GCN5L1 Depletion Promotes Left Ventricular Fibrosis in Failing Hearts via Upregulation of RAB7A

Pathologic cardiac fibrosis is one of the key determinants of adverse remodeling and progression to heart failure. Although GCN5-like 1 (GCN5L1) is documented to regulate cardiac metabolic homeostasis, its role in myocardial remodeling and fibrosis is unknown. In a murine transverse aortic constriction (TAC) pressure overload model, GCN5L1 protein abundance was significantly reduced in the left ventricular (LV) tissues from wild type (WT) mice. This finding was concurrent with increased collagen 1α1 expression in the same tissues. Interestingly, LVs from cardiomyocyte-specific GCN5L1 knockout (GCN5L1 cKO) mice showed exacerbated TAC-induced collagen 1α1 expression among profibrotic genes identified by bulk RNA sequencing, when compared with corresponding WT mice. These finding are consistent with our previous report of increased fibrotic tissue and decreased fractional shortening (a marker of contractile function) in GCN5L1 cKO mice under TAC stress. Consistently, analysis of human hearts with heart failure with reduced ejection fraction demonstrated reduced GCN5L1 expression accompanied by increased collagen 1α1, revealing a conserved inverse relationship. In vitro, we further demonstrate that conditioned media collected from GCN5L1-depleted AC16 human ventricular cardiomyocyte–like cells induced upregulation of collagen 1α1 expression in human cardiac fibroblasts. Proteomic profiling of WT and GCN5L1 cKO cardiac tissues aligned with our in vitro findings in WT and GCN5L1 knockout (KO) mouse embryonic fibroblasts, revealing increased expression of lysosomal, endo-lysosomal, and autophagy markers (including RAB7A) in response to GCN5L1 deficiency. In vivo, RAB7A protein was increased following TAC, which was exacerbated in GCN5L1-deficient hearts under the same conditions. Furthermore, in human ventricular fibroblasts, TGF-β1 stimulated RAB7A and collagen 1α1 expression. Importantly, RAB7A knockdown attenuated TGF-β1–induced collagen 1α1, whereas GCN5L1 knockdown altered expression of fibrosis related markers and increased RAB7A without directly altering collagen expression. Collectively, these findings identify GCN5L1 as a negative regulator of pressure overload–induced cardiac fibrosis, and implicate a GCN5L1– RAB7A axis linking lysosomal pathways to collagen deposition in ventricular remodeling. These findings highlight a potential therapeutic target to attenuate LV fibrosis.