Lee 2024 ACS Nano

Lee CH, Wallace DC, Burke PJ (2024) Super-resolution imaging of voltages in the interior of individual, vital mitochondria. ACS Nano 18:1345−56. https://doi.org/10.1021/acsnano.3c02768

» https://doi.org/10.1021/acsnano.3c02768

Lee CH, Wallace DC, Burke PJ (2024) ACS Nano

Abstract: We present super-resolution microscopy of isolated functional mitochondria, enabling real-time studies of structure and function (voltages) in response to pharmacological manipulation. Changes in mitochondrial membrane potential as a function of time and position can be imaged in different metabolic states (not possible in whole cells), created by the addition of substrates and inhibitors of the electron transport chain, enabled by the isolation of vital mitochondria. By careful analysis of structure dyes and voltage dyes (lipophilic cations), we demonstrate that most of the fluorescent signal seen from voltage dyes is due to membrane bound dyes, and develop a model for the membrane potential dependence of the fluorescence contrast for the case of super-resolution imaging, and how it relates to membrane potential. This permits direct analysis of mitochondrial structure and function (voltage) of isolated, individual mitochondria as well as submitochondrial structures in the functional, intact state, a major advance in super-resolution studies of living organelles.

• Bioblast editor: Gnaiger E

Labels: MiParea: Respiration, mt-Structure;fission;fusion, mt-Membrane 

Preparation: Isolated mitochondria 

Regulation: mt-Membrane potential  Coupling state: LEAK, OXPHOS, ET 

Selected quotes

• OXPHOS consists of the electron transport chain (ETC) plus the ATP synthase.

Comment: This definition is too narrow: The ANT and the inorganic phosphate carrier are additional essential components of the OXPHOS system. - Gnaiger E et al ― MitoEAGLE Task Group (2020) Mitochondrial physiology. Bioenerg Commun 2020.1. https://doi.org/10.26124/bec:2020-0001.v1

• The four multisubunit enzyme complexes of the mitochondrial inner membrane ETC (complexes I−IV) oxidize hydrogen derived from carbohydrates and fats with oxygen to generate H2O.

Comment: Another multisubunit enzyme complex, electron transferring flavoprotein dehydrogenase Complex (CETFDH), is involved in fatty acid oxidation. - Gnaiger E (2024) Complex II ambiguities ― FADH2 in the electron transfer system. J Biol Chem 300:105470. https://doi.org/10.1016/j.jbc.2023.105470

• the electrochemical gradient ΔP consists of a membrane potential (ΔΨm), also called voltage, and a pH gradient (ΔμH+) with the pH gradient typically less significant: ΔP = ΔΨm + ΔμH+.

Comment: ΔP (delta P) indicates a difference. A gradient would be indicated as dP/dz in the direction of z. The units of the voltage difference [V] and the chemical potential difference [kJ.mol-1] do not match. - Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. https://doi.org/10.26124/bec:2020-0002

• NADH-linked substrates such as pyruvate and glutamate feed electrons through complex I while succinate feeds electrons into complex II. The addition of these substrates results in electron transport, increased ΔP, and oxygen consumption known as state II respiration.

Comment: Chance and Williams (1955) defined 'state 2' as high ADP level and ~0 substrate level. The use of state II is ambiguous. - Gnaiger E et al ― MitoEAGLE Task Group (2020) Mitochondrial physiology. Bioenerg Commun 2020.1. https://doi.org/10.26124/bec:2020-0001.v1