The overall aim of this project is to uncover the role of the mTOR (mammalian target of rapamycin) pathway and its relationship to p53 during normal and heart failure (HF) conditions. Myocardial mTOR activity, while increased in the early phases of pressure overload hypertrophy, eventually decreases when compensated hypertrophy switches to decompensation, ending in frank HF. We hypothesized therefore that mTOR and its downstream substrates are central in this process. For proving this, we therefore generated an inducible and cardiac-specific mouse model defective in mTOR (mTOR-cKO). We found that upon loss of mTOR, mice developed dilated heart phenotype that progressed rapidly to death. Markers of autophagy and apoptosis increased significantly;importantly, the tumor suppressor gene p53 significantly accumulated in the heart of mTOR KO mice;moreover, there was a remarkable myocardial accumulation of active 4E-BP1, a downstream member of the mTOR pathway which negatively controls mRNA translation in its dephosphorylated form and a major substrate of TORC-1, one of the two mTOR kinase multiprotein complexes. We found that acumulation of dephosphorylated 4E-BP1 is a feature of HF of diverse etiologies, and thus might represent a common mechanism underlying this state. We also found that deleting 4E-BP1 in mice determines a very significant improvement of cardiac function and survival in the context of cardiac mTOR KO. In other cellular systems, 4E-BPs were shown to regulate p53 protein levels.
The specific aims of this project therefore are 1) to determine the relative role of apoptosis and autophagy in mTOR-defective HF and in particular the role of the key gene p53 and 2) determine the role of 4E-BPs in mTOR-dependent HF as well as the reciprocal control between 4E-BPs and p53. These tasks will be accomplished through cross-breeding experiments of mTOR-cKO mice with strains in which Atg5, a gene critical for autophagy, or Nix, a gene critical for apoptosis, are deleted. Also, the role of p53 will be assessed by crossing our model with mice with p53-floxed alleles. Gene expression and proteomic studies will be conducted with the aim to identify genes critical for mTOR-cKO HF. The involvement of 4E-BPs in regulating cardiac function as well as p53 levels will be addressed by crossing mTOR-cKO with double 4E-BP1/4E-BP2 KO mice and by studying the role of p53 in regulating 4E-BP1 expression. Results of our research will assess the relative and reciprocal role of mTOR/4E-BP1 and p53 in controlling cardiac function in the normal and diseased heart, opening the possibility to interfere with these molecules for therapeutic purposes.

Public Health Relevance

Alteration of mTOR signaling may play a very relevant role in the pathogenesis of heart failure and is an important target of anti-cancer treatment. The proposed study will help us ascertain the involvement of mTOR in regulating cardiomyocyte homeostasis and function in normal and diseased myocardium. This project will help the understanding of molecular mechanisms of anti-cancer drug-induced cardiac toxicity and finding new target molecules regulating cardiac function.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL078797-08
Application #
8386980
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Wong, Renee P
Project Start
2004-12-01
Project End
2014-11-30
Budget Start
2012-12-01
Budget End
2013-11-30
Support Year
8
Fiscal Year
2013
Total Cost
$359,916
Indirect Cost
$121,916
Name
University of California San Diego
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Lim, Byung-Kwan; Peter, Angela K; Xiong, Dingding et al. (2013) Inhibition of Coxsackievirus-associated dystrophin cleavage prevents cardiomyopathy. J Clin Invest 123:5146-51
Sciarretta, Sebastiano; Zhai, Peiyong; Shao, Dan et al. (2012) Rheb is a critical regulator of autophagy during myocardial ischemia: pathophysiological implications in obesity and metabolic syndrome. Circulation 125:1134-46
Zhang, Denghong; Contu, Riccardo; Latronico, Michael V G et al. (2010) MTORC1 regulates cardiac function and myocyte survival through 4E-BP1 inhibition in mice. J Clin Invest 120:2805-16
Catalucci, Daniele; Latronico, Michael V G; Ceci, Marcello et al. (2009) Akt increases sarcoplasmic reticulum Ca2+ cycling by direct phosphorylation of phospholamban at Thr17. J Biol Chem 284:28180-7
Elia, Leonardo; Contu, Riccardo; Quintavalle, Manuela et al. (2009) Reciprocal regulation of microRNA-1 and insulin-like growth factor-1 signal transduction cascade in cardiac and skeletal muscle in physiological and pathological conditions. Circulation 120:2377-85
Catalucci, Daniele; Gallo, Paolo; Condorelli, Gianluigi (2009) MicroRNAs in cardiovascular biology and heart disease. Circ Cardiovasc Genet 2:402-8
Elia, L; Quintavalle, M; Zhang, J et al. (2009) The knockout of miR-143 and -145 alters smooth muscle cell maintenance and vascular homeostasis in mice: correlates with human disease. Cell Death Differ 16:1590-8
Catalucci, Daniele; Zhang, Deng-Hong; DeSantiago, Jaime et al. (2009) Akt regulates L-type Ca2+ channel activity by modulating Cavalpha1 protein stability. J Cell Biol 184:923-33
Catalucci, Daniele; Latronico, Michael V G; Ellingsen, Oyvind et al. (2008) Physiological myocardial hypertrophy: how and why? Front Biosci 13:312-24
Kemi, Ole Johan; Ceci, Marcello; Condorelli, Gianluigi et al. (2008) Myocardial sarcoplasmic reticulum Ca2+ ATPase function is increased by aerobic interval training. Eur J Cardiovasc Prev Rehabil 15:145-8

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