scholarly journals The Mechanism of MICU-Dependent Gating of the Mitochondrial Ca2+ Uniporter

2020 ◽  
Author(s):  
Vivek Garg ◽  
Ishan Paranjpe ◽  
Tiffany Unsulangi ◽  
Junji Suzuki ◽  
Lorin S. Milescu ◽  
...  
Keyword(s):  
Cell Death ◽  
Patch Clamp ◽  
Activation Threshold ◽  
Auxiliary Subunits ◽  
Atp Production ◽  
Ef Hand ◽  
Ef Hands ◽  
Active Channel ◽  
Constitutively Active

AbstractMitochondrial Ca2+ uniporter (MCU) mediates mitochondrial Ca2+ uptake, regulating ATP production and cell death. According to the existing paradigm, MCU is occluded at the resting cytosolic [Ca2+] and only opens above an ∼400 nM threshold. This Ca2+-dependent gating is putatively conferred by MICUs, EF hand-containing auxiliary subunits that block/unblock the MCU pore depending on cytosolic [Ca2+]. Here we provide the first direct, patch-clamp based analysis of the Ca2+-dependent MCU gating and the role played by MICUs. Surprisingly, MICUs do not occlude the MCU pore, and MCU is a constitutively active channel without cytosolic [Ca2+] activation threshold. Instead, MICUs potentiate MCU activity when cytosolic Ca2+ binds to their EF hands. MICUs cause this potentiation by increasing the probability of open state of the MCU channel.One Sentence SummaryAuxiliary MICU subunits do not occlude the mitochondrial Ca2+ uniporter (MCU) but increase its activity as cytosolic Ca2+ is elevated.

scholarly journals The Highly Conservative Cysteine of Oncomodulin as a Feasible Redox Sensor

Biomolecules ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 66
Author(s):  
Alisa A. Vologzhannikova ◽  
Polina A. Khorn ◽  
Marina P. Shevelyova ◽  
Alexei S. Kazakov ◽  
Victor I. Emelyanenko ◽  
...  
Keyword(s):  
Solvent Accessibility ◽  
Sensory Function ◽  
Hydrophobic Residues ◽  
Metal Free ◽  
Helix Loop Helix ◽  
Redox Sensor ◽  
Ef Hand ◽  
Functional Consequences ◽  
Ef Hands ◽  
Ph Range

Oncomodulin (Ocm), or parvalbumin β, is an 11–12 kDa Ca2+-binding protein found inside and outside of vertebrate cells, which regulates numerous processes via poorly understood mechanisms. Ocm consists of two active Ca2+-specific domains of the EF-hand type (“helix-loop-helix” motif), covered by an EF-hand domain with inactive EF-hand loop, which contains a highly conservative cysteine with unknown function. In this study, we have explored peculiarities of the microenvironment of the conservative Cys18 of recombinant rat Ocm (rWT Ocm), redox properties of this residue, and structural/functional sensitivity of rWT Ocm to the homologous C18S substitution. We have found that pKa of the Cys18 thiol lays beyond the physiological pH range. The measurement of redox dependence of rWT Ocm thiol–disulfide equilibrium (glutathione redox pair) showed that redox potential of Cys18 for the metal-free and Ca2+-loaded protein is of −168 mV and −176 mV, respectively. Therefore, the conservative thiol of rWT Ocm is prone to disulfide dimerization under physiological redox conditions. The C18S substitution drastically reduces α-helices content of the metal-free and Mg2+-bound Ocm, increases solvent accessibility of its hydrophobic residues, eliminates the cooperative thermal transition in the apo-protein, suppresses Ca2+/Mg2+ affinity of the EF site, and accelerates Ca2+ dissociation from Ocm. The distinct structural and functional consequences of the minor structural modification of Cys18 indicate its possible redox sensory function. Since some other EF-hand proteins also contain a conservative redox-sensitive cysteine located in an inactive EF-hand loop, it is reasonable to suggest that in the course of evolution, some of the EF-hands attained redox sensitivity at the expense of the loss of their Ca2+ affinity.

scholarly journals Neurotoxic Effect of Flavonol Myricetin in the Presence of Excess Copper

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 845
Author(s):  
Anja Sadžak ◽  
Ignacija Vlašić ◽  
Zoran Kiralj ◽  
Marijana Batarelo ◽  
Nada Oršolić ◽  
...  
Keyword(s):  
Cell Death ◽  
Intracellular Signaling ◽  
Chromatin Condensation ◽  
Membrane Integrity ◽  
Toxic Effects ◽  
Trypan Blue Exclusion ◽  
Atp Production ◽  
Mtt Method ◽  
Biophysical Approach ◽  
Induced Changes

Oxidative stress (OS) induced by the disturbed homeostasis of metal ions is one of the pivotal factors contributing to neurodegeneration. The aim of the present study was to investigate the effects of flavonoid myricetin on copper-induced toxicity in neuroblastoma SH-SY5Y cells. As determined by the MTT method, trypan blue exclusion assay and measurement of ATP production, myricetin heightened the toxic effects of copper and exacerbated cell death. It also increased copper-induced generation of reactive oxygen species, indicating the prooxidative nature of its action. Furthermore, myricetin provoked chromatin condensation and loss of membrane integrity without caspase-3 activation, suggesting the activation of both caspase-independent programmed cell death and necrosis. At the protein level, myricetin-induced upregulation of PARP-1 and decreased expression of Bcl-2, whereas copper-induced changes in the expression of p53, p73, Bax and NME1 were not further affected by myricetin. Inhibitors of ERK1/2 and JNK kinases, protein kinase A and L-type calcium channels exacerbated the toxic effects of myricetin, indicating the involvement of intracellular signaling pathways in cell death. We also employed atomic force microscopy (AFM) to evaluate the morphological and mechanical properties of SH-SY5Y cells at the nanoscale. Consistent with the cellular and molecular methods, this biophysical approach also revealed a myricetin-induced increase in cell surface roughness and reduced elasticity. Taken together, we demonstrated the adverse effects of myricetin, pointing out that caution is required when considering powerful antioxidants for adjuvant therapy in copper-related neurodegeneration.

scholarly journals Mitochondria and Pharmacologic Cardiac Conditioning—At the Heart of Ischemic Injury

2021 ◽  
Vol 22 (6) ◽  
pp. 3224
Author(s):  
Christopher Lotz ◽  
Johannes Herrmann ◽  
Quirin Notz ◽  
Patrick Meybohm ◽  
Franz Kehl
Keyword(s):  
Cell Death ◽  
Mitochondrial Permeability Transition ◽  
Permeability Transition ◽  
Research Field ◽  
Calcium Handling ◽  
Control Mechanisms ◽  
Intrinsic Resistance ◽  
Atp Production ◽  
Cardiac Conditioning ◽  
A Cell

Pharmacologic cardiac conditioning increases the intrinsic resistance against ischemia and reperfusion (I/R) injury. The cardiac conditioning response is mediated via complex signaling networks. These networks have been an intriguing research field for decades, largely advancing our knowledge on cardiac signaling beyond the conditioning response. The centerpieces of this system are the mitochondria, a dynamic organelle, almost acting as a cell within the cell. Mitochondria comprise a plethora of functions at the crossroads of cell death or survival. These include the maintenance of aerobic ATP production and redox signaling, closely entwined with mitochondrial calcium handling and mitochondrial permeability transition. Moreover, mitochondria host pathways of programmed cell death impact the inflammatory response and contain their own mechanisms of fusion and fission (division). These act as quality control mechanisms in cellular ageing, release of pro-apoptotic factors and mitophagy. Furthermore, recently identified mechanisms of mitochondrial regeneration can increase the capacity for oxidative phosphorylation, decrease oxidative stress and might help to beneficially impact myocardial remodeling, as well as invigorate the heart against subsequent ischemic insults. The current review highlights different pathways and unresolved questions surrounding mitochondria in myocardial I/R injury and pharmacological cardiac conditioning.

scholarly journals IREN, a novel EF-hand motif-containing nuclease, functions in the degradation of nuclear DNA during the hypersensitive response cell death in rice

2016 ◽  
Vol 80 (4) ◽  
pp. 748-760 ◽  
Author(s):  
Yuka Ootsubo ◽  
Takanori Hibino ◽  
Takahito Wakazono ◽  
Yukio Mukai ◽  
Fang-Sik Che
Keyword(s):  
Cell Death ◽  
Hypersensitive Response ◽  
Nuclear Dna ◽  
Ef Hand

scholarly journals Pathogenic Connexin-31 Forms Constitutively Active Hemichannels to Promote Necrotic Cell Death

PLoS ONE ◽  
2012 ◽  
Vol 7 (2) ◽  
pp. e32531 ◽  
Author(s):  
Jingwei Chi ◽  
Li Li ◽  
Mujun Liu ◽  
Jieqiong Tan ◽  
Chengyuan Tang ◽  
...  
Keyword(s):  
Cell Death ◽  
Necrotic Cell Death ◽  
Necrotic Cell ◽  
Constitutively Active

scholarly journals Binding of Gd3+to the neuronal signalling protein calexcitin identifies an exchangeable Ca2+-binding site

2016 ◽  
Vol 72 (4) ◽  
pp. 276-281
Author(s):  
Lucas Chataigner ◽  
Jingxu Guo ◽  
Peter T. Erskine ◽  
Alun R. Coker ◽  
Steve P. Wood ◽  
...  
Keyword(s):  
Metal Ions ◽  
Binding Site ◽  
Metal Binding ◽  
Calcium Signalling ◽  
Specific Protein ◽  
Metal Binding Sites ◽  
Calcium Sensing ◽  
Neuronal Signalling ◽  
Ef Hand ◽  
Ef Hands

Calexcitin was first identified in the marine snailHermissenda crassicornisas a neuronal-specific protein that becomes upregulated and phosphorylated in associative learning. Calexcitin possesses four EF-hand motifs, but only the first three (EF-1 to EF-3) are involved in binding metal ions. Past work has indicated that under physiological conditions EF-1 and EF-2 bind Mg2+and Ca2+, while EF-3 is likely to bind only Ca2+. The fourth EF-hand is nonfunctional owing to a lack of key metal-binding residues. The aim of this study was to use a crystallographic approach to determine which of the three metal-binding sites of calexcitin is most readily replaced by exogenous metal ions, potentially shedding light on which of the EF-hands play a `sensory' role in neuronal calcium signalling. By co-crystallizing recombinant calexcitin with equimolar Gd3+in the presence of trace Ca2+, EF-1 was shown to become fully occupied by Gd3+ions, while the other two sites remain fully occupied by Ca2+. The structure of the Gd3+–calexcitin complex has been refined to anRfactor of 21.5% and anRfreeof 30.4% at 2.2 Å resolution. These findings suggest that EF-1 of calexcitin is the Ca2+-binding site with the lowest selectivity for Ca2+, and the implications of this finding for calcium sensing in neuronal signalling pathways are discussed.

scholarly journals Antitumor effects of the small molecule DMAMCL in neuroblastoma via suppressing aerobic glycolysis and targeting PFKL

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Simeng Zhang ◽  
Zhongyan Hua ◽  
Gen Ba ◽  
Ning Xu ◽  
Jianing Miao ◽  
...  
Keyword(s):  
Cell Death ◽  
Synergistic Effects ◽  
Aerobic Glycolysis ◽  
Single Agent ◽  
Molecular Compound ◽  
Dependent Manner ◽  
Antitumor Effects ◽  
Atp Production

Abstract Background Neuroblastoma (NB) is a common solid malignancy in children that is associated with a poor prognosis. Although the novel small molecular compound Dimethylaminomicheliolide (DMAMCL) has been shown to induce cell death in some tumors, little is known about its role in NB. Methods We examined the effect of DMAMCL on four NB cell lines (NPG, AS, KCNR, BE2). Cellular confluence, survival, apoptosis, and glycolysis were detected using Incucyte ZOOM, CCK-8 assays, Annexin V-PE/7-AAD flow cytometry, and Seahorse XFe96, respectively. Synergistic effects between agents were evaluated using CompuSyn and the effect of DMAMCL in vivo was evaluated using a xenograft mouse model. Phosphofructokinase-1, liver type (PFKL) expression was up- and down-regulated using overexpression plasmids or siRNA. Results When administered as a single agent, DMAMCL decreased cell proliferation in a time- and dose-dependent manner, increased the percentage of cells in SubG1 phase, and induced apoptosis in vitro, as well as inhibiting tumor growth and prolonging survival in tumor-bearing mice (NGP, BE2) in vivo. In addition, DMAMCL exerted synergistic effects when combined with etoposide or cisplatin in vitro and displayed increased antitumor effects when combined with etoposide in vivo compared to either agent alone. Mechanistically, DMAMCL suppressed aerobic glycolysis by decreasing glucose consumption, lactate excretion, and ATP production, as well as reducing the expression of PFKL, a key glycolysis enzyme, in vitro and in vivo. Furthermore, PFKL overexpression attenuated DMAMCL-induced cell death, whereas PFKL silencing promoted NB cell death. Conclusions The results of this study suggest that DMAMCL exerts antitumor effects on NB both in vitro and in vivo by suppressing aerobic glycolysis and that PFKL could be a potential target of DMAMCL in NB.

scholarly journals DC3, the 21-kDa Subunit of the Outer Dynein Arm-Docking Complex (ODA-DC), Is a Novel EF-Hand Protein Important for Assembly of Both the Outer Arm and the ODA-DC

2003 ◽  
Vol 14 (9) ◽  
pp. 3650-3663 ◽  
Author(s):  
Diane M. Casey ◽  
Kazuo Inaba ◽  
Gregory J. Pazour ◽  
Saeko Takada ◽  
Ken-ichi Wakabayashi ◽  
...  
Keyword(s):  
Troponin C ◽  
Light Chains ◽  
Myosin Light Chains ◽  
Cdna Clones ◽  
Wild Type ◽  
Ef Hand ◽  
Dynein Arms ◽  
Ef Hands ◽  
Flagellar Axoneme ◽  
Chlamydomonas Mutants

The outer dynein arm-docking complex (ODA-DC) is a microtubule-associated structure that targets the outer dynein arm to its binding site on the flagellar axoneme ( Takada et al. 2002 . Mol. Biol. Cell 13, 1015–1029). The ODA-DC of Chlamydomonas contains three proteins, referred to as DC1, DC2, and DC3. We here report the isolation and sequencing of genomic and full-length cDNA clones encoding DC3. The sequence predicts a 21,341 Da protein with four EF-hands that is a member of the CTER (calmodulin, troponin C, essential and regulatory myosin light chains) group and is most closely related to a predicted protein from Plasmodium. The DC3 gene, termed ODA14, is intronless. Chlamydomonas mutants that lack DC3 exhibit slow, jerky swimming because of loss of some but not all outer dynein arms. Some outer doublet microtubules without arms had a “partial” docking complex, indicating that DC1 and DC2 can assemble in the absence of DC3. In contrast, DC3 cannot assemble in the absence of DC1 or DC2. Transformation of a DC3-deletion strain with the wild-type DC3 gene rescued both the motility phenotype and the structural defect, whereas a mutated DC3 gene was incompetent to rescue. The results indicate that DC3 is important for both outer arm and ODA-DC assembly.

407 REGULATION OF HUMAN MALE GERM CELL DEATH BY MODULATORS OF ATP PRODUCTION

2005 ◽  
Vol 53 (1) ◽  
pp. S149.5-S149
Author(s):  
K. Erkkila ◽  
L. Dunkel ◽  
S. Kyttanen ◽  
R. S. Swerdloff
Keyword(s):  
Cell Death ◽  
Germ Cell ◽  
Male Germ Cell ◽  
Atp Production ◽  
Human Male

scholarly journals Piceatannol Increases Antioxidant Defense and Reduces Cell Death in Human Periodontal Ligament Fibroblast under Oxidative Stress

Antioxidants ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 16 ◽  
Author(s):  
Flávia Póvoa da Costa ◽  
Bruna Puty ◽  
Lygia S. Nogueira ◽  
Geovanni Pereira Mitre ◽  
Sávio Monteiro dos Santos ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Cell Death ◽  
Cell Viability ◽  
Antioxidant Capacity ◽  
Periodontal Ligament ◽  
Cellular Metabolism ◽  
Mitochondrial Activity ◽  
Oxygen Species ◽  
Atp Production

Piceatannol is a resveratrol metabolite that is considered a potent antioxidant and cytoprotector because of its high capacity to chelate/sequester reactive oxygen species. In pathogenesis of periodontal diseases, the imbalance of reactive oxygen species is closely related to the disorder in the cells and may cause changes in cellular metabolism and mitochondrial activity, which is implicated in oxidative stress status or even in cell death. In this way, this study aimed to evaluate piceatannol as cytoprotector in culture of human periodontal ligament fibroblasts through in vitro analyses of cell viability and oxidative stress parameters after oxidative stress induced as an injury simulator. Fibroblasts were seeded and divided into the following study groups: control, vehicle, control piceatannol, H2O2 exposure, and H2O2 exposure combined with the maintenance in piceatannol ranging from 0.1 to 20 μM. The parameters analyzed following exposure were cell viability by trypan blue exclusion test, general metabolism status by the 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) method, mitochondrial activity through the ATP production, total antioxidant capacity, and reduced gluthatione. Piceatannol was shown to be cytoprotective due the maintenance of cell viability between 1 and 10 μM even in the presence of H2O2. In a concentration of 0.1 μM piceatannol decreased significantly cell viability but increased cellular metabolism and antioxidant capacity of the fibroblasts. On the other hand, the fibroblasts treated with piceatannol at 1 μM presented low metabolism and antioxidant capacity. However, piceatannol did not protect cells from mitochondrial damage as measured by ATP production. In summary, piceatannol is a potent antioxidant in low concentrations with cytoprotective capacity, but it does not prevent all damage caused by hydrogen peroxide.

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