This work was financially supported by Kansas City University&#39;s intramural grant for Abdulbaki Agbas and Summer Research Fellowship for Daniel Barrera. The authors are thankful for Dr. Jan Talley&#39;s editorial work.

<ol>
	<li>Gross, V. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+functional+mitochondria+from+rat+kidney+and+skeletal+muscle+without+manual+homogenization.">Isolation of functional mitochondria from rat kidney and skeletal muscle without manual homogenization.</a> Analytical Biochemistry. 418 (2), 213-223 (2011).</li><li>Osto, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+mitochondrial+respiration+in+previously+frozen+biological+samples.">Measuring mitochondrial respiration in previously frozen biological samples.</a> Current Protocols in Cell Biology. 89 (1), 116 (2020).</li><li>Agbas, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+electron+transfer+cascade+enzyme+activity+assessment+in+cultured+neurons+and+select+brain+regions.">Mitochondrial electron transfer cascade enzyme activity assessment in cultured neurons and select brain regions.</a> Current Protocols in Toxicology. 80, 73 (2019).</li><li>Hathaway, Q. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maternal-engineered+nanomaterial+exposure+disrupts+progeny+cardiac+function+and+bioenergetics.">Maternal-engineered nanomaterial exposure disrupts progeny cardiac function and bioenergetics.</a> American Journal of Physiology-Heart and Circulatory Physiology. 312 (3), 446-458 (2017).</li><li>May, L. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+maternal+aerobic+exercise+during+pregnancy+on+fetal+cardiac+function+and+outflow.">Influence of maternal aerobic exercise during pregnancy on fetal cardiac function and outflow.</a> American Journal of Obstetrics &amp; Gynecology MFM. 2 (2), 100095 (2020).</li><li>Ehler, W. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Avoidance+of+malignant+hyperthermia+in+a+porcine+model+for+experimental+open+heart+surgery.">Avoidance of malignant hyperthermia in a porcine model for experimental open heart surgery.</a> Laboratory Animal Science. 35 (2), 172-175 (1985).</li><li>Panov, A. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+bovine+serum+albumin+on+mitochondrial+respiration+in+the+brain+and+liver+of+mice+and+rats.">Effect of bovine serum albumin on mitochondrial respiration in the brain and liver of mice and rats.</a> Bulletin of Experimental Biology and Medicine. 149 (2), 187-190 (2010).</li><li>Jha, P., Wang, X., Auwerx, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+mitochondrial+respiratory+chain+supercomplexes+using+blue+native+polyacrylamide+gel+electrophoresis+(BN-PAGE).">Analysis of mitochondrial respiratory chain supercomplexes using blue native polyacrylamide gel electrophoresis (BN-PAGE).</a> Current Protocols in Mouse Biology. 6 (1), 1-14 (2016).</li><li>Pressure Biosciences Inc. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Isolation of Functional Mitochondria from Whole Rat Heart Using a PBI Shredder and Pressure Cycling Technology (PCT). , (2010).</li><li>McLaughlin, K. 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The authors declare no conflicts of interest.

The critical steps for this protocol are indicated here. First, tissue homogenization should be carefully handled so that excessive sheer effects will not be applied during the tissue homogenization process. A tissue shredder should be used, which is a part of pressure cycling technology (PCT) for initial tissue homogenization9. This step will reduce the excessive stroke cycle of glass-on-glass homogenizer (Figure 1B) that may further destroy already fragile mitochond...

The goal of this protocol was to provide detailed steps to obtain mitochondria-enriched preparation from previously frozen heart tissue with a new technology of low energy mechanical disruption of tissue that improves tissue lysis and extraction of mitochondria. With this method, improved extraction efficiency without generating high shear stress or high temperature and short homogenization time (10-12 s) become achievable1.
To obtain mitochondria from archived frozen tissue is a valuable asset to perform both functional2 and biochemical studies3 otherwise not easily repeatable under the exact experimental conditions. A classic Potter-Elvehjem Teflon pestle glass homogenizer or Dounce homogenizer has been used and is still being used in research laboratories to homogenize soft tissues such as liver, kidney, and brain. However, homogenizing hard tissues such as muscle and heart require more homogenization time, enzyme treatment, high-speed homogenization, and extensive user experience. This is disadvantageous for extracting intact organelles such as mitochondria from hard tissue such as muscle and heart. The method described in this protocol is used to obtain high yield mitochondria-enriched preparation to analyze mitochondrial electron transport chain (ETC) protein complexes and their supercomplex formation in heart tissues harvested from offspring born to exercised and sedentary sow, flash-frozen in liquid nitrogen, and stored at -80 &#176;C for future use. This method allows the user to isolate mitochondria enriched preparation from previously frozen archived tissues.
External nanomaterial exposure to pregnant rodents can negatively affect cardiac function and mitochondrial respiration and bioenergetics on progeny during gestation4. Nevertheless, aerobic exercise-induced positive changes in fetal myocyte bioenergetics during pregnancy are yet to be documented. However, emerging studies provide evidence that maternal aerobic exercise during pregnancy has a positive influence on fetal cardiac function5. In order to provide further evidence, an analysis of the longitudinal effects of maternal exercise on offspring cardiac mitochondrial respiratory chain complexes (i.e., Complex I through Complex V) during pregnancy was performed.
This study has significant health relevance since the results may suggest that maternal exercise improves the efficiency of energy production in the cardiac mitochondria of the offspring. In this study, sows (female pig) were used as an animal model for two reasons: (i) cardiac physiology is similar to human6, and (ii) heart tissue harvest from offspring from different time points is feasible under an institutional IACUC approval. The proposed study aims to answer many of the fundamental questions linking maternal exercise and its potential positive effects on the cellular and biochemical makeup of the offspring&#39;s heart tissue. This approach requires gentle yet effective mitochondria isolation techniques from previously frozen cardiac tissue obtained from the lengthy and costly longitudinal studies that addressed the issues of the bioenergetic changes within fetal cardiac myocytes during the pregnancy. The method described in this study allows utilizing large sums of previously frozen archived tissue for mitochondria-enriched preparation for both analytical and functional studies. The study will also help fill the knowledge gap in this field by providing preliminary data, which could lead to future studies determining the effects of maternal exercise on heart health in utero and beyond.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Amino caproic acid</td>
			<td>Sigma/Aldrich</td>
			<td>A2504-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Hu Total OxPhos complex kit</td>
			<td>Invitrogen</td>
			<td>458199</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-VDAC antibody</td>
			<td>abcam</td>
			<td>ab15895</td>
			<td>use 1 &#181;g/mL</td>
		</tr>
		<tr>
			<td>Coomassie G-250</td>
			<td>ThermoSientific</td>
			<td>20279</td>
			<td></td>
		</tr>
		<tr>
			<td>Coomassie GelCode Blue</td>
			<td>ThermoScientific</td>
			<td>24592</td>
			<td></td>
		</tr>
		<tr>
			<td>Digitonin</td>
			<td>Cabiochem</td>
			<td>300410</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass-Glass pestle homogenizer</td>
			<td>VWR</td>
			<td>KT885451-0020</td>
			<td></td>
		</tr>
		<tr>
			<td>Image Studio</td>
			<td>LICOR</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>IR-Dye conjugated anti-Rabbit Ab</td>
			<td>LICOR</td>
			<td>LC0725</td>
			<td></td>
		</tr>
		<tr>
			<td>Multiwell plate reader</td>
			<td>BioTek</td>
			<td>Synergy HT</td>
			<td></td>
		</tr>
		<tr>
			<td>Native molecular weight marker</td>
			<td>ThermoFisher</td>
			<td>BN2001</td>
			<td></td>
		</tr>
		<tr>
			<td>Nylon mesh monofilament</td>
			<td>Small Part Inc</td>
			<td>CMN-74</td>
			<td></td>
		</tr>
		<tr>
			<td>Orbital shaker</td>
			<td>ThermoScientfic</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PCT Shredder</td>
			<td>Pressure Bioscience Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SEA BLOCK Blocking buffer</td>
			<td>ThermoScienctific</td>
			<td>37527</td>
			<td></td>
		</tr>
		<tr>
			<td>Shredder PULSE Tube</td>
			<td>Pressure Bioscience Inc</td>
			<td>FT500-PS</td>
			<td></td>
		</tr>
		<tr>
			<td>Table top centrifuge</td>
			<td>Eppendorf</td>
			<td>5418</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Amresco</td>
			<td>M150-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin inhibitor</td>
			<td>Amresco</td>
			<td>M191-1G</td>
			<td>Requires fresh preparation</td>
		</tr>
	</tbody>
</table>

measuring mitochondrial electron transfer complexes in previously frozen cardiac tissue from the offspring of sow: a model to assess exercise-induced mitochondrial bioenergetics changes

The mitochondrial electron transfer complex (ETC) profile is modified in the heart tissue of the offspring born to an exercised sow. The hypothesis proposed and tested was that a regular maternal exercise of a sow during pregnancy would increase the mitochondrial efficiency of offspring heart bioenergetics. This hypothesis was tested by isolating mitochondria using a mild-isolation procedure to assess mitochondrial ETC and supercomplex profiles. The procedure described here allowed for the processing of previously frozen archived heart tissues and eliminated the necessity of fresh mitochondria preparation for the assessment of mitochondrial ETC complexes, supercomplexes, and ETC complex activity profiles. This protocol describes the optimal ETC protein complex measurement in multiplexed antibody-based immunoblotting and super complex assessment using blue-native gel electrophoresis.

Following the protocol, a good yield of mitochondria-enriched protein mixture from heart tissue was prepared. Approximately 15 mg/mL of mitochondria-enriched protein mixture was obtained from an average of 1.2 g frozen heart tissue harvested from the offspring of the sow. Observations indicated that less than 0.5 g of frozen heart tissue did not yield a sufficient amount of mitochondrial-enriched protein mixture to carry out a BN-PAGE assay. The amount of mitochondrial preparation was sufficient to perform (i) a standard...

Watch this Scientific Journal Video about Measuring Mitochondrial Electron Transfer Complexes in Previously Frozen Cardiac Tissue from the Offspring of Sow: A Model to Assess Exercise-Induced Mitochon

Measuring Mitochondrial Electron Transfer Complexes in Previously Frozen Cardiac Tissue from the Offspring of Sow: A Model to Assess Exercise-Induced Mitochondrial Bioenergetics Changes

Preparation of mitochondria-enriched samples from previously frozen archived solid tissues allowed the investigators to perform both functional and analytical assessments of mitochondria in various experimental modalities. This study demonstrates how to prepare mitochondria-enriched preparations from frozen heart tissue and perform analytical assessments of mitochondria.

The mitochondrial electron transfer complex (ETC) profile is modified in the heart tissue of the offspring born to an exercised sow. The hypothesis ...

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2.5K Views.  AdventHelath. Preparation of mitochondria-enriched samples from previously frozen archived solid tissues allowed the investigators to perform both functional and analytical assessments of mitochondria in various experimental modalities. This study demonstrates how to prepare mitochondria-enriched preparations from frozen heart tissue and perform analytical assessments of mitochondria.

Video: Measuring Mitochondrial Electron Transfer Complexes in Previously Frozen Cardiac Tissue from the Offspring of Sow: A Model to Assess Exercise-Induced Mitochondrial Bioenergetics Changes

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating these studies, reincorporation of detergent-solubilized membrane proteins into liposomes is a stochastic process where protein topology is impossible to enforce. This paper offers an alternative method to these challenging techniques that utilizes a liposome-based scaffold. Protein solubility is enhanced by deletion of the transmembrane domain, and these amino acids are replaced with a tethering moiety, such as a His-tag. This tether interacts with an anchoring group (Ni2+ coordinated by nitrilotriacetic acid (NTA(Ni2+)) for His-tagged proteins), which enforces a uniform protein topology at the surface of the liposome. An example is presented wherein the interaction between Dynamin-related protein 1 (Drp1) with an integral membrane protein, Mitochondrial Fission Factor (Mff), was investigated using this scaffold liposome method. In this work, we have demonstrated the ability of Mff to efficiently recruit soluble Drp1 to the surface of liposomes, which stimulated its GTPase activity. Moreover, Drp1 was able to tubulate the Mff-decorated lipid template in the presence of specific lipids. This example demonstrates the effectiveness of scaffold liposomes using structural and functional assays and highlights the role of Mff in regulating Drp1 activity.

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

This paper describes a method for assessing the interactions and assemblies of integral membrane proteins in vitro with various partner factors in a lipid-proximal environment.

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating ...

Analyzing Supercomplexes of the Mitochondrial Electron Transport Chain with Native Electrophoresis, In-gel Assays, and Electroelution

The mitochondrial electron transport chain (ETC) transduces the energy derived from the breakdown of various fuels into the bioenergetic currency of the cell, ATP. The ETC is composed of 5 massive protein complexes, which also assemble into supercomplexes called respirasomes (C-I, C-III, and C-IV) and synthasomes (C-V) that increase the efficiency of electron transport and ATP production. Various methods have been used for over 50 years to measure ETC function, but these protocols do not provide information on the assembly of individual complexes and supercomplexes. This protocol describes the technique of native gel polyacrylamide gel electrophoresis (PAGE), a method that was modified more than 20 years ago to study ETC complex structure. Native electrophoresis permits the separation of ETC complexes into their active forms, and these complexes can then be studied using immunoblotting, in-gel assays (IGA), and purification by electroelution. By combining the results of native gel PAGE with those of other mitochondrial assays, it is possible to obtain a completer picture of ETC activity, its dynamic assembly and disassembly, and how this regulates mitochondrial structure and function. This work will also discuss limitations of these techniques. In summary, the technique of native PAGE, followed by immunoblotting, IGA, and electroelution, presented below, is a powerful way to investigate the functionality and composition of mitochondrial ETC supercomplexes.

This protocol describes the separation of functional mitochondrial electron transport chain complexes (Cx) I-V and supercomplexes thereof using native electrophoresis to reveal information about their assembly and structure. The native gel can be subjected to immunoblotting, in-gel assays, and purification by electroelution to further characterize individual complexes.

The mitochondrial electron transport chain (ETC) transduces the energy derived from the breakdown of various fuels into the bioenergetic currency of the ...

Measurement of Mitochondrial Oxygen Consumption in Permeabilized Fibers of Drosophila Using Minimal Amounts of Tissue

The fruit fly, Drosophila melanogaster, represents an emerging model for the study of metabolism. Indeed, drosophila have structures homologous to human organs, possess highly conserved metabolic pathways and have a relatively short lifespan that allows the study of different fundamental mechanisms in a short period of time. It is, however, surprising that one of the mechanisms essential for cellular metabolism, the mitochondrial respiration, has not been thoroughly investigated in this model. It is likely because the measure of the mitochondrial respiration in Drosophila usually requires a very large number of individuals and the results obtained are not highly reproducible. Here, a method allowing the precise measurement of mitochondrial oxygen consumption using minimal amounts of tissue from Drosophila is described. In this method, the thoraxes are dissected and permeabilized both mechanically with sharp forceps and chemically with saponin, allowing different compounds to cross the cell membrane and modulate the mitochondrial respiration. After permeabilization, a protocol is performed to evaluate the capacity of the different complexes of the electron transport system (ETS) to oxidize different substrates, as well as their response to an uncoupler and to several inhibitors. This method presents many advantages compared to methods using mitochondrial isolations, as it is more physiologically relevant because the mitochondria are still interacting with the other cellular components and the mitochondrial morphology is conserved. Moreover, sample preparations are faster, and the results obtained are highly reproducible. By combining the advantages of Drosophila as a model for the study of metabolism with the evaluation of mitochondrial respiration, important new insights can be unveiled, especially when the flies are experiencing different environmental or pathophysiological conditions.

In this paper, a method to measure oxygen consumption using high-resolution respirometry in permeabilized thoraxes of Drosophila is described. This technique requires a minimal amount of tissue compared to the classic mitochondrial isolation technique and the results obtained are more physiologically relevant.

The fruit fly, Drosophila melanogaster, represents an emerging model for the study of metabolism. Indeed, drosophila have structures homologous to human ...

Measuring Liver Mitochondrial Oxygen Consumption and Proton Leak Kinetics to Estimate Mitochondrial Respiration in Holstein Dairy Cattle

Oxygen consumption, proton motive force (PMF) and proton leak are measurements of mitochondrial respiration, or how well mitochondria are able to convert NADH and FADH into ATP. Since mitochondria are also the primary site for oxygen use and nutrient oxidation to carbon dioxide and water, how efficiently they use oxygen and produce ATP directly relates to the efficiency of nutrient metabolism, nutrient requirements of the animal, and health of the animal. The purpose of this method is to examine mitochondrial respiration, which can be used to examine the effects of different drugs, diets and environmental effects on mitochondrial metabolism. Results include oxygen consumption measured as proton dependent respiration (State 3) and proton leak dependent respiration (State 4). The ratio of State 3 / State 4 respiration is defined as respiratory control ratio (RCR) and can represent mitochondrial energetic efficiency. Mitochondrial proton leak is a process that allows dissipation of mitochondrial membrane potential (MMP) by uncoupling oxidative phosphorylation from ADP decreasing the efficiency of ATP synthesis. Oxygen and TRMP+ sensitive electrodes with mitochondrial substrates and electron transport chain inhibitors are used to measure State 3 and State 4 respiration, mitochondrial membrane PMF (or the potential to produce ATP) and proton leak. Limitations to this method are that liver tissue must be as fresh as possible and all biopsies and assays must be performed in less than 10 h. This limits the number of samples that can be collected and processed by a single person in a day to approximately 5. However, only 1 g of liver tissue is needed, so in large animals, such as dairy cattle, the amount of sample needed is small relative to liver size and there is little recovery time needed.

Here, we share methods for measuring mitochondrial oxygen consumption, a defining concept of nutritional energetics, and proton leak, the primary cause of inefficiency in mitochondrial generation of ATP. These results can account for 30% of the energy lost in nutrient utilization to help evaluate mitochondrial function.

Oxygen consumption, proton motive force (PMF) and proton leak are measurements of mitochondrial respiration, or how well mitochondria are able to convert ...

A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics

Mitochondrial dynamics is essential for the organelle&#8217;s diverse functions and cellular responses. The crowded, spatially complex, mitochondrial membrane is a challenging environment to distinguish regulatory factors. Experimental control of protein and lipid components can help answer specific questions of regulation. Yet, quantitative manipulation of these factors is challenging in cellular assays. To investigate the molecular mechanism of mitochondria inner-membrane fusion, we introduced an in vitro reconstitution platform that mimics the lipid environment of the mitochondrial inner-membrane. Here we describe detailed steps for preparing lipid bilayers and reconstituting mitochondrial membrane proteins. The platform allowed analysis of intermediates in mitochondrial inner-membrane fusion, and the kinetics for individual transitions, in a quantitative manner. This protocol describes the fabrication of bilayers with asymmetric lipid composition and describes general considerations for reconstituting transmembrane proteins into a cushioned bilayer. The method may be applied to study other membrane systems.

Mitochondrial fusion is an important homeostatic reaction underlying mitochondrial dynamics. Described here is an in vitro reconstitution system to study mitochondrial inner-membrane fusion that can resolve membrane tethering, docking, hemifusion, and pore opening. The versatility of this approach in exploring cell membrane systems is discussed.

Mitochondrial dynamics is essential for the organelle&#8217;s diverse functions and cellular responses. The crowded, spatially complex, mitochondrial ...

Stable Isotope Tracing & LC-MS Analysis to Measure DHODH and SDH Activities

Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals

The flow of electrons in the mitochondrial electron transport chain (ETC) supports multifaceted biosynthetic, bioenergetic, and signaling functions in mammalian cells. As oxygen (O2) is the most ubiquitous terminal electron acceptor for the mammalian ETC, the O2 consumption rate is frequently used as a proxy for mitochondrial function. However, emerging research demonstrates that this parameter is not always indicative of mitochondrial function, as fumarate can be employed as an alternative electron acceptor to sustain mitochondrial functions in hypoxia. This article compiles a series of protocols that allow researchers to measure mitochondrial function independently of the O2 consumption rate. These assays are particularly useful when studying mitochondrial function in hypoxic environments. Specifically, we describe methods to measure mitochondrial ATP production, de novo pyrimidine biosynthesis, NADH oxidation by complex I, and superoxide production. In combination with classical respirometry experiments, these orthogonal and economical assays will provide researchers with a more comprehensive assessment of mitochondrial function in their system of interest.

Author Spotlight: Oxygen-Independent Assays to Measure Mitochondrial Function in Mammals  

Here, we present a compilation of assays to directly measure mitochondrial function in mammalian cells independently of their ability to consume molecular oxygen.

The flow of electrons in the mitochondrial electron transport chain (ETC) supports multifaceted biosynthetic, bioenergetic, and signaling functions in ...

Isolation of Mitochondrial Contact Sites

An Improved Method to Isolate Mitochondrial Contact Sites

Mitochondria are present in virtually all eukaryotic cells and perform essential functions that go far beyond energy production, for instance, the synthesis of iron-sulfur clusters, lipids, or proteins, Ca2+ buffering, and the induction of apoptosis. Likewise, mitochondrial dysfunction results in severe human diseases such as cancer, diabetes, and neurodegeneration. In order to perform these functions, mitochondria have to communicate with the rest of the cell across their envelope, which consists of two membranes. Therefore, these two membranes have to interact constantly. Proteinaceous contact sites between the mitochondrial inner and outer membranes are essential in this respect. So far, several contact sites have been identified. In the method described here, Saccharomyces cerevisiae mitochondria are used to isolate contact sites and, thus, identify candidates that qualify for contact site proteins. We used this method to identify the mitochondrial contact site and cristae organizing system (MICOS) complex, one of the major contact site-forming complexes in the mitochondrial inner membrane, which is conserved from yeast to humans. Recently, we further improved this method to identify a novel contact site consisting of Cqd1 and the Por1-Om14 complex.

Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights 

Mitochondrial contact sites are protein complexes that interact with mitochondrial inner and outer membrane proteins. These sites are essential for the communication between the mitochondrial membranes and, thus, between the cytosol and the mitochondrial matrix. Here, we describe a method to identify candidates qualifying for this specific class of proteins.

Mitochondria are present in virtually all eukaryotic cells and perform essential functions that go far beyond energy production, for instance, the ...

Mitochondrial Fractionation in Small Tissue Samples for Supercomplex Analysis

Isolation of Mitochondria for Mitochondrial Supercomplex Analysis from Small Tissue and Cell Culture Samples

Over the last decades, the evidence accumulated about the existence of respiratory supercomplexes (SCs) has changed our understanding of the mitochondrial electron transport chain organization, giving rise to the proposal of the "plasticity model." This model postulates the coexistence of different proportions of SCs and complexes depending on the tissue or the cellular metabolic status. The dynamic nature of the assembly in SCs would allow cells to optimize the use of available fuels and the efficiency of electron transfer, minimizing reactive oxygen species generation and favoring the ability of cells to adapt to environmental changes. 
More recently, abnormalities in SC assembly have been reported in different diseases such as neurodegenerative disorders (Alzheimer's and Parkinson's disease), Barth Syndrome, Leigh syndrome, or cancer. The role of SC assembly alterations in disease progression still needs to be confirmed. Nevertheless, the availability of enough amounts of samples to determine the SC assembly status is often a challenge. This happens with biopsy or tissue samples that are small or have to be divided for multiple analyses, with cell cultures that have slow growth or come from microfluidic devices, with some primary cultures or rare cells, or when the effect of particular costly treatments has to be analyzed (with nanoparticles, very expensive compounds, etc.). In these cases, an efficient and easy-to-apply method is required. This paper presents a method adapted to obtain enriched mitochondrial fractions from small amounts of cells or tissues to analyze the structure and function of mitochondrial SCs by native electrophoresis followed by in-gel activity assays or western blot.

Author Spotlight: Unveiling Oxidative Phosphorylation System Dynamics and Mitochondrial Roles in Health and Disease

This protocol describes a technique for the analysis of respiratory supercomplexes when only small amounts of samples are available.

Over the last decades, the evidence accumulated about the existence of respiratory supercomplexes (SCs) has changed our understanding of the mitochondrial ...

Mitochondrial Isolation from Rodents for High-Quality Bioenergetic Studies

Robust Mitochondrial Isolation from Rodent Cardiac Tissue 

Mitochondrial isolation has been practiced for decades, following procedures established by pioneers in the fields of molecular biology and biochemistry to study metabolic impairments and disease. Consistent mitochondrial quality is necessary to properly investigate mitochondrial physiology and bioenergetics; however, many different published isolation methods are available for researchers. Although different experimental strategies require different isolation methods, the basic principles and procedures are similar. This protocol details a method capable of extracting well-coupled mitochondria from a variety of tissue sources, including small animals and cells. The steps outlined include organ dissection, mitochondrial purification, protein quantification, and various quality control checks. The primary quality control metric used to identify high-quality mitochondria is the respiratory control ratio (RCR). The RCR is the ratio of the respiratory rate during oxidative phosphorylation to the rate in the absence of ADP. Alternative metrics are discussed. While high RCR values relative to their tissue source are obtained using this protocol, several steps can be optimized to suit the individual needs of researchers. This procedure is robust and has consistently resulted in isolated mitochondria with above-average RCR values across animal models and tissue sources.

Author Spotlight: Uncovering the Role of Mitochondrial Calcium Phosphate in Heart Failure and Bioenergetics

Bioenergetic and metabolomic studies on mitochondria have revealed their multifaceted role in many diseases, but the isolation methods for these organelles vary. The method detailed here is capable of purifying high-quality mitochondria from multiple tissue sources. Quality is determined by respiratory control ratios and other metrics assessed with high-resolution respirometry.

Mitochondrial isolation has been practiced for decades, following procedures established by pioneers in the fields of molecular biology and biochemistry ...