Mitochondrial bioenergetics is crucial for cell survival and death. The bioenergetic maintenance primarily depends on the integrity of mitochondrial membranes. The impermeable nature of the mitochondrial inner membrane sets the stage for redox reactions to generate ATP. Mitochondria also participate in cytosolic Ca2+ phenotype via rapid Ca2+ buffering. There are two sides to the effects of Ca2+ on mitochondrial function. Under physiological conditions, Ca2+ is beneficial for mitochondrial function to stimulate oxidation-phosphorylation and ATP synthesis. It is questionable whether these effects remain the same under pathological conditions when mitochondrial Ca2+ ([Ca2+]m) overload occurs. While [Ca2+]m signaling is crucial for both physiological and pathological processes, molecules that facilitate [Ca2+]m uptake remain unclear. [Ca2+]m buffering is exquisitely controlled by inner mitochondrial membrane transporters, exchangers and uniporter. Several proteins have been implicated to participate in [Ca2+]m uptake, including LETM1, MICU1 and MCU. Our targeted RNAi screen identified a mitochondrial inner membrane protein, Mitochondrial Ca2+ Uniporter Regulator 1 (MCUR1) that augments [Ca2+]m uptake. MCUR1 silencing abrogates [Ca2+]m uptake under normal mitochondrial membrane potential. Our results demonstrate that MCUR1 interacts with the Ru360 sensitive core component of the mitochondrial uniporter complex, Mitochondrial Ca2+ Uniporter (MCU). Based on our recent discovery, we hypothesize that MCUR1 promotes MCU-dependent [Ca2+]m overload during I/R injury, triggering mitochondrial membrane depolarization, that results in bioenergetic collapse and mitochondrial dysfunction. This proposal applies RNAi technology, mutagenesis of MCUR1 and MCU channel, biochemical, state-of-the-art imaging and an animal model system to understand how MCUR1 elicits cardiomyocyte [Ca2+]m uptake. Based on our recent identification of MCUR1 as a regulator of the uniporter complex, here in Aim 1, we will characterize the MCUR1 role in cardiomyocyte [Ca2+]m uptake, critical regions of MCUR1-MCU interaction and transcriptional regulation of MCUR1.
In Aim 2 we will investigate how MCUR1 controls mitochondrial bioenergetics, ROS production and autophagy. Finally, in Aim 3 we will apply cardiac ischemia/reperfusion in vivo murine model studies to show that knockdown of MCUR1 ameliorates I/R-induced mitochondrial dysfunction and cardiomyocyte damage. Overall, the results of these studies will advance our understanding of how MCU activity is augmented under pathophysiological conditions, and suggest new strategies for controlling [Ca2+]m influx as a new treatment for cardiovascular diseases.

Public Health Relevance

Mitochondrial Ca2+ uptake is essential for bioenergetics, cytoplasmic Ca2+ signals and activation of cell death pathways. By investigating the interaction and functional role of MCUR1, we will learn which cardiomyocyte perturbations are amplified by MCUR1. This characterization of MCUR1, an integral component of the mitochondrial Ca2+ uptake machinery, will provide a new target for regulation of [Ca2+]m uptake in the heart.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL119306-02
Application #
8824559
Study Section
Myocardial Ischemia and Metabolism Study Section (MIM)
Program Officer
Wong, Renee P
Project Start
2014-04-01
Project End
2018-03-31
Budget Start
2015-04-01
Budget End
2016-03-31
Support Year
2
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Temple University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
057123192
City
Philadelphia
State
PA
Country
United States
Zip Code
19122
Nemani, Neeharika; Carvalho, Edmund; Tomar, Dhanendra et al. (2018) MIRO-1 Determines Mitochondrial Shape Transition upon GPCR Activation and Ca2+ Stress. Cell Rep 23:1005-1019
Nemani, Neeharika; Shanmughapriya, Santhanam; Madesh, Muniswamy (2018) Molecular regulation of MCU: Implications in physiology and disease. Cell Calcium 74:86-93
Michael, James V; Wurtzel, Jeremy G T; Mao, Guang Fen et al. (2017) Platelet microparticles infiltrating solid tumors transfer miRNAs that suppress tumor growth. Blood 130:567-580
Dong, Zhiwei; Shanmughapriya, Santhanam; Tomar, Dhanendra et al. (2017) Mitochondrial Ca2+Uniporter Is a Mitochondrial Luminal Redox Sensor that Augments MCU Channel Activity. Mol Cell 65:1014-1028.e7
Gupta, Manish K; Kaminski, Rafal; Mullen, Brian et al. (2017) HIV-1 Nef-induced cardiotoxicity through dysregulation of autophagy. Sci Rep 7:8572
Joseph, Leroy C; Kokkinaki, Dimitra; Valenti, Mesele-Christina et al. (2017) Inhibition of NADPH oxidase 2 (NOX2) prevents sepsis-induced cardiomyopathy by improving calcium handling and mitochondrial function. JCI Insight 2:
Bao, Lei; Chen, Shu-Jen; Conrad, Kathleen et al. (2016) Depletion of the Human Ion Channel TRPM2 in Neuroblastoma Demonstrates Its Key Role in Cell Survival through Modulation of Mitochondrial Reactive Oxygen Species and Bioenergetics. J Biol Chem 291:24449-24464
Scheitlin, Christopher G; Julian, Justin A; Shanmughapriya, Santhanam et al. (2016) Endothelial mitochondria regulate the intracellular Ca2+ response to fluid shear stress. Am J Physiol Cell Physiol 310:C479-90
Tomar, Dhanendra; Dong, Zhiwei; Shanmughapriya, Santhanam et al. (2016) MCUR1 Is a Scaffold Factor for the MCU Complex Function and Promotes Mitochondrial Bioenergetics. Cell Rep 15:1673-85
Lee, Samuel K; Shanmughapriya, Santhanam; Mok, Mac C Y et al. (2016) Structural Insights into Mitochondrial Calcium Uniporter Regulation by Divalent Cations. Cell Chem Biol 23:1157-1169

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