Abstract 843: Non-oxidized Protein Kinase G 1 Alpha Antagonizes mTORC1 Signaling in a Tuberin-dependent Manner to Ameliorate Cardiac Disease

Abstract

Rationale: Protein kinase G 1α (PKG1α) confers anti-hypertrophic effects in hearts subjected to mechanical and neurohumoral stress. Human heart failure with a reduced ejection fraction (HFrEF) and mouse pressure overloaded hearts present with increased mechanistic target of rapamycin complex 1 (mTORC1) activity, protein aggregation, oxidative stress, and, as we previously described, increased PKG1α disulfide dimer formation indicative of PKG1α oxidation. Recently we demonstrated that stimulation of PKG1α phosphorylates tuberin (TSC2) at one specific serine, S1365, to inhibit mTORC1 signaling and attenuate pathological hypertrophy. Objective: To determine if the redox state of PKG1α impacts its ability to target TSC2 signaling in a chronic pressure-overload mouse model exhibiting pathologic hypertrophy. We hypothesize non-oxidized PKG1α will increase TSC2 S1365 phosphorylation to antagonize mTORC1 signaling, thereby enhancing autophagic flux to clear protein aggregates, culminating in ameliorated cardiac disease. Methods and Results: Mice expressing a non-oxidizable (redox-dead) PKG1α (cysteine 42 serine, CS) knock-in mutation and wild type (WT) littermate controls were subjected cardiac pressure overload stress via transaortic constriction (TAC) or sham surgeries. Following TAC, PKG1α CS mice exhibited reduced mTORC1 activation leading to increased autophagic flux and preventing protein aggregation, compared to WT mice. PKG1α CS TAC mice had decreased expression of the hypertrophic genes, attenuated cardiac hypertrophy (p<0.0001), and improve fractional shortening compared to WT TAC mice (28.14%±10.82 in WT vs. 47.42%±15.62 in CS; p<0.01). Treating WT TAC mice with an mTORC1 inhibitor (everolimus) abrogated mTORC1 hyperactivation, which lead to enhanced autophagic flux, attenuated hypertrophy, and improved cardiac function. Crossing PKG1α CS mice with TSC2 S1365 phospho-null mice resulted in increased cardiac hypertrophy and reduced lifespan (p<0.05). Conclusions: Preventing PKG1α oxidation attenuates mTORC1 activation to enhance autophagic flux, prevent protein aggregation, and ameliorate pathological hypertrophy in following cardiac pressure overload, dependent onTSC2 S1365 phosphorylation.