Loss of the redox mitochondrial protein mitoNEET leads to mitochondrial dysfunction in B-cell acute lymphoblastic leukemia

Ancient complexes of iron and sulfur modulate oncogenes and oncometabolism

Inorganic complexes of iron and sulfur, that is, iron-sulfur [FeS] clusters, have played a fundamental role in life on Earth since the prebiotic period. These clusters were involved in elementary reactions leading to the emergence of life and, since then, gained function in processes, such as respiration, replication, transcription, and the immune response. We discuss how three [FeS] proteins involved in the innate immune response play a role in oncogene expression/function and oncometabolism. Our analysis highlights the importance of future research into understanding the [FeS] clusters' roles in cancer progression and proliferation. The outcomes of these studies will help identify new targets and develop new anticancer therapeutics.

Mitochondrial miR-12294-5p regulated copper-induced mitochondrial oxidative stress and mitochondrial quality control imbalance by targeted inhibition of CISD1 in chicken livers

Copper (Cu) is hazardous metal contaminant, which induced hepatotoxicity is closely related to mitochondrial disorder, but exact regulatory mechanism has not yet been revealed. Mitochondrial microRNAs (mitomiRs) are a novel and critical regulator of mitochondrial function and mitochondrial homeostasis. Hence, this study revealed the impact of Cu-exposure on mitomiR expression profiles in chicken livers, and further identified mitomiR-12294-5p and its target gene CISD1 as core regulators involved in Cu-induced hepatotoxicity. Additionally, our results showed that Cu-exposure induced mitochondrial oxidative damage, and mitochondrial quality control imbalance mediated by mitochondrial dynamics disturbances, mitochondrial biogenesis inhibition and abnormal mitophagy flux in chicken livers and primary chicken embryo hepatocytes (CEHs). Meaningfully, we discovered that inhibition of the expression of mitomiR-12294-5p effectively alleviated Cu-induced mitochondrial oxidative stress and mitochondrial quality control imbalance, while the up-regulation of mitomiR-12294-5p expression exacerbated Cu-induced mitochondrial damage. Simultaneously, the above Cu-induced mitochondrial damage can be effectively rescued by the overexpression of CISD1, while knockdown of CISD1 dramatically reverses the mitigating effect that inhibition of mitomiR-12294-5p expression on Cu-induced mitochondrial oxidative stress and mitochondrial quality control imbalance. Overall, these results suggested that mitomiR-12294-5p/CISD1 axis mediated mitochondrial damage is a novel molecular mechanism involved in regulating Cu-induced hepatotoxicity in chickens.

Chemotherapeutic Activity of Pitavastatin in Vincristine Resistant B-Cell Acute Lymphoblastic Leukemia

B-cell acute lymphoblastic leukemia (ALL) is derived from an accumulation of malignant, immature B cells in the bone marrow and blood. Relapse due, in part, to the emergence of tumor cells that are resistant to front line standard chemotherapy is associated with poor patient outcomes. This challenge highlights the need for new treatment strategies to eliminate residual chemoresistant tumor cells. Based on the use of pitavastatin in acute myeloid leukemia (AML), we evaluated its efficacy in an REH ALL cell line derived to be resistant to vincristine. We found that pitavastatin inhibited the proliferation of both parental and vincristine-resistant REH tumor cells at an IC50 of 449 nM and 217 nM, respectively. Mitochondrial bioenergetic assays demonstrated that neither vincristine resistance nor pitavastatin treatment affected cellular oxidative phosphorylation, beta-oxidation, or glycolytic metabolism in ALL cells. In a co-culture model of ALL cells with bone marrow stromal cells, pitavastatin significantly decreased cell viability more robustly in the vincristine-resistant ALL cells compared with their parental controls. Subsequently, NSG mice were used to develop an in vivo model of B-cell ALL using both parental and vincristine-resistant ALL cells. Pitavastatin (10 mg/kg i.p.) significantly reduced the number of human CD45+ REH ALL cells in the bone marrow of mice after 4 weeks of treatment. Mechanistic studies showed that pitavastatin treatment in the vincristine-resistant cells led to apoptosis, with increased levels of cleaved PARP and protein-signaling changes for AMP-activated protein kinase/FoxO3a/Puma. Our data suggest the possible repurposing of pitavastatin as a chemotherapeutic agent in a model of vincristine-resistant B-cell ALL.

CISD1 Is a Breast Cancer Prognostic Biomarker Associated with Diabetes Mellitus

Women with diabetes mellitus are believed to have increased risk of developing breast cancer and lower life expectancies. This study aims to depict the association between the CISD1, the co-expressed genes, and diabetes mellitus to offer potential therapeutic targets for further mechanical research. The TCGA-BRCA RNAseq data is acquired. All the data and analyzed using R packages and web-based bioinformatics tools. CISD1 gene expression was evaluated between tumor bulk and adjacent tissue. Immune cell infiltration evaluation was performed. CISD1 expressed significantly higher in tumor tissue than that of the normal tissue, indicating poor overall survival rates. High expression level of CISD1 in tumor shows less pDC and NK cells penetration. There are 138 genes shared between CISD1 co-expressed gene pool in BRCA and diabetes mellitus related genes using "diabetes" as the term for text mining. These shared genes enrich in "cell cycle" and other pathways. MCODE analysis demonstrates that p53-independent G1/S DNA damage checkpoint, p53-independent DNA damage response, and ubiquitin mediated degradation of phosphorylated cdc25A are top-ranked than other terms. CISD1 and co-expressed genes, especially shared ones with diabetes mellitus, can be the focused genes considered when addressing clinical problems in breast cancer with a diabetes mellitus background.

Structure and biological evaluation of Caenorhabditis elegans CISD-1/mitoNEET, a KLP-17 tail domain homologue, supports attenuation of paraquat-induced oxidative stress through a p38 MAPK-mediated antioxidant defense response

CISD-1/mitoNEET is an evolutionarily conserved outer mitochondrial membrane [2Fe-2S] protein that regulates mitochondrial function and morphology. The [2Fe-2S] clusters are redox reactive and shown to mediate oxidative stress in vitro and in vivo. However, there is limited research studying CISD-1/mitoNEET mediation of oxidative stress in response to environmental stressors. In this study, we have determined the X-ray crystal structure of Caenorhabditis elegans CISD-1/mitoNEET homologue and evaluated the mechanisms of oxidative stress resistance to the pro-oxidant paraquat in age-synchronized populations by generating C. elegans gain and loss of function CISD-1 models. The structure of the C. elegans CISD-1/mitoNEET soluble domain refined at 1.70-Å resolution uniquely shows a reversible disulfide linkage at the homo-dimeric interface and also represents the N-terminal tail domain for dimerization of the cognate kinesin motor protein KLP-17 involved in chromosome segregation dynamics and germline development of the nematode. Moreover, overexpression of CISD-1/mitoNEET in C. elegans has revealed beneficial effects on oxidative stress resistance against paraquat-induced reactive oxygen species generation, corroborated by increased activation of the p38 mitogen-activated protein kinase (MAPK) signaling cascade.

The Mitochondrial Protein MitoNEET as a Probe for the Allostery of Glutamate Dehydrogenase

The proteins glutamate dehydrogenase (GDH) and mitoNEET are both targets of drug development efforts to treat metabolic disorders, cancer, and neurodegenerative diseases. However, these two proteins differ starkly in the current knowledge about ligand binding sites. MitoNEET is a [2Fe-2S]-containing protein with no obvious binding site for small ligands observed in its crystal structures. In contrast, GDH is known to have a variety of ligands at multiple allosteric sites thereby leading to complex regulation in activity. In fact, while GDH can utilize either NAD(H) or NADP(H) for catalysis at the active site, only NAD(H) binds at a regulatory site to inhibit GDH activity. Previously, we found that mitoNEET forms a covalent bond with GDH in vitro and increases the catalytic activity of the enzyme. In this study we evaluated the effects of mitoNEET binding on the allosteric control of GDH conferred by inhibitors. We examined all effectors using NAD or NADP as the coenzyme to determine allosteric linkage by the NAD-binding regulatory site. We found that GDH activity, in the presence of the inhibitory palmitoyl-CoA and EGCG, can be rescued by mitoNEET, regardless of the coenzyme used. This suggests that mitoNEET rescues GDH by stabilizing the open conformation.

The Intriguing mitoNEET: Functional and Spectroscopic Properties of a Unique [2Fe-2S] Cluster Coordination Geometry

Despite the number of cellular and pathological mitoNEET-related processes, very few details are known about the mechanism of action of the protein. The recently discovered existence of a link between NEET proteins and cancer pave the way to consider mitoNEET and its Fe-S clusters as suitable targets to inhibit cancer cell proliferation. Here, we will review the variety of spectroscopic techniques that have been applied to study mitoNEET in an attempt to explain the drastic difference in clusters stability and reactivity observed for the two redox states, and to elucidate the cellular function of the protein. In particular, the extensive NMR assignment and the characterization of first coordination sphere provide a molecular fingerprint helpful to assist the design of drugs able to impair cellular processes or to directly participate in redox reactions or protein-protein recognition mechanisms.

Nitric oxide reversibly binds the reduced [2Fe-2S] cluster in mitochondrial outer membrane protein mitoNEET and inhibits its electron transfer activity

MitoNEET is a mitochondrial outer membrane protein that regulates energy metabolism, iron homeostasis, and production of reactive oxygen species in cells. Aberrant expression of mitoNEET in tissues has been linked to type II diabetes, neurodegenerative diseases, and several types of cancer. Structurally, the N-terminal domain of mitoNEET has a single transmembrane alpha helix that anchors the protein to mitochondrial outer membrane. The C-terminal cytosolic domain of mitoNEET hosts a redox active [2Fe-2S] cluster via an unusual ligand arrangement of three cysteine and one histidine residues. Here we report that the reduced [2Fe-2S] cluster in the C-terminal cytosolic domain of mitoNEET (mitoNEET45-108) is able to bind nitric oxide (NO) without disruption of the cluster. Importantly, binding of NO at the reduced [2Fe-2S] cluster effectively inhibits the redox transition of the cluster in mitoNEET45-108. While the NO-bound [2Fe-2S] cluster in mitoNEET45-108 is stable, light excitation releases NO from the NO-bound [2Fe-2S] cluster and restores the redox transition activity of the cluster in mitoNEET45-108. The results suggest that NO may regulate the electron transfer activity of mitoNEET in mitochondrial outer membrane via reversible binding to its reduced [2Fe-2S] cluster.

Electron transfer activity of the nanodisc-bound mitochondrial outer membrane protein mitoNEET

MitoNEET is the first iron-sulfur protein found in mitochondrial outer membrane. Abnormal expression of mitoNEET in cells has been linked to several types of cancer, type II diabetes, and neurodegenerative diseases. Structurally, mitoNEET is anchored to mitochondrial outer membrane via its N-terminal single transmembrane alpha helix. The C-terminal cytosolic domain of mitoNEET binds a [2Fe-2S] cluster via three cysteine and one histidine residues. It has been shown that mitoNEET has a crucial role in energy metabolism, iron homeostasis, and free radical production in cells. However, the exact function of mitoNEET remains elusive. Previously, we reported that the C-terminal soluble domain of mitoNEET has a specific binding site for flavin mononucleotide (FMN) and can transfer electrons from FMNH2 to oxygen or ubiquinone-2 via its [2Fe-2S] cluster. Here we have constructed a hybrid protein using the N-terminal transmembrane domain of Escherichia coli YneM and the C-terminal soluble domain of human mitoNEET and assembled the hybrid protein YneM-mitoNEET into phospholipid nanodiscs. The results show that the [2Fe-S] clusters in the nanodisc-bound YneM-mitoNEET can be rapidly reduced by FMNH2 which is reduced by flavin reductase using NADH as the electron donor. Addition of lumichrome, a FMN analog, effectively inhibits the FMNH2-mediated reduction of the [2Fe-2S] clusters in the nanodisc-bound YneM-mitoNEET. The reduced [2Fe-2S] clusters in the nanodisc-bound YneM-mitoNEET are quickly oxidized by oxygen under aerobic conditions or by ubiquinone-10 in the nanodiscs under anaerobic conditions. Because NADH oxidation is required for cellular glycolytic activity, we propose that the mitochondrial outer membrane protein mitoNEET may promote glycolysis by transferring electrons from FMNH2 to oxygen or ubiquinone-10 in mitochondria.

Novel mitoNEET ligand NL-1 improves therapeutic outcomes in an aged rat model of cerebral ischemia/reperfusion injury

Cerebral ischemic stroke is a leading cause of mortality and disability worldwide. Currently, there are a lack of drugs capable of reducing neuronal cell loss due to ischemia/reperfusion-injury after stroke. Previously, we identified mitoNEET, a [2Fe-2S] redox mitochondrial protein, as a putative drug target for ischemic stroke. In this study, we tested NL-1, a novel mitoNEET ligand, in a preclinical model of ischemic stroke with reperfusion using aged female rats. Using a transient middle cerebral artery occlusion (tMCAO), we induced a 2 h ischemic injury and then evaluated the effects of NL-1 treatment on ischemic/reperfusion brain injury at 24 and 72 h. Test compounds were administered at time of reperfusion via intravenous dosing. Results of the study demonstrated that NL-1 (10 mg/kg) treatment markedly improved survival and reduced infarct volume and hemispheric swelling in the brain as compared aged rats treated with vehicle or a lower dose of NL-1 (0.25 mg/kg). Interestingly, the protective effect of NL-1 was significantly improved when encapsulated in PLGA nanoparticles, where a 40-fold lesser dose (0.25 mg/kg) of NL-1 produced an equivalent effect as the 10 mg/kg dose. Evaluation of changes in blood-brain barrier permeability and lipid peroxidation corroborated the protective actions of NL-1 (10 mg/kg) or NL-1 NP treatment demonstrated a reduced accumulation of parenchymal IgG, decreased levels of 4-hydroxynonenal (4-HNE) and a decreased TUNEL positive cells in the brains of aged female rats at 72 h after tMCAO with reperfusion. Our studies indicate that targeting mitoNEET following ischemia/reperfusion-injury is a novel drug target pathway that warrants further investigation.