rac-dependent F-actin polymerization in the cell cytoplasm to promote primary granule exocytosis.
    Document Type:
    Reference
    Product Catalog Number:
    07-604

  • Characterization of an activation factor released from human neutrophils after stimulation by triclinic monosodium urate crystals. 16652423

    OBJECTIVE: To determine the presence and characterize the activity of a soluble activation factor rapidly released by human neutrophils after stimulation with monosodium urate (MSU) crystals. METHODS: Supernatants from human neutrophils stimulated by MSU crystals for 5 to 60 min were tested for their ability to stimulate a chemotactic response, induce a mobilization of calcium, and increase the tyrosine phosphorylation levels in naive neutrophils. RESULTS: Supernatant from neutrophils stimulated or= 15 min by MSU crystals was chemotactic for neutrophils, induced a mobilization of calcium, and increased the levels of tyrosine phosphorylation in fresh neutrophils. Generation of activity in the supernatant was independent of protein synthesis and was eliminated after digestion with trypsin. Leukotriene B4 (LTB4), platelet-activating factor (PAF), and formyl peptide receptor antagonists as well as neutralizing anti-interleukin 8 (IL-8) antibodies did not inhibit the chemotactic activity in the supernatant, although pertussis toxin did inhibit the mobilization of calcium observed in response to the supernatant. Stimulation of neutrophils with formyl-methionine-leucine-phenylalanine, IL-8, and LTB4 inhibited subsequent mobilization of calcium by the supernatant. CONCLUSION: There is rapid liberation of a potent activation signal from neutrophils after interaction with MSU crystals. This activation factor can further stimulate surrounding neutrophils and contribute to amplification of the inflammatory response induced by MSU crystals.
    Document Type:
    Reference
    Product Catalog Number:
    05-321
    Product Catalog Name:
    Anti-Phosphotyrosine Antibody, clone 4G10®

  • Targeted nanoparticles containing the proresolving peptide Ac2-26 protect against advanced atherosclerosis in hypercholesterolemic mice. 25695999

    Chronic, nonresolving inflammation is a critical factor in the clinical progression of advanced atherosclerotic lesions. In the normal inflammatory response, resolution is mediated by several agonists, among which is the glucocorticoid-regulated protein called annexin A1. The proresolving actions of annexin A1, which are mediated through its receptor N-formyl peptide receptor 2 (FPR2/ALX), can be mimicked by an amino-terminal peptide encompassing amino acids 2-26 (Ac2-26). Collagen IV (Col IV)-targeted nanoparticles (NPs) containing Ac2-26 were evaluated for their therapeutic effect on chronic, advanced atherosclerosis in fat-fed Ldlr(-/-) mice. When administered to mice with preexisting lesions, Col IV-Ac2-26 NPs were targeted to lesions and led to a marked improvement in key advanced plaque properties, including an increase in the protective collagen layer overlying lesions (which was associated with a decrease in lesional collagenase activity), suppression of oxidative stress, and a decrease in plaque necrosis. In mice lacking FPR2/ALX in myeloid cells, these improvements were not seen. Thus, administration of a resolution-mediating peptide in a targeted NP activates its receptor on myeloid cells to stabilize advanced atherosclerotic lesions. These findings support the concept that defective inflammation resolution plays a role in advanced atherosclerosis, and suggest a new form of therapy.
    Document Type:
    Reference
    Product Catalog Number:
    AB5830
    Product Catalog Name:
    Anti-8-Hydroxydeoxyguanosine Antibody

  • Signaling through CD16b in human neutrophils involves the Tec family of tyrosine kinases. 15899983

    Tec kinases belong to the second largest family of nonreceptor tyrosine kinases. Although these kinases are expressed in myeloid cells, little is known about their implication in neutrophil function. We recently reported the participation of Tec kinases in the responses of human neutrophils to the bacterial peptide N-formyl-l-methionyl-l-leucyl-l-phenylalanine via G-coupled protein receptors. In this study, we extended our investigations of Tec kinases to the signaling of the glycosylphosphatidylinositol-linked receptor CD16b, which is highly and specifically expressed in neutrophils. The results obtained indicate that Tec is translocated to the plasma membrane, phosphorylated, and activated upon CD16b cross-linking and that the activation of Tec is inhibited by Src-specific inhibitors as well as by the phosphatidylinositol-3 kinase inhibitor, wortmannin. As no specific inhibitor of Tec exists, the role of Tec kinases was further investigated using a-Cyano-b-hydroxy-b-methyl-N-(2,5-dibromophenyl)propenamide (LFM-A13), a compound known to inhibit Bruton's tyrosine kinase. We show that this compound also inhibits the kinase activity of Tec and provide evidence that the mobilization of intracellular calcium and the tyrosine phosphorylation of phospholipase Cgamma2 (PLCgamma2) induced upon CD16b engagement are inhibited by LFM-A13. We also show that Tec kinases are important for CD16b-dependent degranulation of neutrophils. In summary, we provide direct evidence for the implication of Tec in CD16b signaling and suggest that Tec kinases are involved in the phosphorylation and activation of PLCgamma2 and subsequently, in the mobilization of calcium in human neutrophils.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple
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