Mitochondrial ion circuits

2010 ◽  
Vol 47 ◽  
pp. 25-35 ◽  
Author(s):  
David G. Nicholls
Keyword(s):  
Electron Transport Chain ◽  
Mitochondrial Membrane ◽  
Primary Energy ◽  
Proton Leak ◽  
Primary Proton ◽  
Inner Mitochondrial Membrane ◽  
Intact Cells ◽  
Transport Chain ◽  
Proton Current ◽  
Circuit Techniques

Proton circuits across the inner mitochondrial membrane link the primary energy generators, namely the complexes of the electron transport chain, to multiple energy utilizing processes, including the ATP synthase, inherent proton leak pathways, metabolite transport and linked circuits of sodium and calcium. These mitochondrial circuits can be monitored in both isolated preparations and intact cells and, for the primary proton circuit techniques, exist to follow both the proton current and proton electrochemical potential components of the circuit in parallel experiments, providing a quantitative means of assessing mitochondrial function and, equally importantly, dysfunction.

scholarly journals Oxidation and reduction of pyridine nucleotides in alamethicin-permeabilized plant mitochondria

2004 ◽  
Vol 380 (1) ◽  
pp. 193-202 ◽  
Author(s):  
Fredrik I. JOHANSSON ◽  
Agnieszka M. MICHALECKA ◽  
Ian M. MØLLER ◽  
Allan G. RASMUSSON
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Electron Transport Chain ◽  
Nadh Dehydrogenase ◽  
Plant Mitochondria ◽  
Inner Mitochondrial Membrane ◽  
Intact Cells ◽  
Transport Chain ◽  
Invasive Method

The inner mitochondrial membrane is selectively permeable, which limits the transport of solutes and metabolites across the membrane. This constitutes a problem when intramitochondrial enzymes are studied. The channel-forming antibiotic AlaM (alamethicin) was used as a potentially less invasive method to permeabilize mitochondria and study the highly branched electron-transport chain in potato tuber (Solanum tuberosum) and pea leaf (Pisum sativum) mitochondria. We show that AlaM permeabilized the inner membrane of plant mitochondria to NAD(P)H, allowing the quantification of internal NAD(P)H dehydrogenases as well as matrix enzymes in situ. AlaM was found to inhibit the electron-transport chain at the external Ca2+-dependent rotenone-insensitive NADH dehydrogenase and around complexes III and IV. Nevertheless, under optimal conditions, especially complex I-mediated NADH oxidation in AlaM-treated mitochondria was much higher than what has been previously measured by other techniques. Our results also show a difference in substrate specificities for complex I in mitochondria as compared with inside-out submitochondrial particles. AlaM facilitated the passage of cofactors to and from the mitochondrial matrix and allowed the determination of NAD+ requirements of malate oxidation in situ. In summary, we conclude that AlaM provides the best method for quantifying NADH dehydrogenase activities and that AlaM will prove to be an important method to study enzymes under conditions that resemble their native environment not only in plant mitochondria but also in other membrane-enclosed compartments, such as intact cells, chloroplasts and peroxisomes.

scholarly journals Cardiolipin, Non-Bilayer Structures and Mitochondrial Bioenergetics: Relevance to Cardiovascular Disease

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1721
Author(s):  
Edward S. Gasanoff ◽  
Lev S. Yaguzhinsky ◽  
Győző Garab
Keyword(s):  
Electron Transport Chain ◽  
Mitochondrial Membrane ◽  
Mitochondrial Bioenergetics ◽  
Mitochondrial Membranes ◽  
Inner Mitochondrial Membrane ◽  
Atp Production ◽  
Functional Roles ◽  
Transport Chain ◽  
Energy Converting

The present review is an attempt to conceptualize a contemporary understanding about the roles that cardiolipin, a mitochondrial specific conical phospholipid, and non-bilayer structures, predominantly found in the inner mitochondrial membrane (IMM), play in mitochondrial bioenergetics. This review outlines the link between changes in mitochondrial cardiolipin concentration and changes in mitochondrial bioenergetics, including changes in the IMM curvature and surface area, cristae density and architecture, efficiency of electron transport chain (ETC), interaction of ETC proteins, oligomerization of respiratory complexes, and mitochondrial ATP production. A relationship between cardiolipin decline in IMM and mitochondrial dysfunction leading to various diseases, including cardiovascular diseases, is thoroughly presented. Particular attention is paid to the targeting of cardiolipin by Szeto–Schiller tetrapeptides, which leads to rejuvenation of important mitochondrial activities in dysfunctional and aging mitochondria. The role of cardiolipin in triggering non-bilayer structures and the functional roles of non-bilayer structures in energy-converting membranes are reviewed. The latest studies on non-bilayer structures induced by cobra venom peptides are examined in model and mitochondrial membranes, including studies on how non-bilayer structures modulate mitochondrial activities. A mechanism by which non-bilayer compartments are formed in the apex of cristae and by which non-bilayer compartments facilitate ATP synthase dimerization and ATP production is also presented.

Study of the anti-angiogenic effects of cardiolipin by the aortic ring assay

2015 ◽  
Vol 93 (11) ◽  
pp. 1015-1019 ◽  
Author(s):  
Matthew L. Carnevale ◽  
Andreas Bergdahl
Keyword(s):  
Electron Transport Chain ◽  
Mitochondrial Membrane ◽  
Aortic Ring ◽  
Cell Types ◽  
Inner Mitochondrial Membrane ◽  
Transport Chain ◽  
Aortic Ring Assay ◽  
Cervical Dislocation ◽  
Sprout Growth

Cardiolipin (CL), a phospholipid found in the inner mitochondrial membrane in all cell types, is critical for the function of the electron transport chain. The role of CL is not fully understood, but it is assumed that the molecule maintains membrane potential and architecture and compensates for alterations in homeostasis that could affect the energy metabolism. The objective of this project was to determine the effects of increasing CL concentrations on angiogenic sprouting by using the aortic ring assay model. For this, 5-day-old C57Bl/6 pups were euthanized by cervical dislocation prior to removal of the aortas. The vessels were cleaned, cut in 0.5 mm wide rings, and placed in a collagen growth matrix supplemented with CL. The results revealed a highly significant reduction of sprout growth (both length and quantity) at low, physiological concentrations. In conclusion, the results of this study demonstrate that CL significantly reduces microvessel formation and that it could potentially provide an interesting novel therapeutic target for angiogenesis.

scholarly journals Mitochondria-targeted molecules determine the redness of the zebra finch bill

2017 ◽  
Vol 13 (10) ◽  
pp. 20170455 ◽  
Author(s):  
Alejandro Cantarero ◽  
Carlos Alonso-Alvarez
Keyword(s):  
Electron Transport Chain ◽  
Mitochondrial Membrane ◽  
Coenzyme Q ◽  
Antioxidant Properties ◽  
Quality Indices ◽  
Inner Mitochondrial Membrane ◽  
Animal Cells ◽  
Transport Chain ◽  
Sexual Signalling ◽  
Production Mechanisms

The evolution and production mechanisms of red carotenoid-based ornaments in animals are poorly understood. Recently, it has been suggested that enzymes transforming yellow carotenoids to red pigments (ketolases) in animal cells may be positioned in the inner mitochondrial membrane (IMM) intimately linked to the electron transport chain. These enzymes may mostly synthesize coenzyme Q 10 (coQ 10 ), a key redox-cycler antioxidant molecularly similar to yellow carotenoids. It has been hypothesized that this shared pathway favours the evolution of red traits as sexually selected individual quality indices by revealing a well-adjusted oxidative metabolism. We administered mitochondria-targeted molecules to male zebra finches ( Taeniopygia guttata ) measuring their bill redness, a trait produced by transforming yellow carotenoids. One molecule included coQ 10 (mitoquinone mesylate, MitoQ) and the other one (decyl-triphenylphosphonium; dTPP) has the same structure without the coQ 10 aromatic ring. At the highest dose, the bill colour of MitoQ and dTPP birds strongly differed: MitoQ birds' bills were redder and dTPP birds showed paler bills even compared to birds injected with saline only. These results suggest that ketolases are indeed placed at the IMM and that coQ 10 antioxidant properties may improve their efficiency. The implications for evolutionary theories of sexual signalling are discussed.

scholarly journals Palmitic Acid, but Not Lauric Acid, Induces Metabolic Inflammation, Mitochondrial Fragmentation, and a Drop in Mitochondrial Membrane Potential in Human Primary Myotubes

2021 ◽  
Vol 8 ◽  
Author(s):  
Domenico Sergi ◽  
Natalie Luscombe-Marsh ◽  
Nenad Naumovski ◽  
Mahinda Abeywardena ◽  
Nathan O'Callaghan
Keyword(s):  
Insulin Resistance ◽  
Membrane Potential ◽  
Electron Transport ◽  
Mitochondrial Membrane Potential ◽  
Electron Transport Chain ◽  
Mitochondrial Membrane ◽  
Chain Complex ◽  
Mitochondrial Fragmentation ◽  
Metabolic Inflammation ◽  
Transport Chain

The chain length of saturated fatty acids may dictate their impact on inflammation and mitochondrial dysfunction, two pivotal players in the pathogenesis of insulin resistance. However, these paradigms have only been investigated in animal models and cell lines so far. Thus, the aim of this study was to compare the effect of palmitic (PA) (16:0) and lauric (LA) (12:0) acid on human primary myotubes mitochondrial health and metabolic inflammation. Human primary myotubes were challenged with either PA or LA (500 μM). After 24 h, the expression of interleukin 6 (IL-6) was assessed by quantitative polymerase chain reaction (PCR), whereas Western blot was used to quantify the abundance of the inhibitor of nuclear factor κB (IκBα), electron transport chain complex proteins and mitofusin-2 (MFN-2). Mitochondrial membrane potential and dynamics were evaluated using tetraethylbenzimidazolylcarbocyanine iodide (JC-1) and immunocytochemistry, respectively. PA, contrarily to LA, triggered an inflammatory response marked by the upregulation of IL-6 mRNA (11-fold; P < 0.01) and a decrease in IκBα (32%; P < 0.05). Furthermore, whereas PA and LA did not differently modulate the levels of mitochondrial electron transport chain complex proteins, PA induced mitochondrial fragmentation (37%; P < 0.001), decreased MFN-2 (38%; P < 0.05), and caused a drop in mitochondrial membrane potential (11%; P < 0.01) compared to control, with this effect being absent in LA-treated cells. Thus, LA, as opposed to PA, did not trigger pathogenetic mechanisms proposed to be linked with insulin resistance and therefore represents a healthier saturated fatty acid choice to potentially preserve skeletal muscle metabolic health.

The Electron Transport Chain

2014 ◽  
Vol 76 (7) ◽  
pp. 456-458 ◽  
Author(s):  
Chris Romero ◽  
James Choun
Keyword(s):  
Electron Transport ◽  
Advanced Placement ◽  
Electron Transport Chain ◽  
Cellular Respiration ◽  
College Level ◽  
Inner Mitochondrial Membrane ◽  
College Biology ◽  
Everyday Objects ◽  
Transport Chain ◽  
Introductory College

This activity provides students an interactive demonstration of the electron transport chain and chemiosmosis during aerobic respiration. Students use simple, everyday objects as hydrogen ions and electrons and play the roles of the various proteins embedded in the inner mitochondrial membrane to show how this specific process in cellular respiration produces ATP. The activity works best as a supplement after you have already discussed the electron transport chain in lecture but can be used prior to instruction to help students visualize the processes that occur. This demonstration was designed for general college biology for majors at a community college, but it could be used in any introductory college-level or advanced placement biology course.

Spontaneous mitochondrial depolarizations are independent of SR Ca2+ release

2004 ◽  
Vol 286 (5) ◽  
pp. C1139-C1151 ◽  
Author(s):  
Catherine M. O'Reilly ◽  
Kevin E. Fogarty ◽  
Robert M. Drummond ◽  
Richard A. Tuft ◽  
John V. Walsh
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Mitochondrial Membrane ◽  
High Speed ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Inner Mitochondrial Membrane ◽  
Intact Cells ◽  
Mitochondrial Functions ◽  
Intracellular Ca

The mitochondrial membrane potential (ΔΨm) underlies many mitochondrial functions, including Ca2+ influx into the mitochondria, which allows them to serve as buffers of intracellular Ca2+. Spontaneous depolarizations of ΔΨm, flickers, have been observed in isolated mitochondria and intact cells using the fluorescent cationic lipophile tetramethylrhodamine ethyl ester (TMRE), which distributes across the inner mitochondrial membrane in accordance with the Nernst equation. Flickers in cardiomyocytes have been attributed to uptake of Ca2+ released from the sarcoplasmic reticulum (SR) via ryanodine receptors in focal transients called Ca2+ sparks. We have shown previously that an increase in global Ca2+ in smooth muscle cells causes an increase in mitochondrial Ca2+ and depolarization of ΔΨm. Here we sought to determine whether flickers in smooth muscle cells are caused by uptake of Ca2+ released focally in Ca2+ sparks. High-speed three-dimensional imaging was used to monitor ΔΨm in freshly dissociated myocytes from toad stomach that were simultaneously voltage clamped at 0 mV to ensure the cytosolic TMRE concentration was constant and equal to the low level in the bath (2.5 nM). This approach allows quantitative analysis of flickers as we have previously demonstrated. Depletion of SR Ca2+ not only failed to eliminate flickers but rather increased their magnitude and frequency somewhat. Flickers were not altered in magnitude or frequency by ryanodine or xestospongin C, inhibitors of intracellular Ca2+ release, or by cyclosporin A, an inhibitor of the permeability transition pore. Focal Ca2+ release from the SR does not cause flickers in the cells employed here.

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