Chaperone‐Mediated Autophagic Degradation of USP9X in Macrophages Exacerbates Postmyocardial Infarction Inflammation and Cardiac Dysfunction

Excessive macrophage-mediated inflammation following myocardial infarction (MI) exacerbates infarct expansion and impairs cardiac repair; however, the regulatory mechanisms remain poorly understood. Here, it is reported that ubiquitin-specific peptidase 9 X-linked (USP9X) was significantly downregulated in macrophages during early post-MI inflammation. Macrophage-specific deficiency of USP9X enhanced expression of pro-inflammatory genes, thereby impeding cardiac functional recovery. Mechanistically, USP9X deubiquitinated and stabilized tumor necrosis factor receptor-associated factor (TRAF)-type zinc finger domain containing 1 (TRAFD1), a negative regulator of Toll-like receptor (TLR) signaling, thereby restraining inflammatory responses. Moreover, inflammatory stimuli triggered acetylation of USP9X at K2414, exposing a latent KFERQ motif that promoted its recognition by the molecular chaperone heat shock cognate protein 70 (HSC70) and facilitated subsequent lysosomal degradation via chaperone-mediated autophagy (CMA). Consistently, both genetic inhibition of HSC70 and pharmacological blockade of lysosomal degradation prevented USP9X degradation following inflammatory stimulation. Furthermore, a cell-penetrating peptide mimicking the KFERQ sequence of USP9X that blocked its interaction with HSC70 and the subsequent CMA-mediated degradation, thereby promoting inflammation resolution and cardiac repair post-MI. Collectively, these findings establish the USP9X-TRAFD1 axis and its CMA-mediated degradation as critical checkpoints in post-MI inflammation, highlighting USP9X stabilization as a therapeutic strategy for ischemic heart disease.