Shifting FcγRIIA-ITAM from activation to inhibitory configuration ameliorates arthritis
Sanae Ben Mkaddem, … , Pierre Bruhns, Renato C. Monteiro
Sanae Ben Mkaddem, … , Pierre Bruhns, Renato C. Monteiro
Published July 25, 2014
Citation Information: J Clin Invest. 2014;124(9):3945-3959. https://doi.org/10.1172/JCI74572.
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Shifting FcγRIIA-ITAM from activation to inhibitory configuration ameliorates arthritis

Abstract

Rheumatoid arthritis–associated (RA-associated) inflammation is mediated through the interaction between RA IgG immune complexes and IgG Fc receptors on immune cells. Polymorphisms within the gene encoding the human IgG Fc receptor IIA (hFcγRIIA) are associated with an increased risk of developing RA. Within the hFcγRIIA intracytoplasmic domain, there are 2 conserved tyrosine residues arranged in a noncanonical immunoreceptor tyrosine–based activation motif (ITAM). Here, we reveal that inhibitory engagement of the hFcγRIIA ITAM either with anti-hFcγRII F(ab′)2 fragments or intravenous hIgG (IVIg) ameliorates RA-associated inflammation, and this effect was characteristic of previously described inhibitory ITAM (ITAMi) signaling for hFcαRI and hFcγRIIIA, but only involves a single tyrosine. In hFcγRIIA-expressing mice, arthritis induction was inhibited following hFcγRIIA engagement. Moreover, hFcγRIIA ITAMi-signaling reduced ROS and inflammatory cytokine production through inhibition of guanine nucleotide exchange factor VAV-1 and IL-1 receptor–associated kinase 1 (IRAK-1), respectively. ITAMi signaling was mediated by tyrosine 304 (Y304) within the hFcγRIIA ITAM, which was required for recruitment of tyrosine kinase SYK and tyrosine phosphatase SHP-1. Anti-hFcγRII F(ab′)2 treatment of inflammatory synovial cells from RA patients inhibited ROS production through induction of ITAMi signaling. These data suggest that shifting constitutive hFcγRIIA-mediated activation to ITAMi signaling could ameliorate RA-associated inflammation.

Authors

Sanae Ben Mkaddem, Gilles Hayem, Friederike Jönsson, Elisabetta Rossato, Erwan Boedec, Tarek Boussetta, Jamel El Benna, Pierre Launay, Jean-Michel Goujon, Marc Benhamou, Pierre Bruhns, Renato C. Monteiro

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Figure 9

hFcγRIIA ITAMi signaling inhibits ROS production, reversing inflammatory profile in synovial fluid–infiltrating cells from RA patients.

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hFcγRIIA ITAMi signaling inhibits ROS production, reversing inflammatory...
(A) Representative FcγR expression on infiltrating cells from RA patient as in Figure 7A. (B) Infiltrating cells isolated from the synovial fluid of RA patients were preincubated or not with AT-10 F(ab′)2 (10 μg/ml) for 30 minutes at 37°C before cell activation with or without fMLF for 30 minutes. Peak of ROS production was measured by luminol-amplified chemiluminescence 1 minute after stimulation. (C) Activated cells from B were lysed, and lysates were subjected to anti-Rac immunoprecipitation. Eluted material was then subjected to immunoblot analysis for the presence of indicated proteins. Protein amounts were also analyzed in lysates by immunoblotting. (D) Immunoprecipitation of hFcγRIIA from RA synovial fluid–infiltrating cells (left panel) or from healthy donor blood cells (right panel) that had been treated or not by AT-10 F(ab′)2 (10 μg/ml) for 30 minutes. The eluted material was then subjected to immunoblotting analysis for the presence of indicated proteins. Cell lysates were also analyzed by immunoblotting. (E and F) Human leukocytes isolated from the synovial fluid of an RA patient (E) or from a healthy donor’s blood (F) were preincubated or not with AT-10 F(ab′)2 (10 μg/ml) for 0.5 to 2 hours. Cell lysates were then subjected to anti-hFcγRII immunoprecipitation. The eluted material was analyzed by immunoblotting for the presence of Syk, SHP-1, and hFcγRIIA. *P < 0.05. Data represent 1 of 3 independent experiments.