G3BP1 Succinylation at K413 is Critical for Cardiac Function by Modulating PI3K‐AKT‐mTOR Signal Axis

ABSTRACT G3BP1, GTPase activating protein (SH3 domain) binding protein 1, is a core component of stress granules. Homozygous null mutations in the G3bp1 gene result in embryonic lethality, underscoring its essential role in development. While various post‐translational modifications regulate G3BP1 activity, here we first report that G3BP1 undergoes succinylation (Suc) at Lys (K)411 in mouse hearts (corresponding to human K413). G3BP1‐Suc level was diminished in Myosin binding protein C3 (Mybpc3) knockout and transverse aortic constriction (TAC) operated mice, which developed heart failure (HF). Site‐directed mutagenesis confirmed that the K413R mutation compromised the overall Suc level of G3BP1 in vitro. Mice injected with AAV9‐G3BP1 (WT) developed typical phenotypes of dilated cardiomyopathy (DCM) and HF when compared to mice injected with AAV9‐Ctrl and ‐G3BP1 (K411R) mice, suggesting a possible loss of functional effect of de‐Suc at K411. Moreover, Homozygous knock‐in G3bp1 (K411R) mice exhibited compromised cardiac parameters compared to WT littermates. De novo G3BP1 mutation (p.E411G) from a DCM patient disrupts Suc at K413. Mechanistically, G3BP1 de‐Suc at K413 induced Rraga expression and impaired TSC1/2 and IDE binding, ultimately leading to excessive activation of the PI3K‐AKT‐mTOR signaling axis. We demonstrate a critical role for G3BP1 Suc at K413 in cardiac function by modulating the PI3K‐AKT‐mTOR pathway, providing new insights into the non‐canonical function of G3BP1 in cardiomyopathy and HF pathogenesis.