Mitochondrial dynamics, involving mitochondrial fusion, fission and autophagy, plays an important role in maintaining cellular physiological function and homeostasis. Mitochondria are the "energy plant" of human body, so the changes of mitochondrial fusion, division and autophagy are important for cell respiration and energy production. On the other hand, energy metabolism influences mitochondrial dynamics in turn. This paper reviewed the recent advances in studies on the relationship between energy metabolism and the proteins regulating mitochondrial fusion, fission and autophagy. The association of mitochondrial dynamics with electron chain complex expression, oxidative phosphorylation and ATP synthesis upon exercise intervention will provide theoretical references for the further studies in sports training and disease intervention.
Adenosine Triphosphate ; biosynthesis ; Autophagy ; Energy Metabolism ; Exercise ; Humans ; Mitochondria ; physiology ; Mitochondrial Dynamics ; Mitochondrial Proteins ; metabolism

Smac is a mitochondrial protein that interacts with inhibitor of apoptosis proteins (IAPs). Upon apoptotic stimuli, the Smac is released into the cytoplasm to inhibit the capase-binding activity of IAPs. The low expression of Smac in tissues has been reported existing in various cancers. Smac plays key roles in prognosis and chemoradiotherapy resistance of malignant tumor besides neoplasm genesis and growth. Furthermore, Smac may be a molecular therapeutic target in cancer patients. Overexpression of Smac by transfecting extrinsic Smac gene or Smac mimetic into tumor cell can improve their sensitivity to radiotherapy and chemotherapy, which has great significance to the treatment of tumor. Our review will focus on the roles of Smac in structure, pro-apoptotic mechanism, tissue distribution and cancer treatment.
Humans ; Intracellular Signaling Peptides and Proteins ; chemistry ; metabolism ; physiology ; Mitochondrial Proteins ; chemistry ; metabolism ; physiology ; Neoplasms ; therapy ; Tissue Distribution

The aim of the present study was to investigate the effects of exercises with different durations and intensities on mitochondrial autophagy and FUNDC1 in rat skeletal muscles. Sixty male Sprague-Dawley rats were randomly divided into 2- and 4-week control groups (Con), moderate-intensity exercise groups (M-ex groups, treadmill exercise, 16 m/min, 1 h/d, 6 d/week), and high-intensity exercise groups (Hi-ex groups, treadmill exercise, 35 m/min, 20 min/d, 6 d/week). The bilateral soleus muscles were separated after the intervention, and paraffin sections were prepared for transmission electron microscopy. ELISA method was used to detect the content of citrate synthase (CS). The co-localizations of microtubule-associated protein 1 light chain 3 (LC3)/cytochrome c oxidase IV (COX-IV), FUNDC1/COX-IV and LC3/FUNDC1 were observed by immunofluorescent staining in frozen sections. The skeletal muscle mitochondria were extracted, and the expression of autophagy-related proteins, including AMPKα, p-AMPKα, Unc-51 like kinase 1 (ULK1), FUNDC1, LC3 and p62, were detected by Western blot. The results showed that exercise increased mitochondrial function, i.e. peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1α), COX-I protein expression levels and CS content. There was no difference of mitochondrial function parameters between 2-week M-ex and 2-week Hi-ex groups, while mitochondrial function of 4-weeks Hi-ex group was significantly lower than that of 4-week M-ex group. Under the same exercise intensity, mitochondrial autophagy activation in skeletal muscle of 4-week exercise was higher than that in 2-week exercise group; Under the same duration of exercise, mitochondrial autophagy activation of Hi-ex group was higher than that in M-ex group. Both 2- and 4-week exercise intervention increased LC3/COX-IV, COX-IV/FUNDC1, and FUNDC1/LC3 co-localizations. Exercise increased LC3-II/LC3-I ratio, down-regulated p62 protein expression level, up-regulated FUNDC1, ULK1 protein expression levels and AMPKα phosphorylation, and the changes of these proteins in 4-week Hi-ex group were significantly greater than those in 4-week M-ex group. These results suggest exercise induces mitochondrial autophagy in skeletal muscles, and the activity of autophagy is related to the duration and intensity of exercise. The induction mechanism of exercise may involve the mediation of FUNDC1 expression through AMPK-ULK1 pathway.
Animals ; Autophagy ; Exercise Therapy ; Humans ; Male ; Membrane Proteins/physiology* ; Mitochondria ; Mitochondrial Proteins/physiology* ; Muscle, Skeletal/metabolism* ; Rats ; Rats, Sprague-Dawley

Opening of mitochondrial permeability transition (MPT) pores leads to mitochondrial injury during oxidative stress. The peripheral benzodiazepine receptor (PBR) located at mitochondrial outer-membrane has been shown to be involved in several mitochondrial functions. In the present study, we used Ro5-4864, a PBR agonist, to test if activation of PBR could prevent MPT pore opening during Ca(2+) overloading. Cardiac mitochondria isolated from Sprague-Dawley rats were treated by 150 mmol/L Ca(2+) to induce MPT. Ro5-4864 (50, 100 and 200 micromol/L) was added into incubation buffer before adding 150 micromol/L Ca(2+). In additional group, atractyloside (ATR, 20 micromol/L), an opener of MPT pores was added 5 min before the addition of 100 micromol/L Ro5-4864. The change of absorbance at 520 nm was monitored with a spectrophotometer at 30 degrees C for 10 min. Western blot was used to detect cytochrome C loss. The mitochondrial membrane potential was monitored with the fluorescence dye JC-1. Ro5-4864 inhibited the decrease of absorbance at 520 nm compared to that in the untreated Ca(2+) group (P<0.01, P<0.05). In the presence of ATR, Ro5-4864 was not able to prevent MPT anymore. Opening of MPT pores by Ca(2+) decreased the content of cytochrome C in mitochondria, but increased cytochrome C content in cytosol. Ro5-4864 preserved cytochrome C content in mitochondria and led to less cytochrome C release to cytosol. ATR treatment reversed the protective effect of Ro5-4864 on cytochrome C content. Opening of MPT pores led to mitochondrial depolarization, whereas Ro5-4864 treatment maintained mitochondrial membrane potential. Thus, prevention of MPT by activation of PBR during calcium overloading maintains mitochondrial cytochrome C content and membrane potential. Activation of PBR during cardiac ischemia and reperfusion may be an alternative way for cardioprotection.
Animals ; Atractyloside ; pharmacology ; Benzodiazepinones ; pharmacology ; Carrier Proteins ; agonists ; metabolism ; physiology ; Female ; Male ; Membrane Potential, Mitochondrial ; physiology ; radiation effects ; Mitochondria, Heart ; physiology ; Mitochondrial Membrane Transport Proteins ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; metabolism ; physiology

While the field of ATP synthase research has a long history filled with landmark discoveries, recent structural works provide us with important insights into the mechanisms that links the proton movement with the rotation of the Fo motor. Here, we propose a mechanism of unidirectional rotation of the Fo complex, which is in agreement with these new structural insights as well as our more general ΔΨ-driving hypothesis of membrane proteins: A proton path in the rotor-stator interface is formed dynamically in concert with the rotation of the Fo rotor. The trajectory of the proton viewed in the reference system of the rotor (R-path) must lag behind that of the stator (S-path). The proton moves from a higher energy site to a lower site following both trajectories simultaneously. The two trajectories meet each other at the transient proton-binding site, resulting in a relative rotation between the rotor and stator. The kinetic energy of protons gained from ΔΨ is transferred to the c-ring as the protons are captured sequentially by the binding sites along the proton path, thus driving the unidirectional rotation of the c-ring. Our ΔΨ-driving hypothesis on Fo motor is an attempt to unveil the robust mechanism of energy conversion in the highly conserved, ubiquitously expressed rotary ATP synthases.
Membrane Potentials ; physiology ; Membrane Proteins ; chemistry ; metabolism ; Mitochondrial Proton-Translocating ATPases ; chemistry ; metabolism ; Protein Conformation

The three dimensional structures of both pro-apoptotic Bax and anti-apoptotic Bcl-2 are strikingly similar to that of pore-forming domains of diphtheria toxin and E. coli colicins. Consistent with the structural similarity, both Bax and Bcl-2 have been shown to possess pore-forming property in the membrane. However, these pore-forming proteins form pores via different mechanisms. While Bax and diphtheria toxin form pores via oligomerization, the colicin pore is formed only by colicin monomers. Although the oligomers of Bcl-2 proteins have been found in the mitochondria of both healthy and apoptotic cells, it is unknown whether or not oligomerization is involved in the pore formation. To determine the mechanism of Bcl-2 pore formation, we reconstituted the pore-forming process of Bcl-2 using purified proteins and liposomes. We found that Bcl-2 pore size depended on Bcl-2 concentration, and the release of smaller entrapped molecules was faster than that of larger ones from liposomes at a given Bcl-2 concentration. Moreover, the rate of dye release mediated by pre-formed wild-type Bcl-2 oligomers or by the mutant Bcl-2 monomers with a higher homo-association affinity was much higher than that by wild-type Bcl-2 monomers. Together, it is suggested that oligomerization is likely involved in Bcl-2 pore formation.
Apoptosis ; physiology ; Cytosol ; metabolism ; Humans ; Hydrogen-Ion Concentration ; Liposomes ; metabolism ; Mitochondrial Membrane Transport Proteins ; metabolism ; Mitochondrial Membranes ; metabolism ; Protein Multimerization ; Proto-Oncogene Proteins c-bcl-2 ; metabolism

OBJECTIVE: To investigate whether autophagy mediates the effects of aldehyde dehydrogenase 2 (ALDH2) on the proliferation of neonatal rat cardiac fibroblasts cultured in high glucose. METHODS: Cardiac fibroblasts were isolated from neonatal (within 3 days) SD rats and subcultured. The fibroblasts of the third passage, after identification with immunofluorescence staining for vimentin, were treated with 5.5 mmol/L glucose (control group), 30 mmol/L glucose (high glucose group), or 30 mmol/L glucose in the presence of Alda-1 (an ALDH2 agonist), daidzin (an ALDH2 2 inhibitor), or both. Western blotting was employed to detect ALDH2, microtubule-associated protein 1 light chain 3B subunit (LC3B) and Beclin-1 in the cells, and a hydroxyproline detection kit was used for determining hydroxyproline content in cell culture medium; CCK- 8 kit was used for assessing the proliferation ability of the cardiac fibroblasts after the treatments. RESULTS: Compared with the control cells, the cells exposed to high glucose exhibited obviously decreased expressions of ALDH2, Beclin-1 and LC3B and increased cell number and hydroxyproline content in the culture medium. Treatment of the high glucose-exposed cells with Alda-1 significantly increased Beclin-1, LC3B, and ALDH2 protein expressions and lowered the cell number and intracellular hydroxyproline content, whereas the application of daidzin resulted in reverse changes in the expressions of ALDH2, Beclin-1 and LC3B, viable cell number and intracellular hydroxyproline content in high glucose-exposed cells. CONCLUSIONS Mitochondrial ALDH2 inhibits the proliferation of neonatal rat cardiac fibroblasts induced by high glucose, and the effect is possibly mediated by the up-regulation of autophagy-related proteins Beclin-1 and LC3B.
Aldehyde Dehydrogenase ; Aldehyde Dehydrogenase, Mitochondrial ; metabolism ; Animals ; Animals, Newborn ; Autophagy ; Beclin-1 ; physiology ; Fibroblasts ; Glucose ; Microtubule-Associated Proteins ; Mitochondrial Proteins ; Rats ; Rats, Sprague-Dawley

ATP-NAD kinase phosphorylates NAD to produce NADP by using ATP, whereas ATP-NADH kinase phosphorylates both NAD and NADH. Three NAD kinase homologues, namely, Utr1p, Pos5p and Utr1p, exist in the yeast Saccharomyces cerevisiae, which were all confirmed as ATP-NADH kinases and found to be important to supply NADP(H) for yeast cells. In S. cerevisiae, fatty acid beta-oxidation is restricted to peroxisomes and peroxisomal NADPH is required for beta-oxidation of unsaturated fatty acids with the double bonds at even positions. Single and double gene disruption strains of NAD kinase genes, i.e., utr1, pos5, yef1, utr1yef1, utr1pos5 and yef1pos5 were constructed by PCR-targeting method. The utilization ability of these mutants for unsaturated fatty acids with the double bonds at even or uneven positions was examined, with wild type BY4742 as positive control cell, and fatty-acyl-CoA oxidase gene deletion mutant (fox1) and peroxisomal NADP-dependent isocitrate dehydrogenase isoenzymes gene deletion mutant (idp3) as negative control cells. The results indicated that the NAD kinase homologues, especially Pos5p, were critical for supplying NADP and then NADPH in peroxisomal matrix. NADP, which was supplied mainly by Utr1p, Pos5p and Yef1p, particularly by Pos5p, was proposed to be able to transfer from outside of peroxisome into peroxisomal matrix and then converted to NADPH by Idp3p.
Fatty Acids, Unsaturated ; metabolism ; Mitochondrial Proteins ; physiology ; NADP ; metabolism ; Oxidation-Reduction ; Phosphotransferases (Alcohol Group Acceptor) ; physiology ; Saccharomyces cerevisiae ; growth & development ; metabolism ; Saccharomyces cerevisiae Proteins ; physiology

Animals ; Apoptosis ; physiology ; Calcium ; metabolism ; Humans ; Mitochondrial Membrane Transport Proteins ; physiology ; Proto-Oncogene Proteins c-bcl-2 ; physiology ; Reactive Oxygen Species ; metabolism

Mesenchymal stem cells (MSCs) are progenitors of connective tissues, which have emerged as important tools for tissue engineering due to their differentiation potential along various cell types. In recent years, accumulating evidence has suggested that the regulation of mitochondria dynamics and function is essential for successful differentiation of MSCs. In this paper, we review and provide an integrated view on the role of mitochondria in MSC differentiation. The mitochondria are maintained at a relatively low activity level in MSCs, and upon induction, mtDNA copy number, protein levels of respiratory enzymes, the oxygen consumption rate, mRNA levels of mitochondrial biogenesis-associated genes, and intracellular ATP content are increased. The regulated level of mitochondrial ROS is found not only to influence differentiation but also to contribute to the direction determination of differentiation. Understanding the roles of mitochondrial dynamics during MSC differentiation will facilitate the optimization of differentiation protocols by adjusting biochemical properties, such as energy production or the redox status of stem cells, and ultimately, benefit the development of new pharmacologic strategies in regenerative medicine.
Adipogenesis ; physiology ; Animals ; Cell Differentiation ; physiology ; Chondrogenesis ; physiology ; Humans ; Mesenchymal Stem Cells ; cytology ; metabolism ; Mitochondria ; genetics ; metabolism ; Mitochondrial Proteins ; genetics ; metabolism ; Osteogenesis ; physiology ; RNA ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; RNA, Mitochondrial ; Reactive Oxygen Species ; metabolism