Shifting FcγRIIA-ITAM from activation to inhibitory configuration ameliorates arthritis
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
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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Research Article Inflammation

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 7

hFcγRIIA-ITAMi signaling modulates inflammatory responses through inhibition of IRAK-1.

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hFcγRIIA-ITAMi signaling modulates inflammatory responses through inhibi...
(A) THP-1–hFcγRIIA–R131+–CD14+ cells transfected or not with the indicated siRNA were incubated with AT-10 F(ab′)2 for 30 minutes before addition of LPS (10 ng/ml) for 6 hours. Released IL-8 was measured by ELISA. (B) Blood monocytes were transfected with the indicated siRNA, incubated with AT-10 F(ab′)2 for 30 minutes, and stimulated with LPS (10 ng/ml) for 6 hours. TNF-α, IL-6, and IL-8 levels in cell supernatants were measured by ELISA. (C) THP-1–hFcγRIIA–R131+–CD14+ cells were transfected with the indicated siRNA and pretreated with AT-10 F(ab′)2 (10 μg/ml) for 30 minutes, followed by LPS for 15 minutes. Immunoblot analysis of the indicated proteins in cell lysates is represented. (D) THP-1–hFcγRIIA–R131+–CD14+ cells were treated and stimulated as described in C, and cell lysates were subjected to immunoprecipitation using anti–IRAK-1 antibody (IRAK-1). Eluates and cell lysates were immunoblotted with antibodies specific for the indicated proteins. (E) Proposed mechanism by which hFcγRIIA-mediated ITAMi signalling regulates the LPS-induced proinflammatory response. *P < 0.05. Data in blots are from 1 representative out of 3 independent experiments.