scholarly journals Generation of a mitochondrial membrane potential in trypanosomes in the absence of proton transport: A key role for mutations in the γ subunit that uncouple ATP synthase

2012 ◽  
Vol 1817 ◽  
pp. S12-S13
Author(s):  
Caroline Dewar ◽  
Matthew Gould ◽  
Sam Dean ◽  
Achim Schnaufer
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Proton Transport ◽  
Mitochondrial Membrane ◽  
Γ Subunit

Glucosamine-induced alterations of mitochondrial function in pancreatic β-cells: possible role of protein glycosylation

2004 ◽  
Vol 287 (4) ◽  
pp. E602-E608 ◽  
Author(s):  
Marcello Anello ◽  
Daniela Spampinato ◽  
Salvatore Piro ◽  
Francesco Purrello ◽  
Agata Maria Rabuazzo
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Function ◽  
Chronic Exposure ◽  
Mitochondrial Membrane ◽  
Protein Glycosylation ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Protein Levels

Chronic exposure of rat pancreatic islets and INS-1 insulinoma cells to glucosamine (GlcN) produced a reduction of glucose-induced (22.2 mM) insulin release that was associated with a reduction of ATP levels and ATP/ADP ratio compared with control groups. To further evaluate mitochondrial function and ATP metabolism, we then studied uncoupling protein-2 (UCP2), F1-F0-ATP-synthase, and mitochondrial membrane potential, a marker of F1-F0-ATP-synthase activity. UCP2 protein levels were unchanged after chronic exposure to GlcN on both pancreatic islets and INS-1 β-cells. Due to the high number of cells required to measure mitochondrial F1-F0-ATP-synthase protein levels and mitochondrial membrane potential, we used INS-1 cells, and we found that chronic culture with GlcN increased F1-F0-ATP-synthase protein levels but decreased glucose-stimulated changes of mitochondrial membrane potential. Moreover, F1-F0-ATP-synthase was highly glycosylated, as demonstrated by experiments with N-glycosidase F and glycoprotein staining. Tunicamycin (an inhibitor of protein N-glycosylation), when added with GlcN in the culture medium, was able to partially prevent all these negative effects on insulin secretion, adenine nucleotide content, mitochondrial membrane potential, and protein glycosylation. Thus we suggest that GlcN-induced pancreatic β-cell toxicity might be mediated by reduced cell energy production. An excessive protein N-glycosylation of mitochondrial F1-F0-ATP-synthase might lead to cell damage and secretory alterations in pancreatic β-cells.

Mitochondrial Membrane Potential and ATP Production in Primary Disorders of ATP Synthase

2004 ◽  
Vol 14 (1-2) ◽  
pp. 7-11 ◽  
Author(s):  
Alena Vojtíšková ◽  
Pavel Ješina ◽  
Martin Kalous ◽  
Vilma Kaplanová ◽  
Josef Houštěk ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Atp Production

Effect of BDM, verapamil, and cardiac work on mitochondrial membrane potential in perfused rat hearts

1995 ◽  
Vol 269 (2) ◽  
pp. H515-H523 ◽  
Author(s):  
C. Doumen ◽  
B. Wan ◽  
O. Ondrejickova
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Cardiac Work ◽  
Beta Adrenergic ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Butanedione Monoxime ◽  
Adrenergic Agent

The biochemical link providing effective coordination between the mitochondrial ATP synthetic machinery and the contractile apparatus following transitions in cardiac work remains enigmatic. Studies were designed to determine whether activation of the actomyosin adenosinetriphosphatase (ATPase) is a necessary part of the signaling mechanism to the mitochondrial ATP synthase or whether a rise in cytosolic free Ca2+ is sufficient to activate the synthase. With the use of Langendorff-perfused rat hearts, cardiac work was varied via changes in perfusion pressure and by the inclusion of a beta-adrenergic agent. Furthermore, 2,3-butanedione monoxime and verapamil were used to vary independently either the activity of the actomyosin ATPase or the level of cytosolic free Ca2+. Determinations of the in vivo mitochondrial membrane potential [delta psi m; see Wan et al. Am. J. Physiol. 265 (Heart Circ. Physiol. 34): H445-H452, 1993] and its vectorial displacement during work transitions provide valuable information concerning direct activation of the ATP synthase and proton movement through the membrane domain of the synthase. Increased cardiac work in the presence of the beta-adrenergic agent resulted in a decrease in delta psi m. Addition of 2,3-butanedione monoxime decreased cardiac work but did not change delta psi m. The inclusion of verapamil resulted in similar decreases in cardiac work. However, delta psi m reversed back to a value observed under control, low-work conditions. These results in conjunction with data regarding levels of high-energy phosphates, free Mg2+, and adenosine 3',5'-cyclic monophosphate suggest a Ca(2+)-mediated increase in the activity of the ATP synthase.

ATP synthase activity is required for fructose to protect cultured hepatocytes from the toxicity of cyanide

1993 ◽  
Vol 264 (3) ◽  
pp. C709-C714 ◽  
Author(s):  
J. W. Snyder ◽  
J. G. Pastorino ◽  
A. P. Thomas ◽  
J. B. Hoek ◽  
J. L. Farber
Keyword(s):  
Membrane Potential ◽  
Protective Effect ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Cultured Hepatocytes ◽  
Intracellular Acidosis ◽  
Mitochondrial Atp Synthase ◽  
Carbonyl Cyanide

The contributions of the loss of the mitochondrial membrane potential (MMP) and a depletion of ATP to the genesis of lethal injury were evaluated in the killing of cultured hepatocytes by cyanide (CN). The glycolytic production of ATP from fructose (Fru) maintained the MMP and prevented the killing by CN. Inhibition of the mitochondrial ATP synthase by 0.1 micrograms/ml oligomycin (Oligo) reduced ATP stores at the same rate and to the same extent as did 1 mM CN. With Oligo there was no loss of the MMP, and the hepatocytes maintained viability over the 6 h during which CN killed all of the cells. Oligo had no effect on the rate of killing by CN. However, Oligo reversed the protective effect of Fru on CN-induced killing, a result that correlated with the loss of MMP but not with the depletion of ATP. Neither Fru nor Oligo affected the intracellular acidosis achieved with CN alone. Fru also prevented toxicity of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP), a result that correlated with the preservation of MMP. Oligo potentiated the toxicity of CCCP. It is concluded that a functioning mitochondrial ATP synthase is required for the production of ATP from Fru to prevent the killing of hepatocytes by CN. The extent of killing correlated closely with changes in the MMP but not with changes in the content of ATP.

scholarly journals Bcl-xL regulates mitochondrial energetics by stabilizing the inner membrane potential

2011 ◽  
Vol 195 (2) ◽  
pp. 263-276 ◽  
Author(s):  
Ying-bei Chen ◽  
Miguel A. Aon ◽  
Yi-Te Hsu ◽  
Lucian Soane ◽  
Xinchen Teng ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Ion Flux ◽  
Β Subunit ◽  
Inner Mitochondrial Membrane ◽  
Two Photon Microscopy ◽  
Mitochondrial Atp Synthase ◽  
Large Fluctuations

Mammalian Bcl-xL protein localizes to the outer mitochondrial membrane, where it inhibits apoptosis by binding Bax and inhibiting Bax-induced outer membrane permeabilization. Contrary to expectation, we found by electron microscopy and biochemical approaches that endogenous Bcl-xL also localized to inner mitochondrial cristae. Two-photon microscopy of cultured neurons revealed large fluctuations in inner mitochondrial membrane potential when Bcl-xL was genetically deleted or pharmacologically inhibited, indicating increased total ion flux into and out of mitochondria. Computational, biochemical, and genetic evidence indicated that Bcl-xL reduces futile ion flux across the inner mitochondrial membrane to prevent a wasteful drain on cellular resources, thereby preventing an energetic crisis during stress. Given that F1FO–ATP synthase directly affects mitochondrial membrane potential and having identified the mitochondrial ATP synthase β subunit in a screen for Bcl-xL–binding partners, we tested and found that Bcl-xL failed to protect β subunit–deficient yeast. Thus, by bolstering mitochondrial energetic capacity, Bcl-xL may contribute importantly to cell survival independently of other Bcl-2 family proteins.

Glucose Protection from MPP+-Induced Apoptosis Depends on Mitochondrial Membrane Potential and ATP Synthase

1999 ◽  
Vol 257 (2) ◽  
pp. 440-447 ◽  
Author(s):  
Ruth M.E. Chalmers-Redman ◽  
Andrew D. MacLean Fraser ◽  
Graeme W. Carlile ◽  
Amanda Pong ◽  
William G. Tatton
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Induced Apoptosis

scholarly journals Efficaciousness of Low Affinity Compared to High Affinity TSPO Ligands in the Inhibition of Hypoxic Mitochondrial Cellular Damage Induced by Cobalt Chloride in Human Lung H1299 Cells

Biomedicines ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 106
Author(s):  
Nidal Zeineh ◽  
Nunzio Denora ◽  
Valentino Laquintana ◽  
Massimo Franco ◽  
Abraham Weizman ◽  
...  
Keyword(s):  
Cell Death ◽  
Membrane Potential ◽  
Cell Line ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Cobalt Chloride ◽  
Ros Generation ◽  
High Affinity ◽  
Affinity Ligand

The 18 kDa translocator protein (TSPO) plays an important role in apoptotic cell death, including apoptosis induced by the hypoxia mimicking agent cobalt chloride (CoCl2). In this study, the protective effects of a high (CB86; Ki = 1.6 nM) and a low (CB204; Ki = 117.7 nM) affinity TSPO ligands were investigated in H1299 lung cancer cell line exposed to CoCl2. The lung cell line H1299 was chosen in the present study since they express TSPO and able to undergo programmed cell death. The examined cell death markers included: ATP synthase reversal, reactive oxygen species (ROS) generation, mitochondrial membrane potential (Δψm) depolarization, cellular toxicity, and cellular viability. Pretreatment of the cells with the low affinity ligand CB204 at a concentration of 100 µM suppressed significantly (p < 0.05 for all) CoCl2-induced cellular cytotoxicity (100%), ATP synthase reversal (67%), ROS generation (82%), Δψm depolarization (100%), reduction in cellular density (97%), and also increased cell viability (85%). Furthermore, the low affinity TSPO ligand CB204, was harmless when given by itself at 100 µM. In contrast, the high affinity ligand (CB86) was significantly effective only in the prevention of CoCl2–induced ROS generation (39%, p < 0.001), and showed significant cytotoxic effects when given alone at 100 µM, as reflected in alterations in ADP/ATP ratio, oxidative stress, mitochondrial membrane potential depolarization and cell death. It appears that similar to previous studies on brain-derived cells, the relatively low affinity for the TSPO target enhances the potency of TSPO ligands in the protection from hypoxic cell death. Moreover, the high affinity TSPO ligand CB86, but not the low affinity ligand CB204, was lethal to the lung cells at high concentration (100 µM). The low affinity TSPO ligand CB204 may be a candidate for the treatment of pulmonary diseases related to hypoxia, such as pulmonary ischemia and chronic obstructive pulmonary disease COPD.

scholarly journals Depletion of cardiolipin induces major changes in energy metabolism in Trypanosoma brucei bloodstream forms

2020 ◽  
Author(s):  
Mauro Serricchio ◽  
Carolina Hierro-Yap ◽  
David Schädeli ◽  
Hisham Ben Hamidane ◽  
Andrew Hemphill ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Trypanosoma Brucei ◽  
Mitochondrial Membrane Potential ◽  
Atp Synthase ◽  
Mitochondrial Membrane ◽  
Alternative Oxidase ◽  
Mitochondrial Proteins ◽  
Cellular Respiration ◽  
Atp Levels ◽  
Glycerol 3 Phosphate Dehydrogenase

AbstractCardiolipin (CL) is a mitochondrial inner membrane glycerophospholipid that associates with mitochondrial proteins to promote their activities and to facilitate protein complex and super-complex formation. Loss of CL leads to destabilized respiratory complexes and mitochondrial dysfunction. The role of CL in an organism lacking a conventional electron transport chain (ETC) has not been elucidated so far. We now report that in Trypanosoma brucei bloodstream forms, in which the ETC is truncated and composed of alternative oxidase and glycerol-3-phosphate dehydrogenase, and the mitochondrial membrane potential is generated by the hydrolytic action of the FoF1-ATP synthase, the inducible depletion of cardiolipin synthase (TbCls) is essential for parasite survival. Loss of TbCls and CL caused a rapid drop in ATP levels and a decline in the mitochondrial membrane potential. Unbiased proteomic analyses revealed a reduction in the levels of many mitochondrial proteins, most notably of FoF1-ATP synthase subunits and of the alternative oxidase, resulting in a strong decline of glycerol-3-phosphate-stimulated oxygen consumption. Interestingly, the changes in cellular respiration preceded the observed decrease in FoF1-ATPase stability, suggesting that the truncated ETC is the first pathway responding to the decline in CL. In addition, proteomic and metabolomic analyses revealed that select proteins and pathways involved in glucose and amino acid transport and metabolism are up-regulated during CL depletion, possibly as a stress response to restore cellular ATP levels.

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