Mitochondrial Voltage-dependent Anion Channel Research Articles

Stress granules inhibit fatty acid oxidation by modulating mitochondrial permeability.

SummaryThe formation of stress granules (SGs) is an essential aspect of the cellular response to many kinds of stress, but its adaptive role is far from clear. SG dysfunction is implicated in aging-onset neurodegenerative diseases, prompting interest in their physiological function. Here, we report that during starvation stress, SGs interact with mitochondria and regulate metabolic remodeling. We show that SG formation leads to a downregulation of fatty acid β-oxidation (FAO) through the modulation of mitochondrial voltage-dependent anion channels (VDACs), which import fatty acids (FAs) into mitochondria. The subsequent decrease in FAO during long-term starvation reduces oxidative damage and rations FAs for longer use. Failure to form SGs, whether caused by the genetic deletion of SG components or an amyotrophic lateral sclerosis (ALS)-associated mutation, translates into an inability to downregulate FAO. Because metabolic dysfunction is a common pathological element of neurodegenerative diseases, including ALS, our findings provide a direction for studying the clinical relevance of SGs.

Alpha-Synuclein and Mitochondrial Dysfunction in Parkinson's Disease: The Emerging Role of VDAC.

Alpha-Synuclein (αSyn) is a protein whose function is still debated, as well as its role in modulation of mitochondrial function in both physiological and pathological conditions. Mitochondrial porins or Voltage-Dependent Anion Channel (VDAC) proteins are the main gates for ADP/ATP and various substrates towards the organelle. Furthermore, they act as a mitochondrial hub for many cytosolic proteins, including αSyn. This review analyzes the main aspects of αSyn-mitochondria interaction, focusing on the role of VDAC and its emerging involvement in the pathological processes.

Ferroptosis in myocardial infarction: not a marker but a maker.

Identification of effective cardiac biomarkers and therapeutic targets for myocardial infarction (MI) will play an important role in early diagnosis and improving prognosis. Ferroptosis, a cell death process driven by cellular metabolism and iron-dependent lipid peroxidation, has been implicated in diseases such as ischaemic organ damage, cancer and neurological diseases. Its modulators were involved in transferrin receptor, iron chelator, clock protein ARNTL, etc. Its mechanisms included the inhibition of system XC-, diminished GPX4 activity, change of mitochondrial voltage-dependent anion channels and rising intracellular reactive oxygen species level. Further, the inhibitors of apoptosis, pyroptosis and autophagy did not prevent the occurrence of ferroptosis, but iron chelating agents and antioxidants could inhibit it. Noticeably, ferroptosis is an important pattern of cardiomyocyte death in the infarcted area, which may play a vital role in support of the myocardial pathological process of heart disease. However, the molecular mechanism of ferroptosis in the pathogenesis and the development of MI is not clear. Therefore, a greater depth of exploration of the mechanism of ferroptosis and its inhibitors will undoubtedly improve the pathological process of MI, which may be expected to identify ferroptosis as novel diagnostic and therapeutic targets of MI.

LvHemB1, a novel cationic antimicrobial peptide derived from the hemocyanin of Litopenaeus vannamei, induces cancer cell death by targeting mitochondrial voltage-dependent anion channel 1.

Current cancer treatment regimens such as chemotherapy and traditional chemical drugs have adverse side effects including the appearance of drug-resistant tumor cells. For these reasons, it is imperative to find novel therapeutic agents that overcome these factors. To this end, we explored a cationic antimicrobial peptide derived from Litopenaeus vannamei hemocyanin (designated LvHemB1) that induces cancer cell death, but sparing normal cells. LvHemB1 inhibits the proliferation of human cervical (HeLa), esophageal (EC109), hepatocellular (HepG2), and bladder (EJ) cancer cell lines, but had no significant effect on normal liver cell lines (T-antigen-immortalized human liver epithelial (THLE-3) cells). In addition to its antiproliferative effects, LvHemB1 induced apoptosis, by permeating cells and targeting mitochondrial voltage-dependent anion channel 1 (VDAC1). Colocalization studies revealed the localization of LvHemB1 in mitochondria, while molecular docking and pull-down analyses confirmed LvHemB1-VDAC1 interaction. Moreover, LvHemB1 causes loss in mitochondrial membrane potential and increases levels of reactive oxygen species (ROS) and apoptotic proteins (caspase-9, caspase-3, and Bax (Bcl-2-associated X)), which results in mitochondrial-mediated apoptosis. Thus, peptide LvHemB1 has the potential of being used as an anticancer agent due to its antiproliferation effect and targeting to VDAC1 to cause mitochondrial dysfunction in cancer cells, as well as its ability to induce apoptosis by increasing ROS levels, and the expression of proapoptotic proteins.

Involvement of a Conserved Intramembrane Acidic Residue in Cholesterol Binding of Mitochondrial VDAC1 Revealed by Microsecond-Scale Simulations

Voltage-dependent anion channel 1 (VDAC1), a β-barrel membrane protein abundant in the mitochondrial outer membrane, mediates the exchange of ions and metabolites between the mitochondrial matrix and the cytosol. Both experimental and previous computational studies suggest that a conserved, membrane-facing residue in VDAC1, glutamate 73 (E73), plays an essential role in the function of the channel, including its oligomerization and interaction with other cytosolic partner proteins. In addition, a recent photoaffinity labeling study identified E73 as a specific binding site for cholesterol, an endogenous membrane lipid that also regulates VDAC functions. However, how cholesterol interacts with E73 and the effects of cholesterol binding at E73 remain poorly understood. Here, we performed an extensive set of microsecond-long atomistic molecular dynamics simulations on both wildtype and mutant forms and in different protonation states (totaling 14 μs) to characterize cholesterol interactions with VDAC1. Analysis of lipid occupancy showed that cholesterol exhibited distinct preferred binding sites from phospholipids on VDAC1. Spontaneous binding and unbinding of cholesterol to E73 in its deprotonated state was captured, a process accompanied by local membrane deformation and water solvation at the E73 side-chain in the middle of the lipid bilayer. Compared to VDAC1 in a pure phospholipid environment, the presence of cholesterol reduces the fluctuations of the β-strands in proximity to E73. Based on our results, we propose a stabilizing role of cholesterol in regulating the VDAC1 dynamics in the region close to E73, which might further modulate VDAC1 function as an ion channel.

Mitochondrial Content, but Not Function, Is Altered With a Multimodal Resistance Training Protocol and Adequate Protein Intake in Leucine-Supplemented Pre/Frail Women.

Background: Frailty is a clinical condition associated with loss of muscle mass and strength (sarcopenia). Mitochondria are centrally implicated in frailty and sarcopenia. Leucine (Leu) can alter mitochondrial content in myocytes, while resistance training (RT) is the strongest stimulus to counteract sarcopenia and may enhance mitochondrial biogenesis.Objective: We determined the effects of Leu supplementation and RT on mitochondrial content and function in pre/frail elderly women in a randomized double-blinded placebo-controlled study.Methods: Nineteen pre/frail elderly women (77.5 ± 1.3 y, BMI: 25.1 ± 0.9 kg/m2), based on the Frailty Phenotype, underwent 3-months of RT 3×/week with protein-optimized diet and were randomized to 7.5 g/d of Leu supplementation or placebo alanine (Ala). Pre/post-intervention mitochondrial respiration, reactive oxygen species (ROS) production, calcium retention capacity (CRC), time to permeability transition pore (mPTP) opening, mitochondrial voltage-dependent anion channel (VDAC) protein content, leg press 1-repetition maximum (1RM), and 6-min walk test (6MWT) were measured.Results: No time, supplementation, or interaction effects were observed for respiration, ROS, time to mPTP opening, and CRC. VDAC levels significantly increased in the Leu group post-intervention (p = 0.012). Both groups significantly increased leg press 1RM and 6MWT, with no effect of supplementation.Discussion: Leu supplementation with 3 months of RT increased mitochondrial content. Future studies should investigate if there is an increase in mitochondrial turnover or a shift in quality control (mitophagy) in leucine supplemented pre/frail elderly women who undergo 12 weeks of RT.Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT01922167.

Tubular Mas receptor mediates lipid-induced kidney injury

Obesity-related kidney diseases are becoming serious health problems worldwide, yet the mechanism by which obesity causes kidney injury is not fully understood. The purpose of current study was to investigate the role of Mas receptor in lipid-induced kidney injury. In mice fed with high-fat diet (HFD), the protein abundance of markers of autophagy, endoplasmic reticulum stress (ER stress) and apoptosis was dramatically increased in the kidney cortex, which was markedly prevented by Mas deletion (Mas−/−) or Mas receptor antagonist A779. Palmitic acid (PA) induced persistently increased autophagy, ER stress, and apoptosis as well as mitochondrial injuries in primary cultured proximal tubular cells from wild type, but not from Mas−/− mice. In human proximal tubular HK2 cells, PA-induced autophagy and ER stress was aggravated by Mas agonists Ang (1–7) or AVE0991, but attenuated by A779 or Mas knockdown. Stimulation of Mas resulted in elevated intracellular calcium levels [Ca2+]i in HK2 cells treated with PA, whereas inhibition or knockdown of Mas decreased [Ca2+]i. Mitochondrial outer membrane located voltage-dependent anion channel (VDAC1) was markedly upregulated in HK2 cells treated with PA, which was associated with impaired mitochondrial morphology and depolarization. These were enhanced by AVE0991 and suppressed by A779 or Mas knockdown. Mas knockdown in HK2 cells prevented impaired interactions among VDAC1, autophagy adaptor P62, and ubiquitin, induced by PA, leading to a potential ubiquitination of VDAC1. In conclusion, Mas receptor-mediated lipid-induced impaired autophagy and ER stress in the kidney, likely contributing to tubular injuries in obesity-related kidney diseases.

Physical, genetic and functional interactions between the eisosome protein Pil1 and the MBOAT O-acyltransferase Gup1

The Saccharomyces cerevisiae MBOAT O-acyltransferase Gup1 is involved in many processes, including cell wall and membrane composition and integrity, and acetic acid-induced cell death. Gup1 was previously shown to interact physically with the mitochondrial membrane VDAC (Voltage-Dependent Anion Channel) protein Por1 and the ammonium transceptor Mep2. By co-immunoprecipitation, the eisosome core component Pil1 was identified as a novel physical interaction partner of Gup1. The expression of PIL1 and Pil1 protein levels were found to be unaffected by GUP1 deletion. In ∆gup1 cells, Pil1 was distributed in dots (likely representing eisosomes) in the membrane, identically to wt cells. However, ∆gup1 cells presented 50% less Pil1-GFP dots/eisosomes, suggesting that Gup1 is important for eisosome formation. The two proteins also interact genetically in the maintenance of cell wall integrity, and during arsenite and acetic acid exposure. We show that Δgup1 Δpil1 cells take up more arsenite than wt and are extremely sensitive to arsenite and to acetic acid treatments. The latter causes a severe apoptotic wt-like cell death phenotype, epistatically reverting the ∆gup1 necrotic type of death. Gup1 and Pil1 are thus physically, genetically and functionally connected.

Adverse effects of Δ9-tetrahydrocannabinol on neuronal bioenergetics during postnatal development.

Ongoing societal changes in views on the medical and recreational roles of cannabis increased the use of concentrated plant extracts with a Δ9-tetrahydrocannabinol (THC) content of more than 90%. Even though prenatal THC exposure is widely considered adverse for neuronal development, equivalent experimental data for young age cohorts are largely lacking. Here, we administered plant-derived THC (1 or 5 mg/kg) to mice daily during P5–P16 and P5–P35 and monitored its effects on hippocampal neuronal survival and specification by high-resolution imaging and iTRAQ proteomics, respectively. We found that THC indiscriminately affects pyramidal cells and both cannabinoid receptor 1+ (CB1R)+ and CB1R– interneurons by P16. THC particularly disrupted the expression of mitochondrial proteins (complexes I–IV), a change that had persisted even 4 months after the end of drug exposure. This was reflected by a THC-induced loss of membrane integrity occluding mitochondrial respiration and could be partially or completely rescued by pH stabilization, antioxidants, bypassed glycolysis, and targeting either mitochondrial soluble adenylyl cyclase or the mitochondrial voltage-dependent anion channel. Overall, THC exposure during infancy induces significant and long-lasting reorganization of neuronal circuits through mechanisms that, in large part, render cellular bioenergetics insufficient to sustain key developmental processes in otherwise healthy neurons.

Evidences of a Direct Relationship between Cellular Fuel Supply and Ciliogenesis Regulated by Hypoxic VDAC1-ΔC.

Simple SummaryHere, we demonstrate that the hypoxia-induced cleaved form of VDAC1 (VDAC1-ΔC) reprograms the cell to utilize more metabolites and is implicated in up-regulation of glycolysis and mitochondrial respiration, conferring a direct survival advantage in hypoxic microenvironment. We further highlight a direct relationship between VDAC1-ΔC, the primary cilium and cell metabolism.Metabolic flexibility is the ability of a cell to adapt its metabolism to changes in its surrounding environment. Such adaptability, combined with apoptosis resistance provides cancer cells with a survival advantage. Mitochondrial voltage-dependent anion channel 1 (VDAC1) has been defined as a metabolic checkpoint at the crossroad of these two processes. Here, we show that the hypoxia-induced cleaved form of VDAC1 (VDAC1-ΔC) is implicated in both the up-regulation of glycolysis and the mitochondrial respiration. We demonstrate that VDAC1-ΔC, due to the loss of the putative phosphorylation site at serine 215, concomitantly with the loss of interaction with tubulin and microtubules, reprograms the cell to utilize more metabolites, favoring cell growth in hypoxic microenvironment. We further found that VDAC1-ΔC represses ciliogenesis and thus participates in ciliopathy, a group of genetic disorders involving dysfunctional primary cilium. Cancer, although not representing a ciliopathy, is tightly linked to cilia. Moreover, we highlight, for the first time, a direct relationship between the cilium and cancer cell metabolism. Our study provides the first new comprehensive molecular-level model centered on VDAC1-ΔC integrating metabolic flexibility, ciliogenesis, and enhanced survival in a hypoxic microenvironment.

Antidepressant drug sertraline modulates AMPK-MTOR signaling-mediated autophagy via targeting mitochondrial VDAC1 protein

ABSTRACT Macroautophagy/autophagy (hereafter autophagy), the process of mass degradation of unnecessary elements within the cell, is often dysregulated in many diseases such as cancer, atherosclerosis, and neurodegenerative diseases. Hence, autophagy modulating agents have a great potential to be therapeutic agents for the autophagy-related diseases. Here we report that an anti-depressant drug sertraline (Sert) is an autophagy-inducing agent. Mechanistically, Sert potentially binds to and antagonizes the mitochondrial VDAC1 (voltage dependent anion channel 1), resulting in reduced cellular ATP (adenosine triphosphate) level, activation of AMP-activated protein kinase (AMPK) and inhibition of its downstream, MTOR (mechanistic target of rapamycin kinase)-RPS6KB1 (ribosomal protein S6 kinase B1) signaling pathway. Cells lacking VDAC1 expression completely abrogate the modulatory effect of Sert on AMPK-MTOR pathway and autophagy-inducing activity. We further show that Sert suppresses tauopathy by promoting the autophagic degradation of MAPT (microtubule associated protein tau) protein via inducing autophagy. Our study demonstrates the potential of Sert as a novel small molecule autophagy-inducing agent and provides a new drug candidate to treat autophagy related diseases by targeting VDAC1. Abbreviations: AMP: adenosine monophosphate; AMPK: AMP-activated protein kinase; ATP: adenosine triphosphate; Baf: bafilomycin A1; BiFC: biomolecular fluorescence complementation; CAMKK2/CAMKKB: calcium/calmodulin dependent protein kinase kinase 2; CC: compound C; DARTS: drug affinity responsive target stability; HUVECs: human umbilical vein endothelial cells; Inda: indatraline; STK11/LKB1: serine/threonine kinase 11; MAPT: microtubule associated protein tau; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; 3-MA: 3-methyladenine; MEFs: mouse embryonic fibroblasts; MTOR: mechanistic target of rapamycin kinase; PI3K: phosphoinositide 3-kinase; Rapa: rapamycin; Sert: sertraline; RPS6KB1: ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; SLC6A4/SERT1: solute carrier family 6 member 4; TFEB: transcription factor EB; VDAC1: voltage dependent anion channel 1; WT: wild-type; WM: wortmannin.

Modulation of the mitochondrial voltage-dependent anion channel (VDAC) by hydrogen peroxide and its recovery by curcumin.

The Voltage-Dependent Anion Channel (VDAC) plays a vital role in mitochondria-mediated transport of ions and metabolites. It is well established that mitochondria are a site for production of hydrogen peroxide (H2O2). Excess production of H2O2 is toxic to the cell and causes oxidative stress. Therefore, the effect of H2O2 on the single-channel conductance of VDAC was investigated. In vitro bilayer electrophysiology experiments were performed on VDAC isolated from rat brain mitochondria, which consists predominately of the isoform VDAC1. VDAC was treated with H2O2 on a planar bilayer membrane (BLM). The conductance of VDAC increased upon H2O2 treatment, whereas the same concentration of H2O2 was unable to affect the BLM (without protein) over a long period of time. Subsequently, the sequential addition of curcumin to H2O2-treated VDAC reduced the conductance. Experimental results (bilayer electrophysiology) demonstrate the role of curcumin in the restoration of the activity of VDAC affected by H2O2. In silico docking studies enables identification of the probable binding site of H2O2 on VDAC. We further find that the oligomerization of VDAC that results in its increased conductance is an effect of lipid oxidation by H2O2.

The effect of eleutherococcus senticosus on metabolism-associated protein expression in 3T3-L1 and C2C12 cells.

[Purpose] In vivo studies have demonstrated the ergogenic benefits of eleutherococcus senticosus (ES) supplementation. ES has been observed to enhance endurance capacity, improve cardiovascular function, and alter metabolic functions (e.g., increased fat utilization); however, the exact mechanisms involved remain unknown. We aimed to determine whether ES could effectively induce fat loss and improve muscle metabolic profiles through increases in lipolysis- and lipid metabolism-associated protein expression in 3T3-L1 adipocytes and C2C12 skeletal muscle cells, respectively, to uncover the direct effects of ES on adipocytes and skeletal muscle cells.[Methods] Different doses of ES extracts (0.2, 0.5, and 1.0 mg/mL) were added to cells (0.2 ES, 0.5 ES, and 1.0 ES, respectively) for 72 h and compared to the vehicle control (control).[Results] The intracellular triacylglycerol (TG) content significantly decreased (p < 0.05 for 0.2 ES, p < 0.01 for 0.5 ES and 1.0 ES) in 3T3-L1 cells. Adipose triglyceride lipase, which is involved in active lipolysis, was significantly higher in the 1.0 ES group than in the control group (p < 0.01) of 3T3-L1 adipocytes. In C2C12 cells, the mitochondrial protein voltage-dependent anion channel (VDAC) was significantly increased in the 1.0 ES group (p < 0.01). Furthermore, we found that 1.0 ES activated both 5' AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) in skeletal muscle cells (p < 0.01).[Conclusion] These findings suggest that ES extracts decreased TG content, presumably by increasing lipase in adipocytes and metabolism-associated protein expression as well as mitochondrial biogenesis in muscle cells. These effects may corroborate previous in vivo findings regarding the ergogenic effects of ES supplementation.

Disruption in iron homeostasis and impaired activity of iron-sulfur cluster containing proteins in the yeast model of Shwachman-Diamond syndrome

BackgroundShwachman-Diamond syndrome (SDS) is a congenital disease that affects the bone marrow, skeletal system, and pancreas. The majority of patients with SDS have mutations in the SBDS gene, involved in ribosome biogenesis as well as other processes. A Saccharomyces cerevisiae model of SDS, lacking Sdo1p the yeast orthologue of SBDS, was utilized to better understand the molecular pathogenesis in the development of this disease.ResultsDeletion of SDO1 resulted in a three-fold over-accumulation of intracellular iron. Phenotypes associated with impaired iron-sulfur (ISC) assembly, up-regulation of the high affinity iron uptake pathway, and reduced activities of ISC containing enzymes aconitase and succinate dehydrogenase, were observed in sdo1∆ yeast. In cells lacking Sdo1p, elevated levels of reactive oxygen species (ROS) and protein oxidation were reduced with iron chelation, using a cell impermeable iron chelator. In addition, the low activity of manganese superoxide dismutase (Sod2p) seen in sdo1∆ cells was improved with iron chelation, consistent with the presence of reactive iron from the ISC assembly pathway. In yeast lacking Sdo1p, the mitochondrial voltage-dependent anion channel (VDAC) Por1p is over-expressed and its deletion limits iron accumulation and increases activity of aconitase and succinate dehydrogenase.ConclusionsWe propose that oxidative stress from POR1 over-expression, resulting in impaired activity of ISC containing proteins and disruptions in iron homeostasis, may play a role in disease pathogenesis in SDS patients.

Metabolomic and Signaling Programs Induced by Immobilized versus Soluble IFN γ in Neural Stem Cells.

Neural stem cells (NSCs) provide a strategy to replace damaged neurons following traumatic central nervous system injuries. A major hurdle to translation of this therapy is that direct application of NSCs to CNS injury does not support sufficient neurogenesis due to lack of proper cues. To provide prolonged spatial cues to NSCs IFN-γ was immobilized to biomimetic hydrogel substrate to supply physical and biochemical signals to instruct the encapsulated NSCs to be neurogenic. However, the immobilization of factors, including IFN-γ, versus soluble delivery of the same factor, has been incompletely characterized especially with respect to activation of signaling and metabolism in cells over longer time points. In this study, protein and metabolite changes in NSCs induced by immobilized versus soluble IFN-γ at 7 days were evaluated. Soluble IFN-γ, refreshed daily over 7 days, elicited stronger responses in NSCs compared to immobilized IFN-γ, indicating that immobilization may not sustain signaling or has altered ligand/receptor interaction and integrity. However, both IFN-γ delivery types supported increased βIII tubulin expression in parallel with canonical and noncanonical receptor-signaling compared to no IFN-γ. Global metabolomics and pathway analysis revealed that soluble and immobilized IFN-γ altered metabolic pathway activities including energy, lipid, and amino acid synthesis, with soluble IFN-γ having the greatest metabolic impact overall. Finally, soluble and immobilized IFN-γ support mitochondrial voltage-dependent anion channel (VDAC) expression that correlates to differentiated NSCs. This work utilizes new methods to evaluate cell responses to protein delivery and provides insight into mode of action that can be harnessed to improve regenerative medicine-based strategies.

Regulation of Single-Channel Conductance of Voltage-Dependent Anion Channel by Mercuric Chloride in a Planar Lipid Bilayer.

The existence of mercury in various forms, e.g., elemental, organic, and inorganic has been known for decades. In any of these forms, it is poisonous to metabolism. In this, an investigation about the effect of the inorganic form of mercury, i.e., mercuric chloride (HgCl2) to the mitochondrial voltage-dependent anion channel (VDAC), has been done after isolation from the cardiac and brain tissues of Wistar rats. In vitro electrophysiology experiments were performed in Cardiolipin planar lipid bilayer membrane (BLM) to study the change in the conductance, selectivity, and gating charge of VDAC post HgCl2 treatment. A reduction in mean conductance of VDAC from 4.3 ± 0.18 to 1.66 ± 0.11 nS was observed. Further, the Gating charge calculated before (± 3.5) and after HgCl2 treatment (± 2.3) showed significant difference. Later, VDAC's behavior was studied at different concentrations of HgCl2 ranging from 0.1μM to 1mM. The Inhibitory concentration (IC50) was calculated from the linear regression plot. The IC50 was found to be 488.1μM. In the asymmetrical HgCl2 (5:1), a permeability ratio of cation to anion was found to be 4.2. It is interpreted that VDAC functioning is affected due to the application of 4mM HgCl2 and a reduction in the conductance, gating charge, and permeability of VDAC was detected. The results provide clues to HgCl2-induced toxicity mediated through VDAC in the Cardiolipin BLM.

Olesoxime, a cholesterol-like neuroprotectant restrains synaptic vesicle exocytosis in the mice motor nerve terminals: Possible role of VDACs

Olesoxime is a cholesterol-like neuroprotective compound that targets to mitochondrial voltage dependent anion channels (VDACs). VDACs were also found in the plasma membrane and highly expressed in the presynaptic compartment. Here, we studied the effects of olesoxime and VDAC inhibitors on neurotransmission in the mouse neuromuscular junction. Electrophysiological analysis revealed that olesoxime suppressed selectively evoked neurotransmitter release in response to a single stimulus and 20 Hz activity. Also olesoxime decreased the rate of FM1–43 dye loss (an indicator of synaptic vesicle exocytosis) at low frequency stimulation and 20 Hz. Furthermore, an increase in extracellular Cl− enhanced the action of olesoxime on the exocytosis and olesoxime increased intracellular Cl− levels. The effects of olesoxime on the evoked synaptic vesicle exocytosis and [Cl−]i were blocked by membrane-permeable and impermeable VDAC inhibitors. Immunofluorescent labeling pointed on the presence of VDACs on the synaptic membranes. Rotenone-induced mitochondrial dysfunction perturbed the exocytotic release of FM1–43 and cell-permeable VDAC inhibitor (but not olesoxime or impermeable VDAC inhibitor) partially mitigated the rotenone-driven alterations in the FM1–43 unloading and mitochondrial superoxide production. Thus, olesoxime restrains neurotransmission by acting on plasmalemmal VDACs whose activation can limit synaptic vesicle exocytosis probably via increasing anion flux into the nerve terminals.

Quinidine partially blocks mitochondrial voltage-dependent anion channel (VDAC).

Quinidine is an antiarrhythmic drug commonly used for the treatment of cardiac ailments. It affects oxidative phosphorylation, calcium uptake, and ion channels of mitochondria. We have investigated the interaction of Quinidine and mitochondrial voltage-dependent anion channel (VDAC). VDAC was purified from neuronal tissue of Wistar rats and in vitro bilayer electrophysiology experiments were performed on it. 50-mM Quinidine treatment on VDAC leads to a sudden drop in its conductance. The dose of Quinidine leading to a half-maximal current through a single-channel VDAC was calculated using Quinidine at different concentrations. In silico molecular docking studies using Autodock-4.2 software indicate interaction between Quinidine and VDAC. Docking results demonstrate the interaction of Quinidine and VDAC on its Glutamic acid residue (Glu-206 of VDAC). Fluorescence spectroscopy results on Quinidine and Glutamic acidinteraction show an increase in the intensity and wavelength of Quinidine fluorescence, whereas no interaction between Quinidine and Cysteine was observed. This further supports the Glutamic acid and Quinidine interaction. In conclusion, we report Quinidine partially blocks VDAC due to the interaction of Glutamic acid and Quinidine in the channel pore.

Arabidopsis Mitochondrial Voltage-Dependent Anion Channels Are Involved in Maintaining Reactive Oxygen Species Homeostasis, Oxidative and Salt Stress Tolerance in Yeast

Voltage-dependent anion channels (VDACs) are conserved proteins of the mitochondria. We have functionally compared Arabidopsis VDACs using Saccharomyces cerevisiae Δpor1 and M3 yeast system. VDAC (1, 2, and 4) were able to restore Δpor1 growth in elevated temperature, in oxidative and salt stresses, whereas VDAC3 only partially rescued Δpor1 in these conditions. The ectopic expression of VDAC (1, 2, 3, and 4) in mutant yeast recapitulated the mitochondrial membrane potential thus, enabled it to maintain reactive oxygen species homeostasis. Overexpression of these VDACs (AtVDACs) in M3 strain did not display any synergistic or antagonistic activity with the native yeast VDAC1 (ScVDAC1). Collectively, our data suggest that Arabidopsis VDACs are involved in regulating respiration, reactive oxygen species homeostasis, and stress tolerance in yeast.

Targeting Mitochondrial Fission to Trigger Cancer Cell Death.

Carefully orchestrated interactions between mitochondrial proteins that facilitate cell death remain a topic of intense research, however, key steps remain to be elucidated, especially those that drive selective killing in cancer cells. How mitochondrial dysfunction and its regulation in cancer can be robustly leveraged for anticancer cell killing in a heterogeneous population of cells within a tumor also remains a promising but unfulfilled premise. Toward this goal, in this issue of Cancer Research, Seo and colleagues have identified the protein complex between mitochondrial fission factor (MFF1 and MFF2) and voltage-dependent anion channel (VDAC1) as a novel regulator of mitochondrial cell death and a potential target for selective cancer cell killing.See related article by Seo et al., p. 6215.