Abstract 283: SGK1-Dependent Sirt3 Phosphorylation Regulates Mitochondrial Dynamics

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Dallas Ellis ◽  
Takara Scott ◽  
Wei Zhong ◽  
Oguljahan Babayeva ◽  
Sharon C Francis
Keyword(s):  
Molecular Mechanisms ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Ectopic Expression ◽  
Mitochondrial Fragmentation ◽  
Proteomic Screen ◽  
Protein Levels ◽  
Stimulation Of

Mitochondrial dynamics (i.e. fusion and fission) is impaired in models of obesity and can result in target organ dysfunction. However, the mechanisms that regulate mitochondrial dynamics in the setting of obesity are not completely understood. The objectives of this study are to examine a role for and determine the molecular mechanisms of serum and glucocorticoid-inducible kinase 1 (SGK1) in obesity-related mitochondrial dynamics in the vasculature. We recently reported that aortic expression of SGK1 is elevated in a model of diet-induced obesity (DIO) in vivo and by resistin; a fat-derived adipokine, in human aortic smooth muscle cells (SMC) in vitro . To directly examine the effects of SMC-derived SGK1 on mitochondrial dynamics, wildtype and SMC-specific SGK1 knockout mice were subjected to DIO for eight weeks. Our results indicate that SMC-specific deletion of SGK1 induced a fused, elongated mitochondrial phenotype in aortic SMC in vivo and attenuated obesity-mediated arterial mitochondrial fragmentation suggesting a role for SGK1 in stimulation of mitochondrial fission. To determine the molecular mechanism for this effect, we performed a proteomic screen for novel SGK1 substrates and identified the mitochondrial deacetylase SIRT3 as a novel SGK1 target. Mass spectrometry indicates SGK1 phosphorylates SIRT3 on serine103. Increasing doses of resistin augmented SIRT3-S103 phosphorylation and caused a concomitant decrease in total SIRT3 in rat aortic SMC in vitro . To examine whether SGK1-dependent SIRT3 phosphorylation regulates the mitochondrial fission protein machinery; we evaluated total and activated levels of Drp1, the mitochondrial fission regulator, in response to ectopic expression of SIRT3 wildtype, phospho-memetic (S103D) and phospho-deficient (S103A) mutants. SIRT3-S103D increased total Drp1 and activated Drp1 protein levels an effect inhibited by SIRT3-S103A. These findings implicate elevated resistin observed during obesity in stimulation of SGK1 and subsequent phosphorylation of SIRT3 leading to activation of Drp1 and stimulation of arterial mitochondrial fragmentation.

scholarly journals All-Trans Retinoic Acid Increases DRP1 Levels and Promotes Mitochondrial Fission

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1202
Author(s):  
Bojjibabu Chidipi ◽  
Syed Islamuddin Shah ◽  
Michelle Reiser ◽  
Manasa Kanithi ◽  
Amanda Garces ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Mitochondrial Fission ◽  
Normal Function ◽  
Mitochondrial Network ◽  
Protein Levels ◽  
Trans Retinoic Acid ◽  
All Trans Retinoic Acid ◽  
Area And Perimeter

In the heart, mitochondrial homeostasis is critical for sustaining normal function and optimal responses to metabolic and environmental stressors. Mitochondrial fusion and fission are thought to be necessary for maintaining a robust population of mitochondria, and disruptions in mitochondrial fission and/or fusion can lead to cellular dysfunction. The dynamin-related protein (DRP1) is an important mediator of mitochondrial fission. In this study, we investigated the direct effects of the micronutrient retinoid all-trans retinoic acid (ATRA) on the mitochondrial structure in vivo and in vitro using Western blot, confocal, and transmission electron microscopy, as well as mitochondrial network quantification using stochastic modeling. Our results showed that ATRA increases DRP1 protein levels, increases the localization of DRP1 to mitochondria in isolated mitochondrial preparations. Our results also suggested that ATRA remodels the mitochondrial ultrastructure where the mitochondrial area and perimeter were decreased and the circularity was increased. Microscopically, mitochondrial network remodeling is driven by an increased rate of fission over fusion events in ATRA, as suggested by our numerical modeling. In conclusion, ATRA results in a pharmacologically mediated increase in the DRP1 protein. It also results in the modulation of cardiac mitochondria by promoting fission events, altering the mitochondrial network, and modifying the ultrastructure of mitochondria in the heart.

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.

scholarly journals Non-alcoholic fatty liver disease in mice with hepatocyte-specific deletion of mitochondrial fission factor

Diabetologia ◽  
2021 ◽  
Author(s):  
Yukina Takeichi ◽  
Takashi Miyazawa ◽  
Shohei Sakamoto ◽  
Yuki Hanada ◽  
Lixiang Wang ◽  
...  
Keyword(s):  
Er Stress ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Primary Hepatocytes ◽  
Alcoholic Fatty Liver ◽  
Expression Of Genes ◽  
Specific Deletion

Abstract Aims/hypothesis Mitochondria are highly dynamic organelles continuously undergoing fission and fusion, referred to as mitochondrial dynamics, to adapt to nutritional demands. Evidence suggests that impaired mitochondrial dynamics leads to metabolic abnormalities such as non-alcoholic steatohepatitis (NASH) phenotypes. However, how mitochondrial dynamics are involved in the development of NASH is poorly understood. This study aimed to elucidate the role of mitochondrial fission factor (MFF) in the development of NASH. Methods We created mice with hepatocyte-specific deletion of MFF (MffLiKO). MffLiKO mice fed normal chow diet (NCD) or high-fat diet (HFD) were evaluated for metabolic variables and their livers were examined by histological analysis. To elucidate the mechanism of development of NASH, we examined the expression of genes related to endoplasmic reticulum (ER) stress and lipid metabolism, and the secretion of triacylglycerol (TG) using the liver and primary hepatocytes isolated from MffLiKO and control mice. Results MffLiKO mice showed aberrant mitochondrial morphologies with no obvious NASH phenotypes during NCD, while they developed full-blown NASH phenotypes in response to HFD. Expression of genes related to ER stress was markedly upregulated in the liver from MffLiKO mice. In addition, expression of genes related to hepatic TG secretion was downregulated, with reduced hepatic TG secretion in MffLiKO mice in vivo and in primary cultures of MFF-deficient hepatocytes in vitro. Furthermore, thapsigargin-induced ER stress suppressed TG secretion in primary hepatocytes isolated from control mice. Conclusions/interpretation We demonstrated that ablation of MFF in liver provoked ER stress and reduced hepatic TG secretion in vivo and in vitro. Moreover, MffLiKO mice were more susceptible to HFD-induced NASH phenotype than control mice, partly because of ER stress-induced apoptosis of hepatocytes and suppression of TG secretion from hepatocytes. This study provides evidence for the role of mitochondrial fission in the development of NASH. Graphical abstract

scholarly journals Mfn2 Overexpression Attenuates MPTP Neurotoxicity In Vivo

2021 ◽  
Vol 22 (2) ◽  
pp. 601
Author(s):  
Fanpeng Zhao ◽  
Quillan Austria ◽  
Wenzhang Wang ◽  
Xiongwei Zhu
Keyword(s):  
Mitochondrial Dysfunction ◽  
Mitochondrial Dynamics ◽  
Significant Loss ◽  
Critical Event ◽  
Mitochondrial Fragmentation ◽  
Wild Type Littermate ◽  
Littermate Control ◽  
Mptp Administration

Mitochondrial dysfunction represents a critical event in the pathogenesis of Parkinson’s disease (PD). Increasing evidence demonstrates that disturbed mitochondrial dynamics and quality control play an important role in mitochondrial dysfunction in PD. Our previous study demonstrated that MPP+ induces mitochondrial fragmentation in vitro. In this study, we aimed to assess whether blocking MPTP-induced mitochondrial fragmentation by overexpressing Mfn2 affords neuroprotection in vivo. We found that the significant loss of dopaminergic neurons in the substantia nigra (SN) induced by MPTP treatment, as seen in wild-type littermate control mice, was almost completely blocked in mice overexpressing Mfn2 (hMfn2 mice). The dramatic reduction in dopamine neuronal fibers and dopamine levels in the striatum caused by MPTP administration was also partially inhibited in hMfn2 mice. MPTP-induced oxidative stress and inflammatory response in the SN and striatum were significantly alleviated in hMfn2 mice. The impairment of motor function caused by MPTP was also blocked in hMfn2 mice. Overall, our work demonstrates that restoration of mitochondrial dynamics by Mfn2 overexpression protects against neuronal toxicity in an MPTP-based PD mouse model, which supports the modulation of mitochondrial dynamics as a potential therapeutic target for PD treatment.

scholarly journals miR-125b Disrupts Mitochondrial Dynamics via Targeting Mitofusin 1 in Cisplatin-Induced Acute Kidney Injury

2021 ◽  
pp. 1-11
Author(s):  
Yue Zhao ◽  
Yue Lang ◽  
Mingchao Zhang ◽  
Shaoshan Liang ◽  
Xiaodong Zhu ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Molecular Mechanisms ◽  
Mitochondrial Dynamics ◽  
Kidney Injury ◽  
Immunofluorescent Staining ◽  
Luciferase Reporter ◽  
Mitochondrial Fragmentation ◽  
Tubular Cells ◽  
Renal Tubular Cells

<b><i>Background:</i></b> Mitochondria are dynamic organelles whose structure are maintained by continuous fusion and fission. During acute kidney injury (AKI) progression, mitochondrial fission in renal tubular cells was elevated, characterized by mitochondrial fragmentation. It is tightly associated with mitochondrial dysfunction, which has been proven as a critical mechanism responsible for AKI. However, the initiating factor for the disruption of mitochondrial dynamics in AKI was not well understood. <b><i>Objectives:</i></b> To explore the molecular mechanisms of mitochondrial disorders and kidney damage. <b><i>Methods:</i></b> We established cisplatin-induced AKI model in C57BL/6 mice and proximal tubular cells, and detected the expression of miR-125b by qPCR. Then we delivered miR-125b antagomir after cisplatin treatment in mice via hydrodynamic-based gene transfer technique. Subsequently, we performed luciferase reporter and immunoblotting ­assays to prove miR-125b could directly modulate mitofusin1 (MFN1) expression. We also tested the role of miR-125b in mitochondrial and renal injury through immunofluorescent staining, qPCR, and immunoblotting assays. <b><i>Results:</i></b> miR-125b levels were induced in cisplatin-challenged mice and cultured tubular cells. Anti-miR-125b could effectively alleviate cisplatin-induced mitochondrial fragmentation and kidney injury both in vitro and in vivo. Furthermore, miR-125b could directly regulate MFN1, which is a key regulator of mitochondrial fusion. Our study indicated that miR-125b is upregulated during cisplatin-induced AKI. Inhibition of miR-125b may suppress mitochondrial and renal damage through upregulating MFN1. This study suggests that miR-125b could be a potential therapeutic target in AKI.

scholarly journals Linc00426 accelerates lung adenocarcinoma progression by regulating miR-455-5p as a molecular sponge

2020 ◽  
Vol 11 (12) ◽  
Author(s):  
Hongli Li ◽  
Qingjie Mu ◽  
Guoxin Zhang ◽  
Zhixin Shen ◽  
Yuanyuan Zhang ◽  
...  
Keyword(s):  
Lung Adenocarcinoma ◽  
Molecular Mechanisms ◽  
Epithelial Mesenchymal Transition ◽  
Ectopic Expression ◽  
Tumor Development ◽  
Biological Significance ◽  
Mesenchymal Transition

AbstractIncreasing lines of evidence indicate the role of long non-coding RNAs (LncRNAs) in gene regulation and tumor development. Hence, it is important to elucidate the mechanisms of LncRNAs underlying the proliferation, metastasis, and invasion of lung adenocarcinoma (LUAD). We employed microarrays to screen LncRNAs in LUAD tissues with and without lymph node metastasis and revealed their effects on LUAD. Among them, Linc00426 was selected for further exploration in its expression, the biological significance, and the underlying molecular mechanisms. Linc00426 exhibits ectopic expression in LUAD tissues and cells. The ectopic expression has been clinically linked to tumor size, lymphatic metastasis, and tumor differentiation of patients with LUAD. The deregulation of Linc00426 contributes to a notable impairment in proliferation, invasion, metastasis, and epithelial–mesenchymal transition (EMT) in vitro and in vivo. Mechanistically, the deregulation of Linc00426 could reduce cytoskeleton rearrangement and matrix metalloproteinase expression. Meanwhile, decreasing the level of Linc00426 or increasing miR-455-5p could down-regulate the level of UBE2V1. Thus, Linc00426 may act as a competing endogenous RNA (ceRNA) to abate miR-455-5p-dependent UBE2V1 reduction. We conclude that Linc00426 accelerates LUAD progression by acting as a molecular sponge to regulate miR-455-5p, and may be a potential novel tumor marker for LUAD.

scholarly journals PIM Kinases Alter Mitochondrial Dynamics and Chemosensitivity in Lung Cancer

2019 ◽  
Author(s):  
Shailender S. Chauhan ◽  
Rachel K. Toth ◽  
Corbin C. Jensen ◽  
Andrea L. Casillas ◽  
David F. Kashatus ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Mitochondrial Dynamics ◽  
Nsclc Patient ◽  
Mitochondrial Fission ◽  
Inverse Correlation ◽  
Mitochondrial Superoxide ◽  
Pim Kinases ◽  
Response To Chemotherapy

AbstractResistance to chemotherapy represents a major obstacle to the successful treatment of non-small cell lung cancer (NSCLC). The goal of this study was to determine how PIM kinases impact mitochondrial dynamics, ROS production, and response to chemotherapy in lung cancer. Live cell imaging and microscopy were used to determine the effect of PIM loss or inhibition on mitochondrial phenotype and ROS. Inhibition of PIM kinases caused excessive mitochondrial fission and significant upregulation of mitochondrial superoxide, increasing intercellular ROS. Mechanistically, we define a signaling axis linking PIM1 to Drp1 and mitochondrial fission in lung cancer. PIM inhibition significantly increased the protein levels and mitochondrial localization of Drp1, causing marked fragmentation of mitochondria. An inverse correlation between PIM1 and Drp1 was confirmed in NSCLC patient samples. Inhibition of PIM sensitized NSCLC to chemotherapy and produced a synergistic anti-tumor response in vitro and in vivo. Immunohistochemistry and transmission electron microscopy verified that PIM inhibitors promote mitochondrial fission and apoptosis in vivo. These data improve our knowledge about how PIM1 regulates mitochondria and provide justification for combining PIM inhibition with chemotherapy in NSCLC.

scholarly journals Repeated hypoglycemia blunts the responsiveness of glucose-inhibited GHRH neurons by remodeling neural inputs and disrupting mitochondrial structure and function

2019 ◽  
Author(s):  
M Bayne ◽  
A Alvarsson ◽  
K Devarakonda ◽  
R Li ◽  
M Jimenez-Gonzalez ◽  
...  
Keyword(s):  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Glucose Deprivation ◽  
Glucose Sensing ◽  
Diabetic Patients ◽  
Hypoglycemia Unawareness ◽  
Atp Production ◽  
Low Glucose

AbstractHypoglycemia is a frequent complication of diabetes, limiting therapy and increasing morbidity and mortality. With recurrent hypoglycemia, the counter-regulatory response (CRR) to decreased blood glucose is blunted, resulting in hypoglycemia unawareness. The mechanisms leading to these blunted effects remain incompletely understood. Here, we identify, with in situ hybridization, immunohistochemistry and the tissue clearing capability of iDisco, that GHRH neurons represent a unique population of arcuate nucleus neurons activated by glucose deprivation in vivo. Repeated glucose deprivation reduces GHRH neuron activation and remodels excitatory and inhibitory inputs to GHRH neurons. We show low glucose sensing is coupled to GHRH neuron depolarization, decreased ATP production and mitochondrial fusion. Repeated hypoglycemia attenuates these responses during low glucose. By maintaining mitochondrial length with the small molecule, mdivi-1, we preserved hypoglycemia sensitivity in vitro and in vivo. Our findings present possible mechanisms for the blunting of the CRR, broaden significantly our understanding of the structure of GHRH neurons and for the fist time, propose that mitochondrial dynamics play an important role in hypoglycemia unawareness. We conclude that interventions targeting mitochondrial fission in GHRH neurons may offer a new pathway to prevent hypoglycemia unawareness in diabetic patients.

Abstract 568: Deletion of AMP-activated Protein Kinase-alpha Triggers Mitochondrial Fission and Endothelial Dysfunction

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Qqilong Wang ◽  
Zhonglin Xie ◽  
Huaiping Zhu ◽  
Ye Ding ◽  
Ming-Hui Zou
Keyword(s):  
Protein Kinase ◽  
Endothelial Dysfunction ◽  
Molecular Mechanisms ◽  
Kinase Inhibitor ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Chronic Administration ◽  
Mitochondrial Fragmentation ◽  
Aortic Endothelium ◽  
Amp Activated Protein Kinase

Introduction: AMP-activated protein kinase (AMPK) has been reported to regulate mitochondrial biogenesis, function, and turnover. However, the molecular mechanisms by which AMPK regulates mitochondrial dynamics remain poorly characterized. We hypothesized that AMPK deficiency regulates mitochondrial fission that will result in endothelial dysfunction. Methods/Results: Deletion of AMPKα2 resulted in defective autophagy, dynamin-related protein (Drp1) accumulation, and aberrant mitochondrial fragmentation in the aortic endothelium of mice. Furthermore, autophagy inhibition by chloroquine treatment or Atg7 small interfering RNA (siRNA) transfection upregulated Drp1 expression and triggered Drp1-mediated mitochondrial fragmentation. In contrast, autophagy activation by overexpression of Atg7 or chronic administration of rapamycin, the mammalian target of rapamycin kinase inhibitor, promoted Drp1 degradation and attenuated mitochondrial fission in AMPKα2 -/- mice, suggesting that defective autophagy contributes to enhanced Drp1 expression and mitochondrial fragmentation. Interesting, the genetic (Drp1 siRNA) or pharmacological (mdivi-1) inhibition of Drp1 ablated mitochondrial fragmentation in the mouse aortic endothelium and prevented the acetylcholine-induced relaxation of isolated mouse aortas from AMPKα2 -/- mice. This suggests that aberrant Drp1 is responsible for enhanced mitochondrial fission and endothelial dysfunction in AMPKα knockout mice. Conclusions: Our results show that AMPKα deletion promoted mitochondrial fission in vascular endothelial cells by inhibiting the autophagy-dependent degradation of Drp1.

scholarly journals UBAC2 promotes bladder cancer proliferation through BCRC-3/miRNA-182-5p/p27 axis

2020 ◽  
Vol 11 (9) ◽  
Author(s):  
Chaohui Gu ◽  
Keyuan Zhao ◽  
Naichun Zhou ◽  
Feng Liu ◽  
Fei Xie ◽  
...  
Keyword(s):  
Bladder Cancer ◽  
Posttranscriptional Regulation ◽  
Molecular Mechanisms ◽  
Malignant Tumors ◽  
Circular Rna ◽  
Cancer Proliferation ◽  
Lower Survival Rate ◽  
Protein Levels

Abstract Emerging evidences have demonstrated that ubiquitin-associated domain-containing protein 2 (UBAC2) is closely related to the occurrence and development of malignant tumors. However, the functions and underlying molecular mechanisms of UBAC2 in bladder cancer (BC) development have not been defined. In this study, we found that both UBAC2 mRNA and protein levels were upregulated in BC tissues and cell lines, and knockdown of UBAC2 inhibited BC cells proliferation both in vitro and in vivo. Meanwhile, Kaplan–Meier survival plots of 406 BC cases from TCGA database showed that higher expression of UBAC2 in BC patients was associated with lower survival rate. Mechanistic studies revealed that knockdown of UBAC2 increased the expression of p27 by posttranscriptional regulation. Our previous study indicated that circular RNA BCRC-3 (BCRC-3) promoted the expression of p27 through interacting with miR-182-5p, and reversed miR-182-5p-induced inhibition of p27 3′UTR activity. In the present study, we found that UBAC2 could bind to BCRC-3, and subsequently affected the interaction of BCRC-3 with miR-182-5p to inhibit the expression of p27. Furthermore, knockdown of BCRC-3 partly reversed the upregulation of p27 expression induced by knockdown of UBAC2. Our findings highlight a novel mechanism of UBAC2 in regulating p27 through affecting the function of BCRC-3, and provide a research basis for the diagnostic and therapeutic application of BC.

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