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Ednacot EMQ, Nabhani A, Dinh DM, Morehouse BR. Pharmacological potential of cyclic nucleotide signaling in immunity. Pharmacol Ther 2024; 258:108653. [PMID: 38679204 DOI: 10.1016/j.pharmthera.2024.108653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 03/16/2024] [Accepted: 04/17/2024] [Indexed: 05/01/2024]
Abstract
Cyclic nucleotides are important signaling molecules that play many critical physiological roles including controlling cell fate and development, regulation of metabolic processes, and responding to changes in the environment. Cyclic nucleotides are also pivotal regulators in immune signaling, orchestrating intricate processes that maintain homeostasis and defend against pathogenic threats. This review provides a comprehensive examination of the pharmacological potential of cyclic nucleotide signaling pathways within the realm of immunity. Beginning with an overview of the fundamental roles of cAMP and cGMP as ubiquitous second messengers, this review delves into the complexities of their involvement in immune responses. Special attention is given to the challenges associated with modulating these signaling pathways for therapeutic purposes, emphasizing the necessity for achieving cell-type specificity to avert unintended consequences. A major focus of the review is on the recent paradigm-shifting discoveries regarding specialized cyclic nucleotide signals in the innate immune system, notably the cGAS-STING pathway. The significance of cyclic dinucleotides, exemplified by 2'3'-cGAMP, in controlling immune responses against pathogens and cancer, is explored. The evolutionarily conserved nature of cyclic dinucleotides as antiviral agents, spanning across diverse organisms, underscores their potential as targets for innovative immunotherapies. Findings from the last several years have revealed a striking diversity of novel bacterial cyclic nucleotide second messengers which are involved in antiviral responses. Knowledge of the existence and precise identity of these molecules coupled with accurate descriptions of their associated immune defense pathways will be essential to the future development of novel antibacterial therapeutic strategies. The insights presented herein may help researchers navigate the evolving landscape of immunopharmacology as it pertains to cyclic nucleotides and point toward new avenues or lines of thinking about development of therapeutics against the pathways they regulate.
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Affiliation(s)
- Eirene Marie Q Ednacot
- Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of California Irvine, Irvine, CA 92697, USA; Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California Irvine, Irvine, CA 92697, USA
| | - Ali Nabhani
- Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of California Irvine, Irvine, CA 92697, USA
| | - David M Dinh
- Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of California Irvine, Irvine, CA 92697, USA
| | - Benjamin R Morehouse
- Department of Molecular Biology and Biochemistry, School of Biological Sciences, University of California Irvine, Irvine, CA 92697, USA; Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California Irvine, Irvine, CA 92697, USA; Institute for Immunology, University of California Irvine, Irvine, CA 92697, USA; Center for Virus Research, University of California Irvine, Irvine, CA 92697, USA.
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2
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Filograna R, Gerlach J, Choi HN, Rigoni G, Barbaro M, Oscarson M, Lee S, Tiklova K, Ringnér M, Koolmeister C, Wibom R, Riggare S, Nennesmo I, Perlmann T, Wredenberg A, Wedell A, Motori E, Svenningsson P, Larsson NG. PARKIN is not required to sustain OXPHOS function in adult mammalian tissues. NPJ Parkinsons Dis 2024; 10:93. [PMID: 38684669 PMCID: PMC11058849 DOI: 10.1038/s41531-024-00707-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 04/11/2024] [Indexed: 05/02/2024] Open
Abstract
Loss-of-function variants in the PRKN gene encoding the ubiquitin E3 ligase PARKIN cause autosomal recessive early-onset Parkinson's disease (PD). Extensive in vitro and in vivo studies have reported that PARKIN is involved in multiple pathways of mitochondrial quality control, including mitochondrial degradation and biogenesis. However, these findings are surrounded by substantial controversy due to conflicting experimental data. In addition, the existing PARKIN-deficient mouse models have failed to faithfully recapitulate PD phenotypes. Therefore, we have investigated the mitochondrial role of PARKIN during ageing and in response to stress by employing a series of conditional Parkin knockout mice. We report that PARKIN loss does not affect oxidative phosphorylation (OXPHOS) capacity and mitochondrial DNA (mtDNA) levels in the brain, heart, and skeletal muscle of aged mice. We also demonstrate that PARKIN deficiency does not exacerbate the brain defects and the pro-inflammatory phenotype observed in mice carrying high levels of mtDNA mutations. To rule out compensatory mechanisms activated during embryonic development of Parkin-deficient mice, we generated a mouse model where loss of PARKIN was induced in adult dopaminergic (DA) neurons. Surprisingly, also these mice did not show motor impairment or neurodegeneration, and no major transcriptional changes were found in isolated midbrain DA neurons. Finally, we report a patient with compound heterozygous PRKN pathogenic variants that lacks PARKIN and has developed PD. The PARKIN deficiency did not impair OXPHOS activities or induce mitochondrial pathology in skeletal muscle from the patient. Altogether, our results argue that PARKIN is dispensable for OXPHOS function in adult mammalian tissues.
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Affiliation(s)
- Roberta Filograna
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
| | - Jule Gerlach
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Hae-Na Choi
- Institute for Biochemistry, University of Cologne, Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Giovanni Rigoni
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Michela Barbaro
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Mikael Oscarson
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Seungmin Lee
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Katarina Tiklova
- Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Markus Ringnér
- Department of Biology, National Bioinformatics Infrastructure Sweden, Science for Life Laboratory, Lund University, Lund, Sweden
| | - Camilla Koolmeister
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Rolf Wibom
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Sara Riggare
- Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | - Inger Nennesmo
- Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Thomas Perlmann
- Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
| | - Anna Wredenberg
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Anna Wedell
- Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
- Department of Molecular Medicine and Surgery, Karolinska Institute, Stockholm, Sweden
| | - Elisa Motori
- Institute for Biochemistry, University of Cologne, Cologne, Germany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Per Svenningsson
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
- Department of Neurology, Karolinska University Hospital, Stockholm, Sweden
| | - Nils-Göran Larsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
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3
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Zou S, Wang B, Yi K, Su D, Chen Y, Li N, Geng Q. The critical roles of STING in mitochondrial homeostasis. Biochem Pharmacol 2024; 220:115938. [PMID: 38086488 DOI: 10.1016/j.bcp.2023.115938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/18/2023] [Accepted: 11/21/2023] [Indexed: 12/20/2023]
Abstract
The stimulator of interferon genes (STING) is a crucial signaling hub in the immune system's antiviral and antimicrobial defense by detecting exogenous and endogenous DNA. The multifaceted functions of STING have been uncovered gradually during past decades, including homeostasis maintenance and overfull immunity or inflammation induction. However, the subcellular regulation of STING and mitochondria is poorly understood. The main functions of STING are outlined in this review. Moreover, we discuss how mitochondria and STING interact through multiple mechanisms, including the release of mitochondrial DNA (mtDNA), modulation of mitochondria-associated membrane (MAM) and mitochondrial dynamics, alterations in mitochondrial metabolism, regulation of reactive oxygen species (ROS) production, and mitochondria-related cell death. Finally, we discuss how STING is crucial to disease development, providing a novel perspective on its role in cellular physiology and pathology.
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Affiliation(s)
- Shishi Zou
- Department of Thoracic Surgery, Wuhan University Renmin Hospital, 430060, China
| | - Bo Wang
- Department of Thoracic Surgery, Wuhan University Renmin Hospital, 430060, China
| | - Ke Yi
- Department of Thoracic Surgery, Wuhan University Renmin Hospital, 430060, China
| | - Dandan Su
- Department of Neurology, Wuhan University Renmin Hospital, 430060, China
| | - Yukai Chen
- Department of Oncology, Wuhan University Renmin Hospital, 430060, China
| | - Ning Li
- Department of Thoracic Surgery, Wuhan University Renmin Hospital, 430060, China.
| | - Qing Geng
- Department of Thoracic Surgery, Wuhan University Renmin Hospital, 430060, China.
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Moehlman AT, Kanfer G, Youle RJ. Loss of STING in parkin mutant flies suppresses muscle defects and mitochondria damage. PLoS Genet 2023; 19:e1010828. [PMID: 37440574 PMCID: PMC10368295 DOI: 10.1371/journal.pgen.1010828] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 06/13/2023] [Indexed: 07/15/2023] Open
Abstract
The early pathogenesis and underlying molecular causes of motor neuron degeneration in Parkinson's Disease (PD) remains unresolved. In the model organism Drosophila melanogaster, loss of the early-onset PD gene parkin (the ortholog of human PRKN) results in impaired climbing ability, damage to the indirect flight muscles, and mitochondrial fragmentation with swelling. These stressed mitochondria have been proposed to activate innate immune pathways through release of damage associated molecular patterns (DAMPs). Parkin-mediated mitophagy is hypothesized to suppress mitochondrial damage and subsequent activation of the cGAS/STING innate immunity pathway, but the relevance of this interaction in the fly remains unresolved. Using a combination of genetics, immunoassays, and RNA sequencing, we investigated a potential role for STING in the onset of parkin-null phenotypes. Our findings demonstrate that loss of Drosophila STING in flies rescues the thorax muscle defects and the climbing ability of parkin-/- mutants. Loss of STING also suppresses the disrupted mitochondrial morphology in parkin-/- flight muscles, suggesting unexpected feedback of STING on mitochondria integrity or activation of a compensatory mitochondrial pathway. In the animals lacking both parkin and sting, PINK1 is activated and cell death pathways are suppressed. These findings support a unique, non-canonical role for Drosophila STING in the cellular and organismal response to mitochondria stress.
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Affiliation(s)
- Andrew T Moehlman
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
- Postdoctoral Research Associate Training Program, National Institute of General Medical Sciences, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Gil Kanfer
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Richard J Youle
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
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Scott L, Karuppagounder SS, Neifert S, Kang BG, Wang H, Dawson VL, Dawson TM. The Absence of Parkin Does Not Promote Dopamine or Mitochondrial Dysfunction in PolgA D257A/D257A Mitochondrial Mutator Mice. J Neurosci 2022; 42:9263-9277. [PMID: 36280265 PMCID: PMC9761676 DOI: 10.1523/jneurosci.0545-22.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 10/10/2022] [Accepted: 10/16/2022] [Indexed: 11/05/2022] Open
Abstract
Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). In this study, we generated a transgenic model by crossing germline Parkin-/- mice with PolgAD257A mice, an established model of premature aging and mitochondrial stress. We hypothesized that loss of Parkin-/- in PolgAD257A/D257A mice would exacerbate mitochondrial dysfunction, leading to loss of dopamine neurons and nigral-striatal specific neurobehavioral motor dysfunction. We found that aged Parkin-/-/PolgAD257A/D257A male and female mice exhibited severe behavioral deficits, nonspecific to the nigral-striatal pathway, with neither dopaminergic neurodegeneration nor reductions in striatal dopamine. We saw no difference in expression levels of nuclear-encoded subunits of mitochondrial markers and mitochondrial Complex I and IV activities, although we did observe substantial reductions in mitochondrial-encoded COX41I, indicating mitochondrial dysfunction as a result of PolgAD257A/D257A mtDNA mutations. Expression levels of mitophagy markers LC3I/LC3II remained unchanged between cohorts, suggesting no overt mitophagy defects. Expression levels of the parkin substrates, VDAC, NLRP3, and AIMP2 remained unchanged, suggesting no parkin dysfunction. In summary, we were unable to observe dopaminergic neurodegeneration with corresponding nigral-striatal neurobehavioral deficits, nor Parkin or mitochondrial dysfunction in Parkin-/-/PolgAD257A/D257A mice. These findings support a lack of synergism of Parkin loss on mitochondrial dysfunction in mouse models of mitochondrial deficits.SIGNIFICANCE STATEMENT Producing a mouse model of Parkinson's disease (PD) that is etiologically relevant, recapitulates clinical hallmarks, and exhibits reproducible results is crucial to understanding the underlying pathology and in developing disease-modifying therapies. Here, we show that Parkin-/-/PolgAD257A/D257A mice, a previously reported PD mouse model, fails to reproduce a Parkinsonian phenotype. We show that these mice do not display dopaminergic neurodegeneration nor nigral-striatal-dependent motor deficits. Furthermore, we report that Parkin loss does not synergize with mitochondrial dysfunction. Our results demonstrate that Parkin-/-/PolgAD257A/D257A mice are not a reliable model for PD and adds to a growing body of work demonstrating that Parkin loss does not synergize with mitochondrial dysfunction in mouse models of mitochondrial deficits.
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Affiliation(s)
- Laura Scott
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Cellular and Molecular Medicine Program, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Adrienne Helis Malvin Medical Research Foundation, New Orleans, Louisiana 70130-2685
| | - Senthilkumar S Karuppagounder
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Stewart Neifert
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Adrienne Helis Malvin Medical Research Foundation, New Orleans, Louisiana 70130-2685
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Bong Gu Kang
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Hu Wang
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Valina L Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Cellular and Molecular Medicine Program, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Adrienne Helis Malvin Medical Research Foundation, New Orleans, Louisiana 70130-2685
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Ted M Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Cellular and Molecular Medicine Program, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Adrienne Helis Malvin Medical Research Foundation, New Orleans, Louisiana 70130-2685
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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6
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Cossu D, Yokoyama K, Sato S, Noda S, Sakanishi T, Sechi LA, Hattori N. Age related immune modulation of experimental autoimmune encephalomyelitis in PINK1 knockout mice. Front Immunol 2022; 13:1036680. [PMID: 36466826 PMCID: PMC9714542 DOI: 10.3389/fimmu.2022.1036680] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 11/07/2022] [Indexed: 07/30/2023] Open
Abstract
OBJECTIVE Recent research has shown that Parkin, an E3 ubiquitin ligase, modulates peripheral immune cells-mediated immunity during experimental autoimmune encephalomyelitis (EAE). Because the PTEN-induced putative kinase 1 (PINK1) protein acts upstream of Parkin in a common mitochondrial quality control pathway, we hypothesized that the systemic deletion of PINK1 could also modify the clinical course of EAE, altering the peripheral and central nervous systems' immune responses. METHODS EAE was induced in female PINK1-/- mice of different age groups by immunization with myelin oligodendrocyte glycoprotein peptide. RESULTS Compared to young wild-type controls, PINK1-/- mice showed earlier disease onset, albeit with a slightly less severe disease, while adult PINK1-/- mice displayed early onset and more severe acute symptoms than controls, showing persistent disease during the recovery phase. In adult mice, EAE severity was associated with significant increases in frequency of dendritic cells (CD11C+, IAIE+), lymphocytes (CD8+), neutrophils (Ly6G+, CD11b+), and a dysregulated cytokine profile in spleen. Furthermore, a massive macrophage (CD68+) infiltration and microglia (TMEM119+) and astrocyte (GFAP+) activation were detected in the spinal cord of adult PINK1-/- mice. CONCLUSIONS PINK1 plays an age-related role in modulating the peripheral inflammatory response during EAE, potentially contributing to the pathogenesis of neuroinflammatory and other associated conditions.
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Affiliation(s)
- Davide Cossu
- Department of Neurology, Juntendo University, Tokyo, Japan
- Biomedical Research Core Facilities, Juntendo University, Tokyo, Japan
- Department of Biomedical Sciences, Division of Microbiology and Virology, University of Sassari, Sassari, Italy
| | | | - Shigeto Sato
- Department of Neurology, Juntendo University, Tokyo, Japan
| | - Sachiko Noda
- Department of Neurology, Juntendo University, Tokyo, Japan
| | | | - Leonardo Antonio Sechi
- Department of Biomedical Sciences, Division of Microbiology and Virology, University of Sassari, Sassari, Italy
- SC Microbiologia Azienda Ospedaliero Universitaria (AOU) Sassari, Sassari, Italy
| | - Nobutaka Hattori
- Department of Neurology, Juntendo University, Tokyo, Japan
- Neurodegenerative Disorders Collaborative laboratory, RIKEN Center for Brain Science, Saitama, Japan
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Arena G, Sharma K, Agyeah G, Krüger R, Grünewald A, Fitzgerald JC. Neurodegeneration and Neuroinflammation in Parkinson's Disease: a Self-Sustained Loop. Curr Neurol Neurosci Rep 2022; 22:427-440. [PMID: 35674870 PMCID: PMC9174445 DOI: 10.1007/s11910-022-01207-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2022] [Indexed: 02/06/2023]
Abstract
Purpose of Review Neuroinflammation plays a significant role in Parkinson’s disease (PD) etiology along with mitochondrial dysfunction and impaired proteostasis. In this context, mechanisms related to immune response can act as modifiers at different steps of the neurodegenerative process and justify the growing interest in anti-inflammatory agents as potential disease-modifying treatments in PD. The discovery of inherited gene mutations in PD has allowed researchers to develop cellular and animal models to study the mechanisms of the underlying biology, but the original cause of neuroinflammation in PD is still debated to date. Recent Findings Cell autonomous alterations in neuronal cells, including mitochondrial damage and protein aggregation, could play a role, but recent findings also highlighted the importance of intercellular communication at both local and systemic level. This has given rise to debate about the role of non-neuronal cells in PD and reignited intense research into the gut-brain axis and other non-neuronal interactions in the development of the disease. Whatever the original trigger of neuroinflammation in PD, what appears quite clear is that the aberrant activation of glial cells and other components of the immune system creates a vicious circle in which neurodegeneration and neuroinflammation nourish each other. Summary In this review, we will provide an up-to-date summary of the main cellular alterations underlying neuroinflammation in PD, including those induced by environmental factors (e.g. the gut microbiome) and those related to the genetic background of affected patients. Starting from the lesson provided by familial forms of PD, we will discuss pathophysiological mechanisms linked to inflammation that could also play a role in idiopathic forms. Finally, we will comment on the potential clinical translatability of immunobiomarkers identified in PD patient cohorts and provide an update on current therapeutic strategies aimed at overcoming or preventing inflammation in PD.
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Affiliation(s)
- G Arena
- Luxembourg Center for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg.
| | - K Sharma
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - G Agyeah
- Luxembourg Center for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - R Krüger
- Luxembourg Center for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg.,Transversal Translational Medicine, Luxembourg Institute of Health, Strassen, Luxembourg.,Centre Hospitalier de Luxembourg (CHL), Luxembourg, Luxembourg
| | - A Grünewald
- Luxembourg Center for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg.,Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - J C Fitzgerald
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
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Morais VA, Vos M. Reduced penetrance of Parkinson's disease models. MED GENET-BERLIN 2022; 34:117-124. [PMID: 38835909 PMCID: PMC11006373 DOI: 10.1515/medgen-2022-2138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
The etiology and progression of Parkinson's Disease (PD), the second most prevalent neurological disorder, have been widely investigated for several decades; however, a cure is still lacking. Despite the development of several neurotoxins and animal models to study this rather heterogeneous disease, a complete recapitulation of the neurophysiology and neuropathology of PD has not been fully achieved. One underlying cause for this could be that mutations in PD-associated genes have reduced penetrance. Therefore, the quest for novel PD models is required where a double hit approach needs to be evoked - a combination of genetic alterations and environmental factors need to be accounted for in one unique model simultaneously.
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Affiliation(s)
- Vanessa A Morais
- iMM, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, 1649-028, Portugal
| | - Melissa Vos
- Institute of Neurogenetics, University of Luebeck, Ratzeburger Allee 160 building 67, 23562 Luebeck, Germany
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Fedele G, Loh SHY, Celardo I, Leal NS, Lehmann S, Costa AC, Martins LM. Suppression of intestinal dysfunction in a Drosophila model of Parkinson's disease is neuroprotective. NATURE AGING 2022; 2:317-331. [PMID: 37117744 DOI: 10.1038/s43587-022-00194-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/16/2022] [Indexed: 04/30/2023]
Abstract
The innate immune response mounts a defense against foreign invaders and declines with age. An inappropriate induction of this response can cause diseases. Previous studies showed that mitochondria can be repurposed to promote inflammatory signaling. Damaged mitochondria can also trigger inflammation and promote diseases. Mutations in pink1, a gene required for mitochondrial health, cause Parkinson's disease, and Drosophila melanogaster pink1 mutants accumulate damaged mitochondria. Here, we show that defective mitochondria in pink1 mutants activate Relish targets and demonstrate that inflammatory signaling causes age-dependent intestinal dysfunction in pink1-mutant flies. These effects result in the death of intestinal cells, metabolic reprogramming and neurotoxicity. We found that Relish signaling is activated downstream of a pathway stimulated by cytosolic DNA. Suppression of Relish in the intestinal midgut of pink1-mutant flies restores mitochondrial function and is neuroprotective. We thus conclude that gut-brain communication modulates neurotoxicity in a fly model of Parkinson's disease through a mechanism involving mitochondrial dysfunction.
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Affiliation(s)
- Giorgio Fedele
- MRC Toxicology Unit, University of Cambridge, Cambridge, UK
| | | | - Ivana Celardo
- MRC Toxicology Unit, University of Cambridge, Cambridge, UK
| | | | - Susann Lehmann
- MRC Toxicology Unit, University of Cambridge, Cambridge, UK
| | - Ana C Costa
- MRC Toxicology Unit, University of Cambridge, Cambridge, UK
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10
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Disruption of Mitochondrial Homeostasis: The Role of PINK1 in Parkinson's Disease. Cells 2021; 10:cells10113022. [PMID: 34831247 PMCID: PMC8616241 DOI: 10.3390/cells10113022] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 10/29/2021] [Accepted: 11/01/2021] [Indexed: 12/18/2022] Open
Abstract
The progressive reduction of the dopaminergic neurons of the substantia nigra is the fundamental process underlying Parkinson’s disease (PD), while the mechanism of susceptibility of this specific neuronal population is largely unclear. Disturbances in mitochondrial function have been recognized as one of the main pathways in sporadic PD since the finding of respiratory chain impairment in animal models of PD. Studies on genetic forms of PD have provided new insight on the role of mitochondrial bioenergetics, homeostasis, and autophagy. PINK1 (PTEN-induced putative kinase 1) gene mutations, although rare, are the second most common cause of recessively inherited early-onset PD, after Parkin gene mutations. Our knowledge of PINK1 and Parkin function has increased dramatically in the last years, with the discovery that a process called mitophagy, which plays a key role in the maintenance of mitochondrial health, is mediated by the PINK1/Parkin pathway. In vitro and in vivo models have been developed, supporting the role of PINK1 in synaptic transmission, particularly affecting dopaminergic neurons. It is of paramount importance to further define the role of PINK1 in mitophagy and mitochondrial homeostasis in PD pathogenesis in order to delineate novel therapeutic targets.
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11
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Li F, Wang N, Zheng Y, Luo Y, Zhang Y. cGAS- Stimulator of Interferon Genes Signaling in Central Nervous System Disorders. Aging Dis 2021; 12:1658-1674. [PMID: 34631213 PMCID: PMC8460300 DOI: 10.14336/ad.2021.0304] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/04/2021] [Indexed: 12/19/2022] Open
Abstract
Cytosolic nucleic acid sensors contribute to the initiation of innate immune responses by playing a critical role in the detection of pathogens and endogenous nucleic acids. The cytosolic DNA sensor cyclic-GMP-AMP synthase (cGAS) and its downstream effector, stimulator of interferon genes (STING), mediate innate immune signaling by promoting the release of type I interferons (IFNs) and other inflammatory cytokines. These biomolecules are suggested to play critical roles in host defense, senescence, and tumor immunity. Recent studies have demonstrated that cGAS-STING signaling is strongly implicated in the pathogenesis of central nervous system (CNS) diseases which are underscored by neuroinflammatory-driven disease progression. Understanding and regulating the interactions between cGAS-STING signaling and the nervous system may thus provide an effective approach to prevent or delay late-onset CNS disorders. Here, we present a review of recent advances in the literature on cGAS-STING signaling and provide a comprehensive overview of the modulatory patterns of the cGAS-STING pathway in CNS disorders.
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Affiliation(s)
- Fengjuan Li
- 1Department of Neurology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Ningqun Wang
- 2Institute of Cerebrovascular Disease Research and Department of Neurology, Xuanwu Hospital of Capital Medical University, Beijing 100053, China
| | - Yangmin Zheng
- 2Institute of Cerebrovascular Disease Research and Department of Neurology, Xuanwu Hospital of Capital Medical University, Beijing 100053, China
| | - Yumin Luo
- 2Institute of Cerebrovascular Disease Research and Department of Neurology, Xuanwu Hospital of Capital Medical University, Beijing 100053, China
| | - Yongbo Zhang
- 1Department of Neurology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
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12
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Li Y, Li W, Hoffman AR, Cui J, Hu JF. The Nucleus/Mitochondria-Shuttling LncRNAs Function as New Epigenetic Regulators of Mitophagy in Cancer. Front Cell Dev Biol 2021; 9:699621. [PMID: 34568319 PMCID: PMC8455849 DOI: 10.3389/fcell.2021.699621] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/20/2021] [Indexed: 12/18/2022] Open
Abstract
Mitophagy is a specialized autophagic pathway responsible for the selective removal of damaged or dysfunctional mitochondria by targeting them to the autophagosome in order to maintain mitochondria quality. The role of mitophagy in tumorigenesis has been conflicting, with the process both supporting tumor cell survival and promoting cell death. Cancer cells may utilize the mitophagy pathway to augment their metabolic requirements and resistance to cell death, thereby leading to increased cell proliferation and invasiveness. This review highlights major regulatory pathways of mitophagy involved in cancer. In particular, we summarize recent progress regarding how nuclear-encoded long non-coding RNAs (lncRNAs) function as novel epigenetic players in the mitochondria of cancer cells, affecting the malignant behavior of tumors by regulating mitophagy. Finally, we discuss the potential application of regulating mitophagy as a new target for cancer therapy.
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Affiliation(s)
- Yan Li
- Key Laboratory of Organ Regeneration and Transplantation of Ministry of Education, Cancer Center, First Hospital of Jilin University, Changchun, China.,Stanford University Medical School, VA Palo Alto Health Care System, Palo Alto, CA, United States
| | - Wei Li
- Key Laboratory of Organ Regeneration and Transplantation of Ministry of Education, Cancer Center, First Hospital of Jilin University, Changchun, China
| | - Andrew R Hoffman
- Stanford University Medical School, VA Palo Alto Health Care System, Palo Alto, CA, United States
| | - Jiuwei Cui
- Key Laboratory of Organ Regeneration and Transplantation of Ministry of Education, Cancer Center, First Hospital of Jilin University, Changchun, China
| | - Ji-Fan Hu
- Key Laboratory of Organ Regeneration and Transplantation of Ministry of Education, Cancer Center, First Hospital of Jilin University, Changchun, China.,Stanford University Medical School, VA Palo Alto Health Care System, Palo Alto, CA, United States
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13
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Mitochondria-Induced Immune Response as a Trigger for Neurodegeneration: A Pathogen from Within. Int J Mol Sci 2021; 22:ijms22168523. [PMID: 34445229 PMCID: PMC8395232 DOI: 10.3390/ijms22168523] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/02/2021] [Accepted: 08/03/2021] [Indexed: 01/14/2023] Open
Abstract
Symbiosis between the mitochondrion and the ancestor of the eukaryotic cell allowed cellular complexity and supported life. Mitochondria have specialized in many key functions ensuring cell homeostasis and survival. Thus, proper communication between mitochondria and cell nucleus is paramount for cellular health. However, due to their archaebacterial origin, mitochondria possess a high immunogenic potential. Indeed, mitochondria have been identified as an intracellular source of molecules that can elicit cellular responses to pathogens. Compromised mitochondrial integrity leads to release of mitochondrial content into the cytosol, which triggers an unwanted cellular immune response. Mitochondrial nucleic acids (mtDNA and mtRNA) can interact with the same cytoplasmic sensors that are specialized in recognizing genetic material from pathogens. High-energy demanding cells, such as neurons, are highly affected by deficits in mitochondrial function. Notably, mitochondrial dysfunction, neurodegeneration, and chronic inflammation are concurrent events in many severe debilitating disorders. Interestingly in this context of pathology, increasing number of studies have detected immune-activating mtDNA and mtRNA that induce an aberrant production of pro-inflammatory cytokines and interferon effectors. Thus, this review provides new insights on mitochondria-driven inflammation as a potential therapeutic target for neurodegenerative and primary mitochondrial diseases.
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14
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Abstract
Mitochondria are organelles with vital functions in almost all eukaryotic cells. Often described as the cellular 'powerhouses' due to their essential role in aerobic oxidative phosphorylation, mitochondria perform many other essential functions beyond energy production. As signaling organelles, mitochondria communicate with the nucleus and other organelles to help maintain cellular homeostasis, allow cellular adaptation to diverse stresses, and help steer cell fate decisions during development. Mitochondria have taken center stage in the research of normal and pathological processes, including normal tissue homeostasis and metabolism, neurodegeneration, immunity and infectious diseases. The central role that mitochondria assume within cells is evidenced by the broad impact of mitochondrial diseases, caused by defects in either mitochondrial or nuclear genes encoding for mitochondrial proteins, on different organ systems. In this Review, we will provide the reader with a foundation of the mitochondrial 'hardware', the mitochondrion itself, with its specific dynamics, quality control mechanisms and cross-organelle communication, including its roles as a driver of an innate immune response, all with a focus on development, disease and aging. We will further discuss how mitochondrial DNA is inherited, how its mutation affects cell and organismal fitness, and current therapeutic approaches for mitochondrial diseases in both model organisms and humans.
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Affiliation(s)
- Marlies P. Rossmann
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 01238, USA
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Harvard Medical School, Howard Hughes Medical Institute, Boston, MA 02115, USA
| | - Sonia M. Dubois
- Division of Hematology/Oncology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Suneet Agarwal
- Division of Hematology/Oncology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Leonard I. Zon
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 01238, USA
- Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital, Harvard Medical School, Howard Hughes Medical Institute, Boston, MA 02115, USA
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15
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Onishi M, Okamoto K. Mitochondrial clearance: mechanisms and roles in cellular fitness. FEBS Lett 2021; 595:1239-1263. [PMID: 33615465 DOI: 10.1002/1873-3468.14060] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 01/29/2021] [Accepted: 02/12/2021] [Indexed: 12/14/2022]
Abstract
Mitophagy is one of the selective autophagy pathways that catabolizes dysfunctional or superfluous mitochondria. Under mitophagy-inducing conditions, mitochondria are labeled with specific molecular landmarks that recruit the autophagy machinery to the surface of mitochondria, enclosed into autophagosomes, and delivered to lysosomes (vacuoles in yeast) for degradation. As damaged mitochondria are the major sources of reactive oxygen species, mitophagy is critical for mitochondrial quality control and cellular health. Moreover, appropriate control of mitochondrial quantity via mitophagy is vital for the energy supply-demand balance in cells and whole organisms, cell differentiation, and developmental programs. Thus, it seems conceivable that defects in mitophagy could elicit pleiotropic pathologies such as excess inflammation, tissue injury, neurodegeneration, and aging. In this review, we will focus on the molecular basis and physiological relevance of mitophagy, and potential of mitophagy as a therapeutic target to overcome such disorders.
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Affiliation(s)
- Mashun Onishi
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
| | - Koji Okamoto
- Laboratory of Mitochondrial Dynamics, Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
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16
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Vos M, Klein C. The Importance of Drosophila melanogaster Research to UnCover Cellular Pathways Underlying Parkinson's Disease. Cells 2021; 10:579. [PMID: 33800736 PMCID: PMC7998316 DOI: 10.3390/cells10030579] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/01/2021] [Accepted: 03/05/2021] [Indexed: 12/11/2022] Open
Abstract
Parkinson's disease (PD) is a complex neurodegenerative disorder that is currently incurable. As a consequence of an incomplete understanding of the etiology of the disease, therapeutic strategies mainly focus on symptomatic treatment. Even though the majority of PD cases remain idiopathic (~90%), several genes have been identified to be causative for PD, facilitating the generation of animal models that are a good alternative to study disease pathways and to increase our understanding of the underlying mechanisms of PD. Drosophila melanogaster has proven to be an excellent model in these studies. In this review, we will discuss the different PD models in flies and key findings identified in flies in different affected pathways in PD. Several molecular changes have been identified, of which mitochondrial dysfunction and a defective endo-lysosomal pathway emerge to be the most relevant for PD pathogenesis. Studies in flies have significantly contributed to our knowledge of how disease genes affect and interact in these pathways enabling a better understanding of the disease etiology and providing possible therapeutic targets for the treatment of PD, some of which have already resulted in clinical trials.
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Affiliation(s)
- Melissa Vos
- Institute of Neurogenetics, University of Luebeck, Ratzeburger Allee 160, Building 67, 23562 Luebeck, Germany
| | - Christine Klein
- Institute of Neurogenetics, University of Luebeck, Ratzeburger Allee 160, Building 67, 23562 Luebeck, Germany
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17
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Onishi M, Yamano K, Sato M, Matsuda N, Okamoto K. Molecular mechanisms and physiological functions of mitophagy. EMBO J 2021; 40:e104705. [PMID: 33438778 PMCID: PMC7849173 DOI: 10.15252/embj.2020104705] [Citation(s) in RCA: 587] [Impact Index Per Article: 195.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 08/03/2020] [Accepted: 10/02/2020] [Indexed: 12/12/2022] Open
Abstract
Degradation of mitochondria via a selective form of autophagy, named mitophagy, is a fundamental mechanism conserved from yeast to humans that regulates mitochondrial quality and quantity control. Mitophagy is promoted via specific mitochondrial outer membrane receptors, or ubiquitin molecules conjugated to proteins on the mitochondrial surface leading to the formation of autophagosomes surrounding mitochondria. Mitophagy-mediated elimination of mitochondria plays an important role in many processes including early embryonic development, cell differentiation, inflammation, and apoptosis. Recent advances in analyzing mitophagy in vivo also reveal high rates of steady-state mitochondrial turnover in diverse cell types, highlighting the intracellular housekeeping role of mitophagy. Defects in mitophagy are associated with various pathological conditions such as neurodegeneration, heart failure, cancer, and aging, further underscoring the biological relevance. Here, we review our current molecular understanding of mitophagy, and its physiological implications, and discuss how multiple mitophagy pathways coordinately modulate mitochondrial fitness and populations.
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Affiliation(s)
- Mashun Onishi
- Laboratory of Mitochondrial DynamicsGraduate School of Frontier BiosciencesOsaka UniversitySuitaJapan
| | - Koji Yamano
- The Ubiquitin ProjectTokyo Metropolitan Institute of Medical ScienceTokyoJapan
| | - Miyuki Sato
- Laboratory of Molecular Membrane BiologyInstitute for Molecular and Cellular RegulationGunma UniversityMaebashiJapan
| | - Noriyuki Matsuda
- The Ubiquitin ProjectTokyo Metropolitan Institute of Medical ScienceTokyoJapan
| | - Koji Okamoto
- Laboratory of Mitochondrial DynamicsGraduate School of Frontier BiosciencesOsaka UniversitySuitaJapan
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18
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Quinn PMJ, Moreira PI, Ambrósio AF, Alves CH. PINK1/PARKIN signalling in neurodegeneration and neuroinflammation. Acta Neuropathol Commun 2020; 8:189. [PMID: 33168089 PMCID: PMC7654589 DOI: 10.1186/s40478-020-01062-w] [Citation(s) in RCA: 212] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/17/2020] [Indexed: 12/13/2022] Open
Abstract
Mutations in the PTEN-induced kinase 1 (PINK1) and Parkin RBR E3 ubiquitin-protein ligase (PARKIN) genes are associated with familial forms of Parkinson’s disease (PD). PINK1, a protein kinase, and PARKIN, an E3 ubiquitin ligase, control the specific elimination of dysfunctional or superfluous mitochondria, thus fine-tuning mitochondrial network and preserving energy metabolism. PINK1 regulates PARKIN translocation in impaired mitochondria and drives their removal via selective autophagy, a process known as mitophagy. As knowledge obtained using different PINK1 and PARKIN transgenic animal models is being gathered, growing evidence supports the contribution of mitophagy impairment to several human pathologies, including PD and Alzheimer’s diseases (AD). Therefore, therapeutic interventions aiming to modulate PINK1/PARKIN signalling might have the potential to treat these diseases. In this review, we will start by discussing how the interplay of PINK1 and PARKIN signalling helps mediate mitochondrial physiology. We will continue by debating the role of mitochondrial dysfunction in disorders such as amyotrophic lateral sclerosis, Alzheimer’s, Huntington’s and Parkinson’s diseases, as well as eye diseases such as age-related macular degeneration and glaucoma, and the causative factors leading to PINK1/PARKIN-mediated neurodegeneration and neuroinflammation. Finally, we will discuss PINK1/PARKIN gene augmentation possibilities with a particular focus on AD, PD and glaucoma.
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Ma H, Guo Z, Gai C, Cheng C, Zhang J, Zhang Y, Yang L, Feng W, Gao Y, Sun H. Protective effects of Buyinqianzheng Formula on mitochondrial morphology by PINK1/Parkin pathway in SH-SY5Y cells induced by MPP+. JOURNAL OF TRADITIONAL CHINESE MEDICAL SCIENCES 2020. [DOI: 10.1016/j.jtcms.2020.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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20
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Mechanisms and roles of mitochondrial localisation and dynamics in neuronal function. Neuronal Signal 2020; 4:NS20200008. [PMID: 32714603 PMCID: PMC7373250 DOI: 10.1042/ns20200008] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 05/14/2020] [Accepted: 05/15/2020] [Indexed: 01/23/2023] Open
Abstract
Neurons are highly polarised, complex and incredibly energy intensive cells, and their demand for ATP during neuronal transmission is primarily met by oxidative phosphorylation by mitochondria. Thus, maintaining the health and efficient function of mitochondria is vital for neuronal integrity, viability and synaptic activity. Mitochondria do not exist in isolation, but constantly undergo cycles of fusion and fission, and are actively transported around the neuron to sites of high energy demand. Intriguingly, axonal and dendritic mitochondria exhibit different morphologies. In axons mitochondria are small and sparse whereas in dendrites they are larger and more densely packed. The transport mechanisms and mitochondrial dynamics that underlie these differences, and their functional implications, have been the focus of concerted investigation. Moreover, it is now clear that deficiencies in mitochondrial dynamics can be a primary factor in many neurodegenerative diseases. Here, we review the role that mitochondrial dynamics play in neuronal function, how these processes support synaptic transmission and how mitochondrial dysfunction is implicated in neurodegenerative disease.
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