Abstract 92: The Mitochondrial Calcium Uniporter is Necessary for Metabolic Matching of Contractile Demand During Acute Sympathetic Stress

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Timothy S Luongo ◽  
Jonathan P Lambert ◽  
Ancai Yuan ◽  
Xueqian Zhang ◽  
Santhanam Shanmughapriya ◽  
...  
Keyword(s):  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uniporter ◽  
Adult Mice ◽  
Calcium Uniporter ◽  
Myocardial Ischemia Reperfusion ◽  
Sympathetic Stress

Contractility is mediated by a variable flux in intracellular calcium (Ca 2+ ), which is proposed to be integrated into mitochondria to regulate cardiac energetics. Moreover, m Ca 2+ -overload is known to activate the mitochondrial permeability transition pore (MPTP) and induce cell death. Recent studies have reported that the Mcu gene encodes the channel-forming portion of the mitochondrial calcium uniporter (MCU) and is required for m Ca 2+ uptake. To examine the role of m Ca 2+ in the heart, we generated a conditional, cardiac-specific knockout model and deleted Mcu in adult mice ( Mcu-cKO ). Loss of Mcu protected against myocardial ischemia-reperfusion (IR) injury by preventing the activation of the MPTP. In addition while we found no baseline phenotype, Mcu -cKO mice lacked contractile responsiveness to beta-adrenergic receptor stimulation as assessed by invasive hemodynamics (Fig 1) and in parallel were unable to activate mitochondrial dehydrogenases and increase cardiac NADH levels. Further experimental analyses in isolated adult cardiomyocytes confirmed a lack of energetic responsiveness to acute sympathetic stress (isoproterenol failure to mediate an increase in NADH, Fig 2), supporting the hypothesis that the physiological function of the MCU in the heart is to modulate Ca 2+ -dependent metabolism during the ‘fight or flight’ response.

Abstract 435: The Mitochondrial Calcium Uniporter is Necessary for Cardiac Energetic Signaling During Chronic Stress

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Timothy S Luongo ◽  
John W Elrod
Keyword(s):  
Chronic Stress ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Cardiac Contractility ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter ◽  
Stress States

The mitochondrial calcium uniporter (MCU) is a multicomponent channel that is the primary mechanism for mitochondrial Ca 2+ uptake ( m Ca 2+ ). We previously reported that the MCU is required for energetic signaling to meet contractile demand during the ‘fight or flight’ response. In addition, we showed that deletion of the pore-forming component ( Mcu gene) protected against mitochondria permeability transition pore (MPTP) opening and ischemia-reperfusion injury. However, results from our study and others questioned the physiological relevance of MCU-mediated Ca 2+ uptake during chronic stress states featuring sustained intracellular Ca 2+ load ( i Ca 2+ ). To address this, we deleted Mcu from cardiomyocytes in adult mice ( Mcu cKO) and implanted osmotic pumps to deliver the β adrenergic agonist isoproterenol (iso, 70 mg/kg/day for 14d). In contrast to controls, Mcu cKO mice lacked contractile responsiveness to chronic βAR stimulation with evidence of LV dysfunction and failure by d14 ( Fig 1 ). Next, we crossed the Mcu cKO with mice overexpressing the β2a subunit (β2a-Tg) of the L-type Ca 2+ channel (LTCC). This model displays enhanced LTCC activity and cardiac contractility, but with added stress such as iso infusion, Ca 2+ overload eventually leads to MPTP-dependent cell death and heart failure. Surprisingly, loss of Mcu in this model was lethal with all mice dying by d13 ( Fig 2 ). Baseline echocardiography revealed that loss of Mcu ablated all β2a-mediated enhancements in LV contractility and accelerated dysfunction post-iso. These findings demonstrate that MCU-mediated m Ca 2+ uptake is critical to meet energetic demand during chronic stress states featuring sustained i Ca 2+ load.

Abstract MP124: De-palmitoylation of Cysteine 202 of Cyclophilin-D by Calcium is Important for the Activation of the Permeability Transition Pore

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Georgios Amanakis ◽  
Junhui Sun ◽  
Maria Fergusson ◽  
Chengyu Liu ◽  
Jeff D Molkentin ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Cyclophilin D ◽  
Perfused Heart ◽  
Knock Out

Cyclophilin-D (CypD) is a well-known regulator of the mitochondrial permeability transition pore (PTP), the main effector of cardiac ischemia/reperfusion (I/R) injury characterized by oxidative stress and calcium overload. However, the mechanism by which CypD activates PTP is poorly understood. Cysteine 202 of CypD (C202) is highly conserved across species and can undergo redox-sensitive post-translational modifications, such as S-nitrosylation and oxidation. To study the importance of C202, we developed a knock-in mouse model using CRISPR where CypD-C202 was mutated to a serine (C202S). Hearts from these mice are protected against I/R injury. We found C202 to be abundantly S-palmitoylated under baseline conditions while C202 was de-palmitoylated during ischemia in WT hearts. To further investigate the mechanism of de-palmitoylation during ischemia, we considered the increase of matrix calcium, oxidative stress and uncoupling of ATP synthesis from the electron transport chain. We tested the effects of these conditions on the palmitoylation of CypD in isolated cardiac mitochondria. The palmitoylation of CypD was assessed using a resin-assisted capture (Acyl-RAC). We report that oxidative stress (phenylarsenide) and uncoupling (CCCP) had no effect on CypD palmitoylation (p>0.05, n=3 and n=7 respectively). However, calcium overload led to de-palmitoylation of CypD to the level observed at the end ischemia (1±0.10 vs 0.63±0.09, p=0.012, n=9). To further test the hypothesis that calcium regulates S-palmitoylation of CypD we measured S-palmitoylation of CypD in non-perfused heart lysates from global germline mitochondrial calcium uniporter knock-out mice (MCU-KO), which have reduced mitochondrial calcium and we found an increase in S-palmitoylation of CypD (WT 1±0.04 vs MCU-KO 1.603±0.11, p<0.001, n=6). The data are consistent with the hypothesis that C202 is important for the CypD mediated activation of PTP. Ischemia leads to increased matrix calcium which in turn promotes the de-palmitoylation of CypD on C202. The now free C202 can further be oxidized during reperfusion leading to the activation of PTP. Thus, S-palmitoylation and oxidation of CypD-C202 possibly target CypD to the PTP, making them potent regulators of cardiac I/R injury.

scholarly journals Cyclophilin D-mediated regulation of the permeability transition pore is altered in mice lacking the mitochondrial calcium uniporter

2018 ◽  
Vol 115 (2) ◽  
pp. 385-394 ◽  
Author(s):  
Randi J Parks ◽  
Sara Menazza ◽  
Kira M Holmström ◽  
Georgios Amanakis ◽  
Maria Fergusson ◽  
...  
Keyword(s):  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Mitochondrial Calcium ◽  
Cyclophilin D ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter

Abstract 16743: A Kinase Interacting Protein 1 Does Not Protect From Adverse Cardiac Remodelling but Attenuates Myocardial Ischemia - Reperfusion Injury

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Harmen G Booij ◽  
Hongjuan Yu ◽  
Rudolf A de Boer ◽  
Wiek H van Gilst ◽  
Herman H Silljé ◽  
...  
Keyword(s):  
Heart Failure ◽  
Mitochondrial Permeability Transition Pore ◽  
Mitochondrial Permeability Transition ◽  
Ischemia Reperfusion ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Wild Type ◽  
Interacting Protein ◽  
Mitochondrial Permeability ◽  
Myocardial Ischemia Reperfusion

Introduction: A kinase interacting protein 1 (AKIP1) attenuates myocardial ischemia / reperfusion (I/R) injury and stimulates beneficial cardiac remodeling in cultured cardiomyocytes. Whether these findings translate into functional benefits in vivo remains to be established. Hypothesis: We assessed the hypothesis that cardiac overexpression of AKIP1 attenuates myocardial heart failure development or I/R-injury in mice. Methods: We created transgenic mice with cardiac-specific overexpression of AKIP1 (AKIP1-TG). First, AKIP1-TG mice or their wild type littermates were subjected to transverse aortic constriction (TAC) and myocardial infarction (MI) with permanent ligation of the left coronary artery. Second, infarct size after 45 minutes ischemia followed by 24h reperfusion was assessed with Evans Bleu and triphenyltetrazolium chloride staining. Results: AKIP1-TG mice and wild type littermates displayed similar left ventricular remodeling and function after TAC or MI as measured with magnetic resonance imaging. Histological indices of heart failure severity, including cardiomyocyte cross-sectional area, capillary density and fibrosis were also similar. However, infarct size relative to the area at risk was reduced 2-fold in AKIP1-TG mice after I/R (15% ± 3 vs. 29± 4 %, p<0,05) and accompanied with a marked reduction in apoptosis (5,4 ± 0,5% vs. 8,1 ± 1,1%, p<0,05). AKIP1 overexpression did not influence cardiac transcription or signaling. Subcellular fraction studies showed enrichment of AKIP1 in mitochondria. In addition, AKIP1 attenuated calcium induced swelling of mitochondria (0.77 ± 0.01 vs. 0.71 ± 0.01, p<0.05), suggesting a direct role for AKIP1 in the mitochondrial permeability transition pore. Conclusions: In conclusion, AKIP1 does not influence cardiac remodeling in models of chronic heart failure. However, AKIP1 does attenuate myocardial I/R injury through stabilization of the mitochondrial permeability transition pore.

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