Abstract P2002: Mst1 Suppresses Pressure Overload-induced Cardiac Hypertrophy But Reduces Cardiac Function Through PERK Phosphorylation

Abstract

Cardiac hypertrophy in response to hemodynamic overload is initially an adaptive mechanism to maintain normal cardiac function by reducing left ventricular (LV) wall stress. Conversely, insufficient hypertrophy could lead to elevated wall stress, causing increased cell death and cardiac dysfunction. The Hippo pathway plays an important role in determining organ size. Mammalian sterile 20-like kinase 1 (Mst1) is the key serine-threonine kinase in the Hippo pathway, controlling cell death, proliferation, and differentiation. Mice with cardiac-specific overexpression of Mst1 (Tg-Mst1) fail to develop compensatory hypertrophy despite LV dysfunction and dilation at baseline. To elucidate the mechanism through which Mst1 inhibits cardiac hypertrophy, pressure overload (PO) was imposed on WT and Tg-Mst1 mice by transverse aortic constriction (TAC). TAC-induced increases in LV weight/body weight were significantly suppressed in Tg-Mst1 mice (5.8 vs WT 5.1, p<0.05). LV ejection fraction (EF) after TAC was lower in Tg-Mst1 mice than in WT mice (40% vs WT 60%, p<0.01), consistent with the notion that Mst1 promotes PO-induced systolic dysfunction in part by inhibiting compensatory hypertrophy. Mst1 interacted with and induced phosphorylation of protein kinase RNA-like endoplasmic reticulum kinase (PERK). We generated knock-in mice expressing phosphorylation-resistant PERK (PERK-KI) and performed TAC on WT and PERK-KI mice. LVEF was preserved in PERK-KI mice compared to in WT mice (67% vs WT 46%, p<0.05) after 8 weeks of TAC. PO-induced increases in lung congestion were attenuated in PERK-KI mice compared to in WT mice (10 vs WT 11.5, p<0.05). Despite the improvement in cardiac function, cardiac hypertrophy was not attenuated in PERK-KI mice. These results suggest that phosphorylation of PERK by Mst1 is detrimental for the heart during PO, in part due to suppression of compensatory hypertrophy.