Importance of muscle-specific E3 ligase TRIM55 in autoimmune myocarditis

The National Heart, Lung, and Blood Institute awarded The Methodist Hospital Research Institute $755,573 on August 21, 2026, under the Cardiovascular Diseases Research program (CFDA 93.837) to investigate the role of the muscle-specific E3 ligase TRIM55 in autoimmune myocarditis pathogenesis.

The research uses monogenic autoimmune myocarditis models based on TREX1 deficiency to examine how innate immune responses shape disease development. The work combines in vitro studies using human fibroblasts from Aicardi-Goutieres syndrome patients carrying TREX1R114H/R114H mutations—which exhibit elevated type I interferon production—with in vivo studies using TREX1-deficient mice that spontaneously develop autoimmune myocarditis. Through small-interfering RNA screening, the research identified TRIM55 as a critical driver of the disease cascade; TRIM55 knockout in TREX1-deficient mice completely rescued lethal autoimmune myocarditis phenotypes, including reduced cardiac inflammation, autoantibody production, and mortality. The study also examines spermine metabolism and its relationship to cytosolic mitochondrial DNA and cell death in cardiomyocytes as mechanisms underlying TRIM55-driven pathogenesis.

Performance occurs in Houston, Texas, with work concluding May 31, 2030. This is a Project Grant, an assistance type supporting investigator-initiated research under the NHLBI's competitive research funding program.

Abstract

Autoimmune myocarditis (am) is a severe inflammatory heart disease driven by autoimmune processes, often leading to heart failure and sudden death. While adaptive immune responses are implicated in am development, the role of early innate immune responses in shaping am pathogenesis remains poorly understood. To address this GAP, we established monogenic am models based on the 3'-to-5' DNA exonuclease TREX1. These models include human fibroblasts from aicardi-goutières syndrome patients with am harboring TREX1R114H/R114H mutation (TREX1R114H/R114H fibroblasts, which exhibit elevated type i interferon (IFN-i) IFN-α, a key autoimmunity trigger) as an in vitro am model, and TREX1-deficiency (TREX1-/-) mice (which spontaneously develop am) as an in vivo am mouse model. Through small-interfering RNA screen targeting genes regulating IFN-α production in TREX1R114H/R114H fibroblasts, we found knockdown of tripartite motif-containing 55 (TRIM55), a muscle-specific ring finger E3 ligase, resulted in nearly undetectable IFN-α production. TRIM55 is highly expressed in cardiac myocyte and fibroblasts but minimally detected in innate and adaptive immune cells under normal conditions. Remarkably, minimal IFN-α treatment induces significant TRIM55 upregulation in dendritic cells (DC). TRIM55 knockout in TREX1-/- mice completely rescued lethal am phenotypes, including reduced cardiac inflammation, autoantibody production, and mortality, highlignting TRIM55's crucial role in driving am pathogenesis. Spermine and its metabolism are important for DNA-mediated IFN-i production and restraining cytokine-mediated autoimmunity. Importantly, TRIM55 knockout reduced cytosolic mitochondrial DNA (mtdna), z-form DNA, and cell death in cardiomyocytes while restoring intracellular spermine levels in fibroblasts. Based on these findings, we hypothesize that TRIM55 drives a pathogenic cascade by promoting cytosolic DNA-mediated cell death and spermine metabolism in cardiomyocytes (CM) and cardiac fibroblasts (CF), facilitating the release of autoantigens and cytokines (e.g., IFN-α) that induce TRIM55 expression in DC, where IT regulates DC-intrinsic functions to activate pathogenic adaptive immunity, driving am pathogenesis. We proposed 3 aims in this proposal to test this hypothesis. Aim 1 is to elucidate the mechanisms by which TRIM55 mediates cytosolic DNA- induced cell death and autoantigen release in CM to drive am pathogenesis. Aim 2 is to determine how TRIM55 governs spermine-mediated IFN-i signaling and mtdna-triggered integrated stress response signaling in CF to promote am pathogenesis. Aim 3 is to investigate how TRIM55 functions as a molecular switch to regulate DC-intrinsic mechanisms driving am pathogenesis. We believe that the proposed studies will uncover new insights and open new therapeutic opportunities in am and related cardiovascular diseases. The in vitro and in vivo am models, tools, and cutting-edge approaches developed in our lab put US in a unique position to carry out the proposed studies and advance the cardiovascular field.