The protonmotive force and respiratory control

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COST Action CA15203 MitoEAGLE
Evolution-Age-Gender-Lifestyle-Environment: mitochondrial fitness mapping


 

The protonmotive force and respiratory control


Building blocks of mitochondrial physiology MitoEAGLE recommendations Part 1.



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» Manuscript phases and versions

Manuscript phases and versions - an open-access apporach

COST Action MitoEAGLE
This manuscript on ‘Mitochondrial respiratory states and rates’ is a position statement in the frame of COST Action CA15203 MitoEAGLE. The list of coauthors evolved beyond phase 1 in the bottom-up spirit of COST.
The global MitoEAGLE network made it possible to collaborate with a large number of coauthors to reach consensus on the present manuscript. Nevertheless, we do not consider scientific progress to be supported by ‘declaration’ statements (other than on ethical or political issues). Our manuscript aims at providing arguments for further debate rather than pushing opinions. We hope to initiate a much broader process of discussion and want to raise the awareness on the importance of a consistent terminology for reporting of scientific data in the field of bioenergetics, mitochondrial physiology and pathology. Quality of research requires quality of communication. Some established researchers in the field may not want to re-consider the use of jargon which has become established despite deficiencies of accuracy and meaning. In the long run, superior standards will become accepted. We hope to contribute to this evolutionary process, with an emphasis on harmonization rather than standardization.
  • Phase 1: The protonmotive force and respiratory control
» The protonmotive force and respiratory control - Discussion
» MitoEAGLE preprint 2017-09-21 - Discussion
  • Phase 2: Mitochondrial respiratory states and rates: Building blocks of mitochondrial physiology Part 1
» MitoEAGLE Task Group States and rates - Discussion
  • Phase 4: Journal submission
  • Target: CELL METABOLISM, aiming at indexing by The Web of Science and PubMed.
Coauthors



Open invitation

This manuscript on ‘The protonmotive force and respiratory control’ is a position statement in the frame of COST Action CA15203 MitoEAGLE. The list of coauthors evolved from MitoEAGLE Working Group Meetings and a bottom-up spirit of COST: This is an open invitation to scientists and students to join as coauthors, to provide a balanced view on mitochondrial respiratory control, a fundamental introductory presentation of the concept of the protonmotive force, and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. We plan a series of follow-up reports by the expanding MitoEAGLE Network, to increase the scope of consensus-oriented recommendations and facilitate global communication and collaboration.
  • We continue to invite comments and suggestions on the MitoEAGLE preprint (phase 2; until October 12), particularly if you are an early career investigator adding an open future-oriented perspective, or an established scientist providing a balanced historical basis. Your critical input into the quality of the manuscript will be most welcome, improving our aims to be educational, general, consensus-oriented, and practically helpful for students working in mitochondrial respiratory physiology.
  • Please feel free to focus on a particular section in terms of direct input and references, while evaluating the entire scope of the manuscript from the perspective of your expertise.
  • Your comments will be largely posted on the discussion page of the MitoEAGLE preprint website. If you prefer to submit comments in the format of a referee's evaluation rather than a contribution as a coauthor, I will be glad to distribute your views to the updated list of coauthors for a balanced response. We would ask for your consent on this open bottom-up procedure.
We organize a MitoEAGLE session linked to our series of communications at the MiPconference Nov 2017 in Hradec Kralove in close association with the MiPsociety (where you hopefully will attend) and at EBEC 2018 in Budapest.
 » MiP2017_Hradec_Kralove_CZ
I thank you in advance for your feedback.
With best wishes,


Erich Gnaiger
Chair Mitochondrial Physiology Society - http://www.mitophysiology.org
Chair COST Action MitoEAGLE - http://www.mitoeagle.org
Medical University of Innsbruck, Austria
Scope
  • Target a broad audience – introduce the new generation of investigators.
  • List of terms including historical terms; abbreviations (mtDNA, mt to abbreviate mitochondr*); OXPHOS capacity versus State 3 (discuss saturating ADP/Pi .. concentrations).
  • Protonmotive force: not a force defined in physics, but an isomorphic force of statistical and nonequilibrium thermodynamics.
  • Flux and flow: clarification of normalization.
  • Scientific terminology should be general and platform-independent, meeting the demands of all working groups.
‘Every professional group develops its own technical jargon for talking about matters of critical concern. .. People who know a word can share that idea with other members of their group, and a shared vocabulary is part of the glue that holds people together and allows them to create a shared culture’ (Miller 1991).

Three fundamental coupling states of mitochondrial preparations and residual oxygen consumption

Classical terminology for isolated mitochondria

‘When a code is familiar enough, it ceases appearing like a code; one forgets that there is a decoding mechanism. The message is identical with its meaning’ (Hofstadter 1979).


States and rates

Normalization: fluxes and flows

List of selected terms and symbols


Mitochondrial pathways and respiratory control in mt-preparations

Building blocks of mitochondrial physiology Part 2.
‘It is essential to define both the substrate and ADP levels in order to identify the steady-state condition of the mitochondria during the experiment’ (Chance and Williams, 1956).
  • The mitochondrial respiratory system
  • Substrates and inhibitors
  • Switch to pathway-related nomenclature instead of enzyme-linked terminology (N/NS/S versus CI/CI&II/CII)


Mitochondrial respiratory control: cell respiration

Building blocks of mitochondrial physiology Part 3.
Living cells versus mitochondrial preparations
  • Living cells, ce
  • Basal respiration
  • Cell respiration
  • Resting metabolic rate
  • ROUTINE state, state R: ROUTINE respiration of intact, viable cells is regulated according to physiological activity, at intracellular non-saturating ADP levels. R increases under various conditions of activation. When incubated in culture medium, cells maintain a ROUTINE level of activity, R (ROUTINE mitochondrial respiration; corrected for residual oxygen consumption due to oxidative side reactions). ROUTINE activity may include aerobic energy requirements for cell growth and is thus fundamentally different from the definition of basal metabolic rate (BMR). When incubated for short experimental periods in a medium devoid of fuel substrates, the cells respire solely on endogenous substrates at the corresponding state of ROUTINE activity, eR (e, endogenous substrate supply).
It is difficult to stimulate living cells to maximum OXPHOS activity, since ADP and inorganic phosphate do not equilibrate across intact plasma membranes, and thus saturating concentrations of these metabolites can hardly be achieved in living cells. LEAK and ET-pathway states, however, can be induced in viable cells with application of inhibitors of the phosphorylation system and uncouplers, respectively, due to the fact that cell membranes are highy permeable for these substances. External fuel substrates are taken up by living cells to various extents, and intracellular metabolism of exogenous and endogenous substrates supports mitochondrial respiration with a physiological substrate supply. In contrast, mt-preparations depend on the external supply of fuel substrates which support the electron transfer-pathway with reducing equivalents. ET-pathway competence of external substrates is required for all coupling states of mt-preparations (L, P, E) and depends on (i) transport of substrates across the inner mt-membrane or oxidation by dehydrogenases located on the outer face of the inner mt-membrane (e.g. glycerophosphate dehydrogenase complex, CGpDH), (ii) oxidation in the mt-matrix (TCA cycle dehydrogenases and other matrix dehydrogenases, e.g. mtGDH) or on the inner face of the inner mt-membrane (succinate dehydrogenase, CII), (iii) oxidation of substrates without accumulation of inhibitory endproducts (e.g. oxaloacetate inhibiting succinate dehydrogenase; NADH and oxaloacetate inhibiting malate dehydrogenase), and (iv) electron transfer through the membrane-bound ET-pathway (mETS). Endproducts must be either easily exported from the matrix across the inner mt-membrane (e.g. malate formed from succinate via fumarate), or metabolized in the TCA cycle (e.g. malate-derived oxaloacetate forming citrate in the presence of external pyruvate&malate).


Mitochondrial respiratory control: coupling control ratios and control factors

Building blocks of mitochondrial physiology Part 4.


Action

» WG1 Action - WG1 MitoEAGLE protocols, terminology, documentation: Standard operating procedures and user requirement document: Protocols, terminology, documentation
» WG1 Project application
» Gnaiger E, Aasander Frostner E, Abdul Karim N, Abumrad NA, Acuna-Castroviejo D, Adiele RC et al (2019) Mitochondrial respiratory states and rates. MitoFit Preprint Arch doi:10.26124/mitofit:190001. - »Bioblast link«
» Pre-publication: Mitochondrial respiratory control states
» MitoPedia: Respiratory control ratios
» MitoPedia: SUIT