• The Korean Journal of Physiology and Pharmacology
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• v.16 no.6
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• pp.393-398
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• 2012

Mast cells are involved in allergic responses, protection against pathogens and autoimmune diseases. Dexamethasone (Dex) and other glucocorticoids suppress $Fc{\varepsilon}RI$-mediated release of inflammatory mediators from mast cells. The inhibition mechanisms were mainly investigated on the downstream signaling of Fc receptor activations. Here, we addressed the effects of Dex on Fc receptor expressions in rat mast cell line RBL-2H3. We measured mRNA levels of Fc receptors by real-time PCR. As expected, Dex decreased the mRNA levels of activating Fc receptor for IgE ($Fc{\varepsilon}R$) I and increased the mRNA levels of the inhibitory Fc receptor for IgG $Fc{\gamma}RIIb$. Interestingly, Dex stimulated transcriptions of other activating receptors such as Fc receptors for IgG ($Fc{\gamma}R$) I and $Fc{\gamma}RIII$. To investigate the mechanisms underlying transcriptional regulation, we employed a transcription inhibitor actinomycin D and a translation inhibitor cycloheximide. The inhibition of protein synthesis without Dex treatment enhanced $Fc{\gamma}RI$ and $Fc{\gamma}RIII$ mRNA levels potently, while $Fc{\varepsilon}RI$ and $Fc{\gamma}RIIb$ were minimally affected. Next, we examined expressions of the Fc receptors on cell surfaces by the flow cytometric method. Only $Fc{\gamma}RIIb$ protein expression was significantly enhanced by Dex treatment, while $Fc{\gamma}RI$, $Fc{\gamma}RIII$ and $Fc{\varepsilon}RI$ expression levels were marginally changed. Our data showed, for the first time, that Dex regulates Fc receptor expressions resulting in augmentation of the inhibitory receptor $Fc{\gamma}RIIb$.

• IMMUNE NETWORK
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• v.5 no.3
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• pp.144-149
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• 2005

Background: Fc receptor-mediated phagocytosis is a complex process involving the activation of kinases and phosphatases. FcgammaRIIB has been known to transduces inhibitory signals through an immunoreceptor tyrosine-based inhibitory motif (ITIM) in cytoplasmic domains. In this study, we examined the involvement of inositol-phosphatase in the Fc receptor-mediated phagocytosis. Methods: J774 cells were infected using vaccinia viral vector containing SH2 domain-containing inositol-phosphatase (SHIP) cDNA and stimulated with the sensitized sheep red blood cells. Results: Stimulation of J774 cells induced the tyrosine phosphorylation of SHIP which was maximal at 5 minutes. Phosphatidylinositol-3 (PI-3) kinase inhibitor (wortmannin) inhibits J774 cell phagocytosis of sensitized sheep red blood cells in a dose-dependent manner. Heterologious expression of SHIP in J774 cells inhibits phagocytosis of sensitized sheep red blood cells in a dose-dependency manner, but catalytically dead mutants of SHIP has no effect on phagocytosis. Conclusion: These results strongly suggest that the active signals mediated by PI-3 kinase are opposed by inhibitory signals through SHIP in the regulation of Fc receptor-mediated phagocytosis.

• BMB Reports
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• v.42 no.4
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• pp.212-216
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• 2009

The short in vivo half-life of GLP-1 prevents it from being used clinically. This short half-life occurs because GLP-1 is rapidly degraded by dipeptidyl peptidases such as DPP-IV. To overcome this obstacle, a GLP-1/Fc was constructed and evaluated to determine if it was degraded by DPP-IV and in serum. When the degradation of GLP-1/Fc by human DPP-IV and rabbit serum was compared with that of GLP-1 it was found to be reduced by approximately 5- and 4-fold, respectively. Furthermore, GLP-1/Fc showed a potent activity for human GLP-1 receptor activation ($EC_{50}$ approximately 6 nM). Taken together, these results indicate that GLP-1/Fc may have an extended half-life in vivo that occurs as a result of inhibition of degradation by human DPP-IV. Due to the extended half life, GLP-1/Fc may be useful for clinical treatments.

• IMMUNE NETWORK
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• v.7 no.3
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• pp.141-148
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• 2007

Background: Anti-IgE mAb which binds circulating but not receptor-bound IgE has been shown to be effective in treatment for asthma and other allergic diseases. However, the mechanisms by which anti-IgE mAb influences the pathophysiological responses are remained to be illustrated. This study was undertaken to examine the therapeutic efficacy of non-anaphylactogenic anti-mouse IgE mAb using murine models of IgE-induced systemic fatal anaphylaxis. Methods: Active systemic anaphylaxis was induced by either penicillin V(Pen V) or OVA and passive systemic anaphylaxis was induced by either anaphylactogenic anti-mouse IgE or a mixture of anti-chicken gamma globulin (CGG) IgG1 mAb and CGG. The binding of the Fc portion of anti-IgE to CHO-stable cell line expressing mouse Fc ${\gamma}$ RIIb was examined using flow cytometry. Fc fragments of anti-IgE mAb were prepared using papain digestion. The expression of phosphatases in lungs were assessed by Western blotting and immunohistochemistry. Results: Anti-IgE mAb prevented IgE- and IgG-induced active and passive systemic fatal reactions. In both types of anaphylaxis, anti-IgE mAb suppressed antigen-specific IgE responses, but not those of IgG. Anti-IgE mAb neither prevented anaphylaxis nor suppressed the IgE response in Fc ${\gamma}$ RIIb-deficient mice. The Fc portion of anti-IgE mAb was bound to murine Fc ${\gamma}$ RIIb gene-transfected CHO cells and inhibited systemic anaphylaxis. Anti-IgE mAb blocked the anaphylaxis-induced downregulation of Fc ${\gamma}$ RIIb-associated phosphatases such as src homology 2 domain-containing inositol 5-phosphatase (SHIP) and phosphatase and tensin homologue deleted on chromosome ten (PTEN). Conclusion: Anti-IgE mAb prevented anaphylaxis by delivering nonspecific inhibitory signals through the inhibitory IgG receptor, Fc ${\gamma}$ RIIb, rather than targeting IgE.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.11a
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• pp.143-145
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• 1994

Chimeric fusion proteins involving IgG have proven valuable in studying protein-protein interactions and may possess therapeutic applications as well. For example, three receptor subtypes for the natriuretic peptides, when fused to the Fc portion of human IgG ${\gamma}$ chain, were quantitatively and qualitatively indistinguishable from the native receptor, thus allowing detailed structure-function studies of the receptor. In an attempt to block human immunodeficiency virus infectivity with soluble derivatives of CD4, a CD4/IgG Fc chimeric molecule was shown to increase the plasma half life of soluble CD4 and possessed the added advantage of IgG Fc-mediated placental transfer. In the case of the KGFR, this approach provided a framework for dissection of its ligand binding domains and made it possible to demonstrate that high affinity binding sites for two ligands, aFGF and KGF, reside within different receptor Ig-like domains. Chimeric molecules fused to immunoglobulins would have the advantages of secretion from transfected cells as well as detection and purification from medium utilizing Staphylococcus aureus Protein A. In addition, where highly related receptors make their discrimination very hard due to the difficulties in generating specific immunochemical probes, IgG fusion protein with tailor-made specificities confers particular advantages to elucidate patterns of receptor distribution and expression. The approach described here may have general applications in defining ligand-receptor interactions as well as searching for specific agonists and antagonists of receptor function.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2192-2198
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• 2016

The myeloid-specific IgA Fc receptor ($Fc{\alpha}R$) is a cell surface molecule on immunocytes that provides a fundamental connection between humoral and cellular immunity. In this study, the full-length cDNA sequence of swine $Fc{\alpha}RI$ ($swFc{\alpha}RI$) was isolated and characterized and found to contain a 792-base-pair open reading frame, encoding a 264-amino-acid transmembrane glycoprotein with a predicted molecular mass of 29.4 kDa. The $swFc{\alpha}RI$ shares high amino acid sequence homology (>50%) with its counterparts from cattle, seal, and horse. Rosetting analysis confirmed that COS-7 cells transfected with an $swFc{\alpha}RI$ expression plasmid was able to combine with chicken erythrocytes sensitized with porcine IgA, but not IgG.

• BMB Reports
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• v.43 no.2
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• pp.146-149
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• 2010

Exendin-4 (Ex-4), a peptide secreted from the salivary glands of the Gila monster lizard, can increase pancreatic $\beta$-cell growth and insulin secretion by activating glucagon-like peptide-1 receptor. In this study, we expressed a fusion protein consisting of exendin-4 and the human immunoglobulin heavy chain (Ex-4/IgG-Fc) in E. coli and explored its potential therapeutic use for the treatment of insulin-resistant type 2 diabetes. Here, we show that the Ex-4/IgG-Fc fusion protein induces expression of insulin receptor substrate-2 in rat insulinoma INS-1 cells. Our findings therefore suggest that Ex-4/IgG-Fc overexpressed in E. coli could be used as a potential, long-acting glucagon-like peptide-1 mimetic.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.93.3-94
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• 2003

The signaling components of high affinity IgE receptor (Fc RI) were searched by yeast-hybrid screening of the cDNA library constructed from RBL-2H3 cells. The cytoplasmic part of the Fc RI- chain was found to specifically interact with PLC 2, and further comparatives studies were conducted focusing on the differential regulation of two PLC- isoforms through Fc RI. The inhibitors of Src, Syk, and protein kinase C similarly affected the tyrosine phosporylations of PLC 1 and PLC 2 but the inhibitors of PI3-kinase and p42/44 ERK effectively inhibited the activation of PLC 1 but not PLC 2. (omitted)

• BMB Reports
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• v.31 no.1
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• pp.64-69
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• 1998

Recent studies have suggested that integrin (CR3) participates in the signal transduction pathways of certain GPI-anchored phagocytic receptors including $Fc{\gamma}RIIIB$. One consequence of this functional linkage is an inducible association between CR3 and cortical microfilaments that is triggered by $Fc{\gamma}RIIIB$ binding to immobilized immune complexes (IC). That this signaling event requires the co-expression of $Fc{\gamma}RIIIB$ with CR3 was documented by the use of NIH 3T3 transfectants expressing both CR3 and $Fc{\gamma}RIIIB$ (clone 3-23), CR3 alone (clone 3-19), and $Fc{\gamma}RIIIB$ alone (clone 3-15). Pretreatment of 3-23 cells with protein kinase inhibitors such as staurosporine and methyl 2,5-dihydroxycinnamate (MDHC) blocked IC-stimulated CR3 microfilament proximity without affecting the extent to which $Fc{\gamma}RIIIB$ constrains the lateral membrane mobility of a subset of CR3 on the cell surface (as measured in fluorescence recovery after photobleaching experiments). These data support that CR3 and $Fc{\gamma}RIIIB$ molecules are physically and functionally associated and that ligation of FcgRIIIB triggers CR3-dependent signal transduction.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.8
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• pp.1089-1095
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• 2012

Neonatal Fc receptor (FcRn) gene encodes a receptor that binds the Fc region of monomeric immunoglobulin G (IgG) and is responsible for IgG transport and stabilization. In this report, the 8,900 bp porcine FcRn genomic DNA structure was identified and putative FcRn protein included 356 amino acids. Alignment and phylogenetic analysis of the porcine FcRn amino acid sequences with their homologies of other species showed high identity. Tissues expression of FcRn mRNA was detected by real time quantitative polymerase chain reaction (Q-PCR), the results revealed FcRn expressed widely in ten analyzed tissues. One single nucleotide polymorphism (SNP) (HQ026019:g.8526 C>T) in exon6 region of porcine FcRn gene was demonstrated by DNA sequencing analysis. A further analysis of SNP genotypes associated with serum Classical Swine Fever Virus antibody (anti-CSFV) concentration was performed in three pig populations including Large White, Landrace and Songliao Black pig (a Chinese indigenous breed). Our results of statistical analysis showed that the SNP had a highly significant association with the level of anti-CSFV antibody (At d 20; At d 35) in serum (p = 0.008; p = 0.0001). Investigation of expression and polymorphisms of the porcine FcRn gene will help us in further understanding the molecular basis of the antibody regulation pathway in the porcine immune response. All these results indicate that FcRn gene might be regarded as a molecular marker for genetic selection of anti-CSFV antibody level in pig disease resistance breeding programmes.