scholarly journals Cellular acidosis triggers MondoA transcriptional activity by driving mitochondrial ATP production

2018 ◽  
Author(s):  
Blake R. Wilde ◽  
Zhizhou Ye ◽  
Donald E. Ayer
Keyword(s):  
Transcriptional Activity ◽  
Adenine Nucleotide ◽  
Cellular Stress ◽  
Anion Channel ◽  
Glycolytic Flux ◽  
Voltage Dependent Anion Channel ◽  
Interacting Protein ◽  
Atp Production ◽  
Stress Signals ◽  
Regulatory Loop

ABSTRACTMondoA and its transcriptional target thioredoxin-interacting protein (TXNIP) constitute a regulatory loop that senses glycolytic flux and controls glucose availability. Cellular stress also triggers MondoA activity and TXNIP expression. To understand how MondoA integrates glucose and stress signals, we studied its activation by acidosis. We found that acidosis drives mitochondrial ATP (mtATP) synthesis. The subsequent export of mtATP from mitochondria via adenine-nucleotide transporter and voltage-dependent anion channel, and the enzymatic activity of mitochondria-bound hexokinase results in the production of glucose-6-phosphate (G6P), a known activator of MondoA transcriptional activity. MondoA localizes to the outer-mitochondrial membrane (OMM), and in response to G6P, shuttles to the nucleus and activates transcription. Our data suggests that MondoA is a required feature of a glucose- and mtATP-dependent, OMM-localized signaling center. We propose MondoA functions as a coincidence detector and its ability to sense glucose and cellular stress is coupled to the concerted production of G6P.

In the absence of phosphate shuttling, exercise reveals the in vivo importance of creatine-independent mitochondrial ADP transport

2016 ◽  
Vol 473 (18) ◽  
pp. 2831-2843 ◽  
Author(s):  
Paula M. Miotto ◽  
Graham P. Holloway
Keyword(s):  
Energy Homeostasis ◽  
Adenine Nucleotide ◽  
Control Point ◽  
Anion Channel ◽  
Adenosine Monophosphate ◽  
Adenosine Diphosphate ◽  
Glycolytic Flux ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent

The transport of cytosolic adenosine diphosphate (ADP) into the mitochondria is a major control point in metabolic homeostasis, as ADP concentrations directly affect glycolytic flux and oxidative phosphorylation rates within mitochondria. A large contributor to the efficiency of this process is thought to involve phosphocreatine (PCr)/Creatine (Cr) shuttling through mitochondrial creatine kinase (Mi-CK), whereas the biological importance of alterations in Cr-independent ADP transport during exercise remains unknown. Therefore, we utilized an Mi-CK knockout (KO) model to determine whether in vivo Cr-independent mechanisms are biologically important for sustaining energy homeostasis during exercise. Ablating Mi-CK did not alter exercise tolerance, as the time to volitional fatigue was similar between wild-type (WT) and KO mice at various exercise intensities. In addition, skeletal muscle metabolic profiles after exercise, including glycogen, PCr/Cr ratios, free ADP/adenosine monophosphate (AMP), and lactate, were similar between genotypes. While these data suggest that the absence of PCr/Cr shuttling is not detrimental to maintaining energy homeostasis during exercise, KO mice displayed a dramatic increase in Cr-independent mitochondrial ADP sensitivity after exercise. Specifically, whereas mitochondrial ADP sensitivity decreased with exercise in WT mice, in stark contrast, exercise increased mitochondrial Cr-independent ADP sensitivity in KO mice. As a result, the apparent ADP Km was 50% lower in KO mice after exercise, suggesting that in vivo activation of voltage-dependent anion channel (VDAC)/adenine nucleotide translocase (ANT) can support mitochondrial ADP transport. Altogether, we provide insight that Cr-independent ADP transport mechanisms are biologically important for regulating ADP sensitivity during exercise, while highlighting complex regulation and the plasticity of the VDAC/ANT axis to support adenosine triphosphate demand.

scholarly journals Dynamics of enhanced mitochondrial respiration in female compared with male rat cerebral arteries

2015 ◽  
Vol 309 (9) ◽  
pp. H1490-H1500 ◽  
Author(s):  
Ibolya Rutkai ◽  
Somhrita Dutta ◽  
Prasad V. Katakam ◽  
David W. Busija
Keyword(s):  
Mitochondrial Respiration ◽  
Ex Vivo ◽  
Cerebral Arteries ◽  
Anion Channel ◽  
Basal Respiration ◽  
Male Rat ◽  
Sprague Dawley ◽  
Voltage Dependent Anion Channel ◽  
Male And Female ◽  
Atp Production

Mitochondrial respiration has never been directly examined in intact cerebral arteries. We tested the hypothesis that mitochondrial energetics of large cerebral arteries ex vivo are sex dependent. The Seahorse XFe24 analyzer was used to examine mitochondrial respiration in isolated cerebral arteries from adult male and female Sprague-Dawley rats. We examined the role of nitric oxide (NO) on mitochondrial respiration under basal conditions, using Nω-nitro-l-arginine methyl ester, and following pharmacological challenge using diazoxide (DZ), and also determined levels of mitochondrial and nonmitochondrial proteins using Western blot, and vascular diameter responses to DZ. The components of mitochondrial respiration including basal respiration, ATP production, proton leak, maximal respiration, and spare respiratory capacity were elevated in females compared with males, but increased in both male and female arteries in the presence of the NOS inhibitor. Although acute DZ treatment had little effect on mitochondrial respiration of male arteries, it decreased the respiration in female arteries. Levels of mitochondrial proteins in Complexes I–V and the voltage-dependent anion channel protein were elevated in female compared with male cerebral arteries. The DZ-induced vasodilation was greater in females than in males. Our findings show that substantial sex differences in mitochondrial respiratory dynamics exist in large cerebral arteries and may provide the mechanistic basis for observations that the female cerebral vasculature is more adaptable after injury.

The mitochondrial permeability transition pore

1999 ◽  
Vol 66 ◽  
pp. 167-179 ◽  
Author(s):  
Martin Crompton ◽  
Sukaina Virji ◽  
Veronica Doyle ◽  
Nicholas Johnson ◽  
John M. Ward
Keyword(s):  
Mitochondrial Permeability Transition ◽  
Adenine Nucleotide ◽  
Permeability Transition Pore ◽  
Anion Channel ◽  
Permeability Transition ◽  
Adenine Nucleotide Translocase ◽  
Voltage Dependent Anion Channel ◽  
Inner Membrane ◽  
Membrane Pore ◽  
Voltage Dependent

This chapter reviews recent advances in the identification of the structural elements of the permeability transition pore. The discovery that cyclosporin A (CsA) inhibits the pore proved instrumental. Various approaches indicate that CsA blocks the pore by binding to cyclophilin (CyP)-D. In particular, covalent labelling of CyP-D in situ by a photoactive CsA derivative has shown that pore ligands have the same effects on the degree to which CsA both blocks the pore and binds to CyP-D. The recognition that CyP-D is a key component has enabled the other constituents to be resolved. Use of a CyP-D fusion protein as affinity matrix has revealed that CyP-D binds very strongly to 1:1 complexes of the voltage-dependent anion channel (from the outer membrane) and adenine nucleotide translocase (inner membrane). Our current model envisages that the pore arises as a complex between these three components at contact sites between the mitochondrial inner and outer membranes. This is in line with recent reconstitutions of pore activity from protein fractions containing these proteins. The strength of interaction between these proteins suggests that it may be a permanent feature rather than assembled only under pathological conditions. Calcium, the key activator of the pore, does not appear to affect pore assembly; rather, an allosteric action allowing pore flicker into an open state is indicated. CsA inhibits pore flicker and lowers the binding affinity for calcium. Whether adenine nucleotide translocase or the voltage-dependent anion channel (via inner membrane insertion) provides the inner membrane pore has not been settled, and data relevant to this issue are also documented.

scholarly journals Metabolic control analysis of integrated energy metabolism in permeabilized cardiomyocytes - experimental study.

2010 ◽  
Vol 57 (4) ◽  
Author(s):  
Kersti Tepp ◽  
Natalja Timohhina ◽  
Vladimir Chekulayev ◽  
Igor Shevchuk ◽  
Tuuli Kaambre ◽  
...  
Keyword(s):  
Metabolic Control ◽  
Adenine Nucleotide ◽  
Anion Channel ◽  
Metabolic Control Analysis ◽  
Regulation Of Respiration ◽  
Functional Coupling ◽  
Control Analysis ◽  
Voltage Dependent Anion Channel ◽  
Physiological Conditions ◽  
Key Sites

The main focus of this research was to apply Metabolic Control Analysis to quantitative investigation of the regulation of respiration by components of the Mitochondrial Interactosome (MI, a supercomplex consisting of ATP Synthasome, mitochondrial creatine kinase (MtCK), voltage dependent anion channel (VDAC), and tubulin) in permeabilized cardiomyocytes. Flux control coefficients (FCC) were measured using two protocols: 1) with direct ADP activation, and 2) with MtCK activation by creatine (Cr) in the presence of ATP and pyruvate kinase-phosphoenolpyruvate system. The results show that the metabolic control is much stronger in the latter case: the sum of the measured FCC is 2.7 versus 0.74 (ADP activation). This is consistent with previous data showing recycling of ADP and ATP inside the MI due to the functional coupling between MtCK and ANT and limited permeability of VDAC for these compounds, PCr being the major energy carrier between the mitochondria and ATPases. In physiological conditions, when the MI is activated, the key sites of regulation of respiration in mitochondria are MtCK (FCC = 0.93), adenine nucleotide translocase ANT (FCC = 0.95) and CoQ cytochrome c oxidoreductase (FCC = 0.4). These results show clearly that under the physiological conditions the energy transfer from mitochondria to the cytoplasm is regulated by the MI supercomplex and is very sensitive to metabolic signals.

Abstract 5420: Dephosphorylation of the Cardiac Mitochondrial Voltage-Dependent Anion Channel Prevents Inhibition by Hexokinase

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Qunli Cheng ◽  
Zeljko J Bosnjak ◽  
Wai-Meng Kwok
Keyword(s):  
Mitochondrial Membrane ◽  
Mitochondrial Permeability Transition ◽  
Adenine Nucleotide ◽  
Standard Procedure ◽  
Anion Channel ◽  
Mitochondrial Outer Membrane ◽  
Cyclophilin D ◽  
Voltage Dependent Anion Channel ◽  
Voltage Dependent ◽  
The Mean

The mitochondrial permeability transition pore (mPTP) has been implicated as the end effector in ischemic and pharmacological preconditioning. Though the molecular composition of the mPTP is thought to consist of cyclophilin D located in the mitochondrial matrix, adenine nucleotide translocase on the inner mitochondrial membrane, and the voltage-dependent anion channel (VDAC) on the outer mitochondrial membrane, recent studies have raised the possibility that VDAC may be a regulatory, rather than a major, component of mPTP. Nevertheless, VDAC is likely to be a critical component of the preconditioning signaling pathway since it is the main conduit for metabolite diffusion across the mitochondrial outer membrane. Yet, the direct measurements of cardiac VDAC activity and modulation have been limited. In the present study, we purified VDAC from rat hearts using standard procedure and investigated its modulation by phosphatase and hexokinase. VDAC was incorporated into planar lipid bilayer for measurements of channel activities. The channel exhibited the reported voltage-dependent gating. Several conductance states were identified, with the most prevalent between 1.5 to 2 nS in 0.5 M NaCl. Koenig’s polyanion, a VDAC blocker, triggered channel flickering and decreased the mean current by 78±6%. In the presence of phosphatase (1 unit/ml), the mean conductance significantly increased from 1.81±0.03 to 3.68±0.61 nS (n=9; mean±SEM). However, the addition of a recombinant hexokinase (5 units/ml; GenWay Biotech) had no significant effect on the phosphatase-enhanced VDAC current (n=4). In contrast, recombinant hexokinase alone significantly decreased the mean conductance from 1.75±0.05 to 0.79±0.19 nS (n=4). The addition of phosphatase reversed the inhibitory effect of hexokinase and further enhanced VDAC activity, increasing the mean conductance to 2.69±0.19 nS (n=4). Our results suggest that the dephosphorylation of VDAC prevents the inhibitory effects of hexokinase. Furthermore, VDAC activity suppressed by hexokinase can be reversed by dephosphorylation of the channel. In conclusion, we have reported on a novel observation at the functional level that basal phosphorylation of the cardiac VDAC may be required for its modulation by hexokinase.

scholarly journals Rotaviral Enterotoxin Nonstructural Protein 4 Targets Mitochondria for Activation of Apoptosis during Infection

2012 ◽  
Vol 287 (42) ◽  
pp. 35004-35020 ◽  
Author(s):  
Rahul Bhowmick ◽  
Umesh Chandra Halder ◽  
Shiladitya Chattopadhyay ◽  
Shampa Chanda ◽  
Satabdi Nandi ◽  
...  
Keyword(s):  
Adenine Nucleotide ◽  
Early Stage ◽  
Nonstructural Protein ◽  
Anion Channel ◽  
Pi3k Inhibitor ◽  
Voltage Dependent Anion Channel ◽  
Mitochondrial Potential ◽  
Cellular Survival ◽  
Amino Acid Region ◽  
Voltage Dependent

Viruses have evolved to encode multifunctional proteins to control the intricate cellular signaling pathways by using very few viral proteins. Rotavirus is known to express six nonstructural and six structural proteins. Among them, NSP4 is the enterotoxin, known to disrupt cellular Ca2+ homeostasis by translocating to endoplasmic reticulum. In this study, we have observed translocation of NSP4 to mitochondria resulting in dissipation of mitochondrial membrane potential during virus infection and NSP4 overexpression. Furthermore, transfection of the N- and C-terminal truncated NSP4 mutants followed by analyzing NSP4 localization by immunofluorescence microscopy identified the 61–83-amino acid region as the shortest mitochondrial targeting signal. NSP4 exerts its proapoptotic effect by interacting with mitochondrial proteins adenine nucleotide translocator and voltage-dependent anion channel, resulting in dissipation of mitochondrial potential, release of cytochrome c from mitochondria, and caspase activation. During early infection, apoptosis activation by NSP4 was inhibited by the activation of cellular survival pathways (PI3K/AKT), because PI3K inhibitor results in early induction of apoptosis. However, in the presence of both PI3K inhibitor and NSP4 siRNA, apoptosis was delayed suggesting that the early apoptotic signal is initiated by NSP4 expression. This proapoptotic function of NSP4 is balanced by another virus-encoded protein, NSP1, which is implicated in PI3K/AKT activation because overexpression of both NSP4 and NSP1 in cells resulted in reduced apoptosis compared with only NSP4-expressing cells. Overall, this study reports on the mechanism by which enterotoxin NSP4 exerts cytotoxicity and the mechanism by which virus counteracts it at the early stage for efficient infection.

TNF-α-induced mitochondrial oxidative stress and cardiac dysfunction: restoration by superoxide dismutase mimetic Tempol

2007 ◽  
Vol 293 (5) ◽  
pp. H2726-H2737 ◽  
Author(s):  
Nithya Mariappan ◽  
Rajasekaran Namakkal Soorappan ◽  
Masudul Haque ◽  
Srinivas Sriramula ◽  
Joseph Francis
Keyword(s):  
Oxidative Stress ◽  
Cardiac Function ◽  
Mitochondrial Dysfunction ◽  
Molecular Mechanisms ◽  
Adenine Nucleotide ◽  
Redox Homeostasis ◽  
Anion Channel ◽  
Permeability Transition ◽  
Voltage Dependent Anion Channel ◽  
Tnf Α

Mitochondria are indispensable for bioenergetics and for the regulation of physiological/signaling events in cellular life. Although TNF-α-induced oxidative stress and mitochondrial dysfunction are evident in several pathophysiological states, the molecular mechanisms coupled with impaired cardiac function and its potential reversal by drugs such as Tempol or apocyanin have not yet been explored. Here, we hypothesize that TNF-α-induced oxidative stress compromises cardiac function by altering the mitochondrial redox state and the membrane permeability transition pore (MPTP) opening, thereby causing mitochondrial dysfunction. We measured the redox states in the cytosol and mitochondria of the heart to understand the mechanisms related to the MPTP and the antioxidant defense system. Our studies demonstrate that TNF-α-induced oxidative stress alters redox homeostasis by impairing the MPTP proteins adenine nucleotide translocator and voltage-dependent anion channel, thereby resulting in the pore opening, causing uncontrolled transport of substances to alter mitochondrial pH, and subsequently leading to dysfunction of mitochondria and attenuated cardiac function. Interestingly, we show that the supplementation of Tempol along with TNF-α restores mitochondrial and cardiac function.

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