Znrf2-mediated ST2L degradation limits IL-33/ST2L anti-fibrotic signaling and promotes post-infarction cardiac fibrosis.

Myocardial infarction (MI) remains a major cause of heart failure, largely driven by maladaptive ventricular remodeling and excessive cardiac fibrosis. The IL-33/ST2L axis exerts cardioprotective and anti-fibrotic effects, but how the availability of the membrane receptor ST2L is controlled under stress conditions remains incompletely understood. Here, we investigated whether ubiquitin-proteasome-dependent turnover of ST2L, mediated by the E3 ligase Znrf2, constrains IL-33/ST2L signaling and promotes post-MI fibrosis. Using neonatal mouse cardiac fibroblasts, cycloheximide chase and pharmacological inhibition experiments revealed that ST2L is a short-lived protein degraded predominantly through the proteasome rather than the lysosome. IL-33 stimulation enhanced ST2L internalization and induced robust polyubiquitination, thereby accelerating proteasomal degradation. Candidate screening and gain-of-function analyses identified Znrf2 as a functional E3 ligase-associated regulator of ST2L turnover: Znrf2 overexpression selectively reduced ST2L, but not sST2, in a dose-dependent manner, whereas proteasome inhibition stabilized ST2L. Mapping experiments showed that the Znrf2 zinc-finger domain recognizes a 306-315 amino acid motif in ST2L, and deletion of this motif rendered ST2L resistant to Znrf2-induced degradation. In a mouse MI model, Znrf2 expression was upregulated in the infarcted myocardium, accompanied by increased collagen deposition. Systemic administration of the proteasome inhibitor MG-132 or cardiac-specific Znrf2 knockdown preserved ST2L, particularly at the plasma membrane, attenuated myocardial fibrosis, and improved echocardiographic indices of left ventricular function. Importantly, AAV9-mediated silencing of ST2L blunted the anti-fibrotic and functional benefits of MG-132 and Znrf2 knockdown, indicating that these interventions act, at least in part, through ST2L. Collectively, our data identify Znrf2-dependent ST2L ubiquitination and proteasomal degradation as a negative regulatory mechanism that limits IL-33/ST2L cardioprotection after MI. Targeting the Znrf2-ST2L axis to preserve functional ST2L may represent a promising strategy to restrain post-infarction cardiac fibrosis and remodeling.