Inhibition of Macrophage Complement Receptor CRIg by TRIM72 Polarizes Innate Immunity of the Lung

Abstract

The complement system plays a critical role in immune responses against pathogens. However, its identity and regulation in the lung are not fully understood. This study aimed to explore the role of tripartite motif protein (TRIM) 72 in regulating complement receptor (CR) of the Ig superfamily (CRIg) in alveolar macrophage (AM) and innate immunity of the lung. Imaging, absorbance quantification, and flow cytometry were used to evaluate in vitro and in vivo AM phagocytosis with normal, or altered, TRIM72 expression. Pulldown, coimmunoprecipitation, and gradient binding assays were applied to examine TRIM72 and CRIg interaction. A pneumonia model was established by intratracheal injection of Pseudomonas aeruginosa. Mortality, lung bacterial burden, and cytokine levels in BAL fluid and lung tissues were examined. Our data show that TRIM72 inhibited CR-mediated phagocytosis, and release of TRIM72 inhibition led to increased AM phagocytosis. Biochemical assays identified CRIg as a binding partner of TRIM72, and TRIM72 inhibited formation of the CRIg-phagosome. Genetic ablation of TRIM72 led to improved pathogen clearance, reduced cytokine storm, and improved survival in murine models of severe pneumonia, specificity of which was confirmed by adoptive transfer of wild-type or TRIM72 AMs to AM-depleted TRIM72 mice. TRIM72 overexpression promoted bacteria-induced NF-κB activation in murine alveolar macrophage cells. Our data revealed a quiescent, noninflammatory bacterial clearance mechanism in the lung via AM CRIg, which is suppressed by TRIM72. In vivo data suggest that targeted suppression of TRIM72 in AM may be an effective measure to treat fatal pulmonary bacterial infections.

Serum soluble VSIG4 as a surrogate marker for the diagnosis of lymphoma‐associated hemophagocytic lymphohistiocytosis

“…To date, in vitro and in vivo studies have consistently implicated VSIG4 as a receptor of complement C3 on the surface of macrophages playing a vital role in phagocytosis and the clearance of pathogens in the circulation (Helmy et al, 2006;Vogt et al, 2006). Most studies have focused on the function of VSIG4 in phagocytosis (Gorgani et al, 2011;Broadley et al, 2016;Zeng et al, 2016;Nagre et al, 2018), although several recent studies have found that VSIG4 is associated with tumour progression (Liao et al, 2014;Xu et al, 2015;Byun et al, 2017). Normally, VSIG4 is expressed on resting macrophages and expression is lost upon activation, and VSIG4 hi macrophages plays an anti-inflammatory and immunosuppressive role in vivo (Vogt et al, 2006;Irvine et al, 2016).…”

TRIM72 promotes alveolar epithelial cell membrane repair and ameliorates lung fibrosis

“…4c-d), suggesting improved membrane repair. Next, we crossed the inducible T72OE [11,44] male with the Sftpc-eGFP knock-in female [31] to establish the sftpc-EGFP/WT and Sftpc-EGFP/T72 OE mice. Flow cytometry sorting of eGFP positive cells was used to isolate primary ATII cells from these mice ( Fig.…”

Alveolar Macrophage Phagocytosis and Bacteria Clearance in Mice

“…( D ) Statistics of flow cytometry MFI and the percentage of FITC + cells in WT and TRIM72 KO AMs; n = 3 for both groups, * p < 0.05. This figure is reprinted with permission of the American Thoracic Society 13 .…”

“…For the latter, AMs can recognize the targets opsonized with immunoglobulin (IgG) through their Fcγ receptors (FcγR) or the pathogens coated with complement fragments, C3b and C3bi, through their complement receptors (CR) 11 . Among complement receptors, the CR of the immunoglobulin superfamily (CRIg) is selectively expressed in tissue macrophages 12 , and a recent finding highlighted the role of the CRIg in AM phagocytosis in the context of P. aeruginosa pneumonia 13 .…”