Rapid accumulation of Akt in mitochondria following phosphatidylinositol 3-kinase activation

The signaling landscape of insulin-like growth factor 1

The sheer amplitude of biological actions of insulin-like growth factor I (IGF-1) affecting all types of cells in all tissues suggests a vast signaling landscape for this ubiquitous humoral signal. While the canonical signaling pathways primarily involve the Ras/MAPK and PI3K/AKT cascades, the evolutionary conservation of insulin-like peptides (ILPs) and their pathways hints at the potential for novel functions to emerge over time. Indeed, the evolutionary trajectory of ILPs opens the possibility of either novel functions for these two pathways, novel downstream routes, or both. Evidence supporting this notion includes observations of neofunctionalization in bony fishes or crustaceans, and the involvement of ILPs pathways in invertebrate eusociality or in vertebrate bone physiology, respectively. Such evolutionary processes likely contribute to the rich diversity of ILPs signaling observed today. Moreover, the interplay between conserved signaling pathways, such as those implicated in aging (predominantly involving the PI3K-AKT route), and lesser known pathways, such as those mediated by biased G-protein coupled receptors and others even less known, may underpin the context-dependent actions characteristic of ILPs signaling. While canonical IGF-1 signaling is often assumed to account for the intracellular pathways utilized by this growth factor, a comprehensive analysis of all the pathways mediated by the IGF-1 receptor (IGF-1R) remains lacking. This review aims to explore both canonical and non-canonical routes of IGF-1R action across various cell types, offering a detailed examination of the mechanisms underlying IGF-1 signaling and highlighting the significant gaps in our current understanding.

GSK-3: An "Ace" Among Kinases

Background: Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase known to participate in the regulation of β-catenin signaling (Wnt signaling). This aids in the establishment of a multicomponent destruction complex that stimulates phosphorylation, leading to the destruction of β-catenin. Evidence about the role of increasingly active β-catenin signaling is involved in many forms of human cancer. The understanding of GSK-3 remains elusive as recent research aims to focus on developing potent GSK-3 inhibitors to target this kinase. Objective: This short review aims to highlight the regulation of GSK-3 with emphasis on Wnt signaling while highlighting its interaction with miRNAs corresponding to pluripotency and epithelial mesenchymal transition substantiating this kinase as an "Ace" among kinases in regulation of cellular processes. Result: Significant findings of miRNA regulation by GSK-3 exemplify the underpinnings of kinase-mediated transcriptional regulation in cancers. Conclusion: The review provides evidence on the role of GSK-3 as a possible master regulator of proteins and noncoding RNA, thereby implicating the fate of a cell.

Neuronal extracellular vesicles influence the expression, degradation and oligomeric state of fructose 1,6-bisphosphatase 2 in astrocytes affecting their glycolytic capacity

Fructose 1,6-bisphosphatase 2 (Fbp2) is a regulatory enzyme of gluco- and glyconeogenesis which, in the course of evolution, acquired non-catalytic functions. Fbp2 promotes cell survival during calcium stress, regulates glycolysis via inhibition of Hif-1α activity, and is indispensable for the formation of long-term potentiation in hippocampus. In hippocampal astrocytes, the amount of Fbp2 protein is reduced by signals delivered in neuronal extracellular vesicles (NEVs) through an unknown mechanism. The physiological role of Fbp2 (determined by its subcellular localization/interactions) depends on its oligomeric state and thus, we asked whether the cargo of NEVs is sufficient to change also the ratio of Fbp2 dimer/tetramer and, consequently, influence astrocyte basal metabolism. We found that the NEVs cargo reduced the Fbp2 mRNA level, stimulated the enzyme degradation and affected the cellular titers of different oligomeric forms of Fbp2. This was accompanied with increased glucose uptake and lactate release by astrocytes. Our results revealed that neuronal signals delivered to astrocytes in NEVs provide the necessary balance between enzymatic and non-enzymatic functions of Fbp2, influencing not only its amount but also subcellular localization. This may allow for the metabolic adjustments and ensure protection of mitochondrial membrane potential during the neuronal activity-related increase in astrocytic [Ca2+].

The clinical antiprotozoal drug nitazoxanide and its metabolite tizoxanide extend Caenorhabditis elegans lifespan and healthspan

The drugs extending healthspan in clinic have always been searched. Nitazoxanide is an FDA-approved clinical antiprotozoal drug. Nitazoxanide is rapidly metabolized to tizoxanide after absorption in vivo. Our previous studies find that nitazoxanide and its metabolite tizoxanide induce mild mitochondrial uncoupling and activate cellular AMPK, oral nitazoxanide protects against experimental hyperlipidemia, hepatic steatosis, and atherosclerosis. Here, we demonstrate that both nitazoxanide and tizoxanide extend the lifespan and healthspan of Caenorhabditis elegans through Akt/AMPK/sir 2.1/daf16 pathway. Additionally, both nitazoxanide and tizoxanide improve high glucose-induced shortening of C. elegans lifespan. Nitazoxanide has been a clinical drug with a good safety profile, we suggest that it is a novel anti-aging drug.

Systematic investigation of Radix Salviae for treating diabetic peripheral neuropathy disease based on network Pharmacology

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a debilitating complication of diabetes mellitus with limited available treatment options. Radix Salviae, a traditional Chinese herb, has shown promise in treating DPN, but its therapeutic mech-anisms have not been systematically investigated.

AIM

Radix Salviae (Danshen in pinin), a traditional Chinese medicine (TCM), is widely used to treat DPN in China. However, the mechanism through which Radix Salviae treats DPN remains unclear. Therefore, we aimed to explore the mechanism of action of Radix Salviae against DPN using network pharmacology.

METHODS

The active ingredients and target genes of Radix Salviae were screened using the TCM pharmacology database and analysis platform. The genes associated with DPN were obtained from the Gene Cards and OMIM databases, a drug-com-position-target-disease network was constructed, and a protein-protein inter-action network was subsequently constructed to screen the main targets. Gene Ontology (GO) functional annotation and pathway enrichment analysis were performed via the Kyoto Encyclopedia of Genes and Genomes (KEGG) using Bioconductor.

RESULTS

A total of 56 effective components, 108 targets and 4581 DPN-related target genes of Radix Salviae were screened. Intervention with Radix Salviae for DPN mainly involved 81 target genes. The top 30 major targets were selected for enrichment analysis of GO and KEGG pathways.

CONCLUSION

These results suggested that Radix Salviae could treat DPN by regulating the AGE-RAGE signaling pathway and the PI3K-Akt signaling pathway. Therefore, Danshen may affect DPN by regulating inflammation and apoptosis.

Phosphorylations and Acetylations of Cytochrome c Control Mitochondrial Respiration, Mitochondrial Membrane Potential, Energy, ROS, and Apoptosis

Cytochrome c (Cytc) has both life-sustaining and cellular death-related functions, depending on subcellular localization. Within mitochondria, Cytc acts as a single electron carrier as part of the electron transport chain (ETC). When released into the cytosol after cellular insult, Cytc triggers the assembly of the apoptosome, committing the cell to intrinsic apoptosis. Due to these dual natures, Cytc requires strong regulation by the cell, including post-translational modifications, such as phosphorylation and acetylation. Six phosphorylation sites and three acetylation sites have been detected on Cytc in vivo. Phosphorylations at T28, S47, Y48, T49, T58, and Y97 tend to be present under basal conditions in a tissue-specific manner. In contrast, the acetylations at K8, K39, and K53 tend to be present in specific pathophysiological conditions. All of the phosphorylation sites and two of the three acetylation sites partially inhibit respiration, which we propose serves to maintain an optimal, intermediate mitochondrial membrane potential (ΔΨm) to minimize reactive oxygen species (ROS) production. Cytc phosphorylations are lost during ischemia, which drives ETC hyperactivity and ΔΨm hyperpolarization, resulting in exponential ROS production thus causing reperfusion injury following ischemia. One of the acetylation sites, K39, shows a unique behavior in that it is gained during ischemia, stimulating respiration while blocking apoptosis, demonstrating that skeletal muscle, which is particularly resilient to ischemia-reperfusion injury compared to other organs, possesses a different metabolic strategy to handle ischemic stress. The regulation of Cytc by these post-translational modifications underscores the importance of Cytc for the ETC, ΔΨm, ROS production, apoptosis, and the cell as a whole.

Mitochondrial Signaling, the Mechanisms of AKI-to-CKD Transition and Potential Treatment Targets

Acute kidney injury (AKI) is increasing in prevalence and causes a global health burden. AKI is associated with significant mortality and can subsequently develop into chronic kidney disease (CKD). The kidney is one of the most energy-demanding organs in the human body and has a role in active solute transport, maintenance of electrochemical gradients, and regulation of fluid balance. Renal proximal tubular cells (PTCs) are the primary segment to reabsorb and secrete various solutes and take part in AKI initiation. Mitochondria, which are enriched in PTCs, are the main source of adenosine triphosphate (ATP) in cells as generated through oxidative phosphorylation. Mitochondrial dysfunction may result in reactive oxygen species (ROS) production, impaired biogenesis, oxidative stress multiplication, and ultimately leading to cell death. Even though mitochondrial damage and malfunction have been observed in both human kidney disease and animal models of AKI and CKD, the mechanism of mitochondrial signaling in PTC for AKI-to-CKD transition remains unknown. We review the recent findings of the development of AKI-to-CKD transition with a focus on mitochondrial disorders in PTCs. We propose that mitochondrial signaling is a key mechanism of the progression of AKI to CKD and potential targeting for treatment.

Deletion of Aurora kinase A prevents the development of polycystic kidney disease in mice

Aurora Kinase A (AURKA) promotes cell proliferation and is overexpressed in different types of polycystic kidney disease (PKD). To understand AURKA's role in regulating renal cyst development we conditionally deleted the gene in mouse models of Autosomal Dominant PKD (ADPKD) and Joubert Syndrome, caused by Polycystin 1 (Pkd1) and Inositol polyphosphate-5-phosphatase E (Inpp5e) mutations respectively. We show that while Aurka is dispensable for collecting duct development and homeostasis, its deletion prevents cyst formation in both disease models. Cross-comparison of transcriptional changes implicated AKT signaling in cyst prevention and we show that (i) AURKA and AKT physically interact, (ii) AURKA regulates AKT activity in a kinase-independent manner and (iii) inhibition of AKT can reduce disease severity. AKT activation also regulates Aurka expression, creating a feed-forward loop driving renal cystogenesis. We find that the AURKA kinase inhibitor Alisertib stabilises the AURKA protein, agonizing its cystogenic functions. These studies identify AURKA as a master regulator of renal cyst development in different types of PKD, functioning in-part via AKT.

Mitochondrial, cell cycle control and neuritogenesis alterations in an iPSC-based neurodevelopmental model for schizophrenia

Schizophrenia is a severe psychiatric disorder of neurodevelopmental origin that affects around 1% of the world's population. Proteomic studies and other approaches have provided evidence of compromised cellular processes in the disorder, including mitochondrial function. Most of the studies so far have been conducted on postmortem brain tissue from patients, and therefore, do not allow the evaluation of the neurodevelopmental aspect of the disorder. To circumvent that, we studied the mitochondrial and nuclear proteomes of neural stem cells (NSCs) and neurons derived from induced pluripotent stem cells (iPSCs) from schizophrenia patients versus healthy controls to assess possible alterations related to energy metabolism and mitochondrial function during neurodevelopment in the disorder. Our results revealed differentially expressed proteins in pathways related to mitochondrial function, cell cycle control, DNA repair and neuritogenesis and their possible implication in key process of neurodevelopment, such as neuronal differentiation and axonal guidance signaling. Moreover, functional analysis of NSCs revealed alterations in mitochondrial oxygen consumption in schizophrenia-derived cells and a tendency of higher levels of intracellular reactive oxygen species (ROS). Hence, this study shows evidence that alterations in important cellular processes are present during neurodevelopment and could be involved with the establishment of schizophrenia, as well as the phenotypic traits observed in adult patients. Neural stem cells (NSCs) and neurons were derived from induced pluripotent stem cells (iPSCs) from schizophrenia patients and controls. Proteomic analyses were performed on the enriched mitochondrial and nuclear fractions of NSCs and neurons. Whole-cell proteomic analysis was also performed in neurons. Our results revealed alteration in proteins related to mitochondrial function, cell cycle control, among others. We also performed energy pathway analysis and reactive oxygen species (ROS) analysis of NSCs, which revealed alterations in mitochondrial oxygen consumption and a tendency of higher levels of intracellular ROS in schizophrenia-derived cells.

GTPBP8 is required for mitoribosomal biogenesis and mitochondrial translation

Mitochondrial translation occurs on the mitochondrial ribosome, also known as the mitoribosome. The assembly of mitoribosomes is a highly coordinated process. During mitoribosome biogenesis, various assembly factors transiently associate with the nascent ribosome, facilitating the accurate and efficient construction of the mitoribosome. However, the specific factors involved in the assembly process, the precise mechanisms, and the cellular compartments involved in this vital process are not yet fully understood. In this study, we discovered a crucial role for GTP-binding protein 8 (GTPBP8) in the assembly of the mitoribosomal large subunit (mt-LSU) and mitochondrial translation. GTPBP8 is identified as a novel GTPase located in the matrix and peripherally bound to the inner mitochondrial membrane. Importantly, GTPBP8 is specifically associated with the mt-LSU during its assembly. Depletion of GTPBP8 leads to an abnormal accumulation of mt-LSU, indicating that GTPBP8 is critical for proper mt-LSU assembly. Furthermore, the absence of GTPBP8 results in reduced levels of fully assembled 55S monosomes. This impaired assembly leads to compromised mitochondrial translation and, consequently, impaired mitochondrial function. The identification of GTPBP8 as an important player in these processes provides new insights into the molecular mechanisms underlying mitochondrial protein synthesis and its regulation.

HDGF stimulates liver tumorigenesis by enhancing reactive oxygen species generation in mitochondria

Hepatoma-derived growth factor (HDGF) overexpression and uncontrolled reactive oxygen species (ROS) accumulation are involved in malignant transformation and poor prognosis in various types of cancer. However, the interplay between HDGF and ROS generation has not been elucidated in hepatocellular carcinoma. Here, we first analyzed the profile of HDGF expression and ROS production in newly generated orthotopic hepatomas by ultrasound-guided implantation. In situ superoxide detection showed that HDGF-overexpressing hepatomas had significantly elevated ROS levels compared with adjacent nontumor tissues. Consistently, liver tissues from HDGF-deficient mice exhibited lower ROS fluorescence than those from age- and sex-matched WT mice. ROS-detecting fluorescent dyes and flow cytometry revealed that recombinant HDGF (rHDGF) stimulated the production of superoxide anion, hydrogen peroxide, and mitochondrial ROS generation in cultured hepatoma cells in a dose-dependent manner. In contrast, the inactive Ser103Ala rHDGF mutant failed to promote ROS generation or oncogenic behaviors. Seahorse metabolic flux assays revealed that rHDGF dose dependently upregulated bioenergetics through enhanced basal and total oxygen consumption rate, extracellular acidification rate, and oxidative phosphorylation in hepatoma cells. Moreover, antioxidants of N-acetyl cysteine and MitoQ treatment significantly inhibited HDGF-mediated cell proliferation and invasive capacity. Genetic silencing of superoxide dismutase 2 augmented the HDGF-induced ROS generation and oncogenic behaviors of hepatoma cells. Finally, genetic knockdown nucleolin (NCL) and antibody neutralization of surface NCL, the HDGF receptor, abolished the HDGF-induced increase in ROS and mitochondrial energetics. In conclusion, this study has demonstrated for the first time that the HDGF/NCL signaling axis induces ROS generation by elevating ROS generation in mitochondria, thereby stimulating liver carcinogenesis.

IGFBP1 Sustains Cell Survival during Spatially-Confined Migration and Promotes Tumor Metastasis

Cell migration is a pivotal step in metastatic process, which requires cancer cells to navigate a complex spatially-confined environment, including tracks within blood vessels and in the vasculature of target organs. Here it is shown that during spatially-confined migration, the expression of insulin-like growth factor-binding protein 1 (IGFBP1) is upregulated in tumor cells. Secreted IGFBP1 inhibits AKT1-mediated phosphorylation of mitochondrial superoxide dismutase (SOD2) serine (S) 27 and enhances SOD2 activity. Enhanced SOD2 attenuates mitochondrial reactive oxygen species (ROS) accumulation in confined cells, which supports tumor cell survival in blood vessels of lung tissues, thereby accelerating tumor metastasis in mice. The levels of blood IGFBP1 correlate with metastatic recurrence of lung cancer patients. This finding reveals a unique mechanism by which IGFBP1 sustains cell survival during confined migration by enhancing mitochondrial ROS detoxification, thereby promoting tumor metastasis.

Bupi Yishen formula may prevent kidney fibrosis by modulating fatty acid metabolism in renal tubules

BACKGROUND

Bupi Yishen formula (BYF), a traditional Chinese herbal mixture, has demonstrated better effectiveness than Losartan in preserving renal function and preventing composite severe adverse outcomes in patients with advanced chronic kidney disease (CKD) in a recent randomized controlled trial. Prior studies have shown that BYF exerts anti-inflammatory and anti-fibrotic effects in the kidneys of CKD models, but the underlying mechanisms have not been fully elucidated.

PURPOSE

The aim of this study was to investigate the protective effects of BYF administration on profibrotic phenotypic changes in the kidney and to elucidate its fundamental mechanisms of action.

METHODS

Adenine and 5/6 nephrectomy rat models were administered with two doses of BYF extract (15 or 30 g/kg/d) by intragastric administration, and Losartan treatment was used as a positive control group. The relationship between BYF renoprotection and restoration of fatty acid dysregulation was examined using the two fibrosis models and TGFb1-induced human tubular HK2 cells. Transcriptomic profiles of the fibrotic kidneys obtained from adenine-induced CKD rats were used to identify the key mechanisms that are affected by BYF intervention. Human relevance and clinical implications were established by re-analysis of the microarray databases of CKD patients and immunostaining on human biopsy specimens.

RESULTS

BYF effectively prevented kidney histological damage and ameliorated renal malfunction in the adenine rat model of CKD. BYF robustly attenuated the significant increase in profibrotic and proapoptotic markers in fibrotic kidneys of adenine-induced CKD rats. Transcriptomic analyses of the fibrotic kidneys of the adenine rats identified fatty acid metabolism as the key dysregulated pathway affected by BYF prevention. BYF significantly reversed defective fatty acid oxidation (FAO) and the intracellular lipids accumulation in the fibrotic kidneys induced by 5/6 nephrectomy. Furthermore, BYF prevented dysfunctional fatty acid metabolism, which were associated with the significant improvement of TGFb1-induced profibrotic changes in HK2 human proximal tubular cells. Furthermore, analyses of kidney microarray databases and biopsy specimens of CKD patients suggested that FAO defect is common in CKD in humans.

CONCLUSION

Our exploratory study found that BYF may exert protective effects on renal fibrosis by regulating the fatty acid metabolism of renal tubular cells, which may be a key mechanism for preventing kidney fibrosis in CKD.

Intracellular and microenvironmental regulation of mitochondrial membrane potential in cancer cells

Cancer cells have an abnormally high mitochondrial membrane potential (ΔΨm ), which is associated with enhanced invasive properties in vitro and increased metastases in vivo. The mechanisms underlying the abnormal ΔΨm in cancer cells remain unclear. Research on different cell types has shown that ΔΨm is regulated by various intracellular mechanisms such as by mitochondrial inner and outer membrane ion transporters, cytoskeletal elements, and biochemical signaling pathways. On the other hand, the role of extrinsic, tumor microenvironment (TME) derived cues in regulating ΔΨm is not well defined. In this review, we first summarize the existing literature on intercellular mechanisms of ΔΨm regulation, with a focus on cancer cells. We then offer our perspective on the different ways through which the microenvironmental cues such as hypoxia and mechanical stresses may regulate cancer cell ΔΨm . This article is categorized under: Cancer > Environmental Factors Cancer > Biomedical Engineering Cancer > Molecular and Cellular Physiology.

Hericium erinaceus Promotes Anti-Inflammatory Effects and Regulation of Metabolites in an Animal Model of Cerebellar Ataxia

Cerebellar ataxia is a neurodegenerative disorder with no definitive treatment. Although previous study demonstrated the neuroprotective effects of Hericium erinaceus (H.E.), the mechanisms of H.E. treatment on the neuroinflammatory response, neurotransmission, and related metabolites remain largely unknown. We demonstrated that 3-AP rats treated with 25 mg/kg H.E. extracts had improved motor coordination and balance in the accelerated rotarod and rod tests. We showed that the H.E. treatment upregulated the expression of Tgfb1, Tgfb2, and Smad3 genes to levels comparable to those in the non-3-AP control group. Interestingly, we also observed a significant correlation between Tgfb2 gene expression and rod test performance in the 3-AP saline group, but not in the non-3-AP control or H.E.+3-AP groups, indicating a relationship between Tgfb2 gene expression and motor balance in the 3-AP rat model. Additionally, we also found that the H.E. treatment increased mitochondrial COX-IV protein expression and normalized dopamine-serotonin neurotransmission and metabolite levels in the cerebellum of the H.E.+3-AP group compared to the 3-AP saline group. In conclusion, our findings suggest that the H.E. treatment improved motor function in the 3-AP rat model, which was potentially mediated through neuroprotective mechanisms involving TGFB2-Smad3 signaling via normalization of neurotransmission and metabolic pathways.

Mitochondria: Emerging Consequential in Sickle Cell Disease

Advanced mitochondrial multi-omics indicate a multi-facet involvement of mitochondria in the physiology of the cell, changing the perception of mitochondria from being just the energy-generating organelles to organelles that highly influence cell structure, function, signaling, and cell fate. This sets mitochondrial dysfunction in the centerstage of numerous acquired and genetic diseases. Sickle cell disease is also being increasingly associated with mitochondrial anomalies and the pathophysiology of sickle cell disease finds mitochondria at crucial intersections in the pathological cascade. Altered mitophagy, increased ROS, and mitochondrial DNA all contribute to the condition and its severity. Such mitochondrial aberrations lead to consequent mitochondrial retention in red blood cells in sickle cell diseases, increased oxidation in the cellular environment, inflammation, worsened vaso-occlusive crisis, etc. There are increasing studies indicating mitochondrial significance in sickle cell disease, consequently providing an opportunity to target it for improving the outcomes of treatment. Identification of the impaired mitochondrial attributes in sickle cell disease and their modulation by therapeutic interventions can impart a better management of the disease. This review aims to describe the mitochondria in the perspective of sicke cell disease so as to provide the reader an overview of the emerging mitochondrial stance in sickle cell disease.

Free Radicals and Oxidative Stress: Signaling Mechanisms, Redox Basis for Human Diseases, and Cell Cycle Regulation

Free radicals contain one or more unpaired electrons in their valence shell, thus making them unstable, short-lived, and highly reactive species. Excessive generation of these free radicals ultimately leads to oxidative stress causing oxidation and damage to significant macromolecules in the living system and essentially disrupting signal transduction pathways and antioxidants equilibrium. At lower concentrations, ROS serves as "second messengers," influencing many physiological processes in the cell. However, higher concentrations beyond cell capacity cause oxidative stress, contributing to human pathologies such as diabetes, cancer, Parkinson's disease, cardiovascular diseases, cataract, asthma, hypertension, atherosclerosis, arthritis, and Alzheimer's disease. Signaling pathways such as NF-κB, MAPKs, PI3K/Akt/ mTOR, and Keap1-Nrf2- ARE modulate the detrimental effects of oxidative stress by increasing the expression of cellular antioxidant defenses, phase II detoxification enzymes, and decreased production of ROS. Free radicals such as H2O2 are indeed needed for the advancement of the cell cycle as these molecules influence DNA, proteins, and enzymes in the cell cycle pathway. In the course of cell cycle progression, the cellular redox environment becomes more oxidized, moving from the G1 phase, becoming higher in G2/M and moderate in the S phase. Signals in the form of an increase in cellular pro-oxidant levels are required, and these signals are often terminated by a rise in the amount of antioxidants and MnSOD with a decrease in the level of cyclin D1 proteins. Therefore, understanding the mechanism of cell cycle redox regulation will help in the therapy of many diseases.

Sometimes less is more: inhibitory infrared light during early reperfusion calms hyperactive mitochondria and suppresses reperfusion injury

Ischemic stroke affects over 77 million people annually around the globe. Due to the blockage of a blood vessel caused by a stroke, brain tissue becomes ischemic. While prompt restoration of blood flow is necessary to save brain tissue, it also causes reperfusion injury. Mitochondria play a crucial role in early ischemia-reperfusion injury due to the generation of reactive oxygen species (ROS). During ischemia, mitochondria sense energy depletion and futilely attempt to up-regulate energy production. When reperfusion occurs, mitochondria become hyperactive and produce large amounts of ROS which damages neuronal tissue. This ROS burst damages mitochondria and the cell, which results in an eventual decrease in mitochondrial activity and pushes the fate of the cell toward death. This review covers the relationship between the mitochondrial membrane potential (ΔΨm) and ROS production. We also discuss physiological mechanisms that couple mitochondrial energy production to cellular energy demand, focusing on serine 47 dephosphorylation of cytochrome c (Cytc) in the brain during ischemia, which contributes to ischemia-reperfusion injury. Finally, we discuss the use of near infrared light (IRL) to treat stroke. IRL can both stimulate or inhibit mitochondrial activity depending on the wavelength. We emphasize that the use of the correct wavelength is crucial for outcome: inhibitory IRL, applied early during reperfusion, can prevent the ROS burst from occurring, thus preserving neurological tissue.

Angiotensin II Regulates Mitochondrial mTOR Pathway Activity Dependent on Acyl-CoA Synthetase 4 in Adrenocortical Cells

Two well-known protein complexes in mammalian cells, mTOR type 1 and type 2 (mTORC1/2) are involved in several cellular processes such as protein synthesis, cell proliferation, and commonly dysregulated in cancer. An acyl-CoA synthetase type 4 (ACSL4) is one of the most recently mTORC1/2 regulators described, in breast cancer cells. The expression of ACSL4 is hormone-regulated in adrenocortical cells and required for steroid biosynthesis. mTORC1/2 have been reported to be crucial in the proliferation of human adrenocortical tumor cells H295R and interestingly reported at several subcellular locations, which has brought cell biology to the vanguard of the mTOR signaling field. In the present work, we study the regulation of mTORC1/2 activation by angiotensin II (Ang II)-the trophic hormone for adrenocortical cells-the subcellular localization of mTORC1/2 signaling proteins and the role of ACSL4 in the regulation of this pathway, in H295R cells. Ang II promotes activation by phosphorylation of mTORC1/2 pathway proteins in a time-dependent manner. Mitochondrial pools of ribosomal protein S6, protein kinase B (Akt) in threonine 308, and serine 473 and Rictor are phosphorylated and activated. Glycogen synthase kinase type 3 (GSK3) is phosphorylated and inactivated in mitochondria, favoring mTORC1 activation. Epidermal growth factor, a classic mTORC1/2 activator, promoted unique activation kinetics of mTORC1/2 pathway, except for Akt phosphorylation. Here, we demonstrate that ACSL4 is necessary for mTORC1/2 effectors phosphorylation and H295R proliferation, triggered by Ang II. Ang II promotes activation of mitochondrial mTORC1/2 signaling proteins, through ACSL4, with a direct effect on adrenocortical cellular proliferation.

Comprehensive analysis of tissue proteomics in patients with papillary thyroid microcarcinoma uncovers the underlying mechanism of lymph node metastasis and its significant sex disparities

Background

Lymph node metastasis (LNM) in papillary thyroid microcarcinoma (PTMC) is associated with an increased risk of recurrence and poor prognosis. Sex has been regarded as a critical risk factor for LNM. The present study aimed to investigate the molecular mechanisms underlying LNM and its significant sex disparities in PTMC development.

Methods

A direct data-independent acquisition (DIA) proteomics approach was used to identify differentially expressed proteins (DEPs) in PTMC tumorous tissues with or without LNM and from male and female patients with LNM. The functional annotation of DEPs was performed using bioinformatics methods. Furthermore, The Cancer Genome Atlas Thyroid Carcinoma (TCGA-THCA) dataset and immunohistochemistry (IHC) were used to validate selected DEPs.

Results

The proteomics profile in PTMC with LNM differed from that of PTMC without LNM. The metastasis-related DEPs were primarily enriched in categories associated with mitochondrial dysfunction and may promote tumor progression by activating oxidative phosphorylation and PI3K/AKT signaling pathways. Comparative analyses of these DEPs revealed downregulated expression of specific proteins with well-established links to tumor metastasis, such as SLC25A15, DIRAS2, PLA2R1, and MTARC1. Additionally, the proteomics profiles of male and female PTMC patients with LNM were dramatically distinguishable. An elevated level of ECM-associated proteins might be related to more LNM in male PTMC than in female PTMC patients. The upregulated expression levels of MMRN2 and NID2 correlated with sex disparities and showed a positive relationship with unfavorable variables, such as LNMs and poor prognosis.

Conclusions

The proteomics profiles of PTMC show significant differences associated with LNM and its sex disparities, which further expands our understanding of the functional networks and signaling pathways related to PTMC with LNM.

Isobavachalcone disrupts mitochondrial respiration and induces cytotoxicity through ROS accumulation and Akt suppression

Isobavachalcone (IBC) is one of the flavonoid components in Fructus Psoraleae, and has been found multiple pharmacological effects. However, the hepatotoxicity of IBC has been overlooked and not been carefully studied. We aim to find out the cytotoxicity of IBC on HepG2 cells, and explore the underlying mechanisms. HepG2 cells were treated with IBC for 24 h, then MTT assay and LDH assay were used to detect the cell viability. The apoptosis and reactive oxygen species (ROS) production were reflected by the flow cytometry. Using Seahorse Analyzer, we measured the mitochondrial respiratory capacity. The expression of oxidative stress and mitochondrial apoptosis-related proteins were determined by Western blot. The results showed that IBC induced the cell death and apoptosis of HepG2 cells. IBC initiated the accumulation of ROS in cells and impaired the mitochondrial function, triggered apoptosis and suppressed the phosphorylation of Akt. Additionally, scavenging ROS by the antioxidant N-acetyl-l-cysteine (NAC) reduced IBC-induced mitochondria damage and increased Akt phosphorylation. Taken together, IBC caused mitochondrial damage and induced hepatotoxicity by ROS accumulation and Akt suppression. Targeting oxidative stress and depressing mitochondrial damage may provide a theoretical basis for the treatment and prevention of IBC-induced hepatotoxicity in clinic.

The Inositol Phosphate System-A Coordinator of Metabolic Adaptability

All cells rely on nutrients to supply energy and carbon building blocks to support cellular processes. Over time, eukaryotes have developed increasingly complex systems to integrate information about available nutrients with the internal state of energy stores to activate the necessary processes to meet the immediate and ongoing needs of the cell. One such system is the network of soluble and membrane-associated inositol phosphates that coordinate the cellular responses to nutrient uptake and utilization from growth factor signaling to energy homeostasis. In this review, we discuss the coordinated interactions of the inositol polyphosphates, inositol pyrophosphates, and phosphoinositides in major metabolic signaling pathways to illustrate the central importance of the inositol phosphate signaling network in nutrient responses.

Implication of IGF1R signaling in the protective effect of Astragaloside IV on ischemia and reperfusion-induced cardiac microvascular endothelial hyperpermeability

BACKGROUND

Myocardial ischemia-reperfusion (I/R) causes damage to coronary capillary endothelial barrier and microvascular leakage (MVL), aggravating tissue injury and heart dysfunction. However, the effective strategy for protecting endothelium barrier of cardiac vasculature remains limited.

PURPOSE

This study aimed to explore the effect of Astragaloside IV (ASIV) on coronary MVL after cardiac I/R and the underlying mechanism.

STUDY DESIGN

Sprague-Dawley (SD) rats were used for assessment of the efficacy of Astragaloside IV in protection of myocardial I/R injury, while human cardiac microvascular endothelial cells were applied to gain more insight into the underlying mechanism.

METHODS

Sprague-Dawley rats with or without pretreatment by ASIV at 10 mg/kg were subjected to occlusion of left coronary anterior descending artery followed by reperfusion. Endothelial cells were exposed to hypoxia and re-oxygenation (H/R). The distribution of junction proteins was detected by immunofluorescence staining and confocal microscope, the content of junction proteins was detected by Western blot, the level of adenosine triphosphate (ATP) was detected by ELISA, and the signal pathway related to permeability was detected by siRNA infection. The fluorescence intensity of FITC-albumin and FITC-Dextran was measured to evaluate the permeability of endothelial cells.

RESULTS

ASIV exhibited protective effects on capillary damage, myocardium edema, albumin leakage, leucocyte infiltration, and the downregulated expression of endothelial junction proteins after I/R. Moreover, ASIV displayed ability to protect ATP from depletion after I/R or H/R, and the effect of ASIV on regulating vascular permeability and junction proteins was abolished once ATP synthase was inhibited. Notably, ASIV activated the insulin-like growth factor 1 receptor (IGF1R) and downstream signaling after reoxygenation. Knocking IGF1R down abolished the effect of ASIV on restoration of ATP, junction proteins and endothelial barrier after H/R.

CONCLUSION

ASIV was potential to prevent MVL after I/R in heart. Moreover, the study for the first time demonstrated that the beneficial role of ASIV depended on promoting production of ATP through activating IGF1R signaling pathway. This result provided novel insight for better understanding the mechanism underlying the potential of ASIV to cope with cardiac I/R injury.

Insight into the Role of the PI3K/Akt Pathway in Ischemic Injury and Post-Infarct Left Ventricular Remodeling in Normal and Diabetic Heart

Despite the significant decline in mortality, cardiovascular diseases are still the leading cause of death worldwide. Among them, myocardial infarction (MI) seems to be the most important. A further decline in the death rate may be achieved by the introduction of molecularly targeted drugs. It seems that the components of the PI3K/Akt signaling pathway are good candidates for this. The PI3K/Akt pathway plays a key role in the regulation of the growth and survival of cells, such as cardiomyocytes. In addition, it has been shown that the activation of the PI3K/Akt pathway results in the alleviation of the negative post-infarct changes in the myocardium and is impaired in the state of diabetes. In this article, the role of this pathway was described in each step of ischemia and subsequent left ventricular remodeling. In addition, we point out the most promising substances which need more investigation before introduction into clinical practice. Moreover, we present the impact of diabetes and widely used cardiac and antidiabetic drugs on the PI3K/Akt pathway and discuss the molecular mechanism of its effects on myocardial ischemia and left ventricular remodeling.

Energetic metabolic reprogramming in Jurkat DFF40-deficient cancer cells

DNA fragmentation factor 40 (DFF40), or the caspase-activated DNase (CAD), is an endonuclease specific for double-stranded DNA. Alterations in its function and expression have been linked to apoptosis resistance, a mechanism likely used by cancer cells. However, how the DFF40-related apoptosis resistance pathway occurs remains unclear. Here, we sought to determine if DFF40 expression could be linked to cell metabolism through the regulation of mitochondrial integrity and function. We demonstrated that DFF40-deficient cells are more resistant to staurosporine and tributyltin (TBT)-induced apoptosis, and express higher levels of Mcl-1 at basal state. Treatment with TBT induces higher Bcl-2 and caspase-9 mRNA transcripts in DFF40 KO Jurkat cells, as well as enhanced Bcl-2 phosphorylation. A loss of DFF40 expression induces a higher mitochondrial mass, mtDNA copy number, mitochondrial membrane potential, and glycolysis rates in resting T cells. DFF40-deficient cells exhibit the Warburg effect phenotype, where they rely significantly more on glycolysis than oxidative phosphorylation and have a higher proliferative state, demonstrated by a higher Ki-67 transcription factor expression and AKT phosphorylation. Finally, we demonstrated with cell fractioning that DFF40 can translocate to the mitochondria following apoptosis induction. Our study reveals that DFF40 may act as a regulator of mitochondria during cell death and its loss could compromise mitochondrial integrity and cause an energetic reprogramming in pathologies such as cancer.

Cancer Metabolism: The Role of Immune Cells Epigenetic Alteration in Tumorigenesis, Progression, and Metastasis of Glioma

Glioma is a type of brain and spinal cord tumor that begins in glial cells that support the nervous system neurons functions. Age, radiation exposure, and family background of glioma constitute are risk factors of glioma initiation. Gliomas are categorized on a scale of four grades according to their growth rate. Grades one and two grow slowly, while grades three and four grow faster. Glioblastoma is a grade four gliomas and the deadliest due to its aggressive nature (accelerated proliferation, invasion, and migration). As such, multiple therapeutic approaches are required to improve treatment outcomes. Recently, studies have implicated the significant roles of immune cells in tumorigenesis and the progression of glioma. The energy demands of gliomas alter their microenvironment quality, thereby inducing heterogeneity and plasticity change of stromal and immune cells via the PI3K/AKT/mTOR pathway, which ultimately results in epigenetic modifications that facilitates tumor growth. PI3K is utilized by many intracellular signaling pathways ensuring the proper functioning of the cell. The activation of PI3K/AKT/mTOR regulates the plasma membrane activities, contributing to the phosphorylation reaction necessary for transcription factors activities and oncogenes hyperactivation. The pleiotropic nature of PI3K/AKT/mTOR makes its activity unpredictable during altered cellular functions. Modification of cancer cell microenvironment affects many cell types, including immune cells that are the frontline cells involved in inflammatory cascades caused by cancer cells via high cytokines synthesis. Typically, the evasion of immunosurveillance by gliomas and their resistance to treatment has been attributed to epigenetic reprogramming of immune cells in the tumor microenvironment, which results from cancer metabolism. Hence, it is speculative that impeding cancer metabolism and/or circumventing the epigenetic alteration of immune cell functions in the tumor microenvironment might enhance treatment outcomes. Herein, from an oncological and immunological perspective, this review discusses the underlying pathomechanism of cell-cell interactions enhancing glioma initiation and metabolism activation and tumor microenvironment changes that affect epigenetic modifications in immune cells. Finally, prospects for therapeutic intervention were highlighted.

Mitochondrial calcium exchange in physiology and disease

The uptake of calcium into and extrusion of calcium from the mitochondrial matrix is a fundamental biological process that has critical effects on cellular metabolism, signaling, and survival. Disruption of mitochondrial calcium (mCa2+) cycling is implicated in numerous acquired diseases such as heart failure, stroke, neurodegeneration, diabetes, and cancer and is genetically linked to several inherited neuromuscular disorders. Understanding the mechanisms responsible for mCa2+ exchange therefore holds great promise for the treatment of these diseases. The past decade has seen the genetic identification of many of the key proteins that mediate mitochondrial calcium uptake and efflux. Here, we present an overview of the phenomenon of mCa2+ transport and a comprehensive examination of the molecular machinery that mediates calcium flux across the inner mitochondrial membrane: the mitochondrial uniporter complex (consisting of MCU, EMRE, MICU1, MICU2, MICU3, MCUB, and MCUR1), NCLX, LETM1, the mitochondrial ryanodine receptor, and the mitochondrial permeability transition pore. We then consider the physiological implications of mCa2+ flux and evaluate how alterations in mCa2+ homeostasis contribute to human disease. This review concludes by highlighting opportunities and challenges for therapeutic intervention in pathologies characterized by aberrant mCa2+ handling and by summarizing critical unanswered questions regarding the biology of mCa2+ flux.

Mitochondrion-Localized SND1 Promotes Mitophagy and Liver Cancer Progression Through PGAM5

Staphylococcal nuclease domain-containing protein 1 (SND1) is an evolutionarily conserved multifunctional protein that functions mainly in the nucleus and cytoplasm. However, whether SND1 regulates cellular activity through mitochondrial-related functions remains unclear. Herein, we demonstrate that SND1 is localized to mitochondria to promote phosphoglycerate mutase 5 (PGAM5)-mediated mitophagy. We find that SND1 is present in mitochondria based on mass spectrometry data and verified this phenomenon in different liver cancer cell types by performing organelle subcellular isolation. Specifically, The N-terminal amino acids 1-63 of SND1 serve as a mitochondrial targeting sequence (MTS), and the translocase of outer membrane 70 (TOM 70) promotes the import of SND1 into mitochondria. By immunoprecipitation-mass spectrometry (IP-MS), we find that SND1 interacts with PGAM5 in mitochondria and is crucial for the binding of PGAM5 to dynamin-related protein 1 (DRP1). Importantly, we demonstrate that PGAM5 and SND1-MTS are required for SND1-mediated mitophagy under FCCP and glucose deprivation treatment as well as for SND1-mediated cell proliferation and tumor growth both in vitro and in vivo. Aberrant expression of SND1 and PGAM5 predicts poor outcomes in hepatocellular carcinoma (HCC) patients. Taken together, these findings establish a previously unappreciated role of SND1 and the association of mitochondrion-localized SND1 with PGAM5 in mitophagy and tumor progression.

Tourniquet-induced lower limb ischemia/reperfusion reduces mitochondrial function by decreasing mitochondrial biogenesis in acute kidney injury in mice

The mechanisms by which lower limb ischemia/reperfusion induces acute kidney injury (AKI) remain largely uncharacterized. We hypothesized that tourniquet-induced lower limb ischemia/reperfusion (TILLIR) would inhibit mitochondrial function in the renal cortex. We used a murine model to show that TILLIR of the high thigh regions inflicted time-dependent AKI as determined by renal function and histology. This effect was associated with decreased activities of mitochondrial complexes I, II, V and citrate synthase in the kidney cortex. Moreover, TILLIR reduced mRNA levels of a master regulator of mitochondrial biogenesis PGC-1α, and its downstream genes NDUFS1 and ATP5o in the renal cortex. TILLIR also increased serum corticosterone concentrations. TILLIR did not significantly affect protein levels of the critical regulators of mitophagy PINK1 and PARK2, mitochondrial transport proteins Tom20 and Tom70, or heat-shock protein 27. TILLIR had no significant effect on mitochondrial oxidative stress as determined by mitochondrial ability to generate reactive oxygen species, protein carbonylation, or protein levels of MnSOD and peroxiredoxin1. However, TILLIR inhibited classic autophagic flux by increasing p62 protein abundance and preventing the conversion of LC3-I to LC3-II. TILLIR increased phosphorylation of cytosolic and mitochondrial ERK1/2 and mitochondrial AKT1, as well as mitochondrial SGK1 activity. In conclusion, lower limb ischemia/reperfusion induces distal AKI by inhibiting mitochondrial function through reducing mitochondrial biogenesis. This AKI occurs without significantly affecting PINK1-PARK2-mediated mitophagy or mitochondrial oxidative stress in the kidney cortex.

The kinase complex mTORC2 promotes the longevity of virus-specific memory CD4+ T cells by preventing ferroptosis

Antigen-specific memory CD4+ T cells can persist and confer rapid and efficient protection from microbial reinfection. However, the mechanisms underlying the long-term maintenance of the memory CD4+ T cell pool remain largely unknown. Here, using a mouse model of acute infection with lymphocytic choriomeningitis virus (LCMV), we found that the serine/threonine kinase complex mammalian target of rapamycin complex 2 (mTORC2) is critical for the long-term persistence of virus-specific memory CD4+ T cells. The perturbation of mTORC2 signaling at memory phase led to an enormous loss of virus-specific memory CD4+ T cells by a unique form of regulated cell death (RCD), ferroptosis. Mechanistically, mTORC2 inactivation resulted in the impaired phosphorylation of downstream AKT and GSK3β kinases, which induced aberrant mitochondrial reactive oxygen species (ROS) accumulation and ensuing ferroptosis-causative lipid peroxidation in virus-specific memory CD4+ T cells; furthermore, the disruption of this signaling cascade also inhibited glutathione peroxidase 4 (GPX4), a major scavenger of lipid peroxidation. Thus, the mTORC2-AKT-GSK3β axis functions as a key signaling hub to promote the longevity of virus-specific memory CD4+ T cells by preventing ferroptosis.

Heme stimulates platelet mitochondrial oxidant production to induce targeted granule secretion

Hemolysis, a pathological component of many diseases, is associated with thrombosis and vascular dysfunction. Hemolytic products, including cell-free hemoglobin and free heme directly activate platelets. However, the effect of hemolysis on platelet degranulation, a central process in not only thrombosis, but also inflammatory and mitogenic signaling, remains less clear. Our group showed that hemoglobin-induced platelet activation involved the production of mitochondrial reactive oxygen species (mtROS). However, the molecular mechanism by which extracellular hemolysis induces platelet mtROS production, and whether these mtROS regulate platelet degranulation remains unknown. Here, we demonstrate using isolated human platelets that cell free heme is a more potent agonist for platelet activation than hemoglobin, and stimulates the release of a specific set of molecules, including the glycoprotein thrombospondin-1 (TSP-1), from the α-granule of platelets. We uncover the mechanism of heme-mediated platelet mtROS production which is dependent on the activation of platelet toll-like receptor 4 (TLR4) signaling and leads to the downstream phosphorylation and inhibition of complex-V by the serine kinase Akt. Notably, inhibition of platelet TLR4 or Akt, or scavenging of mtROS prevents heme-induced granule release in vitro. Further, heme-dependent granule release is significantly attenuated in vivo in mice lacking TLR4 or those treated with the mtROS scavenger MitoTEMPO. These data elucidate a novel mechanism of TLR4-mediated mitochondrial regulation, establish the mechanistic link between hemolysis and platelet degranulation, and begin to define the heme and mtROS-dependent platelet secretome. These data have implications for hemolysis-induced thrombo-inflammatory signaling and for the consideration of platelet mitochondria as a therapeutic target in hemolytic disorders.

Glycogen synthesis and beyond, a comprehensive review of GSK3 as a key regulator of metabolic pathways and a therapeutic target for treating metabolic diseases

Glycogen synthase kinase‐3 (GSK3) is a highly evolutionarily conserved serine/threonine protein kinase first identified as an enzyme that regulates glycogen synthase (GS) in response to insulin stimulation, which involves GSK3 regulation of glucose metabolism and energy homeostasis. Both isoforms of GSK3, GSK3α, and GSK3β, have been implicated in many biological and pathophysiological processes. The various functions of GSK3 are indicated by its widespread distribution in multiple cell types and tissues. The studies of GSK3 activity using animal models and the observed effects of GSK3‐specific inhibitors provide more insights into the roles of GSK3 in regulating energy metabolism and homeostasis. The cross‐talk between GSK3 and some important energy regulators and sensors and the regulation of GSK3 in mitochondrial activity and component function further highlight the molecular mechanisms in which GSK3 is involved to regulate the metabolic activity, beyond its classical regulatory effect on GS. In this review, we summarize the specific roles of GSK3 in energy metabolism regulation in tissues that are tightly associated with energy metabolism and the functions of GSK3 in the development of metabolic disorders. We also address the impacts of GSK3 on the regulation of mitochondrial function, activity and associated metabolic regulation. The application of GSK3 inhibitors in clinical tests will be highlighted too. Interactions between GSK3 and important energy regulators and GSK3‐mediated responses to different stresses that are related to metabolism are described to provide a brief overview of previously less‐appreciated biological functions of GSK3 in energy metabolism and associated diseases through its regulation of GS and other functions.

Deletion of BCATm increases insulin-stimulated glucose oxidation in the heart

BACKGROUNDS

Branched chain amino acid (BCAA) oxidation is impaired in cardiac insulin resistance, leading to the accumulation of BCAAs and the first products of BCAA oxidation, the branched chain ketoacids. However, it is not clear whether it is the BCAAs, BCKAs or both that are mediating cardiac insulin resistance. To determine this, we produced mice with a cardiac-specific deletion of BCAA aminotransferase (BCATm^-/-), the first enzyme in the BCAA oxidation pathway that is responsible for converting BCAAs to BCKAs.

METHODS

Eight-week-old BCATm cardiac specific knockout (BCATm^-/-) male mice and their α-MHC (myosin heavy chain) - Cre expressing wild type littermates (WT-Cre^+/+) received tamoxifen (50 mg/kg i.p. 6 times over 8 days). At 16-weeks of age, cardiac energy metabolism was assessed in isolated working hearts.

RESULTS

BCATm^-/- mice have decreased cardiac BCAA oxidation rates, increased cardiac BCAAs and a reduction in cardiac BCKAs. Hearts from BCATm^-/- mice showed an increase in insulin stimulation of glucose oxidation and an increase in p-AKT. To determine the impact of reversing these events, we perfused isolated working mice hearts with high levels of BCKAs, which completely abolished insulin-stimulated glucose oxidation rates, an effect associated with decreased p-AKT and inactivation of pyruvate dehydrogenase (PDH), the rate-limiting enzyme in glucose oxidation.

CONCLUSION

This implicates the BCKAs, and not BCAAs, as the actual mediators of cardiac insulin resistance and suggests that lowering cardiac BCKAs can be used as a therapeutic strategy to improve insulin sensitivity in the heart.

A beneficial role for elevated extracellular glutamate in Amyotrophic Lateral Sclerosis and cerebral ischemia

This hypothesis proposes that increased extracellular glutamate in Amyotrophic Lateral Sclerosis (ALS) and cerebral ischemia, currently viewed as a trigger for excitotoxicity, is actually beneficial as it stimulates the utilization of glutamate as metabolic fuel. Renewed appreciation of glutamate oxidation by ischemic neurons has raised questions regarding the role of extracellular glutamate in ischemia. Is it detrimental, as suggested by excitotoxicity in early in vitro studies, or beneficial, as suggested by its oxidation in later in vivo studies? The answer may depend on the activity of N-methyl-D-aspartate (NMDA) glutamate receptors. Early in vitro procedures co-activated NMDA receptors (NMDARs) containing 2A (GluN2A) and 2B (GluN2B) subunits, an event now believed to trigger excitotoxicity; however, during in vivo ischemia D-serine and zinc molecules are released and these ensure only GluN2B receptors are stimulated. This not only prevents excitotoxicity but also initiates signaling cascades that allow ischemic neurons to import and oxidize glutamate.

Mitochondrial Targeting of the Ammonia-Sensitive Uncoupler SLC4A11 by the Chaperone-Mediated Carrier Pathway in Corneal Endothelium

Purpose

SLC4A11, an electrogenic H⁺ transporter, is found in the plasma membrane and mitochondria of corneal endothelium. However, the underlying mechanism of SLC4A11 targeting to mitochondria is unknown.

Methods

The presence of mitochondrial targeting sequences was examined using in silico mitochondrial proteomic analyses. Thiol crosslinked peptide binding to SLC4A11 was screened by untargeted liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis. Direct protein interactions between SLC4A11 and chaperones were examined using coimmunoprecipitation analysis and proximity ligation assay. Knockdown or pharmacologic inhibition of chaperones in human corneal endothelial cells (HCECs) or mouse corneal endothelial cells (MCECs), ex vivo kidney, or HA-SLC4A11–transfected fibroblasts was performed to investigate the functional consequences of interfering with mitochondrial SLC4A11 trafficking.

Results

SLC4A11 does not contain canonical N-terminal mitochondrial targeting sequences. LC-MS/MS analysis showed that HSC70 and/or HSP90 are bound to HA-SLC4A11–transfected PS120 fibroblast whole-cell lysates or isolated mitochondria, suggesting trafficking through the chaperone-mediated carrier pathway. SLC4A11 and either HSP90 or HSC70 complexes are directly bound to the mitochondrial surface receptor, TOM70. Interference with this trafficking leads to dysfunctional mitochondrial glutamine catabolism and increased reactive oxygen species production. In addition, glutamine (Gln) use upregulated SLC4A11, HSP70, and HSP90 expression in whole-cell lysates or purified mitochondria of HCECs and HA-SLC4A11–transfected fibroblasts.

Conclusions

HSP90 and HSC70 are critical in mediating mitochondrial SLC4A11 translocation in corneal endothelial cells and kidney. Gln promotes SLC4A11 import to the mitochondria, and the continuous oxidative stress derived from Gln catabolism induced HSP70 and HSP90, protecting cells against oxidative stress.

Altered insulin pathway compromises mitochondrial function and quality control both in in vitro and in vivo model systems

Altered insulin signaling and insulin resistance are considered the link between Alzheimer's disease (AD) and metabolic syndrome. Here, by using an in vitro and an in vivo model, we investigated the relationship between these disorders focusing on neuronal mitochondrial dysfunction and mitophagy. In vitro Aβ insult induced the opening of mitochondrial permeability transition pore (mPTP), mitochondrial membrane potential (ΔΨm) loss, and apoptosis while insulin addition ameliorated these dysfunctions. The same alterations were detected in a 16 weeks of age mouse model of diet-induced obesity and insulin resistance. In addition, we detected an increase of fission related proteins and activation of mitophagy, proved by the rise of PINK1 and Parkin proteins. Nevertheless, in vitro, the increase of p62 and LC3 indicated an alteration in autophagy, while, in vivo decreased expression of p62 and increase of LC3 suggested removing of damaged mitochondria. Finally, in aged mice (28 and 48 weeks), the data indicated impairment of mitophagy and suggested the accumulation of damaged mitochondria. Taken together these outcomes indicate that alteration of the insulin pathway affects mitochondrial integrity, and effective mitophagy is age-dependent.

Human Placental Transcriptome Reveals Critical Alterations in Inflammation and Energy Metabolism with Fetal Sex Differences in Spontaneous Preterm Birth

A well-functioning placenta is crucial for normal gestation and regulates the nutrient, gas, and waste exchanges between the maternal and fetal circulations and is an important endocrine organ producing hormones that regulate both the maternal and fetal physiologies during pregnancy. Placental insufficiency is implicated in spontaneous preterm birth (SPTB). We proposed that deficits in the capacity of the placenta to maintain bioenergetic and metabolic stability during pregnancy may ultimately result in SPTB. To explore our hypothesis, we performed a RNA-seq study in male and female placentas from women with SPTB (<36 weeks gestation) compared to normal pregnancies (≥38 weeks gestation) to assess the alterations in the gene expression profiles. We focused exclusively on Black women (cases and controls), who are at the highest risk of SPTB. Six hundred and seventy differentially expressed genes were identified in male SPTB placentas. Among them, 313 and 357 transcripts were increased and decreased, respectively. In contrast, only 61 differentially expressed genes were identified in female SPTB placenta. The ingenuity pathway analysis showed alterations in the genes and canonical pathways critical for regulating inflammation, oxidative stress, detoxification, mitochondrial function, energy metabolism, and the extracellular matrix. Many upstream regulators and master regulators important for nutrient-sensing and metabolism were also altered in SPTB placentas, including the PI3K complex, TGFB1/SMADs, SMARCA4, TP63, CDKN2A, BRCA1, and NFAT. The transcriptome was integrated with published human placental metabolome to assess the interactions of altered genes and metabolites. Collectively, significant and biologically relevant alterations in the transcriptome were identified in SPTB placentas with fetal sex disparities. Altered energy metabolism, mitochondrial function, inflammation, and detoxification may underly the mechanisms of placental dysfunction in SPTB.

CUT Domain Proteins in DNA Repair and Cancer

Simple Summary

Genetic integrity is ensured by complex groups of proteins involved in DNA repair. In particular, base damage is repaired by enzymes of the base excision repair pathway. Recent studies have revealed that some transcription factors can function as accessory factors that stimulate the enzymatic activities of these DNA repair enzymes. It is well known that defects in DNA repair mechanisms cause the accumulation of changes in DNA, called mutations, that increase the possibility that cells become tumorigenic. Paradoxically, once they have emerged certain cancer cells are acutely dependent on the heightened activities of base excision repair enzymes because their metabolism generates highly reactive molecules that cause multiple types of damage to bases. In this context, the function of accessory factors becomes essential to cancer cell survival. As a by-product of this adaptation, cancer cells become more resistant to therapies that cause DNA damage, such as chemotherapy and radiation.

Abstract

Recent studies revealed that CUT domains function as accessory factors that accelerate DNA repair by stimulating the enzymatic activities of the base excision repair enzymes OGG1, APE1, and DNA pol β. Strikingly, the role of CUT domain proteins in DNA repair is exploited by cancer cells to facilitate their survival. Cancer cells in which the RAS pathway is activated produce an excess of reactive oxygen species (ROS) which, if not counterbalanced by increased production of antioxidants, causes sustained oxidative DNA damage and, ultimately, cell senescence. These cancer cells can adapt by increasing their capacity to repair oxidative DNA damage in part through elevated expression of CUT domain proteins such as CUX1, CUX2, or SATB1. In particular, CUX1 overexpression was shown to cooperate with RAS in the formation of mammary and lung tumors in mice. Conversely, knockdown of CUX1, CUX2, or SATB1 was found to be synthetic lethal in cancer cells exhibiting high ROS levels as a consequence of activating mutations in KRAS, HRAS, BRAF, or EGFR. Importantly, as a byproduct of their adaptation, cancer cells that overexpress CUT domain proteins exhibit increased resistance to genotoxic treatments such as ionizing radiation, temozolomide, and cisplatin.

Untangling the effect of insulin action on brain mitochondria and metabolism

The regulation of energy homeostasis is controlled by the brain and, besides requiring high amounts of energy, it relies on functional insulin/insulin-like growth factor (IGF)-1 signalling in the central nervous system. This energy is mainly provided by mitochondria in form of ATP. Thus, there is an intricate interplay between mitochondrial function and insulin/IGF-1 action to enable functional brain signalling and, accordingly, propagate a healthy metabolism. To adapt to different nutritional conditions, the brain is able to sense the current energy status via mitochondrial and insulin signalling-dependent pathways and exerts an appropriate metabolic response. However, regional, cell type and receptor-specific consequences of this interaction occur and are linked to diverse outcomes such as altered nutrient sensing, body weight regulation or even cognitive function. Impairments of this cross-talk can lead to obesity and glucose intolerance and are linked to neurodegenerative diseases, yet they also induce a self-sustainable, dysfunctional 'metabolic triangle' characterised by insulin resistance, mitochondrial dysfunction and inflammation in the brain. The identification of causal factors deteriorating insulin action, mitochondrial function and concomitantly a signature of metabolic stress in the brain is of utter importance to offer novel mechanistic insights into development of the continuously rising prevalence of non-communicable diseases such as type 2 diabetes and neurodegeneration. This review aims to determine the effect of insulin action on brain mitochondrial function and energy metabolism. It precisely outlines the interaction and differences between insulin action, insulin-like growth factor (IGF)-1 signalling and mitochondrial function; distinguishes between causality and association; and reveals its consequences for metabolism and cognition. We hypothesise that an improvement of at least one signalling pathway can overcome the vicious cycle of a self-perpetuating metabolic dysfunction in the brain present in metabolic and neurodegenerative diseases.

Multi-omic molecular profiling reveals potentially targetable abnormalities shared across multiple histologies of brain metastasis

The deadly complication of brain metastasis (BM) is largely confined to a relatively narrow cross-section of systemic malignancies, suggesting a fundamental role for biological mechanisms shared across commonly brain metastatic tumor types. To identify and characterize such mechanisms, we performed genomic, transcriptional, and proteomic profiling using whole-exome sequencing, mRNA-seq, and reverse-phase protein array analysis in a cohort of the lung, breast, and renal cell carcinomas consisting of BM and patient-matched primary or extracranial metastatic tissues. While no specific genomic alterations were associated with BM, correlations with impaired cellular immunity, upregulated oxidative phosphorylation (OXPHOS), and canonical oncogenic signaling pathways including phosphoinositide 3-kinase (PI3K) signaling, were apparent across multiple tumor histologies. Multiplexed immunofluorescence analysis confirmed significant T cell depletion in BM, indicative of a fundamentally altered immune microenvironment. Moreover, functional studies using in vitro and in vivo modeling demonstrated heightened oxidative metabolism in BM along with sensitivity to OXPHOS inhibition in murine BM models and brain metastatic derivatives relative to isogenic parentals. These findings demonstrate that pathophysiological rewiring of oncogenic signaling, cellular metabolism, and immune microenvironment broadly characterizes BM. Further clarification of this biology will likely reveal promising targets for therapeutic development against BM arising from a broad variety of systemic cancers.

Energy Metabolism During Osteogenic Differentiation: The Role of Akt

Osteogenic differentiation, the process by which bone marrow mesenchymal stem/stromal (a.k.a. skeletal stem) cells and osteoprogenitors form osteoblasts, is a critical event for bone formation during development, fracture repair, and tissue maintenance. Extra cellular and intracellular signaling pathways triggering osteogenic differentiation are relatively well known; however, the ensuing change in cell energy metabolism is less clearly defined. We and others have previously reported activation of mitochondria during osteogenic differentiation. To further elucidate the involved bioenergetic mechanisms and triggers, we tested the effect of osteogenic media containing ascorbate and β-glycerol phosphate, or various osteogenic hormones and growth factors on energy metabolism in long bone (ST2)- and calvarial bone (MC3T3-E1)-derived osteoprogenitors. We show that osteogenic media and differentiation factors, Wnt3a and BMP2, stimulate mitochondrial oxidative phosphorylation (OxPhos) with little effect on glycolysis. The activation of OxPhos occurs acutely, suggesting a metabolic signaling change rather than protein expression change. To this end, we found that the observed mitochondrial activation is Akt dependent. Akt is activated by osteogenic media, Wnt3a, and BMP2, leading to increased phosphorylation of various mitochondrial Akt targets, a phenomenon known to stimulate OxPhos. In sum, our data provide comprehensive analysis of cellular bioenergetics during osteoinduction in cells of two different origins (mesenchyme vs neural crest) and identify Wnt3a and BMP2 as physiological stimulators of mitochondrial respiration through Akt activation.

The Mitochondrial Proteome of Tumor Cells: A SnapShot on Methodological Approaches and New Biomarkers

Simple Summary

Mitochondria are central hubs of cellular signaling, energy metabolism, and redox balance. The plasticity of these cellular organelles is an essential requisite for the cells to cope with different stimuli and stress conditions. Cancer cells are characterized by changes in energy metabolism, mitochondrial signaling, and dynamics. These changes are driven by alterations in the mitochondrial proteome. For this reason, in the last years a focus of basic and cancer research has been the implementation and optimization of technologies to investigate changes in the mitochondrial proteome during cancer initiation and progression. This review presents an overview of the most used technologies to investigate the mitochondrial proteome and recent evidence on changes in the expression levels and delocalization of certain proteins in and out the mitochondria for shaping the functional properties of tumor cells.

Abstract

Mitochondria are highly dynamic and regulated organelles implicated in a variety of important functions in the cell, including energy production, fatty acid metabolism, iron homeostasis, programmed cell death, and cell signaling. Changes in mitochondrial metabolism, signaling and dynamics are hallmarks of cancer. Understanding whether these modifications are associated with alterations of the mitochondrial proteome is particularly relevant from a translational point of view because it may contribute to better understanding the molecular bases of cancer development and progression and may provide new potential prognostic and diagnostic biomarkers as well as novel molecular targets for anti-cancer treatment. Making an inventory of the mitochondrial proteins has been particularly challenging given that there is no unique consensus targeting sequence that directs protein import into mitochondria, some proteins are present at very low levels, while other proteins are expressed only in some cell types, in a particular developmental stage or under specific stress conditions. This review aims at providing the state-of-the-art on methodologies used to characterize the mitochondrial proteome in tumors and highlighting the biological relevance of changes in expression and delocalization of proteins in and out the mitochondria in cancer biology.

Insulin directly stimulates mitochondrial glucose oxidation in the heart

Background

Glucose oxidation is a major contributor to myocardial energy production and its contribution is orchestrated by insulin. While insulin can increase glucose oxidation indirectly by enhancing glucose uptake and glycolysis, it also directly stimulates mitochondrial glucose oxidation, independent of increasing glucose uptake or glycolysis, through activating mitochondrial pyruvate dehydrogenase (PDH), the rate-limiting enzyme of glucose oxidation. However, how insulin directly stimulates PDH is not known. To determine this, we characterized the impacts of modifying mitochondrial insulin signaling kinases, namely protein kinase B (Akt), protein kinase C-delta (PKC-δ) and glycogen synthase kinase-3 beta (GSK-3β), on the direct insulin stimulation of glucose oxidation.

Methods

We employed an isolated working mouse heart model to measure the effect of insulin on cardiac glycolysis, glucose oxidation and fatty acid oxidation and how that could be affected when mitochondrial Akt, PKC-δ or GSK-3β is disturbed using pharmacological modulators. We also used differential centrifugation to isolate mitochondrial and cytosol fraction to examine the activity of Akt, PKC-δ and GSK-3β between these fractions. Data were analyzed using unpaired t-test and two-way ANOVA.

Results

Here we show that insulin-stimulated phosphorylation of mitochondrial Akt is a prerequisite for transducing insulin’s direct stimulation of glucose oxidation. Inhibition of mitochondrial Akt completely abolishes insulin-stimulated glucose oxidation, independent of glucose uptake or glycolysis. We also show a novel role of mitochondrial PKC-δ in modulating mitochondrial glucose oxidation. Inhibition of mitochondrial PKC-δ mimics insulin stimulation of glucose oxidation and mitochondrial Akt. We also demonstrate that inhibition of mitochondrial GSK3β phosphorylation does not influence insulin-stimulated glucose oxidation.

Conclusion

We identify, for the first time, insulin-stimulated mitochondrial Akt as a prerequisite transmitter of the insulin signal that directly stimulates cardiac glucose oxidation. These novel findings suggest that targeting mitochondrial Akt is a potential therapeutic approach to enhance cardiac insulin sensitivity in condition such as heart failure, diabetes and obesity.

Cancer cell metabolism: Rewiring the mitochondrial hub

To adapt to tumoral environment conditions or even to escape chemotherapy, cells rapidly reprogram their metabolism to handle adversities and survive. Given the rapid rise of studies uncovering novel insights and therapeutic opportunities based on the role of mitochondria in tumor metabolic programing and therapeutics, this review summarizes most significant developments in the field. Taking in mind the key role of mitochondria on carcinogenesis and tumor progression due to their involvement on tumor plasticity, metabolic remodeling, and signaling re-wiring, those organelles are also potential therapeutic targets. Among other topics, we address the recent data intersecting mitochondria as of prognostic value and staging in cancer, by mitochondrial DNA (mtDNA) determination, and current inhibitors developments targeting mtDNA, OXPHOS machinery and metabolic pathways. We contribute for a holistic view of the role of mitochondria metabolism and directed therapeutics to understand tumor metabolism, to circumvent therapy resistance, and to control tumor development.

Intrauterine Inflammation Alters the Transcriptome and Metabolome in Placenta

Placental insufficiency is implicated in spontaneous preterm birth (SPTB) associated with intrauterine inflammation. We hypothesized that intrauterine inflammation leads to deficits in the capacity of the placenta to maintain bioenergetic and metabolic stability during pregnancy ultimately resulting in SPTB. Using a mouse model of intrauterine inflammation that leads to preterm delivery, we performed RNA-seq and metabolomics studies to assess how intrauterine inflammation alters gene expression and/or modulates metabolite production and abundance in the placenta. 1871 differentially expressed genes were identified in LPS-exposed placenta. Among them, 1,149 and 722 transcripts were increased and decreased, respectively. Ingenuity pathway analysis showed alterations in genes and canonical pathways critical for regulating oxidative stress, mitochondrial function, metabolisms of glucose and lipids, and vascular reactivity in LPS-exposed placenta. Many upstream regulators and master regulators important for nutrient-sensing and mitochondrial function were also altered in inflammation exposed placentae, including STAT1, HIF1α, mTOR, AMPK, and PPARα. Comprehensive quantification of metabolites demonstrated significant alterations in the glucose utilization, metabolisms of branched-chain amino acids, lipids, purine and pyrimidine, as well as carbon flow in TCA cycle in LPS-exposed placenta compared to control placenta. The transcriptome and metabolome were also integrated to assess the interactions of altered genes and metabolites. Collectively, significant and biologically relevant alterations in the placenta transcriptome and metabolome were identified in placentae exposed to intrauterine inflammation. Altered mitochondrial function and energy metabolism may underline the mechanisms of inflammation-induced placental dysfunction.

Location Bias as Emerging Paradigm in GPCR Biology and Drug Discovery

GPCRs are the largest receptor family that are involved in virtually all biological processes. Pharmacologically, they are highly druggable targets, as they cover more than 40% of all drugs in the market. Our knowledge of biased signaling provided insight into pharmacology vastly improving drug design to avoid unwanted effects and achieve higher efficacy and selectivity. However, yet another feature of GPCR biology is left largely unexplored, location bias. Recent developments in this field show promising avenues for evolution of new class of pharmaceuticals with greater potential for higher level of precision medicine. Further consideration and understanding of this phenomenon with deep biochemical and molecular insights would pave the road to success. In this review, we critically analyze this perspective and discuss new avenues of investigation.

Distinct intra-mitochondrial localizations of pro-survival kinases and regulation of their functions by DUSP5 and PHLPP-1

ERK and Akt have been shown to regulate cell sensitivity to death-inducing stress by phosphorylating GSK-3β, a major modulator of the threshold for mitochondrial permeability transition. Here we examined intra-mitochondrial localization of the pro-survival kinases and their regulation by phosphatases. Stepwise trypsin digestion of mitochondria isolated from HEK293 or H9c2 cells was performed, and immunoblotting revealed that GSK-3β and ERK localized dominantly in the outer membrane (OM), while Akt resided at comparable levels in OM, the inner membrane (IM) and the matrix. Treatment with IGF-1 increased the protein level of Akt in the matrix, while ERK and GSK-3β protein levels were increased in OM. Simultaneously, IGF-1 treatment elevated the level of Thr202/Tyr204-phospho-ERK in IM and matrix and levels of Ser473-phospho-Akt and Ser9-phospho-GSK-3β in OM, IM and matrix. Exposing cells to reactive oxygen species (ROS) by using antimycin A increased the levels of DUSP5 and PHLPP-1 mainly in OM and induced dephosphorylation of Akt, ERK and GSK-3β. The mitochondrial localization of DUSP5 was confirmed by experiments with mitochondria purified by Percoll gradient centrifugation and by transfection of cells with GFP-tagged DUSP5. Knockdown of either DUSP5 or PHLPP-1 increased the levels of both Thr202/Tyr204-phospho-ERK and Ser473-phospho-Akt in mitochondria. Cell death induced by antimycin A was suppressed by siRNA-mediated knockdown of DUSP5. The results suggest that Akt and ERK in mitochondria show distinct intra-mitochondrial localization and crosstalk in GSK-3β regulation and that recruitment of DUSP5 as well as PHLPP-1 to mitochondria contributes to ROS-induced termination of the protective signaling.

Brain-Specific Serine-47 Modification of Cytochrome c Regulates Cytochrome c Oxidase Activity Attenuating ROS Production and Cell Death: Implications for Ischemia/Reperfusion Injury and Akt Signaling

We previously reported that serine-47 (S47) phosphorylation of cytochrome c (Cytc) in the brain results in lower cytochrome c oxidase (COX) activity and caspase-3 activity in vitro. We here analyze the effect of S47 modification in fibroblast cell lines stably expressing S47E phosphomimetic Cytc, unphosphorylated WT, or S47A Cytc. Our results show that S47E Cytc results in partial inhibition of mitochondrial respiration corresponding with lower mitochondrial membrane potentials (ΔΨm) and reduced reactive oxygen species (ROS) production. When exposed to an oxygen-glucose deprivation/reoxygenation (OGD/R) model simulating ischemia/reperfusion injury, the Cytc S47E phosphomimetic cell line showed minimal ROS generation compared to the unphosphorylated WT Cytc cell line that generated high levels of ROS upon reoxygenation. Consequently, the S47E Cytc cell line also resulted in significantly lower cell death upon exposure to OGD/R, confirming the cytoprotective role of S47 phosphorylation of Cytc. S47E Cytc also resulted in lower cell death upon H2O2 treatment. Finally, we propose that pro-survival kinase Akt (protein kinase B) is a likely mediator of the S47 phosphorylation of Cytc in the brain. Akt inhibitor wortmannin abolished S47 phosphorylation of Cytc, while the Akt activator SC79 maintained S47 phosphorylation of Cytc. Overall, our results suggest that loss of S47 phosphorylation of Cytc during brain ischemia drives reperfusion injury through maximal electron transport chain flux, ΔΨm hyperpolarization, and ROS-triggered cell death.

Growth Hormone Reprograms Macrophages toward an Anti-Inflammatory and Reparative Profile in an MAFB-Dependent Manner

Growth hormone (GH), a pleiotropic hormone secreted by the pituitary gland, regulates immune and inflammatory responses. In this study, we show that GH regulates the phenotypic and functional plasticity of macrophages both in vitro and in vivo. Specifically, GH treatment of GM-CSF-primed monocyte-derived macrophages promotes a significant enrichment of anti-inflammatory genes and dampens the proinflammatory cytokine profile through PI3K-mediated downregulation of activin A and upregulation of MAFB, a critical transcription factor for anti-inflammatory polarization of human macrophages. These in vitro data correlate with improved remission of inflammation and mucosal repair during recovery in the acute dextran sodium sulfate-induced colitis model in GH-overexpressing mice. In this model, in addition to the GH-mediated effects on other immune cells, we observed that macrophages from inflamed gut acquire an anti-inflammatory/reparative profile. Overall, these data indicate that GH reprograms inflammatory macrophages to an anti-inflammatory phenotype and improves resolution during pathologic inflammatory responses.

Enhanced mitochondrial fission suppresses signaling and metastasis in triple-negative breast cancer

BACKGROUND

Mitochondrial dynamics underlies malignant transformation, cancer progression, and response to treatment. Current research presents conflicting evidence for functions of mitochondrial fission and fusion in tumor progression. Here, we investigated how mitochondrial fission and fusion states regulate underlying processes of cancer progression and metastasis in triple-negative breast cancer (TNBC).

METHODS

We enforced mitochondrial fission and fusion states through chemical or genetic approaches and measured migration and invasion of TNBC cells in 2D and 3D in vitro models. We also utilized kinase translocation reporters (KTRs) to identify single cell effects of mitochondrial state on signaling cascades, PI3K/Akt/mTOR and Ras/Raf/MEK/ERK, commonly activated in TNBC. Furthermore, we determined effects of fission and fusion states on metastasis, bone destruction, and signaling in mouse models of breast cancer.

RESULTS

Enforcing mitochondrial fission through chemical or genetic approaches inhibited migration, invasion, and metastasis in TNBC. Breast cancer cells with predominantly fissioned mitochondria exhibited reduced activation of Akt and ERK both in vitro and in mouse models of breast cancer. Treatment with leflunomide, a potent activator of mitochondrial fusion proteins, overcame inhibitory effects of fission on migration, signaling, and metastasis. Mining existing datasets for breast cancer revealed that increased expression of genes associated with mitochondrial fission correlated with improved survival in human breast cancer.

CONCLUSIONS

In TNBC, mitochondrial fission inhibits cellular processes and signaling pathways associated with cancer progression and metastasis. These data suggest that therapies driving mitochondrial fission may benefit patients with breast cancer.