Expression Of Voltage-dependent Anion Channel Research Articles

Identification of potential predictive markers of dexamethasone resistance in childhood acute lymphoblastic leukemia.

Response to dexamethasone (DEXA), as a hallmark drug in the treatment of childhood acute lymphoblastic leukemia (ALL), is one of the pivotal prognostic factors in the prediction of outcome in ALL. Identification of predictive markers of chemoresistance is beneficial to selecting of the best therapeutic protocol with the lowest effect adverse. Hence, we aimed to find drug targets using the 2DE/MS proteomics study of a DEXA-resistant cell line (REH) as a model for poor DEXA responding patients before and after drug treatment. Using the proteomic methods, three differentially expressed proteins were detected, including voltage dependent anion channel 1 (VDAC1), sorting Nexin 3 (SNX3), and prefoldin subunit 6 (PFDN6). We observed low expression of three proteins after DEXA treatment in REH cells. We subsequently verified low expression of resulted proteins at the mRNA level using the quantitative PCR method. These proteins are promising proteins because of their important roles in drug resistance and regulation of apoptosis (VDAC1), protein trafficking (SNX3), and protein folding (PFDN6). Additionally, mRNA expression level of these proteins was assessed in 17 bone marrow samples from children with newly diagnosed ALL and 7 non-cancerous samples as controls. The results indicated that independent of the molecular subtypes of leukemia, mRNA expression of VDAC1, SNX3, and PFDN6 decreased in ALL samples compared with non-cancerous samples particularly in VDAC1 (p < 0.001). Additionally, mRNA expression of three proteins was also declined in high-risk samples compared with standard risk cases. These results demonstrated diagnostic and prognostic value of these proteins in childhood ALL. Furthermore, investigation of protein-protein interaction using STRING database indicated that these proteins involved in the signaling pathway of NR3C1 as dexamethasone target. In conclusion, our proteomic study in DEXA resistant leukemic cells revealed VDAC1, SNX3, and PFDN6 are promising proteins that might serve as potential biomarkers of prognosis and chemotherapy in childhood ALL.

A Single Talent Immunogenic Membrane Antigen and Novel Prognostic Predictor: voltage-dependent anion channel 1 (VDAC1) in Pancreatic Cancer.

Immunogenic membrane antigens associated with multiple biological functions of human cancer cells, have significant value in molecule diagnosis and targeted therapy. Here we screened immunogenic membrane antigens in pancreatic cancer by immunobloting IgG purified from sera of 66 pancreatic cancer patients with membrane proteins separated from two-dimensional PAGE of human pancreatic cancer cell line SWl990, and identified voltage-dependent anion channel 1 (VDAC1) as one of the potential immunogenic membrane antigens. Further studies focusing on VDAC1 demonstrated that VDAC1 mRNA and protein were significantly expressed in the tested pancreatic cancer cell lines. VDAC1 silencing with RNAi significantly decreased cell growth, invasion and migration in the pancreatic cancer cell line Capan-1. Additionally, VDAC1 expression was upregulated in pancreatic cancer tissue compared with normal pancreas samples and patients with low VDAC1 expression had a significantly greater median survival compared to those with high expression (27.0 months vs. 17.8 months, P = 0.039). In multivariable analysis, VDAC1 staining was an independent prognostic factor for survival [(Hazard-Ratio) HR = 1.544, 95% CI = 0.794–3.0, P = 0.021]. These results demonstrated that VDAC1 may be a candidate immunogenic membrane antigen for pancreatic cancer, a potential independent prognostic marker, and an ideal drug target.

Cigarette smoke effects on TSPO and VDAC expression in a cellular lung cancer model.

As redox iron and copper ions are found in lung pleural fluid and parenchyma, we aimed to examine the effect of cigarette smoke (CS) alone and the combined effects of CS and redox metals, iron and copper ions, containing medium (saliva), on epithelial H1299 lung cancer cells. We also examined the expression levels of the anticarcinogenic and proapoptotic 18 kDa translocator protein (TSPO) and its closely associated protein voltage-dependent anion channel (VDAC). H1299 cells were subjected to western blot analysis using anti-TSPO and anti-VDAC antibodies. With the former, the 18 kDa band appeared as expected and a 72 kDa band also appeared. It may be assumed that in H1299 lung cancer cells, an additional form of TSPO protein appears as a four-unit tetrameric complex, which is affected by CS exposure. A significant decrease in the expression level of the 72 kDa protein occurred following only 60 min of CS exposure, whereas VDAC protein levels were increased following only 30 min of CS exposure. These results, together with our previous related studies, suggest a comprehensive two-arm novel paradigm for lung cancer induced by CS, and mediated by an altered TSPO protein, possibly resulting from both the 72 kDa TSPO degradation and redox metal ion-induced enhancement of free radical attack. We suggest that both of the most important proapoptotic and anticancer proteins, p53 and TSPO, are damaged by CS, paving the way for lung cancer initiation and progression.

Proteomics-based identification of VDAC1 as a tumor promoter in cervical carcinoma.

We used oxidative isotope-coded affinity tags (OxICAT) to investigate the global redox status of proteins in human papillomavirus (HPV)-related cervical cancer cells, in order to identify a potential target for gene therapy. Voltage-dependent anion channel 1 (VDAC1) was found to be highly oxidized in HPV-positive cervical cancer cells. VDAC1 expression correlated significantly with the invasion of cervical cancer, the grade of cervical intraepithelial neoplasia (CIN) and the expression of HPV16 E7 in CIN. Knockdown of VDAC1 in cell lines increased the rate of apoptosis, while overexpression of the VDAC1 (respectively) partly reversed the effect. Thus, VDAC1 may promote the malignant progression of HPV-related disease, and treatments designed to suppress VDAC1 could prevent the progression of HPV-induced cervical disease.

Decreased expression of microRNA-320a promotes proliferation and invasion of non-small cell lung cancer cells by increasing VDAC1 expression.

Accumulating evidence indicates that Voltage Dependent Anion Channel 1 (VDAC1) correlates with the initiation and progression of non-small cell lung cancer (NSCLC). However, the regulatory mechanism of VDAC1 in NSCLC remains unclear. Previous studies have reported that expression of miR-320a was decreased in human primary squamous cell lung carcinoma, which prompted us to investigate whether there is a functional link between decreased miR-320a and a high expression of VDAC1. In the present report, using computational analysis, we first show that miR-320a has a potential binding site on VDAC1 mRNA, and expression of miR-320a was decreased in NSCLC cell lines. Using gain-of-function and rescue experiments, we demonstrate that VDAC1 is a direct target of miR-320a in NSCLC cells, and miR-320a inhibits VDAC1 expression in NSCLC cells. Further we show that MiR-320a was significantly decreased in NSCLC tissues compared with adjacent non-tumor tissues, and MiR-320a level is negatively correlated with VDAC1 in NSCLC tissues by Pearson's correlation coefficient analysis. Moreover, using cellular ATP assay, we found that suppression of VDAC1 expression may inhibit cell proliferation and invasion of NSCLC by decreasing cell energy and metabolism. Importantly, we showed that ectopic overexpression of miR-320a blocked tumor cell proliferation and invasion, both in vitro and in vivo, through inhibiting VDAC1. Our results suggest that reduced expression of miR-320a facilitates the development of NSCLCs by increasing VDAC1 expression. We identified a novel regulatory mechanism between miR-320a and VDAC1, and miR-320a may serve as a tumor suppressor gene and a promising therapeutic target of NSCLCs.

VDAC1-interacting anion transport inhibitors inhibit VDAC1 oligomerization and apoptosis

Mitochondria-mediated apoptosis involves pro-apoptotic protein release from the mitochondria to the cytosol, triggering apoptosis. However, the mechanisms by which apoptotic initiators cross the outer mitochondrial membrane (OMM) remain unclear. The voltage-dependent anion channel 1 (VDAC1), an OMM protein, is central to mitochondria-mediated apoptosis. In previous work, we demonstrated that apoptosis induction is associated with VDAC1 oligomerization, forming a mega-pore that mediates pro-apoptotic protein release. Here, we demonstrated that several known anion transport inhibitors, DIDS, SITS, H2DIDS, DNDS, and DPC, all interact with VDAC1, as revealed by micro-scale thermophoresis and decreased conductance of bilayer-reconstituted VDAC1. These compounds inhibited apoptosis stimuli-induced release of mitochondrial pro-apoptotic proteins, apoptosis and VDAC1 oligomerization, as monitored by chemical cross-linking or in living cells by BRET2. Moreover, the compounds inhibited VDAC1 oligomerization in isolated mitochondria and as induced by VDAC1 over-expression, suggesting that the inhibitory effect of the tested compounds involved VDAC1.Finally, the compounds also inhibited apoptosis-associated increases in intracellular Ca2+, ([Ca2+]i), ROS production, mitochondria membrane potential dissipation and the increase in VDAC1 expression levels. The results presented here explored a new mechanism of action for DIDS and its analogs. All inhibited apoptosis via direct interaction with VDAC1 to inhibit its oligomerization and subsequent Cyto c release and apoptosis. Such results may allow the development of a VDAC1-specific inhibitor that would offer substantial insight into the function of VDAC1 in controlling metabolism, energy production, cholesterol transport and apoptosis. Finally, inhibitors of apoptosis could serve in pathological conditions where enhanced apoptosis is found, such as neurodegenerative diseases.

MicroRNA-7 Regulates the Function of Mitochondrial Permeability Transition Pore by Targeting VDAC1 Expression

Mitochondrial dysfunction is one of the major contributors to neurodegenerative disorders including Parkinson disease. The mitochondrial permeability transition pore is a protein complex located on the mitochondrial membrane. Under cellular stress, the pore opens, increasing the release of pro-apoptotic proteins, and ultimately resulting in cell death. MicroRNA-7 (miR-7) is a small non-coding RNA that has been found to exhibit a protective role in the cellular models of Parkinson disease. In the present study, miR-7 was predicted to regulate the function of mitochondria, according to gene ontology analysis of proteins that are down-regulated by miR-7. Indeed, miR-7 overexpression inhibited mitochondrial fragmentation, mitochondrial depolarization, cytochrome c release, reactive oxygen species generation, and release of mitochondrial calcium in response to 1-methyl-4-phenylpyridinium (MPP(+)) in human neuroblastoma SH-SY5Y cells. In addition, several of these findings were confirmed in mouse primary neurons. Among the mitochondrial proteins identified by gene ontology analysis, the expression of voltage-dependent anion channel 1 (VDAC1), a constituent of the mitochondrial permeability transition pore, was down-regulated by miR-7 through targeting 3'-untranslated region of VDAC1 mRNA. Similar to miR-7 overexpression, knockdown of VDAC1 also led to a decrease in intracellular reactive oxygen species generation and subsequent cellular protection against MPP(+). Notably, overexpression of VDAC1 without the 3'-UTR significantly abolished the protective effects of miR-7 against MPP(+)-induced cytotoxicity and mitochondrial dysfunction, suggesting that the protective effect of miR-7 is partly exerted through promoting mitochondrial function by targeting VDAC1 expression. These findings point to a novel mechanism by which miR-7 accomplishes neuroprotection by improving mitochondrial health.

MicroRNA-7 downregulates the oncogene VDAC1 to influence hepatocellular carcinoma proliferation and metastasis

Recent studies have been shown that voltage-dependent anion channel 1 (VDAC1) plays an important role in carcinogenesis. However, its molecular biological function in hepatocellular carcinoma (HCC) has not been entirely clarified. This study investigated the expression of VDAC1 in HCC and its prognostic value for HCC patients. Furthermore, we also identify the relevant VDAC1 direct target. Western blot, real-time quantitative PCR (qRT-PCR), and immunohistochemical (IHC) staining were performed to detect the expression of VDAC1 in HCC. Furthermore, the relationship between the VDAC1 level and clinicopathological features and prognostic values was explored. The effects of VDAC1 on HCC cell proliferation, migration, and invasion were also investigated in vitro. Predicted target gene of VDAC1 was determined by dual-luciferase reporter assay, qRT-PCR, and Western blot analyses. Our results revealed elevated VDAC1 messenger RNA (mRNA) (P = 0.0020) and protein (P = 0.0035) expression in tumor tissue samples compared with paired adjacent non-tumorous tissue samples. High VDAC1 expression was correlated with distant metastasis (P = 0.025), differentiation (P = 0.002), and advanced tumor stage (P = 0.004) in HCC patients. Kaplan-Meier survival analysis demonstrated that high expression of VDAC1 was significantly correlated with a poor prognosis for HCC patients (P < 0.001). The multivariate analysis revealed that VDAC1 expression was an independent prognostic factor of the overall survival rate of HCC patients. Furthermore, knockdown of VDAC1 inhibits HCC cell proliferation, migration, and invasion in vitro. Moreover, further study revealed that miR-7 was a putative target of VDAC1. Our study suggested that miR-7 suppressed the expression of VDAC1. VDAC1 plays an important role in tumor progression and may be used as a potential role in the prognosis of HCC patients.

Clinical implication of voltage-dependent anion channel 1 in uterine cervical cancer and its action on cervical cancer cells.

Two-dimensional gel electrophoresis and liquid chromatography-tandem mass spectrometry were performed to investigate the influence of human nonmetastatic clone 23 type 1 (nm23-H1), a metastasis-associated gene on proteomic alterations in cancer cells of the uterine cervix. It was validated by RT-PCR and Western blot analysis. The expression of voltage-dependent anion channel 1 (VDAC1) was increased in nm23-H1 gene silenced SiHa or CaSki cervical cancer cells. The clinical implication was shown that cervical cancer tissues with positive VDAC1 immunoreactivity exhibited deep stromal invasion (>10 mm in depth) and large tumor size (> 4 cm in diameter). Cervical cancer patients with positive VDAC1 immunoreactivity displayed higher recurrence and poorer overall survival than those with negative VDAC1. Silencing of VDAC1 reduced cell proliferation and migratory ability. Mitochondrial membrane potential was decreased and reactive oxygen species generation was increased in the VDAC1 gene-silenced cervical cancer cells. Cell cycle progression and autophagy were not changed in VDAC1 silencing cells. The cytotoxicity of cisplatin was significantly enhanced by knockdown of cellular VDAC1 and the compounds that interfere with hexokinase binding to VDAC. Therapeutic strategies may be offered using VDAC1 as a target to reduce cell growth and migration, enhance the synergistic therapeutic efficacy of cisplatin and reduce cisplatin dose-limiting toxicity.

Interaction of Transferrin-Endosomes with Mitochondria: Implications for Iron Transport to Ferrochelatase in Erythroid Cells

Delivery of iron (Fe) to most cells occurs following the binding of diferric transferrin (Tf) to its cognate receptors on the cell membrane following which the Tf-receptor complexes are internalized via endocytosis. Iron is then released from Tf within endosomes by a combination of Fe3+ reduction by Steap3 and a decrease in pH (~ pH 5.5). Subsequently, Fe2+ is transported through the endosomal membrane by DMT1. In erythroid cells, more than 90% of Fe has to enter mitochondria where ferrochelatase, the final enzyme in the heme biosynthetic pathway that inserts Fe2+ into protoporphyrin IX, resides.The intracellular path of iron from endosomes to ferrochelatase is still obscure or, at best, controversial. The prevailing opinion is that Fe, after its export from endosomes, spreads into the cytosol, from where the metal mysteriously finds its way into mitochondria. An opposing view is that the highly efficient transport of Fe toward ferrochelatase in erythroid cells requires a direct interaction between transferrin-endosomes and mitochondria ("kiss-and-run" hypothesis;Ponka Blood 89:1, 1997). Despite the longevity of the prevailing opinion, experimental evidence (Richardson et al. Blood 87:3477, 1996; Zhang et al. Blood 105:368, 2005; Sheftel et al. Blood 110: 125, 2007) only supports the latter hypothesis, which sees favorable reception among Cell Biologists (McBride BMC Biology 13:8, 2015).Our laboratory has demonstrated, using both 2D and 3D live confocal imaging, that the intracellular Fe pathway in erythroid cells indeed involves a transient interaction of endosomes with mitochondria. To furtherdemonstrate the contact between these organelles, we have developed a novel method based on flow cytometry analysis ("flow sub-cytometry") of lysates obtained from reticulocytes with fluorescently labeled mitochondria (MitoTracker Deep Red; MTDR) and endosomes (Alexa Green Transferrin; AGTf). Using this strategy, we have identified three distinct populations: endosomes, mitochondria, and a population double-labeled with both fluorescent markers representing endosomes interacting with mitochondria. The size of the double-labeled population increases with the incubation time and plateaus in approximately 20 min.In this study, we examined whether reticulocyte mitochondria interact with Tf in a cell-free system. Lysates obtained by freeze-thawing of reticulocytes previously labeled with MTDR were incubated with AGTf for various time intervals. Examination of lysates by 2D confocal microscopy has revealed a time-dependent increase in the number of mitochondria being in contact with Tf-endosomes (fig 1: Images of mitochondria and endosomes; 20 min incubation with AGTf). This can be prevented by Fe2-Tf, but not by albumin, added to lysates. Moreover, the addition of unlabeled Fe2-Tf to reticulocyte lysates removed AGTf from mitochondria. We conclude that mitochondria from freeze-thawed reticulocyte lysates are associated with TfR that can reversibly bind Tf.We have also embarked on uncovering molecular partners involved in the endosome-mitochondria interactions. Using co-immunoprecipitation and pull-down strategies, we have attempted to detect proteins interacting with the intracellular loops of DMT1 that could be candidates for interactions with mitochondria. The co-immunoprecipitated proteins were separated based on their molecular weights, stained using Coomassie and/or Silver gel and identified by mass spectrometry followed by western blotting. We co-immunoprecipitated (from murine eryhroleukemia [MEL] cells and reticulocytes lysates) proteins that were pulled down with DMT1. One of the proteins that we have recognized is the voltage-dependent anion channel (VDAC), which is located at the outer membrane of the mitochondrion (Graham, et al. Curr Top Dev Biol. 59: 87, 2004). The identity of DMT1 was confirmed by western blotting using specific antibodies against VDAC. These results further support the concept of the physical interaction between endosomes and mitochondria. To examine a possible role of DMT1-VDAC interactions in iron trafficking, we silenced the expression of VDAC in MEL cells followed by the measurement of 59Fe incorporation from 59Fe-Tf into heme. Our finding of decreased 59Fe incorporation into heme of MEL cells with silenced VDAC supports the idea that this outer-membrane mitochondrial protein is involved in the interaction with endosomes. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Voltage-dependent Anion Channel 1 Mediates Amyloid β Toxicity and Represents a Potential Target for Alzheimer Disease Therapy

The voltage-dependent anion channel 1 (VDAC1), found in the mitochondrial outer membrane, forms the main interface between mitochondrial and cellular metabolisms, mediates the passage of a variety of molecules across the mitochondrial outer membrane, and is central to mitochondria-mediated apoptosis. VDAC1 is overexpressed in post-mortem brains of Alzheimer disease (AD) patients. The development and progress of AD are associated with mitochondrial dysfunction resulting from the cytotoxic effects of accumulated amyloid β (Aβ). In this study we demonstrate the involvement of VDAC1 and a VDAC1 N-terminal peptide (VDAC1-N-Ter) in Aβ cell penetration and cell death induction. Aβ directly interacted with VDAC1 and VDAC1-N-Ter, as monitored by VDAC1 channel conductance, surface plasmon resonance, and microscale thermophoresis. Preincubated Aβ interacted with bilayer-reconstituted VDAC1 and increased its conductance ∼ 2-fold. Incubation of cells with Aβ resulted in mitochondria-mediated apoptotic cell death. However, the presence of non-cell-penetrating VDAC1-N-Ter peptide prevented Aβ cellular entry and Aβ-induced mitochondria-mediated apoptosis. Likewise, silencing VDAC1 expression by specific siRNA prevented Aβ entry into the cytosol as well as Aβ-induced toxicity. Finally, the mode of Aβ-mediated action involves detachment of mitochondria-bound hexokinase, induction of VDAC1 oligomerization, and cytochrome c release, a sequence of events leading to apoptosis. As such, we suggest that Aβ-mediated toxicity involves mitochondrial and plasma membrane VDAC1, leading to mitochondrial dysfunction and apoptosis induction. The VDAC1-N-Ter peptide targeting Aβ cytotoxicity is thus a potential new therapeutic strategy for AD treatment.

CREB1-driven expression of miR-320a promotes mitophagy by down-regulating VDAC1 expression during serum starvation in cervical cancer cells.

The altered expression of miRNAs in response to stresses contributes to cancer pathogenesis. However, little is known regarding the mechanism by which cellular stresses drive alterations in miRNA expression. Here, we found that serum starvation enhanced mitophagy by downregulating the mitophagy-associated protein voltage-dependent anion channel 1 (VDAC1) and by inducing the expression of miR-320a and the transcription factor cAMP responsive element binding protein 1(CREB1). Furthermore, we cloned the promoter of miR-320a and identified the core promoter of miR-320a in the upstream -16 to -130 region of pre-miR-320a. Moreover, CREB1 was found to bind to the promoter of miR-320a to activate its expression and to induce mitophagy during serum starvation. Collectively, our results reveal a new mechanism underlying serum starvation-induced mitophagy in which serum starvation induces CREB1 expression, in turn activating miR-320a expression, which then down-regulates VDAC1 expression to facilitate mitophagy. These findings may provide new insights into cancer cell survival in response to environmental stresses.

The effect of paraquat on voltage-dependent anion channel and caspase-3, 8, 9 in the mitochondria of rat lung

To investigate the effects of different concentrations of paraquat (PQ) poisoning on the expression of voltage-dependent anion channel (VDAC) and caspase family in the mitochondria of rat lung tissue, and to explore possible mechanisms of acute lung injury induced by acute PQ poisoning. Two hundred healthy adult Wister rats with equal numbers of male and female ones were randomly and equally divided into control group and poisoned group. The control group received one-time gastric lavage with 1 ml of normal saline, and the poisoned group with PQ (50 mg/kg) diluted in 1 ml of normal saline. Twenty rats were collected at 1, 24, 72, 120, and 168 h after lavage with normal saline or PQ and dissected after anesthesia. Mitochondria were separated from rat lung tissue, and the content of VDAC and caspase-3, -8, and -9 were determined. The expression of VDAC and caspase-3, -8, and -9 in the poisoned rats were significantly higher than that in the control group (P < 0.001). At 1, 24, 72, 120, and 168 h after exposure, acute diffuse damages were found in alveolar capillary endothelial cells, alveolar epithelial cells, and pulmonary interstitial cells. Inflammatory cell infiltration in the pulmonary interstitium, alveolar structural disorder, and substantially increased fibroblasts were also found in rat lung tissue. PQ poisoning can up-regulate the expression of VDAC and caspase-3, -8, and -9 in mitochondria of rat lung tissue to induce acute lung injury.

Conjugated linoleic acid (CLA) stimulates mitochondrial biogenesis signaling by the upregulation of PPARγ coactivator 1α (PGC-1α) in C2C12 cells.

Along with its effect on body fat reduction, dietary conjugated linoleic acid (CLA) has been reported to improve physical activity and endurance capacity in mice. It has been suggested these effects may in part be due to physiological changes in skeletal muscle, however, the mode of action is not completely understood. Thus, the purpose of this study was to determine the relevant mechanisms of CLA isomers for mitochondrial biogenesis, one of the most important adaptive responses in skeletal muscle. Both cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) CLA isomers increased the expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), however, only the t10,c12 isomer, but not c9,t11, increased phosphorylation of AMP-activated protein kinase (AMPK) compared to the control. Among downstream biomarkers of PGC-1α, the CLA mixed isomer enhanced the expression of peroxisome proliferator-activated receptor-δ (PPARδ). Both c9,t11 and t10,c12 CLA isomers increased expression of nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (Tfam), while the c9,t11 increased expression of cytochrome c (Cyt C) and t10,c12 CLA increased expression of voltage-dependent anion channel (VDAC), respectively. Both CLA isomers significantly increased mitochondrial DNA copy number compared to that of control. These findings suggest that the individual CLA isomers potentiate mitochondrial biogenesis via PGC-1α-NRF-1-Tfam signaling cascade, although downstream regulation may be isomer dependent.

Genomic survey and gene expression analysis of the VDAC gene family in rice.

The voltage-dependent anion channel (VDAC), also known as a mitochondrial porin, plays an important role in the regulation of metabolic and energetic functions of mitochondria, as well as in mitochondria-mediated apoptosis. Cytoplasmic male sterility (CMS) is of major economic importance for commercial hybrid production and a research model for the interaction be-tween nuclear and cytoplasmic genomes. Recent research has revealed that CMS is associated with programmed cell death. Here, we used the Honglian (HL)-CMS line of rice (Oryza sativa) as material to investigate the association of O. sativa VDAC (OsVDAC) expression to CMS. Eight VDACs were extracted from rice in this study. Bioinformatic analysis of the rice VDACs was conducted at the DNA, cDNA, and protein level. Expression patterns of OsVDACs were analyzed in different organs and during different stages of pollen development using sterile line YuetaiA (YTA), and its maintainer line YuetaiB (YTB). Differential expression of OsVDACs between YTA and YTB was observed, suggesting that VDACs may be involved in the formation of HL-CMS.

Further Elucidation of the Mechanism of Iron Transport Form Plasma Transferrin to Mitochondrial Ferrochelatase: Further Evidence for the “Kiss and Run” Hypothesis

Normal hemoglobinization of immature red blood cells (RBC) requires iron (Fe) uptake from transferrin (Tf), mediated by Tf receptors (TfR). Following the binding of Fe(III)2-Tf to TfR on the erythroid cell membrane, the Tf-TfR complexes are internalized via endocytosis, following which Fe is released from Tf by a process involving endosomal acidification and reduction by Steap3. Fe2+ is then transported across the endosomal membrane by the divalent metal transporter 1 (DMT1). Unfortunately, the post-endosomal path of Fe within cells remains elusive or is, at best, controversial. It has been commonly accepted that a low molecular weight intermediate chaperones Fe in transit from endosomes to mitochondria and other sites of utilization; however, this much sought Fe binding intermediate has never been identified.In erythroid cells, more than 90% of Fe has to enter mitochondria where ferrochelatase, the final enzyme in the heme biosynthetic pathway that inserts Fe2+ into protoporphyrin IX, resides. Indeed, strong evidence exists for specific targeting of Fe toward mitochondria in developing red blood cells in which Fe acquired from Tf continues to flow into mitochondria even when the synthesis of protoporphyrin IX is suppressed. Thus, it has been hypothesized (Ponka P. Blood 89:1, 1997) that, in hemoglobin-producing cells, there is a direct relaying of iron from the endosomal machinery to that of the mitochondria. Numerous reports from our laboratory support this hypothesis: 1) Iron acquired from Tf accumulates in mitochondria even when the synthesis of protoporphyrin IX is inhibited (Richardson et al. Blood 87:3477,1996); 2) Endosome mobility is essential for the efficient incorporation of 59Fe from 59Fe-Tf-labeled endosomes into heme (Zhang et al. Blood 105:368, 2005) and, 3) Confocal laser microscopy shows that in reticulocytes, endosomes continuously traverse the cytosol and touch mitochondria (Sheftel et al. Blood 110: 125, 2007).Based on this, we propose that erythroid precursors have special adaptations that facilitate the high rate of iron transport from endosomes to mitochondria to meet the exceptionally high demand for heme synthesis. Our lab has previously shown, using 3D live confocal imaging, that the iron delivery pathway in developing RBC involves a transient interaction of endosomes with mitochondria. To further demonstrate the interaction of these organelles, we used a novel method based on flow cytometry analyses (flow sub-cytometry) of lysates obtained from reticulocytes with fluorescently labeled endosomes (Alexa Green Transferrin) and mitochondria (MitoTracker Deep Red). Using this strategy, we have identified three distinct populations: endosomes, mitochondria, and a population double-labeled with both fluorescent markers representing endosomes interacting with mitochondria. This strategy has been used in studies on reticulocytes and erythroblasts subjected to various experimental conditions.In this study, we intended to identify molecular partners involved in the endosme-mitochondria interaction. Using co-immunoprecipitation and pull-down strategies, we attempted to recognize proteins interacting with the extra-endosomal (intracellular) loops of DMT1, which may be involved in interactions with mitochondria. The co-immunoprecipitated proteins were separated based on their molecular weights, stained using Coomassie and/or Silver gel and identified by mass spectrometry and western blotting. Using these strategies, we co-immunoprecipitated (from MEL cells and reticulocytes lysates) proteins that were pulled down with DMT1. Using this approach, we have identified the voltage-dependent anion channel (VDAC), which is located at the outer membrane of the mitochondria (Graham, et al. Curr Top Dev Biol. 59: 87, 2004) as one of DMT1 interacting partners using western blotting and specific antibodies against VDAC. These results indicate the physical contact between endosomes and mitochondria. In addition, to define the possible role of DMT1-VDAC interactions in mediating iron uptake, we used a siRNA approach to silence VDAC expression in MEL cells and then measured 59Fe incorporation into heme. These studies revealed decreased 59Fe incorporation into MEL cells with silenced VDAC. Our findings provide a strong support for the hypothesis that this outer-membrane mitochondrial protein is involved in the interaction with endosomes. DisclosuresNo relevant conflicts of interest to declare.

Inhibition of VDAC1 prevents Ca²⁺-mediated oxidative stress and apoptosis induced by 5-aminolevulinic acid mediated sonodynamic therapy in THP-1 macrophages.

Ultrasound combined with endogenous protoporphyrin IX derived from 5-aminolevulinic acid (ALA-SDT) is known to induce apoptosis in multiple cancer cells and macrophages. Persistent retention of macrophages in the plaque has been implicated in the pathophysiology and progression of atherosclerosis. Here we investigated the effects of inhibition of voltage-dependent anion channel 1 (VDAC1) on ALA-SDT-induced THP-1 macrophages apoptosis. Cells were pre-treated with VDAC1 inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) disodium salt for 1 h or downregulated VDAC1 expression by small interfering RNA and exposed to ultrasound. Cell viability was assessed by MTT assay, and cell apoptosis along with necrosis was evaluated by Hoechst 33342/propidium iodide staining and flow cytometry. Levels of cytochrome c release was assessed by confocal microscope and Western blot. The levels of full length caspases, caspase activation, and VDAC isoforms were analyzed by Western blot. Intracellular reactive oxygen species generation, mitochondrial membrane permeability, and intracellular Ca(2+) [Ca(2+)]i levels were measured with fluorescent probes. We confirmed that the pharmacological inhibition of VDAC1 by DIDS notably prevented ALA-SDT-induced cell apoptosis in THP-1 macrophages. Additionally, DIDS significantly inhibited intracellular ROS generation and apoptotic biochemical changes such as inner mitochondrial membrane permeabilization, loss of mitochondrial membrane potential, cytochrome c release and activation of caspase-3 and caspase-9. Moreover, ALA-SDT elevated the [Ca(2+)]i levels and it was also notably reduced by DIDS. Furthermore, both of intracellular ROS generation and cell apoptosis were predominately inhibited by Ca(2+) chelating reagent BAPTA-AM. Intriguingly, ALA-treatment markedly augmented VDAC1 protein levels exclusively, and the downregulation of VDAC1 expression by specific siRNA also significantly abolished cell apoptosis. Altogether, these results suggest that VDAC1 plays a crucial role in ALA-SDT-induced THP-1 macrophages apoptosis, and targeting VDAC1 is a potential way regulating macrophages apoptosis, a finding that may be relevant to therapeutic strategies against atherosclerosis.

The compound Chinese medicine "Kang Fu Ling" protects against high power microwave-induced myocardial injury.

BackgroundThe prevention and treatment of Microwave-caused cardiovascular injury remains elusive. This study investigated the cardiovascular protective effects of compound Chinese medicine “Kang Fu Ling” (KFL) against high power microwave (HPM)-induced myocardial injury and the role of the mitochondrial permeability transition pore (mPTP) opening in KFL protection.MethodsMale Wistar rats (100) were divided into 5 equal groups: no treatment, radiation only, or radiation followed by treatment with KFL at 0.75, 1.5, or 3 g/kg/day. Electrocardiography was used to Electrophysiological examination. Histological and ultrastructural changes in heart tissue and isolated mitochondria were observed by light microscope and electron microscopy. mPTP opening and mitochondrial membrane potential were detected by confocal laser scanning microscopy and fluorescence analysis. Connexin-43 (Cx-43) and endothelial nitric oxide synthase (eNOS) were detected by immunohistochemistry. The expression of voltage-dependent anion channel (VDAC) was detected by western blotting.ResultsAt 7 days after radiation, rats without KFL treatment showed a significantly lower heart rate (P<0.01) than untreated controls and a J point shift. Myocyte swelling and rearrangement were evident. Mitochondria exhibited rupture, and decreased fluorescence intensity, suggesting opening of mPTP and a consequent reduction in mitochondrial membrane potential. After treatment with 1.5 g/kg/day KFL for 7 d, the heart rate increased significantly (P<0.01), and the J point shift was reduced flavorfully (P<0.05) compared to untreated, irradiated rats; myocytes and mitochondria were of normal morphology. The fluorescence intensities of dye-treated mitochondria were also increased, suggesting inhibition of mPTP opening and preservation of the mitochondrial membrane potential. The microwave-induced decrease of Cx-43 and VDAC protein expression was significantly reversed.ConclusionMicrowave radiation can cause electrophysiological, histological and ultrastructural changes in the heart. KFL at 1.5 g/kg/day had the greatest protective effect on these cardiovascular events. mPTP plays an important role in the protective effects of KFL against microwave-radiation-induced myocardial injury.

Brain-specific knockdown of miR-29 results in neuronal cell death and ataxia in mice.

Several microRNAs have been implicated in neurogenesis, neuronal differentiation, neurodevelopment, and memory. Development of miRNA-based therapeutics, however, needs tools for effective miRNA modulation, tissue-specific delivery, and in vivo evidence of functional effects following the knockdown of miRNA. Expression of miR-29a is reduced in patients and animal models of several neurodegenerative disorders, including Alzheimer's disease, Huntington's disease, and spinocerebellar ataxias. The temporal expression pattern of miR-29b during development also correlates with its protective role in neuronal survival. Here, we report the cellular and behavioral effect of in vivo, brain-specific knockdown of miR-29. We delivered specific anti-miRNAs to the mouse brain using a neurotropic peptide, thus overcoming the blood-brain-barrier and restricting the effect of knockdown to the neuronal cells. Large regions of the hippocampus and cerebellum showed massive cell death, reiterating the role of miR-29 in neuronal survival. The mice showed characteristic features of ataxia, including reduced step length. However, the apoptotic targets of miR-29, such as Puma, Bim, Bak, or Bace1, failed to show expected levels of up-regulation in mice, following knockdown of miR-29. In contrast, another miR-29 target, voltage-dependent anion channel1 (VDAC1), was found to be induced several fold in the hippocampus, cerebellum, and cortex of mice following miRNA knockdown. Partial restoration of apoptosis was achieved by down-regulation of VDAC1 in miR-29 knockdown cells. Our study suggests that regulation of VDAC1 expression by miR-29 is an important determinant of neuronal cell survival in the brain. Loss of miR-29 results in dysregulation of VDAC1, neuronal cell death, and an ataxic phenotype.

MAVS Regulates Apoptotic Cell Death by Decreasing K48-Linked Ubiquitination of Voltage-Dependent Anion Channel 1

The mitochondrial antiviral signaling protein MAVS (IPS-1, VISA, or Cardif) plays an important role in the host defense against viral infection by inducing type I interferon. Recent reports have shown that MAVS is also critical for virus-induced apoptosis. However, the mechanism of MAVS-mediated apoptosis induction remains unclear. Here, we show that MAVS binds to voltage-dependent anion channel 1 (VDAC1) and induces apoptosis by caspase-3 activation, which is independent of its role in innate immunity. MAVS modulates VDAC1 protein stability by decreasing its degradative K48-linked ubiquitination. In addition, MAVS knockout mouse embryonic fibroblasts (MEFs) display reduced VDAC1 expression with a consequent reduction of the vesicular stomatitis virus (VSV)-induced apoptosis response. Notably, the upregulation of VDAC1 triggered by VSV infection is completely abolished in MAVS knockout MEFs. We thus identify VDAC1 as a target of MAVS and describe a novel mechanism of MAVS control of virus-induced apoptotic cell death.