Concanavalin A/IFN-Gamma Triggers Autophagy-Related Necrotic Hepatocyte Death through IRGM1-Mediated Lysosomal Membrane Disruption

Abstract

Interferon-gamma (IFN-γ), a potent Th1 cytokine with multiple biological functions, can induce autophagy to enhance the clearance of the invading microorganism or cause cell death. We have reported that Concanavalin A (Con A) can cause autophagic cell death in hepatocytes and induce both T cell-dependent and -independent acute hepatitis in immunocompetent and immunodeficient mice, respectively. Although IFN-γ is known to enhance liver injury in Con A-induced hepatitis, its role in autophagy-related hepatocyte death is not clear. In this study we report that IFN-γ can enhance Con A-induced autophagic flux and cell death in hepatoma cell lines. A necrotic cell death with increased lysosomal membrane permeabilization (LMP) is observed in Con A-treated hepatoma cells in the presence of IFN-γ. Cathepsin B and L were released from lysosomes to cause cell death. Furthermore, IFN-γ induces immunity related GTPase family M member 1(IRGM1) translocation to lysosomes and prolongs its activity in Con A-treated hepatoma cells. Knockdown of IRGM1 inhibits the IFN-γ/Con A-induced LMP change and cell death. Furthermore, IFN-γ−/− mice are resistant to Con A-induced autophagy-associated necrotic hepatocyte death. We conclude that IFN-γ enhances Con A-induced autophagic flux and causes an IRGM1-dependent lysosome-mediated necrotic cell death in hepatocytes.

Irgm1-deficient mice exhibit Paneth cell abnormalities and increased susceptibility to acute intestinal inflammation

“…In WT fibroblasts, Irgm1 localized strongly to the surface of mitochondria in punctate concentrations (Fig. 7D), as reported previously by others (13). Similar to Irgm1 KO enterocytes, we found a much higher percentage of fused/tubular mitochondrial morphologies in Irgm1 KO fibroblasts (Fig.…”

Irgm1 (LRG-47), a Regulator of Cell-Autonomous Immunity, Does Not Localize to Mycobacterial or Listerial Phagosomes in IFN-γ–Induced Mouse Cells

“…Two further rabbit polyclonal antibodies from Abcam plc (ab69464 and ab69465) were produced by immunisation with a peptide from the human homologue IRGM and were described as cross-reactive on mouse IRGM proteins (e.g. used to detect Irgm1 in (41)). We have now also produced two new reagents against the N-terminal peptide of the short isoform, MAETHYAPLSSAFPC (residues 17-31), in rabbit (rbMAE15) and in chicken (chMAE15).…”

“…Endogenous, interferon-induced mouse Irgm1 has been reported to be associated with mitochondria in RAW264.7 (30) and ML-1 4a hepatoma cells (41), using A19 and rabbit anti-human IRGM antisera respectively to detect Irgm1, and cardiolipin or O-N-nonyl acridine orange and Tom40 respectively as mitochondrial markers. A19 is a relatively weak reagent (Supplemental Fig.…”

“…A19 is a relatively weak reagent (Supplemental Fig. 2), and the rabbit anti-human IRGM serum used by Chang and colleagues (41) does not discriminate between Irgm1 and Irgm2 (see Supplemental Fig. 1B).…”

The Role of Autophagy in Immunity and Autoimmune Diseases / Uloga Autofagije U Imunskom Odgovoru I Autoimunskim Bolestima

“…Consequently, the mitochondrial membrane permeability is altered, and autophagy is activated, leading to lysosomal degradation of the affected mitochondria and caspase-independent cell death (80). Chang et al reported that IFN-γ, a potent Th1 cytokine, enhances autophagic flux and causes necrotic-type cell death in Con A-treated hepatocytes (81). The same group showed that the liver's blood vessels are the first target in both T cell-independent and T cell-dependent hepatitis.…”