scholarly journals Transient assembly of F-actin on the outer mitochondrial membrane contributes to mitochondrial fission

2014 ◽  
Vol 208 (1) ◽  
pp. 109-123 ◽  
Author(s):  
Sunan Li ◽  
Shan Xu ◽  
Brian A. Roelofs ◽  
Liron Boyman ◽  
W. Jonathan Lederer ◽  
...  
Keyword(s):  
De Novo ◽  
Mitochondrial Fission ◽  
Regulatory Proteins ◽  
Actin Assembly ◽  
Membrane Remodeling ◽  
Mitochondrial Fragmentation ◽  
Down Regulation ◽  
Dynamic Assembly ◽  
Actin Regulatory Proteins ◽  
Underlying Mechanisms

In addition to established membrane remodeling roles in various cellular locations, actin has recently emerged as a participant in mitochondrial fission. However, the underlying mechanisms of its participation remain largely unknown. We report that transient de novo F-actin assembly on the mitochondria occurs upon induction of mitochondrial fission and F-actin accumulates on the mitochondria without forming detectable submitochondrial foci. Impairing mitochondrial division through Drp1 knockout or inhibition prolonged the time of mitochondrial accumulation of F-actin and also led to abnormal mitochondrial accumulation of the actin regulatory factors cortactin, cofilin, and Arp2/3 complexes, suggesting that disassembly of mitochondrial F-actin depends on Drp1 activity. Furthermore, down-regulation of actin regulatory proteins led to elongation of mitochondria, associated with mitochondrial accumulation of Drp1. In addition, depletion of cortactin inhibited Mfn2 down-regulation– or FCCP-induced mitochondrial fragmentation. These data indicate that the dynamic assembly and disassembly of F-actin on the mitochondria participates in Drp1-mediated mitochondrial fission.

scholarly journals Roles of the Mammalian Mitochondrial Fission and Fusion Mediators Fis1, Drp1, and Opa1 in Apoptosis

2004 ◽  
Vol 15 (11) ◽  
pp. 5001-5011 ◽  
Author(s):  
Yang-ja Lee ◽  
Seon-Yong Jeong ◽  
Mariusz Karbowski ◽  
Carolyn L. Smith ◽  
Richard J. Youle
Keyword(s):  
Mammalian Cells ◽  
Mitochondrial Fission ◽  
Mitochondrial Morphology ◽  
Apoptosis Induction ◽  
Wild Type ◽  
Mitochondrial Fragmentation ◽  
Down Regulation ◽  
Multiple Components ◽  
Mitochondrial Morphogenesis ◽  
Short Hairpin Rnas

During apoptosis, the mitochondrial network fragments. Using short hairpin RNAs for RNA interference, we manipulated the expression levels of the proteins hFis1, Drp1, and Opa1 that are involved in mitochondrial fission and fusion in mammalian cells, and we characterized their functions in mitochondrial morphology and apoptosis. Down-regulation of hFis1 powerfully inhibits cell death to an extent significantly greater than down-regulation of Drp1 and at a stage of apoptosis distinct from that induced by Drp1 inhibition. Cells depleted of Opa1 are extremely sensitive to exogenous apoptosis induction, and some die spontaneously by a process that requires hFis1 expression. Wild-type Opa1 may function normally as an antiapoptotic protein, keeping spontaneous apoptosis in check. However, if hFis1 is down-regulated, cells do not require Opa1 to prevent apoptosis, suggesting that Opa1 may be normally counteracting the proapoptotic action of hFis1. We also demonstrate in this study that mitochondrial fragmentation per se does not result in apoptosis. However, we provide further evidence that multiple components of the mitochondrial morphogenesis machinery can positively and negatively regulate apoptosis.

The XBP1-MARCH5-MFN2 Axis Confers ER Stress Resistance by Coordinating Mitochondrial Fission and Mitophagy in Melanoma

2020 ◽  
Author(s):  
Huina Wang ◽  
Xiuli Yi ◽  
Sen Guo ◽  
Sijia Wang ◽  
Jinyuan Ma ◽  
...  
Keyword(s):  
Er Stress ◽  
Stress Resistance ◽  
Mitochondrial Fission ◽  
Melanoma Cells ◽  
Stress Sensitivity ◽  
Mitochondrial Genes ◽  
Down Regulation ◽  
Underlying Mechanisms

Abstract Background: Melanoma cells are relatively resistant to ER stress, which contributes to tumor progression under stressful conditions and renders tolerance to ER stress-inducing therapeutic agents. Mitochondria are tightly interconnected with ER. However, whether mitochondria play a role in regulating ER stress resistance in melanoma remains elusive.Methods: Integrative bioinformatics was employed to figure out the implication of mitochondria in the resistance of melanoma cells to ER stress. A panel of biochemical assays and pre-clinical xenograft mouse model were used to investigate the role of mitochondrial fission and mitophagy in affecting ER stress sensitivity and the underlying mechanisms. Results: Our integrative bioinformatics analysis revealed that the down-regulation of mitochondrial genes was highly correlated with UPR activation in melanoma. Then we proved that mitochondrial fission and mitophagy were prominently induced in melanoma cells upon ER stress. Pharmacological inhibition of either mitochondrial fission or mitophagy effectively restored the sensitivity of melanoma cells to ER stress both in vitro and in vivo. Mechanistically, the down-regulation of MFN2 was essential for rendering the resistance by promoting mitochondrial fission and mitophagy. XBP1-mediated transcriptional up-regulation of E3 ligase MARCH5 contributed to the ubiquitination and degradation of MFN2 in ER stress-resistant cells, whereas the impaired transduction of this axis indicated the fragile to ER stress. Finally, the relationships among UPR pathway molecules, MARCH5 and mitochondrial genes were confirmed in both publicly accessible databases and tumor specimens.Conclusions: Together, our findings demonstrate a novel regulatory axis that links mitochondrial fission and mitophagy to the resistance to ER stress. Targeting mitochondrial quality control machinery can be exploited as an approach to reinforce the efficacy of ER stress-inducing agents against cancer.

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

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.

Osmotic stress-induced remodeling of the cortical cytoskeleton

2002 ◽  
Vol 283 (3) ◽  
pp. C850-C865 ◽  
Author(s):  
Caterina Di Ciano ◽  
Zilin Nie ◽  
Katalin Szászi ◽  
Alison Lewis ◽  
Takehito Uruno ◽  
...  
Keyword(s):  
Osmotic Stress ◽  
De Novo ◽  
Small Gtpases ◽  
Dominant Negative ◽  
Actin Binding ◽  
Cell Cortex ◽  
Actin Assembly ◽  
Signaling Mechanism ◽  
Actin Binding Domain ◽  
Cytoskeleton Remodeling

Osmotic stress is known to affect the cytoskeleton; however, this adaptive response has remained poorly characterized, and the underlying signaling pathways are unexplored. Here we show that hypertonicity induces submembranous de novo F-actin assembly concomitant with the peripheral translocation and colocalization of cortactin and the actin-related protein 2/3 (Arp2/3) complex, which are key components of the actin nucleation machinery. Additionally, hyperosmolarity promotes the association of cortactin with Arp2/3 as revealed by coimmunoprecipitation. Using various truncation or phosphorylation-incompetent mutants, we show that cortactin translocation requires the Arp2/3- or the F-actin binding domain, but the process is independent of the shrinkage-induced tyrosine phosphorylation of cortactin. Looking for an alternative signaling mechanism, we found that hypertonicity stimulates Rac and Cdc42. This appears to be a key event in the osmotically triggered cytoskeletal reorganization, because 1) constitutively active small GTPases translocate cortactin, 2) Rac and cortactin colocalize at the periphery of hypertonically challenged cells, and 3) dominant-negative Rac and Cdc42 inhibit the hypertonicity-provoked cortactin and Arp3 translocation. The Rho family-dependent cytoskeleton remodeling may be an important osmoprotective response that reinforces the cell cortex.

A De Novo Dominant Negative Mutation in DNM1L Causes Sudden Onset Status Epilepticus with Subsequent Epileptic Encephalopathy

2019 ◽  
Vol 50 (03) ◽  
pp. 197-201
Author(s):  
S. Schmid ◽  
M. Wagner ◽  
C. Goetz ◽  
C. Makowski ◽  
P. Freisinger ◽  
...  
Keyword(s):  
Status Epilepticus ◽  
Missense Mutation ◽  
De Novo ◽  
Mitochondrial Fission ◽  
Refractory Status Epilepticus ◽  
Sudden Onset ◽  
Epileptic Encephalopathy ◽  
Neurologic Outcome ◽  
Dominant Negative Mutation ◽  
Refractory Status

AbstractMitochondrial dynamics such as fission and fusion play a vital role in normal brain development and neuronal activity. DNM1L encodes a dynamin-related protein 1 (Drp1), which is a GTPase essential for proper mitochondrial fission. The clinical phenotype of DNM1L mutations depends on the degree of mitochondrial fission deficiency, ranging from severe encephalopathy and death shortly after birth to initially normal development and then sudden onset of refractory status epilepticus with very poor neurologic outcome. We describe a case of a previously healthy 3-year-old boy with a mild delay in speech development until the acute onset of a refractory status epilepticus with subsequent epileptic encephalopathy and very poor neurologic outcome. The de novo missense mutation in DNM1L (c.1207C > T, p.R403C), which we identified in this case, seems to determine a unique clinical course, strikingly similar to four previously described patients in literature with the identical de novo heterozygous missense mutation in DNM1L.

scholarly journals The role of VPS4 in ESCRT-III polymer remodeling

2019 ◽  
Vol 47 (1) ◽  
pp. 441-448 ◽  
Author(s):  
Christophe Caillat ◽  
Sourav Maity ◽  
Nolwenn Miguet ◽  
Wouter H. Roos ◽  
Winfried Weissenhorn
Keyword(s):  
Active Role ◽  
Mechanistic Models ◽  
Membrane Remodeling ◽  
Filament Formation ◽  
Enveloped Viruses ◽  
Endosomal Sorting ◽  
Membrane Fission ◽  
Dynamic Assembly ◽  
Inside Out

Abstract The endosomal sorting complex required for transport-III (ESCRT-III) and VPS4 catalyze a variety of membrane-remodeling processes in eukaryotes and archaea. Common to these processes is the dynamic recruitment of ESCRT-III proteins from the cytosol to the inner face of a membrane neck structure, their activation and filament formation inside or at the membrane neck and the subsequent or concomitant recruitment of the AAA-type ATPase VPS4. The dynamic assembly of ESCRT-III filaments and VPS4 on cellular membranes induces constriction of membrane necks with large diameters such as the cytokinetic midbody and necks with small diameters such as those of intraluminal vesicles or enveloped viruses. The two processes seem to use different sets of ESCRT-III filaments. Constriction is then thought to set the stage for membrane fission. Here, we review recent progress in understanding the structural transitions of ESCRT-III proteins required for filament formation, the functional role of VPS4 in dynamic ESCRT-III assembly and its active role in filament constriction. The recent data will be discussed in the context of different mechanistic models for inside-out membrane fission.

scholarly journals Dual modulation of Ras-Mnk and PI3K-AKT-mTOR pathways: A Novel c-FLIP inhibitory mechanism of 3-AWA mediated translational attenuation through dephosphorylation of eIF4E

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Reyaz ur Rasool ◽  
Bilal Rah ◽  
Hina Amin ◽  
Debasis Nayak ◽  
Souneek Chakraborty ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Cell Cycle Progression ◽  
De Novo ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Apoptosis Resistance ◽  
Nih3t3 Cells ◽  
Eukaryotic Translation ◽  
Underlying Mechanisms

Abstract The eukaryotic translation initiation factor 4E (eIF4E) is considered as a key survival protein involved in cell cycle progression, transformation and apoptosis resistance. Herein, we demonstrate that medicinal plant derivative 3-AWA (from Withaferin A) suppressed the proliferation and metastasis of CaP cells through abrogation of eIF4E activation and expression via c-FLIP dependent mechanism. This translational attenuation prevents the de novo synthesis of major players of metastatic cascades viz. c-FLIP, c-Myc and cyclin D1. Moreover, the suppression of c-FLIP due to inhibition of translation initiation complex by 3-AWA enhanced FAS trafficking, BID and caspase 8 cleavage. Further ectopically restored c-Myc and GFP-HRas mediated activation of eIF4E was reduced by 3-AWA in transformed NIH3T3 cells. Detailed underlying mechanisms revealed that 3-AWA inhibited Ras-Mnk and PI3-AKT-mTOR, two major pathways through which eIF4E converges upon eIF4F hub. In addition to in vitro studies, we confirmed that 3-AWA efficiently suppressed tumor growth and metastasis in different mouse models. Given that 3-AWA inhibits c-FLIP through abrogation of translation initiation by co-targeting mTOR and Mnk-eIF4E, it (3-AWA) can be exploited as a lead pharmacophore for promising anti-cancer therapeutic development.

Abstract 431: Mitochondrial Fission in the Heart is an Adaptation to Increased Energetic Demands: The Role of Physiologic Fragmentation

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Michael Coronado ◽  
Giovanni Fajardo ◽  
Kim Nguyen ◽  
Mingming Zhao ◽  
Kristina Bezold Kooiker ◽  
...  
Keyword(s):  
Cell Death ◽  
Exercise Capacity ◽  
Mitochondrial Function ◽  
Adrenergic Receptor ◽  
Mitochondrial Fission ◽  
Physiological Adaptation ◽  
Mitochondrial Fragmentation ◽  
Energetic Demand ◽  
Adaptation To Exercise

Mitochondria play a dual role in the heart, responsible for meeting energetic demands and regulating cell death. Current paradigms hold that mitochondrial fission and fragmentation are the result of pathologic stresses such as ischemia, are an indicator of poor mitochondrial health, and lead to mitophagy and cell death. However, recent studies demonstrate that inhibiting fission also results in cardiac impairment, suggesting that fission is important for maintaining normal mitochondrial function. In this study, we identify a novel role for mitochondrial fragmentation as a normal physiological adaptation to increased energetic demand. Using two models of exercise, we demonstrate that “physiologic” mitochondrial fragmentation occurs, results in enhanced mitochondrial function, and is mediated through beta 1-adrenergic receptor signaling. Similar to pathologic fragmentation, physiologic fragmentation is induced by activation of Drp1; however, unlike pathologic fragmentation, membrane potential is maintained and regulators of mitophagy are downregulated. To confirm the role of fragmentation as a physiological adaptation to exercise, we inhibited the pro-fission mediator Drp1 in mice using the peptide inhibitor P110 and had mice undergo exercise. Mice treated with P110 had significantly decreased exercise capacity, decreased fragmentation and inactive Drp1 vs controls. To further confirm these findings, we generated cardiac-specific Drp1 KO mice and had them undergo exercise. Mice with cardiac specific Drp1 KO had significantly decreased exercise capacity and abnormally large mitochondria compared to controls. These findings indicate the requirement for physiological mitochondrial fragmentation to meet the energetic demands of exercise and support the still evolving conceptual framework, where fragmentation plays a role in the balance between mitochondrial maintenance of normal physiology and response to disease.

LncRNA Prostate Cancer Gene Expression Marker 1 (PCGEM1) Down-Regulation Inhibits the Development of Osteoarthritis by Modulating miR-152-3p

2022 ◽  
Vol 12 (2) ◽  
pp. 306-315
Author(s):  
Jie Song ◽  
Cheng Chen ◽  
Hui Zhang
Keyword(s):  
Cell Model ◽  
Luciferase Reporter ◽  
Down Regulation ◽  
Protein Levels ◽  
Diphenyltetrazolium Bromide ◽  
Proliferation And Apoptosis ◽  
Underlying Mechanisms ◽  
Commercial Kits ◽  
Related Proteins

Osteoarthritis (OA) is a chronic and inflammatory disease, leading to pain or even disability in severe cases. LncRNA PCGEM1 (PCGEM1) is reported to be dysregulated, serving as critical regulators in various human diseases, including OA. However, the biological role of PCGEM1 and its underlying mechanisms during OA remained unclear. In the present study, CHON-001 cells were exposed to interleukin (IL)-1β to construct the OA cell model. Expression of PCGEM1 and miR-152-3p in cells was determined by quantitative real-time polymerase chain reaction (qRT-PCR) assay. Corresponding commercial kits were used to measure the expressions of lactate dehydrogenase (LDH), inter-leukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α. Protein levels of apoptosis-related proteins, cleaved-Caspase3 and Caspase3, were detected by Western blotting. 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) tetrazolium (MTT) and flow cytometry assays were utilized for the determination of cell proliferation and apoptosis. The association between PCGEN1 and miR-152-3p was confirmed by a dual-luciferase reporter assay. From the results, PCGEM1 expression was significantly increased while miR-152-3p was inhibited in CHON-001 cells after IL-1β treatment. In addition, silencing of PCGEM1 could promote proliferation, inhibit the apoptosis, suppress LDH level and alleviate inflammation response caused by IL-1β in CHON-001 cells by sponging miR-152-3p. In a word, PCGEM1 down-regulation suppressed OA progression by the regulation of miR-152-3p expression, functioning as a potential therapeutic target for OA clinical treatment.

scholarly journals Gene-specific mechanisms direct glucocorticoid-receptor-driven repression of inflammatory response genes in macrophages

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Maria A Sacta ◽  
Bowranigan Tharmalingam ◽  
Maddalena Coppo ◽  
David A Rollins ◽  
Dinesh K Deochand ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Binding Sites ◽  
De Novo ◽  
Elongation Factor ◽  
Myeloid Cell ◽  
Genome Wide Analysis ◽  
Genome Wide ◽  
Mouse Macrophages ◽  
Underlying Mechanisms ◽  
Temporal Events

The glucocorticoid receptor (GR) potently represses macrophage-elicited inflammation, however, the underlying mechanisms remain obscure. Our genome-wide analysis in mouse macrophages reveals that pro-inflammatory paused genes, activated via global negative elongation factor (NELF) dissociation and RNA Polymerase (Pol)2 release from early elongation arrest, and non-paused genes, induced by de novo Pol2 recruitment, are equally susceptible to acute glucocorticoid repression. Moreover, in both cases the dominant mechanism involves rapid GR tethering to p65 at NF-kB-binding sites. Yet, specifically at paused genes, GR activation triggers widespread promoter accumulation of NELF, with myeloid cell-specific NELF deletion conferring glucocorticoid resistance. Conversely, at non-paused genes, GR attenuates the recruitment of p300 and histone acetylation, leading to a failure to assemble BRD4 and Mediator at promoters and enhancers, ultimately blocking Pol2 initiation. Thus, GR displays no preference for a specific pro-inflammatory gene class; however, it effects repression by targeting distinct temporal events and components of transcriptional machinery.

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