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Autophagy Mar 2023Age-related macular degeneration (AMD), the leading cause of blindness among the elderly, is without treatment for early disease. Degenerative retinal pigment epithelial...
Age-related macular degeneration (AMD), the leading cause of blindness among the elderly, is without treatment for early disease. Degenerative retinal pigment epithelial (RPE) cell heterogeneity is a well-recognized but understudied pathogenic factor. Due to the daily phagocytosis of photoreceptor outer segments, unique photo-oxidative stress, and high metabolism for maintaining vision, the RPE has robust macroautophagy/autophagy, and mitochondrial and antioxidant networks. However, the autophagy subtype, mitophagy, in the RPE and AMD is understudied. Here, we found decreased PINK1 (PTEN induced kinase 1) in perifoveal RPE of early AMD eyes. PINK1-deficient RPE have impaired mitophagy and mitochondrial function that triggers death-resistant epithelial-mesenchymal transition (EMT). This reprogramming is mediated by novel retrograde mitochondrial-nuclear signaling (RMNS) through superoxide, NFE2L2 (NFE2 like bZIP transcription factor 2), TXNRD1 (thioredoxin reductase 1), and phosphoinositide 3-kinase (PI3K)-AKT (AKT serine/threonine kinase) that induced canonical transcription factors ZEB1 (zinc finger E-box binding homeobox 1) and SNAI1 (Snail family transcriptional repressor 1) and an EMT transcriptome. NFE2L2 deficiency disrupted RMNS that paradoxically normalized morphology but decreased function and viability. Thus, RPE heterogeneity is defined by the interaction of two cytoprotective pathways that is triggered by mitophagy function. By neutralizing the consequences of impaired mitophagy, an antioxidant dendrimer tropic for the RPE and mitochondria, EMT (a recognized AMD alteration) was abrogated to offer potential therapy for early AMD, a stage without treatment.: ACTB: actin beta; AKT: AKT serine/threonine kinase; AMD: age-related macular degeneration; CCCP: cyanide m-chlorophenyl hydrazone; CDH1: cadherin 1; DAVID: Database for Annotation, Visualization and Integrated Discovery; DHE: dihydroethidium; D-NAC: N-acetyl-l-cysteine conjugated to a poly(amido amine) dendrimer; ECAR: extracellular acidification rate; EMT: epithelial-mesenchymal transition; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GSEA: Gene Set Enrichment Analysis; HSPD1: heat shock protein family D (Hsp60) member 1; IVT: intravitreal; KD: knockdown; LMNA, lamin A/C; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MMP: mitochondrial membrane potential; NAC: N-acetyl-l-cysteine; NQO1: NAD(P)H quinone dehydrogenase 1; NFE2L2: NFE2 like bZIP transcription factor 2; O: superoxide anion; OCR: oxygen consumption rate; PI3K: phosphoinositide 3-kinase; PINK1: PTEN induced kinase 1; RMNS: retrograde mitochondrial-nuclear signaling; ROS: reactive oxygen species; RPE: retinal pigment epithelium; SNAI1: snail family transcriptional repressor 1; TJP1: tight junction protein 1; TPP-D-NAC: triphenyl phosphinium and N-acetyl-l-cysteine conjugated to a poly(amido amine) dendrimer; TIMM23: translocase of inner mitochondrial membrane 23; TOMM20: translocase of outer mitochondrial membrane 20; Trig: trigonelline; TXNRD1: thioredoxin reductase 1; VIM: vimentin; WT: wild-type; ZEB1: zinc finger E-box binding homeobox 1.
Topics: Humans; Aged; Mitophagy; Autophagy; Thioredoxin Reductase 1; Antioxidants; Acetylcysteine; Dendrimers; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Retinal Pigment Epithelium; Macular Degeneration; Phosphatidylinositol 3-Kinase; Basic-Leucine Zipper Transcription Factors; Amines; Retinal Pigments; Serine
PubMed: 35921555
DOI: 10.1080/15548627.2022.2109286 -
Advanced Science (Weinheim,... Mar 2023Cadmium (Cd) is a high-risk pathogenic toxin for hepatic diseases. Excessive mitophagy is a hallmark in Cd-induced hepatotoxicity. However, the underlying mechanism...
Cadmium (Cd) is a high-risk pathogenic toxin for hepatic diseases. Excessive mitophagy is a hallmark in Cd-induced hepatotoxicity. However, the underlying mechanism remains obscure. Mitochondrial calcium uniporter (MCU) is a key regulator for mitochondrial and cellular homeostasis. Here, Cd exposure upregulated MCU expression and increased mitochondrial Ca uptake are found. MCU inhibition through siRNA or by Ru360 significantly attenuates Cd-induced excessive mitophagy, thereby rescues mitochondrial dysfunction and increases hepatocyte viability. Heterozygous MCU knockout mice exhibit improved liver function, ameliorated pathological damage, less mitochondrial fragmentation, and mitophagy after Cd exposure. Mechanistically, Cd upregulates MCU expression through phosphorylation activation of cAMP-response element binding protein at Ser133(CREB ) and subsequent binding of MCU promoter at the TGAGGTCT, ACGTCA, and CTCCGTGATGTA regions, leading to increased MCU gene transcription. The upregulated MCU intensively interacts with voltage-dependent anion-selective channel protein 1 (VDAC1), enhances its dimerization and ubiquitination, resulting in excessive mitophagy. This study reveals a novel mechanism, through which Cd upregulates MCU to enhance mitophagy and hepatotoxicity.
Topics: Animals; Mice; Cadmium; Calcium Channels; Chemical and Drug Induced Liver Injury; Dimerization; Mitochondrial Proteins; Mitophagy; Ubiquitination; Up-Regulation; Voltage-Dependent Anion Channel 1
PubMed: 36642847
DOI: 10.1002/advs.202203869 -
Cell Reports Oct 2023Dysfunctional mitochondria are removed via multiple pathways, such as mitophagy, a selective autophagy process. Here, we identify an intracellular hybrid...
Dysfunctional mitochondria are removed via multiple pathways, such as mitophagy, a selective autophagy process. Here, we identify an intracellular hybrid mitochondria-lysosome organelle (termed the mitochondria-lysosome-related organelle [MLRO]), which regulates mitochondrial homeostasis independent of canonical mitophagy during hepatocyte dedifferentiation. The MLRO is an electron-dense organelle that has either a single or double membrane with both mitochondria and lysosome markers. Mechanistically, the MLRO is likely formed from the fusion of mitochondria-derived vesicles (MDVs) with lysosomes through a PARKIN-, ATG5-, and DRP1-independent process, which is negatively regulated by transcription factor EB (TFEB) and associated with mitochondrial protein degradation and hepatocyte dedifferentiation. The MLRO, which is galectin-3 positive, is reminiscent of damaged lysosome and could be cleared by overexpression of TFEB, resulting in attenuation of hepatocyte dedifferentiation. Together, results from this study suggest that the MLRO may act as an alternative mechanism for mitochondrial quality control independent of canonical autophagy/mitophagy involved in cell dedifferentiation.
Topics: Mitochondria; Organelles; Lysosomes; Autophagy; Mitophagy
PubMed: 37862166
DOI: 10.1016/j.celrep.2023.113291 -
Cell Proliferation Mar 2021Mitophagy is considered to be a key mechanism in the pathogenesis of intestinal ischaemic reperfusion (IR) injury. NOD-like receptor X1 (NLRX1) is located in the...
OBJECTIVES
Mitophagy is considered to be a key mechanism in the pathogenesis of intestinal ischaemic reperfusion (IR) injury. NOD-like receptor X1 (NLRX1) is located in the mitochondria and is highly expressed in the intestine, and is known to modulate ROS production, mitochondrial damage, autophagy and apoptosis. However, the function of NLRX1 in intestinal IR injury is unclear.
MATERIALS AND METHODS
NLRX1 in rats with IR injury or in IEC-6 cells with hypoxia reoxygenation (HR) injury were measured by Western blotting, real-time PCR and immunohistochemistry. The function of NLRX1-FUNDC1-NIPSNAP1/NIPSNAP2 axis in mitochondrial homeostasis and cell apoptosis were assessed in vitro.
RESULTS
NLRX1 is significantly downregulated following intestinal IR injury. In vivo studies showed that rats overexpressing NLRX1 exhibited resistance against intestinal IR injury and mitochondrial dysfunction. These beneficial effects of NLRX1 overexpression were dependent on mitophagy activation. Functional studies showed that HR injury reduced NLRX1 expression, which promoted phosphorylation of FUN14 domain-containing 1 (FUNDC1). Based on immunoprecipitation studies, it was evident that phosphorylated FUNDC1 could not interact with the mitophagy signalling proteins NIPSNAP1 and NIPSNAP2 on the outer membrane of damaged mitochondria, which failed to launch the mitophagy process, resulting in the accumulation of damaged mitochondria and epithelial apoptosis.
CONCLUSIONS
NLRX1 regulates mitophagy via FUNDC1-NIPSNAP1/NIPSNAP2 signalling pathway. Thus, this study provides a potential target for the development of a therapeutic strategy for intestinal IR injury.
Topics: Animals; Autophagy; Intestines; Ischemia; Male; Membrane Proteins; Mitochondria; Mitochondrial Proteins; Mitophagy; Myocardial Reperfusion Injury; Rats, Sprague-Dawley; Rats
PubMed: 33432610
DOI: 10.1111/cpr.12986 -
Autophagy Jan 2019The thyroid hormone triiodothyronine (T) activates thermogenesis by uncoupling electron transport from ATP synthesis in brown adipose tissue (BAT) mitochondria. Although...
The thyroid hormone triiodothyronine (T) activates thermogenesis by uncoupling electron transport from ATP synthesis in brown adipose tissue (BAT) mitochondria. Although T can induce thermogenesis by sympathetic innervation, little is known about its cell autonomous effects on BAT mitochondria. We thus examined effects of T on mitochondrial activity, autophagy, and metabolism in primary brown adipocytes and BAT and found that T increased fatty acid oxidation and mitochondrial respiration as well as autophagic flux, mitophagy, and mitochondrial biogenesis. Interestingly, there was no significant induction of intracellular reactive oxygen species (ROS) despite high mitochondrial respiration and UCP1 induction by T. However, when cells were treated with Atg5 siRNA to block autophagy, induction of mitochondrial respiration by T decreased, and was accompanied by ROS accumulation, demonstrating a critical role for autophagic mitochondrial turnover. We next generated an Atg5 conditional knockout mouse model (Atg5 cKO) by injecting Ucp1 promoter-driven Cre-expressing adenovirus into Atg5 mice to examine effects of BAT-specific autophagy on thermogenesis in vivo. Hyperthyroid Atg5 cKO mice exhibited lower body temperature than hyperthyroid or euthyroid control mice. Metabolomic analysis showed that T increased short and long chain acylcarnitines in BAT, consistent with increased β-oxidation. T also decreased amino acid levels, and in conjunction with SIRT1 activation, decreased MTOR activity to stimulate autophagy. In summary, T has direct effects on mitochondrial autophagy, activity, and turnover in BAT that are essential for thermogenesis. Stimulation of BAT activity by thyroid hormone or its analogs may represent a potential therapeutic strategy for obesity and metabolic diseases. Abbreviations: ACACA: acetyl-Coenzyme A carboxylase alpha; AMPK: AMP-activated protein kinase; Acsl1: acyl-CoA synthetase long-chain family member 1; ATG5: autophagy related 5; ATG7: autophagy related 7; ATP: adenosine triphosphate; BAT: brown adipose tissue; cKO: conditional knockout; COX4I1: cytochrome c oxidase subunit 4I1; Cpt1b: carnitine palmitoyltransferase 1b, muscle; CQ: chloroquine; DAPI: 4',6-diamidino-2-phenylindole; DIO2: deiodinase, iodothyronine, type 2; DMEM: Dulbecco's modified Eagle's medium; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; Fabp4: fatty acid binding protein 4, adipocyte; FBS: fetal bovine serum; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; FGF: fibroblast growth factor; FOXO1: forkhead box O1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; Gpx1: glutathione peroxidase 1; Lipe: lipase, hormone sensitive; MAP1LC3B: microtubule-associated protein 1 light chain 3; mRNA: messenger RNA; MTORC1: mechanistic target of rapamycin kinase complex 1; NAD: nicotinamide adenine dinucleotide; Nrf1: nuclear respiratory factor 1; OCR: oxygen consumption rate; PBS: phosphate-buffered saline; PCR: polymerase chain reaction; PPARGC1A: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; Pnpla2: patatin-like phospholipase domain containing 2; Prdm16: PR domain containing 16; PRKA: protein kinase, AMP-activated; RPS6KB: ribosomal protein S6 kinase; RFP: red fluorescent protein; ROS: reactive oxygen species; SD: standard deviation; SEM: standard error of the mean; siRNA: small interfering RNA; SIRT1: sirtuin 1; Sod1: superoxide dismutase 1, soluble; Sod2: superoxide dismutase 2, mitochondrial; SQSTM1: sequestosome 1; T: 3,5,3'-triiodothyronine; TFEB: transcription factor EB; TOMM20: translocase of outer mitochondrial membrane 20; UCP1: uncoupling protein 1 (mitochondrial, proton carrier); ULK1: unc-51 like kinase 1; VDAC1: voltage-dependent anion channel 1; WAT: white adipose tissue.
Topics: Adipose Tissue, Brown; Animals; Cells, Cultured; Hyperthyroidism; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mitochondria; Mitophagy; Organelle Biogenesis; Signal Transduction; TOR Serine-Threonine Kinases; Triiodothyronine
PubMed: 30209975
DOI: 10.1080/15548627.2018.1511263 -
Neuron May 2022PTEN-induced kinase 1 (PINK1) is a short-lived protein required for the removal of damaged mitochondria through Parkin translocation and mitophagy. Because the short...
PTEN-induced kinase 1 (PINK1) is a short-lived protein required for the removal of damaged mitochondria through Parkin translocation and mitophagy. Because the short half-life of PINK1 limits its ability to be trafficked into neurites, local translation is required for this mitophagy pathway to be active far from the soma. The Pink1 transcript is associated and cotransported with neuronal mitochondria. In concert with translation, the mitochondrial outer membrane proteins synaptojanin 2 binding protein (SYNJ2BP) and synaptojanin 2 (SYNJ2) are required for tethering Pink1 mRNA to mitochondria via an RNA-binding domain in SYNJ2. This neuron-specific adaptation for the local translation of PINK1 provides distal mitochondria with a continuous supply of PINK1 for the activation of mitophagy.
Topics: Mitochondria; Mitophagy; Nerve Tissue Proteins; Neurons; Phosphoric Monoester Hydrolases; Protein Kinases; RNA, Messenger; Ubiquitin-Protein Ligases
PubMed: 35216662
DOI: 10.1016/j.neuron.2022.01.035 -
Nature Communications Nov 2020There is increasing evidence that inducing neuronal mitophagy can be used as a therapeutic intervention for Alzheimer's disease. Here, we screen a library of 2024...
There is increasing evidence that inducing neuronal mitophagy can be used as a therapeutic intervention for Alzheimer's disease. Here, we screen a library of 2024 FDA-approved drugs or drug candidates, revealing UMI-77 as an unexpected mitophagy activator. UMI-77 is an established BH3-mimetic for MCL-1 and was developed to induce apoptosis in cancer cells. We found that at sub-lethal doses, UMI-77 potently induces mitophagy, independent of apoptosis. Our mechanistic studies discovered that MCL-1 is a mitophagy receptor and directly binds to LC3A. Finally, we found that UMI-77 can induce mitophagy in vivo and that it effectively reverses molecular and behavioral phenotypes in the APP/PS1 mouse model of Alzheimer's disease. Our findings shed light on the mechanisms of mitophagy, reveal that MCL-1 is a mitophagy receptor that can be targeted to induce mitophagy, and identify MCL-1 as a drug target for therapeutic intervention in Alzheimer's disease.
Topics: Alzheimer Disease; Animals; Apoptosis; Autophagy-Related Protein 5; Cell Survival; Disease Models, Animal; Gene Knockout Techniques; Glucose; HEK293 Cells; HeLa Cells; High-Throughput Screening Assays; Humans; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microtubule-Associated Proteins; Mitophagy; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins; Nerve Tissue Proteins; Neurons; Oxygen; Receptors, Cytoplasmic and Nuclear; Sulfonamides; Thioglycolates
PubMed: 33184293
DOI: 10.1038/s41467-020-19547-6 -
Autophagy Oct 2021Mitochondrial dysfunction causes energy deficiency and nigrostriatal neurodegeneration which is integral to the pathogenesis of Parkinson disease (PD). Clearance of...
Mitochondrial dysfunction causes energy deficiency and nigrostriatal neurodegeneration which is integral to the pathogenesis of Parkinson disease (PD). Clearance of defective mitochondria involves fission and ubiquitin-dependent degradation via mitophagy to maintain energy homeostasis. We hypothesize that LRRK2 (leucine-rich repeat kinase 2) mutation disrupts mitochondrial turnover causing accumulation of defective mitochondria in aging brain. We found more ubiquitinated mitochondria with aberrant morphology associated with impaired function in aged (but not young) LRRK2 knockin mutant mouse striatum compared to wild-type (WT) controls. LRRK2 mutant mouse embryonic fibroblasts (MEFs) exhibited reduced MAP1LC3/LC3 activation indicating impaired macroautophagy/autophagy. Mutant MEFs under FCCP-induced (mitochondrial uncoupler) stress showed increased LC3-aggregates demonstrating impaired mitophagy. Using a novel flow cytometry assay to quantify mitophagic rates in MEFs expressing photoactivatable -PAmCherry, we found significantly slower mitochondria clearance in mutant cells. Specific LRRK2 kinase inhibition using GNE-7915 did not alleviate impaired mitochondrial clearance suggesting a lack of direct relationship to increased kinase activity alone. DNM1L/Drp1 knockdown in MEFs slowed mitochondrial clearance indicating that DNM1L is a prerequisite for mitophagy. DNM1L knockdown in slowing mitochondrial clearance was less pronounced in mutant MEFs, indicating preexisting impaired DNM1L activation. DNM1L knockdown disrupted mitochondrial network which was more evident in mutant MEFs. DNM1L-Ser616 and MAPK/ERK phosphorylation which mediate mitochondrial fission and downstream mitophagic processes was apparent in WT using FCCP-induced stress but not mutant MEFs, despite similar total MAPK/ERK and DNM1L levels. In conclusion, aberrant mitochondria morphology and dysfunction associated with impaired mitophagy and DNM1L-MAPK/ERK signaling are found in mutant LRRK2 MEFs and mouse brain. ATP: adenosine triphosphate; BAX: BCL2-associated X protein; CDK1: cyclin-dependent kinase 1; CDK5: cyclin-dependent kinase 5; CQ: chloroquine; CSF: cerebrospinal fluid; DNM1L/DRP1: dynamin 1-like; ELISA: enzyme-linked immunosorbent assay; FACS: fluorescence-activated cell sorting; FCCP: carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; LAMP2A: lysosomal-associated membrane protein 2A; LRRK2: leucine-rich repeat kinase 2; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MAPK1/ERK2: mitogen-activated protein kinase 1; MEF: mouse embryonic fibroblast; MFN1: mitofusin 1; MMP: mitochondrial membrane potential; PAmCherry: photoactivatable-mCherry; PD: Parkinson disease; PINK1: PTEN induced putative kinase 1; PRKN/PARKIN: parkin RBR E3 ubiquitin protein ligase; RAB10: RAB10, member RAS oncogene family; RAF: v-raf-leukemia oncogene; SNCA: synuclein, alpha; TEM: transmission electron microscopy; VDAC: voltage-dependent anion channel; WT: wild type; SQSTM1/p62: sequestosome 1.
Topics: Animals; Autophagy; Fibroblasts; Membrane Potential, Mitochondrial; Mice; Mitochondria; Mitophagy; Ubiquitin-Protein Ligases
PubMed: 33300446
DOI: 10.1080/15548627.2020.1850008 -
Signal Transduction and Targeted Therapy Aug 2023
Topics: Humans; Mitophagy; Core Binding Factor Alpha 2 Subunit; Pneumonia; Acute Lung Injury
PubMed: 37544975
DOI: 10.1038/s41392-023-01520-6 -
International Journal of Molecular... Dec 2023Mitochondrial dysregulation, such as mitochondrial complex I deficiency, increased oxidative stress, perturbation of mitochondrial dynamics and mitophagy, has long been... (Review)
Review
Mitochondrial dysregulation, such as mitochondrial complex I deficiency, increased oxidative stress, perturbation of mitochondrial dynamics and mitophagy, has long been implicated in the pathogenesis of PD. Initiating from the observation that mitochondrial toxins cause PD-like symptoms and mitochondrial DNA mutations are associated with increased risk of PD, many mutated genes linked to familial forms of PD, including , , and , have also been found to affect the mitochondrial features. Recent research has uncovered a much more complex involvement of mitochondria in PD. Disruption of mitochondrial quality control coupled with abnormal secretion of mitochondrial contents to dispose damaged organelles may play a role in the pathogenesis of PD. Furthermore, due to its bacterial ancestry, circulating mitochondrial DNAs can function as damage-associated molecular patterns eliciting inflammatory response. In this review, we summarize and discuss the connection between mitochondrial dysfunction and PD, highlighting the molecular triggers of the disease process, the intra- and extracellular roles of mitochondria in PD as well as the therapeutic potential of mitochondrial transplantation.
Topics: Humans; Parkinson Disease; Ubiquitin-Protein Ligases; Mitochondria; DNA, Mitochondrial; Mitophagy
PubMed: 38069350
DOI: 10.3390/ijms242317027