Neuronal mitochondrial dynamics coordinate systemic mitochondrial morphology and stress response to confer pathogen resistance in C. elegans

Women′s reproductive cessation is the earliest sign of human aging and is caused by decreasing oocyte quality. Similarly, C. elegans′ reproduction declines with age and is caused by oocyte quality decline. Aberrant mitochondrial dynamics are a hallmark of age-related dysfunction, but the role of mitochondrial morphology in reproductive aging is largely unknown. We examined the requirements for mitochondrial fusion and fission in oocytes of both wild-type worms and the long-lived, long-reproducing insulin-like receptor mutant daf-2. We find that normal reproduction requires both fusion and fission. By contrast, daf-2 mutants require fission, but not fusion, for reproductive span extension. daf-2 mutant oocytes′ mitochondria are punctate (fissioned) and may be primed for mitophagy, as loss of the mitophagy regulator PINK-1 shortens daf-2′s reproductive span. Our data suggest that daf-2 maintain oocyte mitochondria quality with age via a shift toward punctate mitochondrial morphology and mitophagy to extend reproductive longevity.

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Identification of Novel Therapeutic Targets for Polyglutamine Diseases That Target Mitochondrial Fragmentation

International Journal of Molecular Sciences ◽

10.3390/ijms222413447 ◽

2021 ◽

Vol 22 (24) ◽

pp. 13447

Author(s):

Annika Traa ◽

Emily Machiela ◽

Paige D. Rudich ◽

Sonja K. Soo ◽

Megan M. Senchuk ◽

...

Keyword(s):

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Cag Repeat ◽

Mitochondrial Morphology ◽

Polyglutamine Diseases ◽

Mitochondrial Fragmentation ◽

C Elegans ◽

Beneficial Effects ◽

Negative Side Effects ◽

And Function

Huntington’s disease (HD) is one of at least nine polyglutamine diseases caused by a trinucleotide CAG repeat expansion, all of which lead to age-onset neurodegeneration. Mitochondrial dynamics and function are disrupted in HD and other polyglutamine diseases. While multiple studies have found beneficial effects from decreasing mitochondrial fragmentation in HD models by disrupting the mitochondrial fission protein DRP1, disrupting DRP1 can also have detrimental consequences in wild-type animals and HD models. In this work, we examine the effect of decreasing mitochondrial fragmentation in a neuronal C. elegans model of polyglutamine toxicity called Neur-67Q. We find that Neur-67Q worms exhibit mitochondrial fragmentation in GABAergic neurons and decreased mitochondrial function. Disruption of drp-1 eliminates differences in mitochondrial morphology and rescues deficits in both movement and longevity in Neur-67Q worms. In testing twenty-four RNA interference (RNAi) clones that decrease mitochondrial fragmentation, we identified eleven clones—each targeting a different gene—that increase movement and extend lifespan in Neur-67Q worms. Overall, we show that decreasing mitochondrial fragmentation may be an effective approach to treating polyglutamine diseases and we identify multiple novel genetic targets that circumvent the potential negative side effects of disrupting the primary mitochondrial fission gene drp-1.

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Overexpression of Activated AMPK in the Anopheles stephensi Midgut Impacts Mosquito Metabolism, Reproduction and Plasmodium Resistance

Genes ◽

10.3390/genes12010119 ◽

2021 ◽

Vol 12 (1) ◽

pp. 119

Author(s):

Chioma Oringanje ◽

Lillian R. Delacruz ◽

Yunan Han ◽

Shirley Luckhart ◽

Michael A. Riehle

Keyword(s):

Egg Production ◽

Anopheles Stephensi ◽

Mitochondrial Dynamics ◽

Adult Life ◽

Blood Feeding ◽

Pathogen Resistance ◽

Α Subunit ◽

Significant Difference ◽

Transgenic Lines ◽

Ampk Activity

Mitochondrial integrity and homeostasis in the midgut are key factors controlling mosquito fitness and anti-pathogen resistance. Targeting genes that regulate mitochondrial dynamics represents a potential strategy for limiting mosquito-borne diseases. AMP-activated protein kinase (AMPK) is a key cellular energy sensor found in nearly all eukaryotic cells. When activated, AMPK inhibits anabolic pathways that consume ATP and activates catabolic processes that synthesize ATP. In this study, we overexpressed a truncated and constitutively active α-subunit of AMPK under the control of the midgut-specific carboxypeptidase promotor in the midgut of female Anopheles stephensi. As expected, AMPK overexpression in homozygous transgenic mosquitoes was associated with changes in nutrient storage and metabolism, decreasing glycogen levels at 24 h post-blood feeding when transgene expression was maximal, and concurrently increasing circulating trehalose at the same time point. When transgenic lines were challenged with Plasmodium falciparum, we observed a significant decrease in the prevalence and intensity of infection relative to wild type controls. Surprisingly, we did not observe a significant difference in the survival of adult mosquitoes fed either sugar only or both sugar and bloodmeals throughout adult life. This may be due to the limited period that the transgene was activated before homeostasis was restored. However, we did observe a significant decrease in egg production, suggesting that manipulation of AMPK activity in the mosquito midgut resulted in the re-allocation of resources away from egg production. In summary, this work identifies midgut AMPK activity as an important regulator of metabolism, reproduction, and innate immunity in An. stephensi, a highly invasive and important malaria vector species.

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Machine learning-based classification of mitochondrial morphology in primary neurons and brain

Scientific Reports ◽

10.1038/s41598-021-84528-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Garrett M. Fogo ◽

Anthony R. Anzell ◽

Kathleen J. Maheras ◽

Sarita Raghunayakula ◽

Joseph M. Wider ◽

...

Keyword(s):

Image Analysis ◽

Cortical Neurons ◽

Mitochondrial Dynamics ◽

Automated Image Analysis ◽

Mitochondrial Morphology ◽

Analysis Pipeline ◽

Genetic Ablation ◽

Block Face

AbstractThe mitochondrial network continually undergoes events of fission and fusion. Under physiologic conditions, the network is in equilibrium and is characterized by the presence of both elongated and punctate mitochondria. However, this balanced, homeostatic mitochondrial profile can change morphologic distribution in response to various stressors. Therefore, it is imperative to develop a method that robustly measures mitochondrial morphology with high accuracy. Here, we developed a semi-automated image analysis pipeline for the quantitation of mitochondrial morphology for both in vitro and in vivo applications. The image analysis pipeline was generated and validated utilizing images of primary cortical neurons from transgenic mice, allowing genetic ablation of key components of mitochondrial dynamics. This analysis pipeline was further extended to evaluate mitochondrial morphology in vivo through immunolabeling of brain sections as well as serial block-face scanning electron microscopy. These data demonstrate a highly specific and sensitive method that accurately classifies distinct physiological and pathological mitochondrial morphologies. Furthermore, this workflow employs the use of readily available, free open-source software designed for high throughput image processing, segmentation, and analysis that is customizable to various biological models.

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Mitochondrial fission and mitophagy are independent mechanisms regulating ischemia/reperfusion injury in primary neurons

Cell Death and Disease ◽

10.1038/s41419-021-03752-2 ◽

2021 ◽

Vol 12 (5) ◽

Author(s):

Anthony R. Anzell ◽

Garrett M. Fogo ◽

Zoya Gurm ◽

Sarita Raghunayakula ◽

Joseph M. Wider ◽

...

Keyword(s):

Cortical Neurons ◽

Ischemia Reperfusion Injury ◽

Mitochondrial Dynamics ◽

Ischemia Reperfusion ◽

Mitochondrial Fission ◽

Conditional Knockout ◽

Mitochondrial Morphology ◽

Primary Neurons ◽

Mitochondrial Fragmentation

AbstractMitochondrial dynamics and mitophagy are constitutive and complex systems that ensure a healthy mitochondrial network through the segregation and subsequent degradation of damaged mitochondria. Disruption of these systems can lead to mitochondrial dysfunction and has been established as a central mechanism of ischemia/reperfusion (I/R) injury. Emerging evidence suggests that mitochondrial dynamics and mitophagy are integrated systems; however, the role of this relationship in the context of I/R injury remains unclear. To investigate this concept, we utilized primary cortical neurons isolated from the novel dual-reporter mitochondrial quality control knockin mice (C57BL/6-Gt(ROSA)26Sortm1(CAG-mCherry/GFP)Ganl/J) with conditional knockout (KO) of Drp1 to investigate changes in mitochondrial dynamics and mitophagic flux during in vitro I/R injury. Mitochondrial dynamics was quantitatively measured in an unbiased manner using a machine learning mitochondrial morphology classification system, which consisted of four different classifications: network, unbranched, swollen, and punctate. Evaluation of mitochondrial morphology and mitophagic flux in primary neurons exposed to oxygen-glucose deprivation (OGD) and reoxygenation (OGD/R) revealed extensive mitochondrial fragmentation and swelling, together with a significant upregulation in mitophagic flux. Furthermore, the primary morphology of mitochondria undergoing mitophagy was classified as punctate. Colocalization using immunofluorescence as well as western blot analysis revealed that the PINK1/Parkin pathway of mitophagy was activated following OGD/R. Conditional KO of Drp1 prevented mitochondrial fragmentation and swelling following OGD/R but did not alter mitophagic flux. These data provide novel evidence that Drp1 plays a causal role in the progression of I/R injury, but mitophagy does not require Drp1-mediated mitochondrial fission.

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When the Balance Tips: Dysregulation of Mitochondrial Dynamics as a Culprit in Disease

International Journal of Molecular Sciences ◽

10.3390/ijms22094617 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4617

Author(s):

Styliana Kyriakoudi ◽

Anthi Drousiotou ◽

Petros P. Petrou

Keyword(s):

Insulin Resistance ◽

Mitochondrial Function ◽

Human Disease ◽

Molecular Mechanisms ◽

Mitochondrial Dynamics ◽

Mitochondrial Fusion ◽

Mitochondrial Morphology ◽

Disease Development ◽

Pathological Conditions ◽

Wide Range

Mitochondria are dynamic organelles, the morphology of which is tightly linked to their functions. The interplay between the coordinated events of fusion and fission that are collectively described as mitochondrial dynamics regulates mitochondrial morphology and adjusts mitochondrial function. Over the last few years, accruing evidence established a connection between dysregulated mitochondrial dynamics and disease development and progression. Defects in key components of the machinery mediating mitochondrial fusion and fission have been linked to a wide range of pathological conditions, such as insulin resistance and obesity, neurodegenerative diseases and cancer. Here, we provide an update on the molecular mechanisms promoting mitochondrial fusion and fission in mammals and discuss the emerging association of disturbed mitochondrial dynamics with human disease.

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Nanoscopic quantification of sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells derived from patients with mitochondrial diseases

Journal of Nanobiotechnology ◽

10.1186/s12951-021-00882-9 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Weiwei Zou ◽

Qixin Chen ◽

Jesse Slone ◽

Li Yang ◽

Xiaoting Lou ◽

...

Keyword(s):

Oxidative Phosphorylation ◽

Optic Atrophy ◽

Respiratory Function ◽

Clinical Symptoms ◽

Mitochondrial Dynamics ◽

Cerebellar Atrophy ◽

Mitochondrial Diseases ◽

Living Cells ◽

Mitochondrial Morphology ◽

Mitochondrial Oxidative Phosphorylation

AbstractSLC25A46 mutations have been found to lead to mitochondrial hyper-fusion and reduced mitochondrial respiratory function, which results in optic atrophy, cerebellar atrophy, and other clinical symptoms of mitochondrial disease. However, it is generally believed that mitochondrial fusion is attributable to increased mitochondrial oxidative phosphorylation (OXPHOS), which is inconsistent with the decreased OXPHOS of highly-fused mitochondria observed in previous studies. In this paper, we have used the live-cell nanoscope to observe and quantify the structure of mitochondrial cristae, and the behavior of mitochondria and lysosomes in patient-derived SLC25A46 mutant fibroblasts. The results show that the cristae have been markedly damaged in the mutant fibroblasts, but there is no corresponding increase in mitophagy. This study suggests that severely damaged mitochondrial cristae might be the predominant cause of reduced OXPHOS in SLC25A46 mutant fibroblasts. This study demonstrates the utility of nanoscope-based imaging for realizing the sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells, which may be particularly valuable for the quick evaluation of pathogenesis of mitochondrial morphological abnormalities.

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C. elegans discriminates colors to guide foraging

Science ◽

10.1126/science.abd3010 ◽

2021 ◽

Vol 371 (6533) ◽

pp. 1059-1063 ◽

Cited By ~ 1

Author(s):

D. Dipon Ghosh ◽

Dongyeop Lee ◽

Xin Jin ◽

H. Robert Horvitz ◽

Michael N. Nitabach

Keyword(s):

Stress Response ◽

Cellular Stress ◽

Color Discrimination ◽

Cellular Stress Response ◽

Blue Pigment ◽

Natural Environments ◽

C Elegans ◽

Evolutionarily Conserved ◽

Foraging Decisions ◽

Light Guides

Color detection is used by animals of diverse phyla to navigate colorful natural environments and is thought to require evolutionarily conserved opsin photoreceptor genes. We report that Caenorhabditis elegans roundworms can discriminate between colors despite the fact that they lack eyes and opsins. Specifically, we found that white light guides C. elegans foraging decisions away from a blue-pigment toxin secreted by harmful bacteria. These foraging decisions are guided by specific blue-to-amber ratios of light. The color specificity of color-dependent foraging varies notably among wild C. elegans strains, which indicates that color discrimination is ecologically important. We identified two evolutionarily conserved cellular stress response genes required for opsin-independent, color-dependent foraging by C. elegans, and we speculate that cellular stress response pathways can mediate spectral discrimination by photosensitive cells and organisms—even by those lacking opsins.

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High glucose induces Drp1-mediated mitochondrial fission via the Orai1 calcium channel to participate in diabetic cardiomyocyte hypertrophy

Cell Death and Disease ◽

10.1038/s41419-021-03502-4 ◽

2021 ◽

Vol 12 (2) ◽

Author(s):

Qing-Rui Wu ◽

Dan-Lin Zheng ◽

Pei-Ming Liu ◽

Hui Yang ◽

Lu-An Li ◽

...

Keyword(s):

Calcium Channel ◽

Mitochondrial Dysfunction ◽

High Glucose ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Calcium Handling ◽

Cardiomyocyte Hypertrophy ◽

Mitochondrial Morphology ◽

Calmodulin Binding ◽

Downstream Target

AbstractMitochondrial dysfunction and impaired Ca2+ handling are involved in the development of diabetic cardiomyopathy (DCM). Dynamic relative protein 1 (Drp1) regulates mitochondrial fission by changing its level of phosphorylation, and the Orai1 (Ca2+ release-activated calcium channel protein 1) calcium channel is important for the increase in Ca2+ entry into cardiomyocytes. We aimed to explore the mechanism of Drp1 and Orai1 in cardiomyocyte hypertrophy caused by high glucose (HG). We found that Zucker diabetic fat rats induced by administration of a high-fat diet develop cardiac hypertrophy and impaired cardiac function, accompanied by the activation of mitochondrial dynamics and calcium handling pathway-related proteins. Moreover, HG induces cardiomyocyte hypertrophy, accompanied by abnormal mitochondrial morphology and function, and increased Orai1-mediated Ca2+ influx. Mechanistically, the Drp1 inhibitor mitochondrial division inhibitor 1 (Mdivi-1) prevents cardiomyocyte hypertrophy induced by HG by reducing phosphorylation of Drp1 at serine 616 (S616) and increasing phosphorylation at S637. Inhibition of Orai1 with single guide RNA (sgOrai1) or an inhibitor (BTP2) not only suppressed Drp1 activity and calmodulin-binding catalytic subunit A (CnA) and phosphorylated-extracellular signal-regulated kinase (p-ERK1/2) expression but also alleviated mitochondrial dysfunction and cardiomyocyte hypertrophy caused by HG. In addition, the CnA inhibitor cyclosporin A and p-ERK1/2 inhibitor U0126 improved HG-induced cardiomyocyte hypertrophy by promoting and inhibiting phosphorylation of Drp1 at S637 and S616, respectively. In summary, we identified Drp1 as a downstream target of Orai1-mediated Ca2+ entry, via activation by p-ERK1/2-mediated phosphorylation at S616 or CnA-mediated dephosphorylation at S637 in DCM. Thus, the Orai1–Drp1 axis is a novel target for treating DCM.

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The Role of Intestinal Fatty Acid Binding Proteins in Protecting Cells from Fatty Acid Induced Impairment of Mitochondrial Dynamics and Apoptosis

Cellular Physiology and Biochemistry ◽

10.1159/000495672 ◽

2018 ◽

Vol 51 (4) ◽

pp. 1658-1678 ◽

Cited By ~ 3

Author(s):

Suparna Sarkar-Banerjee ◽

Sourav Chowdhury ◽

Dwipanjan Sanyal ◽

Tulika Mitra ◽

Sib Sankar Roy ◽

...

Keyword(s):

Fatty Acid ◽

Binding Proteins ◽

Apoptotic Cell ◽

Mitochondrial Dynamics ◽

Ectopic Expression ◽

Lipid Binding ◽

Confocal Imaging ◽

Fatty Acid Binding Proteins ◽

Mitochondrial Morphology ◽

Fatty Acid Binding

Background/Aims: The conformation, folding and lipid binding properties of the intestinal fatty acid binding proteins (IFABP) have been extensively investigated. In contrast, the functional aspects of these proteins are not understood and matter of debates. In this study, we aim to address the deleterious effects of FA overload on cellular components, particularly mitochondria; and how IFABP helps in combating this stress by restoring the mitochondrial dynamics. Methods: In the present study the functional aspect of IFABP under conditions of lipid stress was studied by a string of extensive in-cell studies; flow cytometry by fluorescence-activated cell sorting (FACS), confocal imaging, western blotting and quantitative real time PCR. We deployed ectopic expression of IFABP in rescuing cells under the condition of lipid stress. Again in order to unveil the mechanistic insights of functional traits, we arrayed extensive computational approaches by means of studying centrality calculations along with protein-protein association and ligand induced cluster dissociation. While addressing its functional importance, we used FCS and in-silico computational analyses, to show the structural distribution and the underlying mechanism of IFABP’s action. Results: Ectopic expression of IFABP in HeLa cells has been found to rescue mitochondrial morphological dynamics and restore membrane potential, partially preventing apoptotic damage induced by the increased FAs. These findings have been further validated in the functionally relevant intestinal Caco-2 cells, where the native expression of IFABP protects mitochondrial morphology from abrogation induced by FA overload. However, this native level expression is insufficient to protect against apoptotic cell death, which is rescued, at least partially in cells overexpressing IFABP. In addition, shRNA mediated IFABP knockdown in Caco-2 cells compromises mitochondrial dynamics and switches on intrinsic apoptotic pathways under FA-induced metabolic stress. Conclusion: To summarize, the present study implicates functional significance of IFABP in controlling ligand-induced damage in mitochondrial dynamics and apoptosis.

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