Selective Disruption of Drp1-Independent Mitophagy and Mitolysosome Trafficking by an Alzheimer’s Disease Relevant Tau Modification in a Novel C. elegans Model

2021 ◽  
Author(s):  
Sanjib Guha ◽  
Anson Cheng ◽  
Trae Carroll ◽  
Dennisha King ◽  
Shon Koren ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Single Copy ◽  
Dynamic Imaging ◽  
Mitochondrial Morphology ◽  
Single Copy Gene ◽  
C Elegans ◽  
Gene Insertion ◽  
Copy Gene

Abstract Background: Accumulation of inappropriately phosphorylated tau into neurofibrillary tangles (NFT) is a defining feature of Alzheimer’s Disease (AD), with specific epitopes such as Tau pT231 emerging early in the development of tau pathology. Previously, we demonstrated that a phosphomimetic mutant (T231E) of human tau drove the loss of neuronal function and structural integrity with age in a novel C. elegans single-copy gene insertion AD model. A critical finding was that T231E, unlike wild type tau, suppressed oxidative stress-induced mitochondrial autophagy, or mitophagy. Regulation of mitochondrial morphology by fission is important for mitophagy, which has been reported to be dysregulated by AD-relevant tau species. Dynamin Related Protein 1 (Drp1) is a GTPase that plays a central role in mediating mitochondrial fission, and its altered function may contribute to AD pathogenesis. Methods: Genetically-encoded fluorescent biosensors and dynamic imaging approaches were combined with a genomic drp-1(-) loss-of-function and transgenic tau mutants to derive a comprehensive in vivo analysis of age-associated changes in mitochondria and mitolysosome (ML) morphology, abundance, neurite trafficking, and stress-induced mitophagy. Results: Strain expressing disease-associated PTM mimetic Tau T231E demonstrated a surprisingly selective effect on ML development and trafficking, with no effect on lysosomes or autolysosomes, and a subtle effect on mitochondria that was apparent mainly in older animals. Unexpectedly, we found that drp-1(-) mutants mount a robust mitophagy response to oxidative stress, consistent with recent observations that adaptive mitophagy may occur independent of the canonical DRP1 pathway. Moreover, T231E continued to suppress oxidative stress-induced mitophagy in the drp-1(-) background. Conclusions: Our C. elegans single-copy gene insertion model unveils multiple levels of selectivity – phenotypic selectivity for mutations that mimic pathologic tauopathy-associated PTM and physiologic selectivity for organelles that contain damaged mitochondria. In addition, our novel findings provide compelling support for DRP1-independent mechanisms playing a pivotal role in regulating mitochondrial dynamics and function in the context of AD-relevant tau species and age-associated stress.

scholarly journals Alzheimer’s disease-relevant tau modifications selectively impact neurodegeneration and mitophagy in a novel C. elegans single-copy transgenic model

2020 ◽  
Author(s):  
Sanjib Guha ◽  
Sarah Fischer ◽  
Gail VW Johnson ◽  
Keith Nehrke
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Genetic Model ◽  
Neurodegenerative Disorder ◽  
Model Organism ◽  
Single Copy ◽  
Mitochondrial Stress ◽  
C Elegans ◽  
Touch Receptor Neurons ◽  
New Perspective

ABSTRACTBackgroundA defining pathological hallmark of the progressive neurodegenerative disorder Alzheimer’s disease (AD) is the accumulation of misfolded tau with abnormal post-translational modifications (PTMs). These include phosphorylation at Threonine 231 (T231) and acetylation at Lysine 274 (K274) and at Lysine 281 (K281). Although tau is recognized to play a central role in pathogenesis of AD, the precise mechanisms by which these abnormal PTMs contribute to the neural toxicity of tau is unclear.MethodsHuman 0N4R tau (wild type) was expressed in touch receptor neurons of the genetic model organism C. elegans through single-copy gene insertion. Defined mutations were then introduced into the single-copy tau transgene through CRISPR-Cas9 genome editing. These mutations included T231E and T231A, to mimic phosphorylation and phospho-ablation of a commonly observed pathological epitope, respectively, and K274/281Q, to mimic disease-associated lysine acetylation. Stereotypical touch response assays were used to assess behavioral defects in the transgenic strains as a function of age, and genetically-encoded fluorescent biosensors were used to measure the morphological dynamics and turnover of touch neuron mitochondria.ResultsUnlike existing tau overexpression models, C. elegans single-copy expression of tau did not elicit overt pathological phenotypes at baseline. However, strains expressing disease associated PTM-mimetics (T231E and K274/281Q) exhibited reduced touch sensation and morphological abnormalities that increased with age. In addition, the PTM-mimetic mutants lacked the ability to engage mitophagy in response to mitochondrial stress.ConclusionsLimiting the expression of tau results in a genetic model where pathological modifications and age result in evolving phenotypes, which may more closely resemble the normal progression of AD. The finding that disease-associated PTMs suppress compensatory responses to mitochondrial stress provides a new perspective into the pathogenic mechanisms underlying AD.

scholarly journals Mitochondrial Dysfunction and Oxidative Stress in Alzheimer’s Disease

2021 ◽  
Vol 13 ◽  
Author(s):  
Afzal Misrani ◽  
Sidra Tabassum ◽  
Li Yang
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Mitochondrial Dysfunction ◽  
Mitochondrial Function ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Morphology ◽  
Therapeutic Approaches ◽  
The Impact ◽  
And Oxidative Stress

Mitochondria play a pivotal role in bioenergetics and respiratory functions, which are essential for the numerous biochemical processes underpinning cell viability. Mitochondrial morphology changes rapidly in response to external insults and changes in metabolic status via fission and fusion processes (so-called mitochondrial dynamics) that maintain mitochondrial quality and homeostasis. Damaged mitochondria are removed by a process known as mitophagy, which involves their degradation by a specific autophagosomal pathway. Over the last few years, remarkable efforts have been made to investigate the impact on the pathogenesis of Alzheimer’s disease (AD) of various forms of mitochondrial dysfunction, such as excessive reactive oxygen species (ROS) production, mitochondrial Ca2+ dyshomeostasis, loss of ATP, and defects in mitochondrial dynamics and transport, and mitophagy. Recent research suggests that restoration of mitochondrial function by physical exercise, an antioxidant diet, or therapeutic approaches can delay the onset and slow the progression of AD. In this review, we focus on recent progress that highlights the crucial role of alterations in mitochondrial function and oxidative stress in the pathogenesis of AD, emphasizing a framework of existing and potential therapeutic approaches.

scholarly journals Ingredients in Zijuan Pu’er Tea Extract Alleviate β-Amyloid Peptide Toxicity in a Caenorhabditis elegans Model of Alzheimer’s Disease Likely through DAF-16

Molecules ◽  
2019 ◽  
Vol 24 (4) ◽  
pp. 729 ◽  
Author(s):  
Fangzhou Du ◽  
Lin Zhou ◽  
Yan Jiao ◽  
Shuju Bai ◽  
Lu Wang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Caenorhabditis Elegans ◽  
Protective Effect ◽  
Nuclear Translocation ◽  
Amyloid Β ◽  
Amyloid Peptide ◽  
C Elegans ◽  
Β Amyloid

Amyloid-β, one of the hallmarks of Alzheimer’s disease (AD), is toxic to neurons and can also cause brain cell death. Oxidative stress is known to play an important role in AD, and there is strong evidence that oxidative stress is associated with amyloid-β. In the present study we report the protective effect of Zijuan Pu’er tea water extract (ZTWE) and the mixture of main ingredients (+)-catechins, caffeine and procyanidin (MCCP) in ZTWE on β-amyloid-induced toxicity in transgenic Caenorhabditis elegans (C. elegans) CL4176 expressing the human Aβ1–42 gene. ZTWE, (+)-catechins, caffeine, procyanidin and MCCP delayed the β-amyloid-induced paralysis to different degrees. The MCCP treatment did not affect the transcript abundance of amyloid-β transgene (amy-1); however, Thioflavin T staining showed a significant decrease in Aβ accumulation compared to untreated worms. Further research using transgenic worms found that MCCP promoted the translocation of DAF-16 from cytoplasm to nucleus and increased the expression of superoxide dismutase 3 (SOD-3). In addition, MCCP decreased the reactive oxygen species (ROS) content and increased the SOD activity in CL4176 worms. In conclusion, the results suggested that MCCP had a significant protective effect on β-amyloid-induced toxicity in C. elegans by reducing β-amyloid aggregation and inducing DAF-16 nuclear translocation that could activate the downstream signal pathway and enhance resistance to oxidative stress.

Identification of a single-copy gene encoding a Type I chlorophyll a/b-binding polypeptide of photosystem I in Arabidopsis thaliana

1992 ◽  
Vol 84 (4) ◽  
pp. 561-567 ◽  
Author(s):  
Poul E. Jensen ◽  
Michael Kristensen ◽  
Tine Hoff ◽  
Jan Lehmbeck ◽  
Bjarne M. Stummann ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Chlorophyll A ◽  
Photosystem I ◽  
Single Copy ◽  
Type I ◽  
Single Copy Gene ◽  
Gene Encoding ◽  
Copy Gene

Oxidative Stress and Amyloid Beta Toxicity in Alzheimer’s Disease: Intervention in a Complex Relationship by Antioxidants

2013 ◽  
Vol 20 (37) ◽  
pp. 4648-4664 ◽  
Author(s):  
S. Chakrabarti ◽  
M. Sinha ◽  
I. Thakurta ◽  
P. Banerjee ◽  
M. Chattopadhyay
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Beta ◽  
Complex Relationship

Targeting PPARalpha in Alzheimer's Disease

2018 ◽  
Vol 15 (4) ◽  
pp. 345-354 ◽  
Author(s):  
Barbara D'Orio ◽  
Anna Fracassi ◽  
Maria Paola Cerù ◽  
Sandra Moreno
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Molecular Mechanisms ◽  
Redox Homeostasis ◽  
Antioxidant Response ◽  
Peroxisome Proliferator ◽  
Prevailing Paradigm

Background: The molecular mechanisms underlying Alzheimer's disease (AD) are yet to be fully elucidated. The so-called “amyloid cascade hypothesis” has long been the prevailing paradigm for causation of disease, and is today being revisited in relation to other pathogenic pathways, such as oxidative stress, neuroinflammation and energy dysmetabolism. The peroxisome proliferator-activated receptors (PPARs) are expressed in the central nervous system (CNS) and regulate many physiological processes, such as energy metabolism, neurotransmission, redox homeostasis, autophagy and cell cycle. Among the three isotypes (α, β/δ, γ), PPARγ role is the most extensively studied, while information on α and β/δ are still scanty. However, recent in vitro and in vivo evidence point to PPARα as a promising therapeutic target in AD. Conclusion: This review provides an update on this topic, focussing on the effects of natural or synthetic agonists in modulating pathogenetic mechanisms at AD onset and during its progression. Ligandactivated PPARα inihibits amyloidogenic pathway, Tau hyperphosphorylation and neuroinflammation. Concomitantly, the receptor elicits an enzymatic antioxidant response to oxidative stress, ameliorates glucose and lipid dysmetabolism, and stimulates autophagy.

Alpha-1-Antichymotrypsin: a Common Player for Type 2 Diabetes and Alzheimer's Disease

2020 ◽  
Vol 16 ◽  
Author(s):  
Nataly Guzmán-Herrera ◽  
Viridiana C. Pérez-Nájera ◽  
Luis A. Salazar-Olivo
Keyword(s):  
Oxidative Stress ◽  
Alzheimer’S Disease ◽  
Type 2 Diabetes ◽  
Alzheimer's Disease ◽  
Regulatory Networks ◽  
Therapeutic Strategies ◽  
Oxidative Stresses ◽  
Bibliographic Search ◽  
And Oxidative Stress

Background: Numerous studies have shown a significant association between type 2 diabetes mellitus (T2D) and Alzheimer's disease (AD), two pathologies affecting millions of people worldwide. Chronic inflammation and oxidative stress are two conditions common to these diseases also affecting the activity of the serpin alpha-1-antichymotrypsin (ACT), but a possible common role for this serpin in T2D and AD remains unclear. Objective: To explore the possible regulatory networks linking ACT to T2D and AD. Materials and Methods: A bibliographic search was carried out in PubMed, Med-line, Open-i, ScienceDirect, Scopus and SpringerLink for data indicating or suggesting association among T2D, AD, and ACT. Searched terms like “alpha-1-antichymotrypsin”, “type 2 diabetes”, “Alzheimer's disease”, “oxidative stress”, “pro-inflammatory mediators” among others were used. Moreover, common therapeutic strategies between T2D and AD as well as the use of ACT as a therapeutic target for both diseases were included. Results: ACT has been linked with development and maintenance of T2D and AD and studies suggest their participation through activation of inflammatory pathways and oxidative stress, mechanisms also associated with both diseases. Likewise, evidences indicate that diverse therapeutic approaches are common to both diseases. Conclusion: Inflammatory and oxidative stresses constitute a crossroad for T2D and AD where ACT could play an important role. In-depth research on ACT involvement in these two dysfunctions could generate new therapeutic strategies for T2D and AD.

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