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Role of novel rat-specific Fc receptor in macrophage activation associated with crescentic glomerulonephritis.

Page TH, D'Souza Z, Nakanishi S, Serikawa T, Pusey CD, Aitman TJ, Cook HT, Behmoaras J - J. Biol. Chem. (2011)

Bottom Line: In these cells, which lack endogenous Fcgr3 receptors, we show that Fcgr3-rs interacts with the common Fc-γ chain but that Fc receptor-mediated phagocytosis and signaling are defective.This inhibitory effect on phagocytosis was mediated by the novel cytoplasmic domain of Fcgr3-rs.These results suggest that Fcgr3-rs may act to inhibit Fcgr3-mediated signaling and phagocytosis and could be considered as a novel mechanism in the modulation of Fc receptor-mediated cell activation in autoimmune diseases.

View Article: PubMed Central - PubMed

Affiliation: Kennedy Institute of Rheumatology Division, Imperial College London, London W6 8LH, United Kingdom.

ABSTRACT
Crescentic glomerulonephritis (Crgn) is a complex disease where the initial insult is often the glomerular deposition of antibodies against intrinsic or deposited antigens in the glomerulus. The role of Fc receptors in the induction and progression of Crgn is increasingly recognized, and our previous studies have shown that copy number variation in Fcgr3 partially explains the genetic susceptibility of the Wistar-Kyoto (WKY) rat to nephrotoxic nephritis, a rat model of Crgn. The Fcgr3-related sequence (Fcgr3-rs) is a novel rat-specific Fc receptor with a cytoplasmic domain 6 amino acids longer than its paralogue, Fcgr3. The Fcgr3-rs gene is deleted from the WKY rat genome, and this deletion is associated with enhanced macrophage activity in this strain. Here, we investigated the mechanism by which the deletion of Fcgr3-rs in the WKY strain leads to increased macrophage activation. By lentivirus-mediated gene delivery, we generated stably transduced U937 cells expressing either Fcgr3-rs or Fcgr3. In these cells, which lack endogenous Fcgr3 receptors, we show that Fcgr3-rs interacts with the common Fc-γ chain but that Fc receptor-mediated phagocytosis and signaling are defective. Furthermore, in primary macrophages, expression of Fcgr3-rs inhibits Fc receptor-mediated functions, because WKY bone marrow-derived macrophages transduced with Fcgr3-rs had significantly reduced phagocytic activity. This inhibitory effect on phagocytosis was mediated by the novel cytoplasmic domain of Fcgr3-rs. These results suggest that Fcgr3-rs may act to inhibit Fcgr3-mediated signaling and phagocytosis and could be considered as a novel mechanism in the modulation of Fc receptor-mediated cell activation in autoimmune diseases.

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Phylogenetic tree of 134 laboratory rat strains according to the presence or absence of Fcgr3-rs in the genome. A phylogenetic tree of 94 strains is shown. Strains having numerous substrains (i.e. SHR, F344) are shown in capital letters, and all of the substrains showed the same genotype as the founder strain. The tree was developed through a heuristic search for maximum parsimony implemented in PAUP 4.0b10. TreeView was used to display the radial tree. For BD IX, LEC/Tj, and WM/Tj, genotypes could not be determined.
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Figure 2: Phylogenetic tree of 134 laboratory rat strains according to the presence or absence of Fcgr3-rs in the genome. A phylogenetic tree of 94 strains is shown. Strains having numerous substrains (i.e. SHR, F344) are shown in capital letters, and all of the substrains showed the same genotype as the founder strain. The tree was developed through a heuristic search for maximum parsimony implemented in PAUP 4.0b10. TreeView was used to display the radial tree. For BD IX, LEC/Tj, and WM/Tj, genotypes could not be determined.

Mentions: Exon 5 of Fcgr3-rs contains a deletion of a single guanine nucleotide at position 129 (ΔG129) in the coding sequence of the cytoplasmic domain (9). When compared with Fcgr3, this ΔG129 variant results in a frameshift in the Fcgr3-rs coding sequence and generates a novel cytoplasmic domain 6 amino acids longer than that encoded by Fcgr3 that was not found in any other species (Fig. 1). We have previously shown that Fcgr3-rs was deleted from NTN-susceptible Kyoto-derived strains (9), but to investigate the distribution of this deletion throughout the rat genealogical tree, we carried out a phylogenetic tree analysis of 94 inbred laboratory strains and 40 of their substrains (Fig. 2). The results show that the deletion of Fcgr3-rs is widespread throughout the rat phylogeny (32 of 94 strains), suggesting that the origin of the deletion event is earlier then the derivation of these strains. We also investigated the relative levels of Fcgr3 and Fcgr3-rs mRNA levels in Lewis rat BMDMs by qRT-PCR and showed that although there is relatively increased Fcgr3 expression when compared with Fcgr3-rs, LPS stimulation did not change the relative levels of both receptors (Table 1).


Role of novel rat-specific Fc receptor in macrophage activation associated with crescentic glomerulonephritis.

Page TH, D'Souza Z, Nakanishi S, Serikawa T, Pusey CD, Aitman TJ, Cook HT, Behmoaras J - J. Biol. Chem. (2011)

Phylogenetic tree of 134 laboratory rat strains according to the presence or absence of Fcgr3-rs in the genome. A phylogenetic tree of 94 strains is shown. Strains having numerous substrains (i.e. SHR, F344) are shown in capital letters, and all of the substrains showed the same genotype as the founder strain. The tree was developed through a heuristic search for maximum parsimony implemented in PAUP 4.0b10. TreeView was used to display the radial tree. For BD IX, LEC/Tj, and WM/Tj, genotypes could not be determined.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3285343&req=5

Figure 2: Phylogenetic tree of 134 laboratory rat strains according to the presence or absence of Fcgr3-rs in the genome. A phylogenetic tree of 94 strains is shown. Strains having numerous substrains (i.e. SHR, F344) are shown in capital letters, and all of the substrains showed the same genotype as the founder strain. The tree was developed through a heuristic search for maximum parsimony implemented in PAUP 4.0b10. TreeView was used to display the radial tree. For BD IX, LEC/Tj, and WM/Tj, genotypes could not be determined.
Mentions: Exon 5 of Fcgr3-rs contains a deletion of a single guanine nucleotide at position 129 (ΔG129) in the coding sequence of the cytoplasmic domain (9). When compared with Fcgr3, this ΔG129 variant results in a frameshift in the Fcgr3-rs coding sequence and generates a novel cytoplasmic domain 6 amino acids longer than that encoded by Fcgr3 that was not found in any other species (Fig. 1). We have previously shown that Fcgr3-rs was deleted from NTN-susceptible Kyoto-derived strains (9), but to investigate the distribution of this deletion throughout the rat genealogical tree, we carried out a phylogenetic tree analysis of 94 inbred laboratory strains and 40 of their substrains (Fig. 2). The results show that the deletion of Fcgr3-rs is widespread throughout the rat phylogeny (32 of 94 strains), suggesting that the origin of the deletion event is earlier then the derivation of these strains. We also investigated the relative levels of Fcgr3 and Fcgr3-rs mRNA levels in Lewis rat BMDMs by qRT-PCR and showed that although there is relatively increased Fcgr3 expression when compared with Fcgr3-rs, LPS stimulation did not change the relative levels of both receptors (Table 1).

Bottom Line: In these cells, which lack endogenous Fcgr3 receptors, we show that Fcgr3-rs interacts with the common Fc-γ chain but that Fc receptor-mediated phagocytosis and signaling are defective.This inhibitory effect on phagocytosis was mediated by the novel cytoplasmic domain of Fcgr3-rs.These results suggest that Fcgr3-rs may act to inhibit Fcgr3-mediated signaling and phagocytosis and could be considered as a novel mechanism in the modulation of Fc receptor-mediated cell activation in autoimmune diseases.

View Article: PubMed Central - PubMed

Affiliation: Kennedy Institute of Rheumatology Division, Imperial College London, London W6 8LH, United Kingdom.

ABSTRACT
Crescentic glomerulonephritis (Crgn) is a complex disease where the initial insult is often the glomerular deposition of antibodies against intrinsic or deposited antigens in the glomerulus. The role of Fc receptors in the induction and progression of Crgn is increasingly recognized, and our previous studies have shown that copy number variation in Fcgr3 partially explains the genetic susceptibility of the Wistar-Kyoto (WKY) rat to nephrotoxic nephritis, a rat model of Crgn. The Fcgr3-related sequence (Fcgr3-rs) is a novel rat-specific Fc receptor with a cytoplasmic domain 6 amino acids longer than its paralogue, Fcgr3. The Fcgr3-rs gene is deleted from the WKY rat genome, and this deletion is associated with enhanced macrophage activity in this strain. Here, we investigated the mechanism by which the deletion of Fcgr3-rs in the WKY strain leads to increased macrophage activation. By lentivirus-mediated gene delivery, we generated stably transduced U937 cells expressing either Fcgr3-rs or Fcgr3. In these cells, which lack endogenous Fcgr3 receptors, we show that Fcgr3-rs interacts with the common Fc-γ chain but that Fc receptor-mediated phagocytosis and signaling are defective. Furthermore, in primary macrophages, expression of Fcgr3-rs inhibits Fc receptor-mediated functions, because WKY bone marrow-derived macrophages transduced with Fcgr3-rs had significantly reduced phagocytic activity. This inhibitory effect on phagocytosis was mediated by the novel cytoplasmic domain of Fcgr3-rs. These results suggest that Fcgr3-rs may act to inhibit Fcgr3-mediated signaling and phagocytosis and could be considered as a novel mechanism in the modulation of Fc receptor-mediated cell activation in autoimmune diseases.

Show MeSH
Related in: MedlinePlus