• BMB Reports
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• v.52 no.2
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• pp.109-110
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• 2019

Mitochondrial morphology is known to be continuously changing via fusion and fission, but it is unclear what the biological importance of this energy-consuming process is and how it develops. Several data have suggested that mitochondrial fission executed by Drp1 is necessary to select out a damaged spot from the interconnected mitochondrial network, but the precise mechanism for the recognition and isolation of a damaged sub-mitochondrial region during mitochondrial fission is yet unclear. Recently, Cho et al. found that the mitochondrial membrane potential (MMP) is transiently reduced by the physical interaction of Drp1 and mitochondrial Zinc transporter, Zip1, at the fission site prior to the typical mitochondrial division, and we found that this event is essential for a mitochondrial quality surveillance. In this review, Cho et al. discuss the role of a mitochondrial fission in the mitochondrial quality surveillance system.

• Molecules and Cells
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• v.37 no.2
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• pp.89-94
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• 2014

Fission and fusion of mitochondrial tubules are the main processes determining mitochondrial shape and size in cells. As more evidence is found for the involvement of mitochondrial morphology in human pathology, it is important to elucidate the mechanisms of mitochondrial fission and fusion. Mitochondrial morphology is highly sensitive to changing environmental conditions, indicating the involvement of cellular signaling pathways. In addition, the well-established structural connection between the endoplasmic reticulum (ER) and mitochondria has recently been found to play a role in mitochondrial fission. This minireview describes the latest advancements in understanding the regulatory mechanisms controlling mitochondrial morphology, as well as the ER-mediated structural maintenance of mitochondria, with a specific emphasis on mitochondrial fission.

• Biomedical Science Letters
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• v.18 no.2
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• pp.112-122
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• 2012

A gradual change of molecules that are related in fission and fusion is occurred during aging process. Although aging effects on mitochondrial fusion and fission are investigated, it is still unclear that the extent of the change in mitochondria fusion and fission periodically. In this study we investigated the changes of mitochondrial proteins involved in fusion (Mfn2, Opa1) and fission (Drp1, Fis1) in the human gracilis muscle ranging from 10 to 50 years of age (n=40). The gracilis muscle showed a significant increase in muscle apoptotic changes in the age of 50s compared with 10s by using in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL). The expression levels of Drp1 and Fis1 (P<0.01, P<0.05) mRNA were significantly elevated and the Mfn2 and Opa1 (P<0.01, P<0.05) levels were decreased from older individuals. The ratio of fission and fusion was altered and the level of increment of fission gene was greater than fusion gene decrement in the age of 50s. These findings suggest that changes of mitochondrial fusion and fission proteins related with aging might contribute to aged muscle apoptosis.

• BMB Reports
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• v.41 no.1
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• pp.11-22
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• 2008

Apoptosis (programmed cell death) is a cellular self-destruction mechanism that is essential for a variety of biological events, such as developmental sculpturing, tissue homeostasis, and the removal of unwanted cells. Mitochondria play a crucial role in regulating cell death. $Ca^{2+}$ has long been recognized as a participant in apoptotic pathways. Mitochondria are known to modulate and synchronize $Ca^{2+}$ signaling. Massive accumulation of $Ca^{2+}$ in the mitochondria leads to apoptosis. The $Ca^{2+}$ dynamics of ER and mitochondria appear to be modulated by the Bcl-2 family proteins, key factors involved in apoptosis. The number and morphology of mitochondria are precisely controlled through mitochondrial fusion and fission process by numerous mitochondria-shaping proteins. Mitochondrial fission accompanies apoptotic cell death and appears to be important for progression of the apoptotic pathway. Here, we highlight and discuss the role of mitochondrial calcium handling and mitochondrial fusion and fission machinery in apoptosis.

• Biomolecules & Therapeutics
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• v.30 no.5
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• pp.409-417
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• 2022

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, and accumulating evidence indicates that mitochondrial dysfunction is associated with progressive deterioration in PD patients. Previous studies have shown that sinapic acid has a neuroprotective effect, but its mechanisms of action remain unclear. The neuroprotective effect of sinapic acid was assayed in a PD mouse model generated by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as well as in SH-SY5Y cells. Target protein expression was detected by western blotting. Sinapic acid treatment attenuated the behavioral defects and loss of dopaminergic neurons in the PD models. Sinapic acid also improved mitochondrial function in the PD models. MPTP treatment increased the abundance of mitochondrial fission proteins such as dynamin-related protein 1 (Drp1) and phospho-Drp1 Ser616. In addition, MPTP decreased the expression of the REV-ERB α protein. These changes were attenuated by sinapic acid treatment. We used the pharmacological REV-ERB α inhibitor SR8278 to confirmation of protective effect of sinapic acid. Treatment of SR8278 with sinapic acid reversed the protein expression of phospho-Drp1 Ser616 and REV-ERB α on MPTP-treated mice. Our findings demonstrated that sinapic acid protects against MPTP-induced PD and these effects might be related to the inhibiting abnormal mitochondrial fission through REV-ERB α.

• BMB Reports
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• v.50 no.4
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• pp.214-219
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• 2017

Mitochondria play pivotal roles in the ATP production, apoptosis and generation of reactive oxygen species. Although dynamic regulation of mitochondria morphology is a critical step to maintain cellular homeostasis, the regulatory mechanisms are not yet fully elucidated. In this study, we identified miR-200a-3p as a novel regulator of mitochondrial dynamics by targeting mitochondrial fission factor (MFF). We demonstrated that the ectopic expression of miR-200a-3p enhanced mitochondrial elongation, mitochondrial ATP synthesis, mitochondrial membrane potential and oxygen consumption rate. These results indicate that miR-200a-3p positively regulates mitochondrial elongation by downregulating MFF expression.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.6
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• pp.567-577
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• 2017

Obesity is known to induce inhibition of glucose uptake, reduction of lipid metabolism, and progressive loss of skeletal muscle function, which are all associated with mitochondrial dysfunction in skeletal muscle. Mitochondria are dynamic organelles that regulate cellular metabolism and bioenergetics, including ATP production via oxidative phosphorylation. Due to these critical roles of mitochondria, mitochondrial dysfunction results in various diseases such as obesity and type 2 diabetes. Obesity is associated with impairment of mitochondrial function (e.g., decrease in $O_2$ respiration and increase in oxidative stress) in skeletal muscle. The balance between mitochondrial fusion and fission is critical to maintain mitochondrial homeostasis in skeletal muscle. Obesity impairs mitochondrial dynamics, leading to an unbalance between fusion and fission by favorably shifting fission or reducing fusion proteins. Mitophagy is the catabolic process of damaged or unnecessary mitochondria. Obesity reduces mitochondrial biogenesis in skeletal muscle and increases accumulation of dysfunctional cellular organelles, suggesting that mitophagy does not work properly in obesity. Mitochondrial dysfunction and oxidative stress are reported to trigger apoptosis, and mitochondrial apoptosis is induced by obesity in skeletal muscle. It is well known that exercise is the most effective intervention to protect against obesity. Although the cellular and molecular mechanisms by which exercise protects against obesity-induced mitochondrial dysfunction in skeletal muscle are not clearly elucidated, exercise training attenuates mitochondrial dysfunction, allows mitochondria to maintain the balance between mitochondrial dynamics and mitophagy, and reduces apoptotic signaling in obese skeletal muscle.

• Natural Product Sciences
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• v.28 no.4
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• pp.194-200
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• 2022

Albizia julibrissin Durazz. (AJ; family Minosaceae) is widely distributed worldwide, and its stem bark has been used as a traditional herbal medicine. Acute kidney injury (AKI) is a clinical syndrome that results in sudden loss of renal function. This study aimed to investigate the effects of AJ against cisplatin-induced AKI using a human kidney proximal tubule epithelial cell line (HK-2) and cisplatin-treated mice. In vitro, cisplatin treatment increased apoptosis in HK-2 cells. However, AJ treatment decreased apoptosis of cisplatin-treated HK-2 cells. In vivo, cisplatin treatment accelerated renal injury by increasing the levels of renal injury markers, such as blood urea nitrogen, creatinine, kidney injury molecule 1, and neutrophil gelatinase-associated lipocalin, which were reversed by AJ treatment. Histopathologically, AJ treatment resulted in decreased renal damage with less tubular necrosis and brush border desquamation compared with the AKI group. Additionally, cisplatin treatment upregulated mitochondrial fission, a pathological characteristic of AKI, which was downregulated by AJ treatment. Along with increased mitochondrial fission, AJ treatment also reduced cisplatin-induced apoptosis. These results suggest that AJ may be a potential therapeutic agent for cisplatin-induced AKI.

• Molecules and Cells
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• v.41 no.1
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• pp.18-26
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• 2018

Mitochondrial quality control systems are essential for the maintenance of functional mitochondria. At the organelle level, they include mitochondrial biogenesis, fusion and fission, to compensate for mitochondrial function, and mitophagy, for degrading damaged mitochondria. Specifically, in mitophagy, the target mitochondria are recognized by the autophagosomes and delivered to the lysosome for degradation. In this review, we describe the mechanisms of mitophagy and the factors that play an important role in this process. In particular, we focus on the roles of mitophagy adapters and receptors in the recognition of damaged mitochondria by autophagosomes. In addition, we also address a functional association of mitophagy with mitochondrial dynamics through the interaction of mitophagy adaptor and receptor proteins with mitochondrial fusion and fission proteins.

• Molecules and Cells
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• v.42 no.12
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• pp.893-905
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• 2019

Mitochondria are highly dynamic organelles that constantly undergo fission and fusion processes that closely related to their function. Disruption of mitochondrial dynamics has been demonstrated in acute kidney injury (AKI), which could eventually result in cell injury and death. Previously, we reported that augmenter of liver regeneration (ALR) alleviates renal tubular epithelial cell injury. Here, we gained further insights into whether the renoprotective roles of ALR are associated with mitochondrial dynamics. Changes in mitochondrial dynamics were examined in experimental models of renal ischemia-reperfusion (IR). In a model of hypoxia-reoxygenation (HR) injury in vitro, dynamin-related protein 1 (Drp1) and mitochondrial fission process protein 1 (MTFP1), two key proteins of mitochondrial fission, were downregulated in the Lv-ALR + HR group. ALR overexpression additionally had an impact on phosphorylation of Drp1 Ser637 during AKI. The inner membrane fusion protein, Optic Atrophy 1 (OPA1), was significantly increased whereas levels of outer membrane fusion proteins Mitofusin-1 and -2 (Mfn1, Mfn2) were not affected in the Lv-ALR + HR group, compared with the control group. Furthermore, the mTOR/4E-BP1 signaling pathway was highly activated in the Lv-ALR + HR group. ALR overexpression led to suppression of HR-induced apoptosis. Our collective findings indicate that ALR gene transfection alleviates mitochondrial injury, possibly through inhibiting fission and promoting fusion of the mitochondrial inner membrane, both of which contribute to reduction of HK-2 cell apoptosis. Additionally, fission processes are potentially mediated by promoting tubular cell survival through activating the mTOR/4E-BP1 signaling pathway.