Abstract 18976: Protein Kinase G is a Redox Sensor That Controls Autophagic Flux by Phosphorylating Tuberin
Pathological cardiac hypertrophy requires an imbalance that favors protein synthesis over its degradation, the latter being prominently controlled by autophagy. Both changes are induced by mechanistic target of rapamycin (mTOR) signaling. Protein kinase G-1α (PKG1α) counters hypertrophy by suppressing multiple hypertrophic stimulation pathways. Here, we reveal PKG1α also increases autophagy in a redox sensitive manner. Both humans with heart failure and mice subjected to chronic pressure-overload display increased mTOR activity including phosphorylation of Unc-51-like kinase 1 (Ulk-1) that reduces autophagy. PKG1α activated autophagic flux in an Ulk-1-dependent manner, by phosphorylating the mTOR regulator tuberin (TSC2) at a novel Ser-1343 to reduce mTOR activation. Cardiomyocytes expressing a phospho-silenced (S1343A) TSC2 have enhanced mTOR activity and hypertrophy, reduced autophagy, and are insensitive to PKG1α. Cells expressing a phospho-mimetic S1343E TSC2 replicate PKG1α effects. TSC2 S1343A (SA) knock-in mice have normal basal function, but develop early mortality and cardiac failure when exposed to pressure overload, accompanied by increased mTOR activity and reduced autophagy. PKG1α modulation of autophagy in stressed hearts is suppressed when the kinase becomes oxidized at Cys42, whereas mice expressing a redox dead PKG1α (C42S-knock-in) display less mTOR activity and more autophagic flux at rest and with stress, and are better protected against pressure-overload. These results reveal PKG1α as a potent redox-sensitive regulator of autophagy through its modulation of TSC2 and thereby mTOR.
Author Disclosures: M.J. Ranek: None. K.M. Kokkonen: None. R.J. Holewinski: None. D.I. Lee: None. T. Nakamura: None. G. Zhu: None. M. Sasaki: None. J.E. Van Eyk: None. D.A. Kass: None.
- © 2016 by American Heart Association, Inc.