Abstract P401: The Anti-arrhythmic Effects Of VDAC Isoforms Are Mediated By Glutamate 73 Through Regulation Of Mitochondrial Calcium Transport

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Lauren Crisman ◽  
Hirohito Shimizu ◽  
Adam Langenbacher ◽  
Jie Huang ◽  
Kevin Wang ◽  
...  
Keyword(s):  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Cellular Processes ◽  
Excess Calcium ◽  
Evolutionarily Conserved ◽  
Mitochondrial Calcium Uptake

Mitochondria critically regulate cellular processes such as bioenergetics, metabolism, calcium homeostasis and apoptosis. VDAC proteins are abundant proteins that control the passage of ions and metabolites across the outer mitochondrial membrane. We have previously shown that activation of VDAC2, is able to buffer excess calcium and thereby suppress calcium overload induced arrhythmogenic events in vitro and in vivo. However, the mechanism by which VDAC2 regulates calcium transport and cardiac contractions remained unclear. It is also unclear whether all three VDAC isoforms (VDAC1,2 and 3) possess similar cardioprotective activity. The zebrafish tremblor/ncx1 mutant lacks functional NCX1 in cardiomyocytes leading to calcium overload, and the manifestation of fibrillation-like phenotypes. Using the tremblor/ncx1 mutant as a model, we observed isoform-specific differences between the VDAC family members. VDAC1 and VDAC2 enhanced mitochondrial calcium trafficking and restore rhythmic contraction in tremblor mutants, whereas, VDAC3 did not. We found that the differing rescue capabilities of VDAC proteins were dependent upon residues in their N-terminal halves. Phylogenetic analysis further revealed the presence of an evolutionarily conserved glutamate at position 73 (E73) within VDAC1 and VDAC2, but a glutamine (Q73) in VDAC3. Excitingly, we showed that replacing VDAC2 E73 with Q73 ablated its calcium transporting activity. Conversely, substituting the Q73 with E73 allows VDAC3 to gain calcium trafficking and cardioprotective abilities. Overall, our study demonstrates an essential role for the evolutionarily conserved glutamate-73 in determining the anti-arrhythmic effect of VDAC isoforms through their regulation of mitochondrial calcium uptake.

scholarly journals ApoE4 (Δ272–299) induces mitochondrial‐associated membrane formation and mitochondrial impairment by enhancing GRP75-modulated mitochondrial calcium overload in neuron

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tao Liang ◽  
Weijian Hang ◽  
Jiehui Chen ◽  
Yue Wu ◽  
Bin Wen ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Er Stress ◽  
Mitochondrial Dysfunction ◽  
Mitochondrial Function ◽  
Calcium Transport ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Mitochondrial Impairment

Abstract Background Apolipoprotein E4 (apoE4) is a major genetic risk factor of Alzheimer’s disease. Its C-terminal-truncated apoE4 (Δ272–299) has neurotoxicity by affecting mitochondrial respiratory function. However, the molecular mechanism(s) underlying the action of apoE4 (Δ272–299) in mitochondrial function remain poorly understood. Methods The impact of neuronal apoE4 (Δ272–299) expression on ER stress, mitochondrial-associated membrane (MAM) formation, GRP75, calcium transport and mitochondrial impairment was determined in vivo and in vitro. Furthermore, the importance of ER stress or GRP75 activity in the apoE4 (Δ272–299)-promoted mitochondrial dysfunction in neuron was investigated. Results Neuronal apoE4 (Δ272–299) expression induced mitochondrial impairment by inducing ER stress and mitochondrial-associated membrane (MAM) formation in vivo and in vitro. Furthermore, apoE4 (Δ272–299) expression promoted GRP75 expression, mitochondrial dysfunction and calcium transport into the mitochondria in neuron, which were significantly mitigated by treatment with PBA (an inhibitor of ER stress), MKT077 (a specific GRP75 inhibitor) or GRP75 silencing. Conclusions ApoE4 (Δ272–299) significantly impaired neuron mitochondrial function by triggering ER stress, up-regulating GRP75 expression to increase MAM formation, and mitochondrial calcium overload. Our findings may provide new insights into the neurotoxicity of apoE4 (Δ272–299) against mitochondrial function and uncover new therapeutic targets for the intervention of Alzheimer’s disease.

scholarly journals Mitochondrial calcium uptake regulates tumour progression in embryonal rhabdomyosarcoma

2021 ◽  
Author(s):  
Reshma Taneja ◽  
Hsin Yao Chiu ◽  
Amos Hong Pheng Loh
Keyword(s):  
Calcium Homeostasis ◽  
Calcium Uptake ◽  
Cellular Proliferation ◽  
Myogenic Differentiation ◽  
Tumour Progression ◽  
Embryonal Rhabdomyosarcoma ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uptake

Embryonal rhabdomyosarcoma (ERMS) is characterized by a failure of cells to complete skeletal muscle differentiation. Although ERMS cells are vulnerable to oxidative stress, the relevance of mitochondrial calcium homeostasis in oncogenesis is unclear. Here, we show that ERMS cell lines as well as primary tumours exhibit elevated expression of the Mitochondrial Calcium Uniporter (MCU). MCU knockdown resulted in impaired mitochondrial calcium uptake and a reduction in mitochondrial reactive oxygen species (mROS) levels. Phenotypically, MCU knockdown cells exhibited reduced cellular proliferation and motility, with an increased propensity to differentiate in vitro and in vivo. RNA-sequencing of MCU knockdown cells revealed a significant reduction in genes involved in TGF? signalling that play prominent roles in oncogenesis and inhibition of myogenic differentiation. Interestingly, modulation of mROS production impacted TGF? signalling. Our study elucidates mechanisms by which mitochondrial calcium dysregulation promotes tumour progression and suggests that targeting the MCU complex to restore mitochondrial calcium homeostasis could be a therapeutic avenue in ERMS.

scholarly journals Overexpression of SERCA2a Alleviates Cardiac Microvascular Ischemic Injury by Suppressing Mfn2-Mediated ER/Mitochondrial Calcium Tethering

2021 ◽  
Vol 9 ◽  
Author(s):  
Feng Tian ◽  
Ying Zhang
Keyword(s):  
Endoplasmic Reticulum ◽  
Infarct Size ◽  
Myocardial Infarct ◽  
Ischemic Injury ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Myocardial Infarct Size ◽  
Hypoxic Injury

Our previous research has shown that type-2a Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2a) undergoes posttranscriptional oxidative modifications in cardiac microvascular endothelial cells (CMECs) in the context of excessive cardiac oxidative injury. However, whether SERCA2a inactivity induces cytosolic Ca2+ imbalance in mitochondrial homeostasis is far from clear. Mitofusin2 (Mfn2) is well known as an important protein involved in endoplasmic reticulum (ER)/mitochondrial Ca2+ tethering and the regulation of mitochondrial quality. Therefore, the aim of our study was to elucidate the specific mechanism of SERCA2a-mediated Ca2+ overload in the mitochondria via Mfn2 tethering and the survival rate of the heart under conditions of cardiac microvascular ischemic injury. In vitro, CMECs extracted from mice were subjected to 6 h of hypoxic injury to mimic ischemic heart injury. C57-WT and Mfn2KO mice were subjected to a 1 h ischemia procedure via ligation of the left anterior descending branch to establish an in vivo cardiac ischemic injury model. TTC staining, immunohistochemistry and echocardiography were used to assess the myocardial infarct size, microvascular damage, and heart function. In vitro, ischemic injury induced irreversible oxidative modification of SERCA2a, including sulfonylation at cysteine 674 and nitration at tyrosine 294/295, and inactivation of SERCA2a, which initiated calcium overload. In addition, ischemic injury-triggered [Ca2+]c overload and subsequent [Ca2+]m overload led to mPTP opening and ΔΨm dissipation compared with the control. Furthermore, ablation of Mfn2 alleviated SERCA2a-induced mitochondrial calcium overload and subsequent mito-apoptosis in the context of CMEC hypoxic injury. In vivo, compared with that in wild-type mice, the myocardial infarct size in Mfn2KO mice was significantly decreased. In addition, the findings revealed that Mfn2KO mice had better heart contractile function, decreased myocardial infarction indicators, and improved mitochondrial morphology. Taken together, the results of our study suggested that SERCA2a-dependent [Ca2+]c overload led to mitochondrial dysfunction and activation of Mfn2-mediated [Ca2+]m overload. Overexpression of SERCA2a or ablation of Mfn2 expression mitigated mitochondrial morphological and functional damage by modifying the SERCA2a/Ca2+-Mfn2 pathway. Overall, these pathways are promising therapeutic targets for acute cardiac microvascular ischemic injury.

Calcium-transport function of the chick embryonic chorioallantoic membrane. I. In vivo and in vitro characterization

1986 ◽  
Vol 82 (1) ◽  
pp. 73-84
Author(s):  
R.S. Tuan ◽  
M.J. Carson ◽  
J.A. Jozefiak ◽  
K.A. Knowles ◽  
B.A. Shotwell
Keyword(s):  
Calcium Transport ◽  
Calcium Uptake ◽  
Chorioallantoic Membrane ◽  
Transport Function ◽  
In Ovo ◽  
In Vitro Characterization ◽  
Microsomal Membranes

During chick embryonic development, the chorioallantoic membrane (CAM) is responsible for the mobilization of shell calcium into the embryonic circulation. The calcium-transport function of the CAM was studied here by measuring CAM calcium uptake in vivo and in vitro. The in vivo technique involved the use of an uptake chamber constructed on top of the CAM in situ. The in vitro methods included two systems: CAM tissue disks and cell-free microsomal membranes isolated from the CAM. Analyses using these three assays show that calcium uptake by the CAM exhibited characteristics indicative of active transport, such as temperature dependence, saturability, energetic requirement and ion specificity. The data also show that calcium-uptake activities of the CAM increase as a function of embryonic age in a manner coincident with the increased accumulation of calcium by the developing embryo in ovo.

scholarly journals The mitochondrial calcium uniporter promotes arrhythmias caused by high-fat diet

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Leroy C. Joseph ◽  
Michael V. Reyes ◽  
Edwin A. Homan ◽  
Blake Gowen ◽  
Uma Mahesh R. Avula ◽  
...  
Keyword(s):  
Mitochondrial Dysfunction ◽  
High Fat Diet ◽  
Calcium Uptake ◽  
Saturated Fat ◽  
Calcium Handling ◽  
Mitochondrial Calcium ◽  
High Fat ◽  
Calcium Uniporter ◽  
Mitochondrial Calcium Uptake

AbstractObesity and diabetes increase the risk of arrhythmia and sudden cardiac death. However, the molecular mechanisms of arrhythmia caused by metabolic abnormalities are not well understood. We hypothesized that mitochondrial dysfunction caused by high fat diet (HFD) promotes ventricular arrhythmia. Based on our previous work showing that saturated fat causes calcium handling abnormalities in cardiomyocytes, we hypothesized that mitochondrial calcium uptake contributes to HFD-induced mitochondrial dysfunction and arrhythmic events. For experiments, we used mice with conditional cardiac-specific deletion of the mitochondrial calcium uniporter (Mcu), which is required for mitochondrial calcium uptake, and littermate controls. Mice were used for in vivo heart rhythm monitoring, perfused heart experiments, and isolated cardiomyocyte experiments. MCU KO mice are protected from HFD-induced long QT, inducible ventricular tachycardia, and abnormal ventricular repolarization. Abnormal repolarization may be due, at least in part, to a reduction in protein levels of voltage gated potassium channels. Furthermore, isolated cardiomyocytes from MCU KO mice exposed to saturated fat are protected from increased reactive oxygen species (ROS), mitochondrial dysfunction, and abnormal calcium handling. Activation of calmodulin-dependent protein kinase (CaMKII) corresponds with the increase in arrhythmias in vivo. Additional experiments showed that CaMKII inhibition protects cardiomyocytes from the mitochondrial dysfunction caused by saturated fat. Hearts from transgenic CaMKII inhibitor mice were protected from inducible ventricular tachycardia after HFD. These studies identify mitochondrial dysfunction caused by calcium overload as a key mechanism of arrhythmia during HFD. This work indicates that MCU and CaMKII could be therapeutic targets for arrhythmia caused by metabolic abnormalities.

scholarly journals Evolutionarily Conserved Long Non-coding RNA Regulates Gene Expression in Cytokine Storm During COVID-19

2021 ◽  
Vol 8 ◽  
Author(s):  
Olanrewaju B. Morenikeji ◽  
Kahleel Bernard ◽  
Ellis Strutton ◽  
Madeleine Wallace ◽  
Bolaji N. Thomas
Keyword(s):  
Gene Expression ◽  
Drug Targets ◽  
Regulatory Elements ◽  
Cytokine Storm ◽  
Cellular Processes ◽  
Non Coding Rna ◽  
Evolutionarily Conserved ◽  
Multiple Species

Coronavirus is a family of viruses including alpha-, beta-, gamma-, delta-coronaviruses. Only alpha- and betacoronaviruses have been observed to infect humans. Past outbreaks of SARS-CoV and MERS-CoV, both betacoronavirus, are the result of a spillover from animals. Recently, a new strain termed SARS-CoV-2 emerged in December 2019 in Wuhan, China. Severe cases of COVID-19, the disease caused by SARS-CoV-2, lead to acute respiratory distress syndrome (ARDS). One contributor to the development of ARDS is cytokine storm, an overwhelming inflammatory immune response. Long non-coding RNAs (lncRNAs) are genetic regulatory elements that, among many functions, alter gene expression and cellular processes. lncRNAs identified to be pertinent in COVID-19 cytokine storm have the potential to serve as disease markers or drug targets. This project aims to computationally identify conserved lncRNAs potentially regulating gene expression in cytokine storm during COVID-19. We found 22 lncRNAs that can target 10 cytokines overexpressed in COVID-19 cytokine storm, 8 of which targeted two or more cytokine storm cytokines. In particular, the lncRNA non-coding RNA activated by DNA damage (NORAD), targeted five out of the ten identified cytokine storm cytokines, and is evolutionarily conserved across multiple species. These lncRNAs are ideal candidates for further in vitro and in vivo analysis.

scholarly journals Promoting the Calcium-Uptake Bioactivity of Casein Phosphopeptides in vitro and in vivo

2021 ◽  
Vol 8 ◽  
Author(s):  
Guo Liu ◽  
Baoyan Guo ◽  
Shengwei Sun ◽  
Minna Luo ◽  
Fei Liu ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Absorption ◽  
Serum Alkaline Phosphatase ◽  
Binding Capacity ◽  
Animal Experiments ◽  
Casein Phosphopeptides

Casein phosphopeptides have been studied widely for their ability to chelate calcium. However, systematic studies on the effects of casein phosphopeptides (CPP) on calcium absorption in vitro and in vivo are scarce. The purities of two commercially available products, CPP1 and CPP2, are 18.37 and 25.12%, respectively. Here, the in vitro calcium binding capacity of CPP2 was 142.56 ± 7.39 mg/g, which was higher than that of CPP1 (107.15 ± 6.27 mg/g). The calcium transport results in a Caco-2 monolayer model indicated that, relative to controls, CPP1 and CPP2 increased calcium transport by 21.78 and 53.68%, respectively. Subsequent animal experiments showed that the CPP2-Ca-H group (1% Ca, 0.4% CPP2) had significant increases in the femur index, serum Ca2+ and serum osteocalcin levels, and femoral Ca content. The CPP2-Ca-H animal also had decreased serum alkaline phosphatase levels, parathyroid hormone content, and urinary pyridinoline content. Overall, our results demonstrated that CPP2 had stronger effects on promoting calcium uptake than CPP1.

Excitation–contraction coupling in heart. XIX. Effect of hypoxia on calcium transport by subcellular particles in the isolated perfused rat heart

1976 ◽  
Vol 54 (1) ◽  
pp. 49-58 ◽  
Author(s):  
S. L. Lee ◽  
V. Balasubramanian ◽  
N. S. Dhalla
Keyword(s):  
Calcium Binding ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Microsomal Fraction ◽  
Contractile Force ◽  
Mitochondrial Calcium ◽  
Rat Hearts ◽  
Mitochondrial Calcium Uptake ◽  
Contractile Failure

To examine the role of changes in calcium transport by subcellular particles in the pathogenesis of contractile failure due to oxygen lack, both mitochondrial and microsomal fractions were obtained from the isolated hypoxic rat hearts and their calcium binding and uptake abilities were determined by the Millipore filtration technique. The contractile force decreased by about 40, 60 and 70% of the control within 5, 10 and 30 min respectively, of perfusing the heart with hypoxic medium containing glucose. In hearts perfused for 10 min with hypoxic medium containing glucose, calcium binding and uptake by the microsomal fraction decreased significantly. However, mitochondrial calcium binding, but not uptake, decreased significantly on perfusing the hearts with hypoxic medium containing glucose for 20 to 30 min when the microsomal calcium transport was markedly depressed. Reduction in contractile force, calcium binding and uptake by the microsomal fraction as well as calcium binding by mitochondria of hearts made hypoxic for 30 min recovered towards normal upon reperfusion with control medium for 15 min. On the other hand, omitting glucose from the hypoxic medium significantly decreased calcium binding by mitochondrial and microsomal fractions within 10 min of perfusion in comparison to the control and accelerated the effects of hypoxia upon contractile force and microsomal calcium uptake. In contrast to the hypoxic hearts, the mitochondrial calcium uptake decreased significantly and the magnitude of depression in the microsomal calcium binding was appreciably greater in hearts made to fail to a comparable degree upon perfusion with substrate-free medium. The observed defects in calcium transporting properties of microsomal and mitochondrial membranes appear secondary to the contractile failure in hypoxic hearts.

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