FGF13 Regulates Myocardial Ischemia-Reperfusion Injury via PGRN Glycosylation

BACKGROUND: Macrophage polarization and complement activation play a pivotal role in the pathogenesis of myocardial ischemia-reperfusion (I/R) injury. FGF13 (fibroblast growth factor 13) is a critical regulator of cardiac homeostasis. However, the role and mechanism of FGF13 in myocardial I/R injury remain unclear. METHODS: FGF13 expression was detected in cardiomyocytes after hypoxia/reoxygenation and in hearts subjected to myocardial I/R. Cardiomyocyte-specific FGF13 knockout and adeno-associated virus serotype 9-mediated overexpression mice were generated. Transcriptomic and proteomic analyses identified key downstream mechanisms. Immunoprecipitation-mass spectrometry, co-immunoprecipitation, and glycoproteomics identified PGRN (progranulin) as an FGF13-interacting protein and mapped its glycosylation site. Mechanistic studies were performed using Transwell cocultures of neonatal mouse cardiomyocytes and bone marrow-derived macrophages, together with molecular and biochemical approaches. Virtual screening and molecular dynamics simulations identified a small-molecule FGF13 inhibitor. RESULTS: FGF13 was upregulated in cardiomyocytes after myocardial I/R. Cardiomyocyte-specific FGF13 knockout alleviated, whereas overexpression exacerbated, cardiac dysfunction and myocardial injury after I/R. Mechanistically, FGF13, through its asparagine 121 residue, competitively occupied the asparagine 263 glycosylation site of PGRN, sterically preventing STT3A (STT3 oligosaccharyltransferase complex catalytic subunit A)-mediated glycosylation of asparagine 263 and suppressing PGRN secretion. FGF13 depletion restored PGRN glycosylation and secretion, which activated macrophage TNFR2/PI3K/AKT (tumor necrosis factor receptor 2/phosphoinositide 3-kinase/protein kinase B) signaling in a paracrine manner, promoted M2 polarization while suppressing M1 polarization, and inhibited complement activation and inflammation. The small-molecule FGF13 inhibitor CWD8 (1-[2-amino-2-methylpropyl]-5,5-dimethylpiperidin-3-ol) also attenuated myocardial I/R injury. CONCLUSIONS: Our findings highlight the critical role of FGF13 in myocardial I/R injury and reveal a competitive mechanism by which FGF13 hinders STT3A-mediated PGRN glycosylation. We identify the PGRN glycosylation-PI3K/AKT axis as the key downstream pathway mediating FGF13-regulated macrophage polarization and complement activation, suggesting that small-molecule FGF13 inhibitors may represent a promising therapeutic strategy for myocardial I/R injury.