bims-mitmed Biomed News
on Mitochondrial medicine
Issue of 2023‒01‒08
25 papers selected by
Dario Brunetti
Fondazione IRCCS Istituto Neurologico

  1. Sci Rep. 2022 Dec 31. 12(1): 22632
      Mutations in the Mpv17 gene are responsible for MPV17-related hepatocerebral mitochondrial DNA depletion syndrome and Charcot-Marie-Tooth (CMT) disease. Although several models including mouse, zebrafish, and cultured human cells, have been developed, the models do not show any neurological defects, which are often observed in patients. Therefore, we knocked down CG11077 (Drosophila Mpv17; dMpv17), an ortholog of human MPV17, in the nervous system in Drosophila melanogaster and investigated the behavioral and cellular phenotypes. The resulting dMpv17 knockdown larvae showed impaired locomotor activity and learning ability consistent with mitochondrial defects suggested by the reductions in mitochondrial DNA and ATP production and the increases in the levels of lactate and reactive oxygen species. Furthermore, an abnormal morphology of the neuromuscular junction, at the presynaptic terminal, was observed in dMpv17 knockdown larvae. These results reproduce well the symptoms of human diseases and partially reproduce the phenotypes of Mpv17-deficient model organisms. Therefore, we suggest that neuron-specific dMpv17 knockdown in Drosophila is a useful model for investigation of MPV17-related hepatocerebral mitochondrial DNA depletion syndrome and CMT caused by Mpv17 dysfunction.
  2. STAR Protoc. 2022 Dec 16. pii: S2666-1667(22)00702-X. [Epub ahead of print]3(4): 101822
      The accumulation of dysfunctional mitochondria is a hallmark of neurodegenerative diseases, yet the dynamics of mitochondrial turnover in neurons are unclear. Here, we describe a protocol to monitor the degradation of spectrally distinct, "aged" mitochondrial populations. We describe the preparation and transfection of primary rat hippocampal neuron cultures. We detail a mitochondrial-damaging assay, a SNAP pulse-chase labeling paradigm, and live imaging to visualize the mitochondrial network. Finally, we provide steps to quantify mitochondrial turnover via lysosomal fusion. For complete details on the use and execution of this protocol, please refer to Evans and Holzbaur (2020a).
    Keywords:  Cell Biology; Cell culture; Cell-based Assays; Metabolism; Microscopy; Molecular Biology; Molecular/Chemical Probes; Neuroscience
  3. Sci Rep. 2023 Jan 02. 13(1): 18
      Autophagy of damaged mitochondria, called mitophagy, is an important organelle quality control process involved in the pathogenesis of inflammation, cancer, aging, and age-associated diseases. Many of these disorders are associated with altered expression of the inner mitochondrial membrane (IMM) protein Prohibitin 1. The mechanisms whereby dysfunction occurring internally at the IMM and matrix activate events at the outer mitochondrial membrane (OMM) to induce mitophagy are not fully elucidated. Using the gastrointestinal epithelium as a model system highly susceptible to autophagy inhibition, we reveal a specific role of Prohibitin-induced mitophagy in maintaining intestinal homeostasis. We demonstrate that Prohibitin 1 induces mitophagy in response to increased mitochondrial reactive oxygen species (ROS) through binding to mitophagy receptor Nix/Bnip3L and independently of Parkin. Prohibitin 1 is required for ROS-induced Nix localization to mitochondria and maintaining homeostasis of epithelial cells highly susceptible to mitochondrial dysfunction.
  4. Biochem Pharmacol. 2023 Jan 02. pii: S0006-2952(22)00501-9. [Epub ahead of print] 115405
      Mitochondria and mitochondrial proteins represent a group of promising pharmacological-target candidates in the search of new molecular targets and drugs to counteract the onset of hypertension and more in general cardiovascular diseases (CVDs). Indeed, several mitochondrial pathways result impaired in CVDs, showing ATP depletion and ROS production as common traits of cardiac tissue degeneration. Thus, targeting mitochondrial dysfunction in cardiomyocytes can represent a successful strategy to prevent heart failure. In this context, the identification of new pharmacological targets among mitochondrial proteins paves the way for the design of new selective drugs. Thanks to the advances in omics approaches, to a greater availability of mitochondrial crystallized protein structures and to the development of new computational approaches for protein 3D-modelling and drug-design, it is now possible to investigate in detail impaired mitochondrial pathways in CVDs. Furthermore, it is possible to design new powerful drugs able to hit the selected pharmacological targets in a highly selective way to rescue mitochondrial dysfunction and prevent cardiac tissue degeneration. The role of mitochondrial dysfunction in the onset of CVDs appears increasingly evident, as reflected by the impairment of proteins involved in lipid peroxidation, mitochondrial dynamics, respiratory chain complexes, and membrane polarization maintenance in CVD patients. Conversely, little is known about proteins responsible for the cross-talk between mitochondria and cytoplasm in cardiomyocytes. Mitochondrial transporters of the SLC25A family, in particular, are responsible for the translocation of nucleotides (e.g., ATP), amino acids (e.g., aspartate, glutamate, ornithine), organic acids (e.g. malate and 2-oxoglutarate), and other cofactors (e.g., inorganic phosphate, NAD+, FAD, carnitine, CoA derivatives) between the mitochondrial and cytosolic compartments. Thus, mitochondrial transporters play a key role in the mitochondria-cytosol cross-talk by leading metabolic pathways such as the malate/aspartate shuttle, the carnitine shuttle, the ATP export from mitochondria, and the regulation of permeability transition pore opening. Since all these pathways are crucial for maintaining healthy cardiomyocytes, mitochondrial carriers emerge as an interesting class of new possible pharmacological targets for CVD treatments.
    Keywords:  Aquaporin; Cardiolipin; Cardiovascular diseases; Drug-Repurposing; Genomics; Hypertension; Ischemia reperfusion injury; Metabolomics; Mitochondrial carriers; Mitochondrial diseases; Mitochondrial dynamics; Mitochondrial dysfunction; Mitochondrial impairment; Mitochondrial metabolite transport system; Mitochondrial permeability transition pore; Mitochondrial pharmacological targets; Mitochondrial pyruvate carrier; Molecular modeling of mitochondrial proteins; PEPTIDE-based treatments; Phospholipids; Respiratory chain; Transcriptomics; Voltage-dependent anion channels
  5. Subcell Biochem. 2023 ;102 1-6
      We outline the progression of ageing research from ancient history to present day geroscience. Calorie restriction, genetic mutations, and the involvement of the sirtuins are highlighted, along with pharmaceutical interventions, in particular rapamycin. At the cellular level, replicative senescence and telomere shortening are presented in the history of ageing studies. We discuss the roles of macromolecular damage in ageing including damage to nuclear, and mitochondrial DNA, epigenetic and protein damage. The importance inflammation during ageing "inflammageing" is becoming increasingly recognized. Omics-based biomarkers are now proving to be a promising approach, along with comparative studies on long-lived animals. The science is getting closer to understanding the mechanisms of ageing and developing reliable interventions to improve human health.
    Keywords:  Calorie restriction; DNA damage; Genetic mutation; History of ageing; Inflammageing; Omics-based markers; Rapamycin; Senescent cells; Senolytic therapies; Sirtuins; Telomere shortening
  6. J Biol Chem. 2023 Jan 02. pii: S0021-9258(22)01308-4. [Epub ahead of print] 102865
      Mitochondrial ribosomes are specialized to translate the 13 membrane proteins encoded in the mitochondrial genome, which shapes the oxidative phosphorylation (OXPHOS) complexes essential for cellular energy metabolism. Despite the importance of mitochondrial translation control, it is challenging to identify and quantify the mitochondrial-encoded proteins due to their hydrophobic nature and low abundance. Here, we introduce a mass spectrometry-based proteomic method that combines biochemical isolation of mitochondria with pulse stable isotope labeling by amino acids in cell culture (pSILAC). Our method provides the highest protein identification rate with the shortest measurement time among currently available methods, enabling us to quantify 12 out of the 13 mitochondrial-encoded proteins. We applied this method to uncover the global picture of (post-)translational regulation of both mitochondrial- and nuclear-encoded subunits of OXPHOS complexes. We found that inhibition of mitochondrial translation led to degradation of orphan nuclear-encoded subunits that are considered to form subcomplexes with the mitochondrial-encoded subunits. This method should be readily applicable to study mitochondrial translation programs in many contexts, including oxidative stress and mitochondrial disease.
    Keywords:  Mitochondria; OXPHOS; Protein complex; Proteomics; Translation; pulse SILAC
  7. Proc Natl Acad Sci U S A. 2023 Jan 10. 120(2): e2204750120
      Exercise is a nonpharmacological intervention that improves health during aging and a valuable tool in the diagnostics of aging-related diseases. In muscle, exercise transiently alters mitochondrial functionality and metabolism. Mitochondrial fission and fusion are critical effectors of mitochondrial plasticity, which allows a fine-tuned regulation of organelle connectiveness, size, and function. Here we have investigated the role of mitochondrial dynamics during exercise in the model organism Caenorhabditis elegans. We show that in body-wall muscle, a single exercise session induces a cycle of mitochondrial fragmentation followed by fusion after a recovery period, and that daily exercise sessions delay the mitochondrial fragmentation and physical fitness decline that occur with aging. Maintenance of proper mitochondrial dynamics is essential for physical fitness, its enhancement by exercise training, and exercise-induced remodeling of the proteome. Surprisingly, among the long-lived genotypes we analyzed (isp-1,nuo-6, daf-2, eat-2, and CA-AAK-2), constitutive activation of AMP-activated protein kinase (AMPK) uniquely preserves physical fitness during aging, a benefit that is abolished by impairment of mitochondrial fission or fusion. AMPK is also required for physical fitness to be enhanced by exercise, with our findings together suggesting that exercise may enhance muscle function through AMPK regulation of mitochondrial dynamics. Our results indicate that mitochondrial connectivity and the mitochondrial dynamics cycle are essential for maintaining physical fitness and exercise responsiveness during aging and suggest that AMPK activation may recapitulate some exercise benefits. Targeting mechanisms to optimize mitochondrial fission and fusion, as well as AMPK activation, may represent promising strategies for promoting muscle function during aging.
    Keywords:  C. elegans; aging; exercise; mitochondrial fission; mitochondrial fusion
  8. J Cell Sci. 2023 Jan 05. pii: jcs.260060. [Epub ahead of print]
      The TIM22 pathway cargos are essential for sustaining mitochondrial homeostasis as an excess of these proteins leads to proteostatic stress and cell death. Yme1 is an inner membrane metalloprotease that regulates protein quality control with chaperone-like and proteolytic activities. Although the mitochondrial translocase and protease machinery are critical for organelle health, their functional association remains unexplored. The present study unravels a novel genetic connection between the TIM22 complex and YME1 machinery in Saccharomyces cerevisiae required for maintaining mitochondrial health. Our genetic analyses indicate that impairment in the TIM22 complex rescues the respiratory growth defects of cells without Yme1. Further, Yme1 is essential for the stability of the TIM22 complex and regulates the proteostasis of the TIM22 pathway substrates. Moreover, impairment in the TIM22 complex suppressed the mitochondrial structural and functional defects of Yme1 devoid cells. In summary, excessive levels of the TIM22 pathway substrates could be one of the reasons for respiratory growth defects of cells lacking Yme1, and compromising the TIM22 complex can compensate for the imbalance in mitochondrial proteostasis caused by the loss of Yme1.
    Keywords:  Mitochondrial DNA maintenance; Mitochondrial protein translocation; Mitochondrial proteostasis; Mitochondrial quality control; TIM22 complex; YME1 machinery
  9. Sci Adv. 2023 Jan 04. 9(1): eadd3216
      Myopathies secondary to mitochondrial electron transport chain (ETC) dysfunction can result in devastating disease. While the consequences of ETC defects have been extensively studied in culture, little in vivo data are available. Using a mouse model of severe, early-onset mitochondrial myopathy, we characterized the proteomic, transcriptomic, and metabolic characteristics of disease progression. Unexpectedly, ETC dysfunction in muscle results in reduced expression of glycolytic enzymes in our animal model and patient muscle biopsies. The decrease in glycolysis was mediated by loss of constitutive Hif1α signaling, down-regulation of the purine nucleotide cycle enzyme AMPD1, and activation of AMPK. In vivo isotope tracing experiments indicated that myopathic muscle relies on lactate import to supply central carbon metabolites. Inhibition of lactate import reduced steady-state levels of tricarboxylic acid cycle intermediates and compromised the life span of myopathic mice. These data indicate an unexpected mode of metabolic reprogramming in severe mitochondrial myopathy that regulates disease progression.
  10. Pediatr Neurol. 2022 Dec 07. pii: S0887-8994(22)00267-3. [Epub ahead of print]140 40-46
      BACKGROUND: This retrospective chart review evaluated the clinical characteristics of SURF1-related neurological disease spectrum to better characterize the phenotypes.METHODS: Patient demographics, magnetic resonance imaging abnormalities, neurological events, motor abnormalities, and gastrointestinal and respiratory assistance were evaluated in 27 patients with genetically diagnosed SURF1 deficiency.
    RESULTS: The mean (S.D.) age of symptom onset collected from 13 patients was 19.7 (11.8) months. Mean (S.D.) age of diagnosis collected from 24 patients was 44.0 (45.1) months. The most common symptoms were gross motor delay (14 of 14), fine motor delay (10 of 11), verbal delay (9 of 10), and intellectual and learning disability (14 of 19). Neurological symptoms included ataxia (14 of 15), other abnormal movements (8 of 9), hypotonia (9 of 11), and dystonia (6 of 9). Three of nine reporting patients (33.3%) had a history of seizure, and 84.6% (11 of 13) had a history of regression/loss of acquired skills. Extraneurological clinical features included pulmonary complications (10 of 11) and feeding difficulties (13 of 13); cardiac complications were noted in three patients. Brainstem is frequently involved with the medulla and midbrain being the most common sites. As of July 2021, three patients were deceased.
    CONCLUSIONS: The most common clinical symptoms were motor delay, verbal delay, intellectual and learning disability, dysphagia, feeding difficulties, and reflux. Neurological presentations include ataxia, hypotonia, visual/ocular abnormalities, dystonia, and imaging abnormalities include basal ganglia and brainstem lesions. Although heterogeneous, SURF1 deficiency should be considered with these clinical and imaging presentations and may support earlier identification.
    Keywords:  Charcot-Marie-Tooth disease 4K; Leigh syndrome; Mitochondrial disease; SURF1; SURF1 deficiency
  11. Neuroscientist. 2023 Jan 03. 10738584221139761
      Alzheimer's disease (AD) is characterized by the accumulation of amyloid β and phosphorylated τ protein aggregates in the brain, which leads to the loss of neurons. Under the microscope, the function of mitochondria is uniquely primed to play a pivotal role in neuronal cell survival, energy metabolism, and cell death. Research studies indicate that mitochondrial dysfunction, excessive oxidative damage, and defective mitophagy in neurons are early indicators of AD. This review article summarizes the latest development of mitochondria in AD: 1) disease mechanism pathways, 2) the importance of mitochondria in neuronal functions, 3) metabolic pathways and functions, 4) the link between mitochondrial dysfunction and mitophagy mechanisms in AD, and 5) the development of potential mitochondrial-targeted therapeutics and interventions to treat patients with AD.
    Keywords:  Alzheimer disease; adenosine triphosphate; amyloid beta; amyloid precursor protein; dysfunction; mitochondria; mitophagy; neurofibrillary tangle; p-tau; reaction oxidative stress; therapeutics
  12. Biochem Soc Trans. 2023 Jan 06. pii: BST20220762. [Epub ahead of print]
      Adult neurogenesis is a multistage process during which newborn neurons are generated through the activation and proliferation of neural stem cells (NSCs) and integrated into existing neural networks. Impaired adult neurogenesis has been observed in various neurological and psychiatric disorders, suggesting its critical role in cognitive function, brain homeostasis, and neural repair. Over the past decades, mounting evidence has identified a strong association between metabolic status and adult neurogenesis. Here, we aim to summarize how amino acids and their neuroactive metabolites affect adult neurogenesis. Furthermore, we discuss the causal link between amino acid metabolism, adult neurogenesis, and neurological diseases. Finally, we propose that systematic elucidation of how amino acid metabolism regulates adult neurogenesis has profound implications not only for understanding the biological underpinnings of brain development and neurological diseases, but also for providing potential therapeutic strategies to intervene in disease progression.
    Keywords:  adult neurogenesis; amino acid metabolism; arginine metabolism; one-carbon metabolism; tryptophan metabolism
  13. Nat Commun. 2023 Jan 03. 14(1): 39
      The mitochondrial F1FO-ATP synthase produces the bulk of cellular ATP. The soluble F1 domain contains the catalytic head that is linked via the central stalk and the peripheral stalk to the membrane embedded rotor of the FO domain. The assembly of the F1 domain and its linkage to the peripheral stalk is poorly understood. Here we show a dual function of the mitochondrial Hsp70 (mtHsp70) in the formation of the ATP synthase. First, it cooperates with the assembly factors Atp11 and Atp12 to form the F1 domain of the ATP synthase. Second, the chaperone transfers Atp5 into the assembly line to link the catalytic head with the peripheral stalk. Inactivation of mtHsp70 leads to integration of assembly-defective Atp5 variants into the mature complex, reflecting a quality control function of the chaperone. Thus, mtHsp70 acts as an assembly and quality control factor in the biogenesis of the F1FO-ATP synthase.
  14. Nat Commun. 2023 Jan 03. 14(1): 30
      The mitochondrial translation machinery highly diverged from its bacterial counterpart. This includes deviation from the universal genetic code, with AGA and AGG codons lacking cognate tRNAs in human mitochondria. The locations of these codons at the end of COX1 and ND6 open reading frames, respectively, suggest they might function as stop codons. However, while the canonical stop codons UAA and UAG are known to be recognized by mtRF1a, the release mechanism at AGA and AGG codons remains a debated issue. Here, we show that upon the loss of another member of the mitochondrial release factor family, mtRF1, mitoribosomes accumulate specifically at AGA and AGG codons. Stalling of mitoribosomes alters COX1 transcript and protein levels, but not ND6 synthesis. In addition, using an in vitro reconstituted mitochondrial translation system, we demonstrate the specific peptide release activity of mtRF1 at the AGA and AGG codons. Together, our results reveal the role of mtRF1 in translation termination at non-canonical stop codons in mitochondria.
  15. Front Cell Dev Biol. 2022 ;10 1065702
      Mitochondria play an essential role in the regulation of cellular stress responses, including cell death. Damaged mitochondria are removed by fission and fusion cycles and mitophagy, which counteract cell death. BCL-2 family proteins possess one to four BCL-2 homology domains and regulate apoptosis signaling at mitochondria. BCL-RAMBO, also known as BCL2-like 13 (BCL2L13), was initially identified as one of the BCL-2 family proteins inducing apoptosis. Mitophagy receptors recruit the ATG8 family proteins MAP1LC3/GABARAP via the MAP1LC3-interacting region (LIR) motif to initiate mitophagy. In addition to apoptosis, BCL-RAMBO has recently been identified as a mitophagy receptor that possesses the LIR motif and regulates mitochondrial fragmentation and mitophagy. In the 20 years since its discovery, many important findings on BCL-RAMBO have been increasingly reported. The biological properties of BCL-RAMBO are reviewed herein.
    Keywords:  BCL-RAMBO; BCL2L13; apoptosis; cell death; miRNAs; mitochondrial fragmentation; mitophagy; phosphorylation
  16. Mol Neurobiol. 2023 Jan 03.
      Regardless of the progress made in the pathogenesis of ischemic stroke, it remains a leading cause of adult disability and death. To date, the most effective treatment for ischemic stroke is the timely recanalization of the occluded artery. However, the short time window and reperfusion injury have greatly limited its application and efficacy. Mitochondrial dysfunction and ATP depletion have become regarded as being hallmarks of neuropathophysiology following ischemic stroke. Mitochondrial transplantation is a novel potential therapeutic intervention for ischemic stroke that has sparked widespread concern during the past few years. This review summarizes and discusses the effects of mitochondrial transplantation in in vitro and in vivo ischemic stroke models. In addition, pharmacological interventions promoting mitochondrial transplantation are reviewed and discussed. We also discuss the potential challenges to the clinical application of mitochondrial transplantation in the treatment of ischemic stroke.
    Keywords:  Brain; Cerebral ischemia; Cerebral ischemia/reperfusion; Ischemic stroke; Mitochondrial transfer; Mitochondrial transplantation
  17. Stem Cells Dev. 2023 Jan 03.
      Adverse intrauterine environments can cause persistent changes in epigenetic profiles of stem cells, increasing susceptibility of the offspring to developing metabolic diseases later in life. Effective approaches to restore the epigenetic landscape and function of stem cells remain to be determined. Here we investigated the effects of pharmaceutical activation of AMPK, an essential regulator of energy metabolism, on mitochondrial programming of Wharton's Jelly mesenchymal stem cells (WJ-MSCs) from women with diabetes during pregnancy. Induction of myogenic differentiation of WJ-MSCs was associated with increased PGC-1α expression and mitochondrial DNA abundance. Inhibition of DNA methylation by 5 Azacytidine significantly increased PGC-1α expression and mitochondrial DNA abundance in WJ-MSCs, which were abolished by AMPK inhibitor Compound C (CC), suggesting an AMPK-dependent role of DNA demethylation in regulating mitochondrial biogenesis in WJ-MSCs. Further, activation of AMPK in diabetic WJ-MSCs by AICAR or metformin decreased the level of PGC-1α promoter methylation and increased PGC-1α expression. Notably, decreased PGC-1α promoter methylation by transient treatment of AMPK activators persisted following myogenic differentiation. This was associated with enhanced myogenic differentiation capacity of human WJ-MSCs and increased mitochondrial function. Taken together, our findings revealed an important role for AMPK activators in epigenetic regulation of mitochondrial biogenesis and myogenesis in WJ-MSCs, which could lead to potential therapeutics for preventing fetal mitochondrial programming and long-term adverse outcome in offspring of women with diabetes during pregnancy.
  18. Front Mol Neurosci. 2022 ;15 1015220
      Introduction: DYRK1A is a dual-specificity kinase that is overexpressed in Down syndrome (DS) and plays a key role in neurogenesis, neuronal differentiation and function, cognitive phenotypes, and aging. Dyrk1A has also been implicated in cerebellar abnormalities observed in association with DS, and normalization of Dyrk1A dosage rescues granular and Purkinje cell densities in a trisomic DS mouse model. However, the underlying molecular mechanisms governing these processes are unknown.Methods: To shed light on the effects of Dyrk1A overexpression in the cerebellum, here we investigated the cerebellar proteome in transgenic Dyrk1A overexpressing mice in basal conditions and after treatment with green tea extract containing epigallocatechin-3-gallate (EGCG), a DYRK1A inhibitor.
    Results and Discussion: Our results showed that Dyrk1A overexpression alters oxidative phosphorylation and mitochondrial function in the cerebellum of transgenic mice. These alterations are significantly rescued upon EGCG-containing green tea extract treatment, suggesting that its effects in DS could depend in part on targeting mitochondria, as shown by the partially restoration by the treatment of the increased mtDNA copy number in TG non-treated mice.
    Keywords:  DYRK1A; Down syndrome; cerebellum; mitochondria; oxidative phosphorylation system; proteomics
  19. Life Sci Alliance. 2023 Mar;pii: e202201457. [Epub ahead of print]6(3):
      Spinal muscular atrophy (SMA) is a congenital neuromuscular disease caused by the mutation or deletion of the survival motor neuron 1 (SMN1) gene. Although the primary cause of progressive muscle atrophy in SMA has classically been considered the degeneration of motor neurons, recent studies have indicated a skeletal muscle-specific pathological phenotype such as impaired mitochondrial function and enhanced cell death. Here, we found that the down-regulation of SMN causes mitochondrial dysfunction and subsequent cell death in in vitro models of skeletal myogenesis with both a murine C2C12 cell line and human induced pluripotent stem cells. During myogenesis, SMN binds to the upstream genomic regions of MYOD1 and microRNA (miR)-1 and miR-206. Accordingly, the loss of SMN down-regulates these miRs, whereas supplementation of the miRs recovers the mitochondrial function, cell survival, and myotube formation of SMN-deficient C2C12, indicating the SMN-miR axis is essential for myogenic metabolic maturation. In addition, the introduction of the miRs into ex vivo muscle stem cells derived from Δ7-SMA mice caused myotube formation and muscle contraction. In conclusion, our data revealed novel transcriptional roles of SMN during myogenesis, providing an alternative muscle-oriented therapeutic strategy for SMA patients.
  20. Acta Crystallogr D Struct Biol. 2023 Jan 01. 79(Pt 1): 22-30
      Friedreich's ataxia (FRDA) is a hereditary cardiodegenerative and neurodegenerative disease that affects 1 in 50 000 Americans. FRDA arises from either a cellular inability to produce sufficient quantities or the production of a nonfunctional form of the protein frataxin, a key molecule associated with mitochondrial iron-sulfur cluster biosynthesis. Within the mitochondrial iron-sulfur cluster (ISC) assembly pathway, frataxin serves as an allosteric regulator for cysteine desulfurase, the enzyme that provides sulfur for [2Fe-2S] cluster assembly. Frataxin is a known iron-binding protein and is also linked to the delivery of ferrous ions to the scaffold protein, the ISC molecule responsible for the direct assembly of [2Fe-2S] clusters. The goal of this report is to provide structural details of the Drosophila melanogaster frataxin ortholog (Dfh), using both X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy, in order to provide the foundational insight needed to understand the structure-function correlation of the protein. Additionally, NMR iron(II) titrations were used to provide metal contacts on the protein to better understand how it binds iron and aids its delivery to the ISC scaffold protein. Here, the structural and functional similarities of Dfh to its orthologs are also outlined. Structural data show that bacterial, yeast, human and Drosophila frataxins are structurally similar, apart from a structured C-terminus in Dfh that is likely to aid in protein stability. The iron-binding location on helix 1 and strand 1 of Dfh is also conserved across orthologs.
    Keywords:  Drosophila melanogaster; Friedreich's ataxia; ISC pathway; frataxin; iron–sulfur clusters
  21. Nat Neurosci. 2023 Jan 02.
      Alzheimer's disease (AD) is an age-related disease pathologically defined by the deposition of amyloid plaques and neurofibrillary tangles in the brain parenchyma. Single-cell profiling has shown that Alzheimer's dementia involves the complex interplay of virtually every major brain cell type. Here, we highlight cell-type-specific molecular perturbations in AD. We discuss how genomic information from single cells expands existing paradigms of AD pathogenesis and highlight new opportunities for therapeutic interventions.
  22. STAR Protoc. 2023 Jan 05. pii: S2666-1667(22)00879-6. [Epub ahead of print]4(1): 101999
      Metabolic derangement is a key culprit in kidney pathophysiology. Organoids have emerged as a promising in vitro tool for kidney research. Here, we present a fine-tuned protocol to analyze bioenergetics in single human induced-pluripotent-stem-cell (iPSC)-derived kidney organoids using Seahorse XF96. We describe the generation of self-organized three-dimensional kidney organoids, followed by preparation of organoids for Seahorse XF96 analysis. We then detail how to carry out stress tests to determine mitochondrial and glycolytic rates in single kidney organoids.
    Keywords:  Cell Differentiation; Metabolism; Organoids; Stem Cells
  23. Front Endocrinol (Lausanne). 2022 ;13 1074911
      Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor that is involved in lipid metabolism of various tissues. Different metabolites of fatty acids and agonists like fibrates activate PPARα for its transactivative or repressive function. PPARα is known to affect diverse human diseases, and we focus on advanced studies of its transcriptional regulation in these diseases. In MAFLD, PPARα shows a protective function with its upregulation of lipid oxidation and mitochondrial biogenesis and transcriptional repression of inflammatory genes, which is similar in Alzheimer's disease and cardiovascular disease. Activation of PPARα also prevents the progress of diabetes complications; however, its role in diabetes and cancers remains uncertain. Some PPARα-specific agonists, such as Wy14643 and fenofibrate, have been applied in metabolic syndrome treatment, which might own potential in wider application. Future studies may further explore the functions and interventions of PPARα in cancer, diabetes, immunological diseases, and neurodegenerative disease.
    Keywords:  MAFLD; PPARα (peroxisome proliferator-activated receptor alpha); alzhaimer’s disease (AD); cancer; cardiovascular diseases; diabetes; transcription
  24. Free Radic Biol Med. 2022 Dec 31. pii: S0891-5849(22)01135-2. [Epub ahead of print]
      The metabolic patterns and energetics of human induced pluripotent stem cell-derived cardiomyocytes (HiPSC-CMs) are much less than those of normal adult cardiomyocytes, which has limited their application in disease therapy and regenerative medicine. It has been demonstrated that SIRT3, a mitochondria-target deacetylase, controls mitochondrial metabolism in physiological and pathological conditions. In this research, We investigated the role and regulatory mechanism of SIRT3 in energy metabolism in HiPSC-CMs. We found that the expression of SIRT3 was increased during the differentiation and maturation of HiPSC-CMs. Knocking down SIRT3 impaired mitochondrial structure, mitochondrial respiration capacity, and fatty acid oxidation but enhanced glycolysis. However, honokiol, a pharmacological activator of SIRT3, improved the mitochondrial ultrastructure and energetics, and promoted oxidative phosphorylation in HiPSC-CMs. Furthermore, SIRT3 regulated the acetylation of OPA1, and the knockdown of OPA1 blocked the promotion of energy metabolism by honokiol, meanwhile, knocking down OPA1 impaired mitochondrial fusion, mitochondrial respiration capacity, and fatty acid oxidation which were reversed by M1 (a mitochondrial fusion promoter) in HiPSC-CMs. In summary, SIRT3 regulated energetics and promoted metabolism remodeling by targeting the OPA1-controlled mitochondrial dynamics in HiPSC-CMs, and targeting SIRT3 may have revelatory implications in the treatment of cardiovascular diseases and the application of HiPSC-CMs to regenerative medicine.
    Keywords:  Human iPSC-derived cardiomyocytes; Metabolism remodeling; Mitochondrial dynamics; OPA1; SIRT3