The authors acknowledge the Brazilian agency Coordena&#231;&#227;o de Aperfei&#231;oamento de Pesquisa Pessoal de N&#237;vel Superior (CAPES EPIDEMIAS 09 #88887.505377/2020). P.M. (#88887.512821/2020-00) and T.D. (#88887.512883/2020-00) are research fellowship recipients.

We used the strains w1118 (white) and w[*] Pink1[B9]/FM7i, P{w[+mC]=ActGFP}JMR3 (referred to as Pink1B9) (FlyBase ID: FBgn0029891) from the Bloomington Drosophila stock center (ID number: 34749). In this study, male D. melanogaster PINK1B9-null mutants are compared with male D. melanogaster from the w1118&#160;strain, which is used as a control group (genetic background). Other parameters must be analyzed concomitantly with the respirometry experiments to ensure that the flies have the correct genotype (Pink1B9/Y), such as thorax deformities and locomotion problems, which are well described for pink1B9 mutant flies24,25,26.
1. Animals and housing
<ol>
	<li>Keep the flies in glass bottles containing 10 mL of standard diet (yeast 1.73%, soy flour 0.9%, corn flour 7.3%, agar 0.5%, corn syrup 7.6%, and propionic acid 0.48%) at constant temperature and humidity (25 &#176;C and 60%, respectively), with a 12 h:12 h light/dark cycle.</li>
	<li>For each experiment, use two flies aged 1-3 days post-eclosion. 
	&#8203;NOTE: The PINK1B9-null mutant virgin female flies were crossed with w1118 males to obtain the F1 males with genotype Pink1B9/Y.</li>
</ol>
2. Sample preparation
<ol>
	<li>Prepare the MiR05 buffer as described in Table 1.</li>
	<li>Anesthetize the flies on ice and transfer them to microcentrifuge tubes (two flies per tube).</li>
	<li>In each tube, add 200 &#181;L of chilled MiR05 buffer and homogenize the flies. Homogenize manually, applying gentle pressure (approximately 4-6 strokes of the pestle) to prevent the disintegration of mitochondria.</li>
</ol>
3. High-resolution respirometry calibration of polarographic oxygen sensors
NOTE: The OROBOROS chambers have a total volume of approximately 2 mL. Calibration is required to ensure the oxygen flux is close to 0 pmol to start the assay.
<ol>
	<li>Starting the calibration, add 2 mL of MiR05 to the chamber. Cover the chamber with the stopper leaving no air bubbles; then, carefully pull the stopper to form one single air bubble.</li>
	<li>Open the OROBOROS Dat.Lab software. Enter a temperature of 25 &#176;C in the Block temperature field and click on Connect to Oxygraph-2k (Figure 1A).</li>
	<li>Click and select the folder where the calibration is to be saved and click on Save.</li>
	<li>When a new window opens, name the experiment and the samples (if calibrating, simply enter the name calibration) and click on Save.</li>
	<li>Go to the Layout menu and choose the first option: 01 Calibration Exp. Gr.3 - Temp as shown in Figure 1B.</li>
	<li>Wait for the program to redirect to the calibration layout, wait until the red line shows a standard straight line with points around 0 pmol. Then, select two points: one for chamber A and the other for chamber B (Figure 1C) when the red line is exactly at zero. 
	NOTE: The selected points must have oxygen flux (red line) around 0.
	<ol>
		<li>To mark the points of both chambers, select O2 concentration on the right of the screen, select the marked point, and copy both the temperature and barometric pressure values relative to the point. Paste these values in the boxes below and click on Calibrate and Copy to Clipboard in the lower right corner of the screen as shown in Figure 2.</li>
		<li>Carry out this process for both chambers (A and B), then go to the File menu and select Save and Disconnect. 
		&#8203;NOTE: After the calibration process, the program will redirect the user to the home screen so that the software will be ready to start the HRR test. For this test, we will use the SUIT protocol.</li>
	</ol>
	</li>
</ol>
4. SUIT protocol
<ol>
	<li>With the calibration completed, remove the stoppers and open the chambers.</li>
	<li>Wash the stoppers (holding the tip that does not touch the sample) and chambers with 100% ethanol, 70% ethanol, and distilled water, in that order. 
	NOTE: Repeat the process for every sample change.</li>
	<li>Homogenize the flies in 200 &#181;L of buffer, place all sample content in the chamber using a micropipette, and relocate the stopper in the chamber, taking care to not create air bubbles. 
	NOTE: If air bubbles form, remove the stopper gently and add 100 &#181;L of MIR05 buffer.</li>
	<li>Click on the Layout menu and select the option 05 Flow by Corrected Volume as shown in Figure 1B.</li>
	<li>Wait to be redirected to a new window. Click on Save to select the folder where the experiment is to be saved.</li>
	<li>Wait for another new window to open. Name the experiment in the space Experimental Code. Then, name each sample in its respective chamber A and B in the Sample field, and set the field Unit to unit. 
	NOTE: Other units can also be chosen, for example, Millions of cells or mg.</li>
	<li>Considering that this protocol uses two flies (2 units) and the chamber volume is 2 mL, in the Concentration field, define 1 per mL (Figure 1D). 
	NOTE: Here, the sample amount was normalized by the number of flies; however, this normalization may be performed by the protein content of the sample, mitochondrial DNA quantification, or activity of citrate synthase.</li>
	<li>When the oxygen flux signal (red line) is steady on the positive value, start the HRR protocol with the titration of substrates, inhibitors, and uncouplers (Figure 3). All the subsequent reagents and equipment are shown in Table 1.
	<ol>
		<li>Add digitonin (5 &#956;g/mL) to permeabilize the mitochondrial membrane.</li>
		<li>Add pyruvate (5 mM), malate (2 mM), and proline (10 mM) substrates and wait until the oxygen flux increases and stabilizes. To mark the event for each reagent addition, press the F4 key on the keyboard and enter the name of each reagent.</li>
		<li>Add ADP (5mM) to couple the mitochondrial respiratory chain and wait for the increase and stabilization of the oxygen flux.</li>
		<li>Add succinate (10 mM) and wait for the increase and stabilization of the oxygen flux.</li>
		<li>Add Oligomycin (2.5 &#181;M) to inhibit ATP synthase and look for a decrease in oxygen flux.</li>
		<li>Wait until the red line stabilizes and uncouple mitochondrial electron transfer using Carbonyl-4-(trifluoromethoxy) phenylhydrazone cyanide (FCCP) with titers of 0.25 &#181;M until the maximum oxygen consumption is reached, demonstrated by the rise of the red line. After stabilization of the oxygen flux, start adding the inhibitors of each complex, one at a time.</li>
		<li>Add Rotenone (0.5 &#181;M), a complex I inhibitor. Wait for the decrease and stabilization of the oxygen flux to add the next inhibitor.</li>
		<li>Add Malonate (5 mM), a complex II inhibitor. Wait for the decrease and stabilization of the oxygen flux to add the next inhibitor.</li>
		<li>Finally, add Antimycin (2.5 &#181;M), a complex III inhibitor. Wait for the decrease followed by the increase and stabilization of the oxygen flux. 
		NOTE: The oxygen flux should stabilize at a positive value but below the value for the last inhibition of mitochondrial protein complexes.</li>
	</ol>
	</li>
	<li>At the end of the analysis, remove all the content of the chambers using a micropipette. Store at -20 &#176;C for future analysis, when necessary.</li>
</ol>
5. Data analysis
<ol>
	<li>Utilize an appropriate statistical software package for data analysis.</li>
	<li>Perform t-tests to assess differences between the two groups. For situations involving multiple treatments, use Analysis of Variance (ANOVA) as a statistical test 27.</li>
	<li>Extract the O2 flux values from the graph generated by the software. OXPHOS CI refers to the value of O2 flux after adding ADP. OXPHOS CII is obtained by subtracting OXPHOS CI&#38;CII - OXPHOS CI. OXPHOS CI&#38;CII is the value of O2 flux extracted after the addition of succinate. ETS CI&#38;CII is the O2 flux value after adding FCCP. ETS CI = FCCP - Rotenone and ETS CII = Rotenone - Malonate.</li>
	<li>Calculate ATP synthesis as the difference between the OXPHOS (P) and LEAK (L) (P - L)28.</li>
	<li>Determine the Respiratory Control Ratio (RCR) by calculating the ratio OXPHOS/LEAK, where RCR = P/L.11</li>
</ol>

Analyzing Mitochondrial Physiology and Bioenergetics in Fruit Flies

<ol>
	<li>Brand, M. D., Orr, A. L., Perevoshchikova, I. V., Quinlan, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+mitochondrial+function+and+cellular+bioenergetics+in+ageing+and+disease.">The role mitochondrial function and cellular bioenergetics in ageing and disease.</a> Br J Dermatol. 169, 1-8 (2013).</li><li>Ramaccini, D., 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+function+and+dysfunction+in+dilated+cardiomyopathy.">Mitochondrial function and dysfunction in dilated cardiomyopathy.</a> Front Cell Dev Biol. 8, 624216 (2021).</li><li>Zhunina, O. 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=The+role+of+mitochondrial+dysfunction+in+vascular+disease,+tumorigenesis,+and+diabetes.">The role of mitochondrial dysfunction in vascular disease, tumorigenesis, and diabetes.</a> Front Mol Biosci. 8, 671908 (2021).</li><li>Prasun, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+dysfunction+in+metabolic+syndrome.">Mitochondrial dysfunction in metabolic syndrome.</a> Biochim Biophys Acta. 1866 (10), 165838 (2020).</li><li>Bhatti, J. S., Bhatti, G. K., Reddy, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+dysfunction+and+oxidative+stress+in+metabolic+disorders+-+A+Step+towards+mitochondria+based+therapeutic+strategies.">Mitochondrial dysfunction and oxidative stress in metabolic disorders - A Step towards mitochondria based therapeutic strategies.</a> Biochim Biophys Acta. 1863 (5), 1066-1077 (2017).</li><li>Perier, C., Vila, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+biology+and+Parkinson's+disease.">Mitochondrial biology and Parkinson's disease.</a> Cold Spring Harb Perspect Med. 2 (2), 009332 (2012).</li><li>DeMaagd, G., Philip, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parkinson's+disease+and+its+management.">Parkinson's disease and its management.</a> Pharmacy and Therapeutics. 40 (8), 504-532 (2015).</li><li>Miyazaki, N., 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=PINK1-dependent+and+Parkin-independent+mitophagy+is+involved+in+reprogramming+of+glycometabolism+in+pancreatic+cancer+cells.">PINK1-dependent and Parkin-independent mitophagy is involved in reprogramming of glycometabolism in pancreatic cancer cells.</a> Biochem Biophys Res Commun. 625, 167-173 (2022).</li><li>Kopin, I. J., Markey, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MPTP+toxicity:+implications+for+research+in+Parkinson's+disease.">MPTP toxicity: implications for research in Parkinson's disease.</a> Annual Review of Neuroscience. 11, 81-96 (1988).</li><li>Connolly, N. M. 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=Guidelines+on+experimental+methods+to+assess+mitochondrial+dysfunction+in+cellular+models+of+neurodegenerative+diseases.">Guidelines on experimental methods to assess mitochondrial dysfunction in cellular models of neurodegenerative diseases.</a> Cell Death Differ. 25 (3), 542-572 (2018).</li><li>Brand, M. D., Nicholls, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+mitochondrial+dysfunction+in+cells.">Assessing mitochondrial dysfunction in cells.</a> Biochem J. 435, 297-312 (2011).</li><li>Haynes, C. M., Fiorese, C. J., Lin, Y. -. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+and+responding+to+mitochondrial+dysfunction:+The+UPRmt+and+beyond.">Evaluating and responding to mitochondrial dysfunction: The UPRmt and beyond.</a> Trends Cell Mol Biol. 23 (7), 311-318 (2013).</li><li>Long, Q., Huang, L., Huang, K., Yang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+mitochondrial+bioenergetics+in+isolated+mitochondria+from+mouse+heart+tissues+using+oroboros+2k-oxygraph.">Assessing mitochondrial bioenergetics in isolated mitochondria from mouse heart tissues using oroboros 2k-oxygraph.</a> Methods Mol Biol. 1966, 237-246 (2019).</li><li>Scheiber, D., 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=High-resolution+respirometry+in+human+endomyocardial+biopsies+shows+reduced+ventricular+oxidative+capacity+related+to+heart+failure.">High-resolution respirometry in human endomyocardial biopsies shows reduced ventricular oxidative capacity related to heart failure.</a> Exp Mol Med. 51 (2), 1-10 (2019).</li><li>Krumschnabel, G., Eigentler, A., Fasching, M., Gnaiger, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+nine+-+use+of+safranin+for+the+assessment+of+mitochondrial+membrane+potential+by+high-resolution+respirometry+and+fluorometry.">Chapter nine - use of safranin for the assessment of mitochondrial membrane potential by high-resolution respirometry and fluorometry.</a> Methods Enzymol. 542, 163-181 (2014).</li><li>Demir, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+potential+use+of+Drosophila+as+an+in+vivo+model+organism+for+COVID-19-related+research:+a+review.">The potential use of Drosophila as an in vivo model organism for COVID-19-related research: a review.</a> Turk J Biol. 45 (4), 559-569 (2021).</li><li>Hales, K. G., Korey, C. A., Larracuente, A. M., Roberts, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetics+on+the+fly:+a+primer+on+the+Drosophila+model+system.">Genetics on the fly: a primer on the Drosophila model system.</a> Genetics. 201 (3), 815-842 (2015).</li><li>McBride, S. M. J., Holloway, S. L., Jongens, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+Drosophila+as+a+tool+to+identify+pharmacological+therapies+for+fragile+X+syndrome.">Using Drosophila as a tool to identify pharmacological therapies for fragile X syndrome.</a> Drug Discov Today Technol Technologies. 10 (1), e129-e136 (2013).</li><li>Tennessen, J. M., Barry, W. E., Cox, J., Thummel, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+studying+metabolism+in+Drosophila.">Methods for studying metabolism in Drosophila.</a> Methods (San Diego, Calif). 68 (1), 105-115 (2014).</li><li>Bar, S., Prasad, M., Datta, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromuscular+degeneration+and+locomotor+deficit+in+a+Drosophila+model+of+mucopolysaccharidosis+VII+is+attenuated+by+treatment+with+resveratrol).">Neuromuscular degeneration and locomotor deficit in a Drosophila model of mucopolysaccharidosis VII is attenuated by treatment with resveratrol).</a> Dis Model Mech. 11 (11), (2018).</li><li>Imai, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PINK1-Parkin+signaling+in+Parkinson's+disease:+Lessons+from+Drosophila.">PINK1-Parkin signaling in Parkinson's disease: Lessons from Drosophila.</a> Neurosci Res. 159, 40-46 (2020).</li><li>Julienne, H., Buhl, E., Leslie, D. S., Hodge, J. J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+PINK1+and+parkin+loss-of-function+mutants+display+a+range+of+non-motor+Parkinson's+disease+phenotypes.">Drosophila PINK1 and parkin loss-of-function mutants display a range of non-motor Parkinson's disease phenotypes.</a> Neurobiol Dis. 104, 15-23 (2017).</li><li>Biswas, S., Bagchi, A. <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+the+structural+dynamics+of+the+mutations+in+the+kinase+domain+of+PINK1+protein+associated+with+Parkinson's+disease.">Analysis of the structural dynamics of the mutations in the kinase domain of PINK1 protein associated with Parkinson's disease.</a> Gene. 857, 147183 (2023).</li><li>Koh, H., Chung, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PINK1+and+Parkin+to+control+mitochondria+remodeling.">PINK1 and Parkin to control mitochondria remodeling.</a> Anat Cell Biol. 43 (3), 179-184 (2010).</li><li>Zhu, M., Li, X., Tian, X., Wu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mask+loss-of-function+rescues+mitochondrial+impairment+and+muscle+degeneration+of+Drosophila+pink1+and+parkin+mutants.">Mask loss-of-function rescues mitochondrial impairment and muscle degeneration of Drosophila pink1 and parkin mutants.</a> Hum Mol Genet. 24 (11), 3272-3285 (2015).</li><li>Park, 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=Mitochondrial+dysfunction+in+Drosophila+PINK1+mutants+is+complemented+by+parkin.">Mitochondrial dysfunction in Drosophila PINK1 mutants is complemented by parkin.</a> Nature. 441 (7097), 1157-1161 (2006).</li><li>Dytham, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Choosing and using statistics: a biologist's guide. , (2011).</li><li>Bonora, M., 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=ATP+synthesis+and+storage.">ATP synthesis and storage.</a> Purinergic Signal. 8 (3), 343-357 (2012).</li><li>Gon&#231;alves, D. F., 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=Caffeine+improves+mitochondrial+function+in+PINK1B9-null+mutant+Drosophila+melanogaster.">Caffeine improves mitochondrial function in PINK1B9-null mutant Drosophila melanogaster.</a> J Bioenerg Biomembr. 55 (1), 1-13 (2023).</li><li>Gon&#231;alves, D. F., 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+function+and+cellular+energy+maintenance+during+aging+in+a+Drosophila+melanogaster+model+of+Parkinson+disease.">Mitochondrial function and cellular energy maintenance during aging in a Drosophila melanogaster model of Parkinson disease.</a> Mitochondrion. 65, 166-175 (2022).</li><li>Janowska, J. I., 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+respiratory+chain+complex+I+dysfunction+induced+by+N-methyl+carbamate+ex+vivo+can+be+alleviated+with+a+cell-permeable+succinate+prodrug.">Mitochondrial respiratory chain complex I dysfunction induced by N-methyl carbamate ex vivo can be alleviated with a cell-permeable succinate prodrug.</a> Toxicol In Vitro. 65, 104794 (2020).</li><li>Ngo, D. T. M., 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=Oxidative+modifications+of+mitochondrial+complex+II+are+associated+with+insulin+resistance+of+visceral+fat+in+obesity.">Oxidative modifications of mitochondrial complex II are associated with insulin resistance of visceral fat in obesity.</a> Physiol Endocrinol Metab. 316 (2), E168-E177 (2019).</li><li>Stroud, D. 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=Accessory+subunits+are+integral+for+assembly+and+function+of+human+mitochondrial+complex+I.">Accessory subunits are integral for assembly and function of human mitochondrial complex I.</a> Nature. 538 (7623), 123-126 (2016).</li><li>Senyilmaz, D., 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=Regulation+of+mitochondrial+morphology+and+function+by+stearoylation+of+TFR1.">Regulation of mitochondrial morphology and function by stearoylation of TFR1.</a> Nature. 525 (7567), 124-128 (2015).</li><li>Poddighe, 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=Mucuna+pruriens+(Velvet+bean)+rescues+motor,+olfactory,+mitochondrial+and+synaptic+impairment+in+PINK1B9+Drosophila+melanogaster+genetic+model+of+Parkinson's+disease.">Mucuna pruriens (Velvet bean) rescues motor, olfactory, mitochondrial and synaptic impairment in PINK1B9 Drosophila melanogaster genetic model of Parkinson's disease.</a> PloS One. 9 (10), e110802 (2014).</li><li>Pesta, D., Gnaiger, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+respirometry:+OXPHOS+protocols+for+human+cells+and+permeabilized+fibers+from+small+biopsies+of+human+muscle.">High-resolution respirometry: OXPHOS protocols for human cells and permeabilized fibers from small biopsies of human muscle.</a> Methods Mol Biol (Clifton, N.J). 810, 25-58 (2012).</li><li>Winer, L. S. P., Wu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+analysis+of+glycolytic+and+oxidative+substrate+flux+of+cancer+cells+in+a+microplate.">Rapid analysis of glycolytic and oxidative substrate flux of cancer cells in a microplate.</a> PloS One. 9 (10), e109916 (2014).</li><li>Plitzko, B., Loesgen, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+oxygen+consumption+rate+(OCR)+and+extracellular+acidification+rate+(ECAR)+in+culture+cells+for+assessment+of+the+energy+metabolism.">Measurement of oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in culture cells for assessment of the energy metabolism.</a> Bio Protoc. 8 (10), e2850 (2018).</li><li>Wu, M., 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=Multiparameter+metabolic+analysis+reveals+a+close+link+between+attenuated+mitochondrial+bioenergetic+function+and+enhanced+glycolysis+dependency+in+human+tumor+cells.">Multiparameter metabolic analysis reveals a close link between attenuated mitochondrial bioenergetic function and enhanced glycolysis dependency in human tumor cells.</a> Am J Physiol. Cell Physiol. 292 (1), C125-C136 (2007).</li><li>Divakaruni, A. S., Jastroch, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+practical+guide+for+the+analysis,+standardization+and+interpretation+of+oxygen+consumption+measurements.">A practical guide for the analysis, standardization and interpretation of oxygen consumption measurements.</a> Nat Metab. 4 (8), 978-994 (2022).</li><li>Bingol, B., Sheng, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+mitophagy:+PINK1,+Parkin,+USP30+and+beyond.">Mechanisms of mitophagy: PINK1, Parkin, USP30 and beyond.</a> Free Radic Biol Med. 100, 210-222 (2016).</li></ol>

The authors declare no competing interests.

HRR is a powerful technique for studying mitochondrial respiration and energy metabolism in D. melanogaster and other organisms. It provides a detailed and quantitative assessment of mitochondrial function, allowing researchers to gain insights into the bioenergetics of the cells. The protocol presented here describes the evaluation of mitochondrial respiratory chain function and the activity of specific mitochondrial complexes using the SUIT protocol in D. melanogaster. The SUIT protocol involves syste...

Mitochondria are cellular organelles that control important functions, including apoptotic regulation, calcium homeostasis, and participation in biosynthetic pathways. By possessing autonomous genetic material, they are capable of contributing to cellular maintenance and repair processes. Their structure houses the electron transport chain and oxidative phosphorylation, both crucial for cellular energy1,2,3. In particular, energy control is achieved through adenosine triphosphate (ATP) production via oxidative phosphorylation (OXPHOS)2. Disruption of energy metabolism with impairment of mitochondrial functions occurs both in cell survival and death4,5, frequently associated with a wide range of human pathologies, such as cancer, and neurodegenerative diseases such as Parkinson&#39;s Disease (PD)3,6.
PD is a chronic, progressive, and neurological disorder. The primary cause of this disease is the death of brain cells, especially in the substantia nigra, which are responsible for the production of the neurotransmitter dopamine, which controls movement6,7,8. The earliest observation that linked Parkinsonism to mitochondrial dysfunction was made in 1988, in experimental models using toxins that inhibit the respiratory chain Complex I9.
Currently, there are several methods to evaluate mitochondrial dysfunction10,11,12,13; however, compared to conventional approaches, high-resolution respirometry (HRR) presents superior sensitivity and advantages13,14. For example, HRR protocols allow the evaluation of the whole mitochondrial respiratory chain function or the activity of specific mitochondrial complexes14,15. Mitochondrial dysfunctions can be assessed in intact cells, isolated mitochondria, or even ex vivo10,11,13,14.
Mitochondrial dysfunctions are closely associated with many pathological and physiological processes. It is therefore important to study mitochondrial physiology and bioenergetics using genetically and experimentally tractable model systems. In this regard, research on Drosophila melanogaster, the fruit fly, has several advantages. This model shares fundamental cellular characteristics and processes with humans, including the use of DNA as genetic material, common organelles, and conserved molecular pathways involved in development, immunity, and cell signaling. In addition, fruit flies have a rapid life cycle, easy maintenance, low cost, high throughput, and fewer ethical concerns, thus constituting an invaluable tool for dissecting complex cellular processes16,17,18,19,20.
Furthermore, a homolog of the PTEN-induced putative kinase 1 (pink1) gene is expressed in D. melanogaster. It plays a crucial role in the removal of damaged mitochondria through the process of mitophagy8. In humans, mutations in this gene predispose individuals to an autosomal recessive familial form of PD associated with mitochondrial dysfunction8,21,22,23. Consequently, the fruit fly is a powerful animal model for studies on the pathophysiology of PD and screening of drug candidates focusing on mitochondrial dysfunction and bioenergetics. Therefore, the present work explains how to analyze mitochondrial function in a model of PD from D. melanogaster using the HRR technique in the OROBOROS with the Substrate-Uncoupler-Inhibitor-Titration (SUIT) protocol.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>ADP</td>
			<td>Sigma-Aldrich</td>
			<td>A5285</td>
			<td>Adenosine 5&#8242;-diphosphate sodium sal (CAS number 72696-48-1); &#8805;95%; molecular weight = 501.31 g/mol.</td>
		</tr>
		<tr>
			<td>&#193;gar</td>
			<td>Kasv</td>
			<td>K25-1800</td>
			<td>For bacteriologal use</td>
		</tr>
		<tr>
			<td>Antimycin-A</td>
			<td>Sigma-Aldrich</td>
			<td>A8674</td>
			<td>Antimycin A from Streptomyces sp. (CAS number 1397-94-0); molecular weight&#160; 540 g/mol;</td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA)</td>
			<td>Sigma-Aldrich</td>
			<td>A7030</td>
			<td>Bovine Serum Albumin (CAS number 9048-46-8); pH 7,0 &#8805; 98%</td>
		</tr>
		<tr>
			<td>Datlab software</td>
			<td>Oroboros Instruments, Innsbruck, Austria</td>
			<td>20700</td>
			<td>Software for data acquisition and analysis</td>
		</tr>
		<tr>
			<td>Digitonin</td>
			<td>Sigma-Aldrich</td>
			<td>D 5628</td>
			<td>CAS number 11024-24-1</td>
		</tr>
		<tr>
			<td>Distilled water</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Drosophila melanogaster strain w[*] Pink1[B9]/FM7i, P{w[+mC]=ActGFP}JMR3</td>
			<td></td>
			<td></td>
			<td>Obtained from Bloomington Drosophila stock center</td>
		</tr>
		<tr>
			<td>Drosophila melanogaster strain&#160;w1118</td>
			<td></td>
			<td></td>
			<td>Obtained&#160; from the Federal University of Santa Maria</td>
		</tr>
		<tr>
			<td>EGTA</td>
			<td>Sigma-Aldrich</td>
			<td>E8145</td>
			<td>Ethylene glycol-bis(2-aminoethylether)-N,N,N&#39;,N&#39;-tetraacetic acid (CAS number 13638-13-3); &#8805;97%; molecular weight =468.28 g/mol</td>
		</tr>
		<tr>
			<td>FCCP</td>
			<td>Sigma-Aldrich</td>
			<td>C2920</td>
			<td>Carbonyl cyanide 4- (trifluoromethoxy)phenylhydrazone&#160; (CAS number 370-86-5); &#8805;98% (TLC), powder&#160;</td>
		</tr>
		<tr>
			<td>GraphPad Prism version 8.0.1.</td>
			<td></td>
			<td></td>
			<td>Software for data acquisition and analysis</td>
		</tr>
		<tr>
			<td>Hepes</td>
			<td>Sigma-Aldrich</td>
			<td>H4034</td>
			<td>4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid (CAS number 7365-45-9); &#8805;99,5% (titration), cell cultured tested; molecular weight = 238.30 g/mol</td>
		</tr>
		<tr>
			<td>High-resolution respirometer Oxygraph O2K</td>
			<td>Oroboros Instruments, Innsbruck, Austria</td>
			<td>10022-02</td>
			<td>Startup O2K respirometer kit</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>P5379</td>
			<td>Monopotassium phosphate (CAS number 7778-77-0); Reagente Plus, molecular weigt = 136.09 g/mol</td>
		</tr>
		<tr>
			<td>KOH</td>
			<td>Sigma-Aldrich</td>
			<td>211473</td>
			<td>Potassium hydroxide (CAS number 1310-58-3); ACS reagent, &#8805;85%, pellets</td>
		</tr>
		<tr>
			<td>Malate</td>
			<td>Sigma-Aldrich</td>
			<td>M1296</td>
			<td>Malonic acid (CAS number 141-82-2); 99%, molecular weight = 104.06 g/mol). A solution is pH adjusted to approximately 7.0.</td>
		</tr>
		<tr>
			<td>Malic acid</td>
			<td>Sigma-Aldrich</td>
			<td>M1000</td>
			<td>(S)-(&#8722;)-2-Hydroxysuccinic acid (CAS number 97-67-6); &#8805;95% ; molecular weight = 134.09 g/mol</td>
		</tr>
		<tr>
			<td>MES</td>
			<td>Sigma-Aldrich</td>
			<td>M3671</td>
			<td>2-(N-Morpholino)ethanesulfonic acid (CAS number 4432-31-9); &#8805;99% (titration); molecular weight = 195.24 g/mol</td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma-Aldrich</td>
			<td>M8266</td>
			<td>Magnesium chloride (CAS number 7786-30-3); anhydrous, &#8805;98%, molecular weight = 95.21 g/mol</td>
		</tr>
		<tr>
			<td>Microcentrifuge tubes</td>
			<td>Eppendorf</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>O2K-Titration Set</td>
			<td>Oroboros Instruments, Innsbruck, Austria</td>
			<td>20820-03</td>
			<td>Hamilton syringes with different volumes</td>
		</tr>
		<tr>
			<td>Oligomycin</td>
			<td>Sigma-Aldrich</td>
			<td>O 4876</td>
			<td>Oligomycin from&#160;Streptomyces diastatochromogenes (CAS number&#160; 1404-19-9); &#8805;90% total oligomycins basis (HPLC)</td>
		</tr>
		<tr>
			<td>Pistil to homogenization</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Proline</td>
			<td>Sigma-Aldrich</td>
			<td>P0380</td>
			<td>L-Proline (CAS number 147-85-3); powder; 99%; molecular weight = 115.13 g/mol</td>
		</tr>
		<tr>
			<td>Pyruvate</td>
			<td>Sigma-Aldrich</td>
			<td>P2256</td>
			<td>Sodium pyruvate (CAS number 113-24-6), &#8805;99%; molecular weight = 110.04 g/mol</td>
		</tr>
		<tr>
			<td>Rotenone</td>
			<td>Sigma-Aldrich</td>
			<td>R8875</td>
			<td>Rotetone (CAS number 83-79-4); &#8805;95%, molecular weight 394.42 g/ mol</td>
		</tr>
		<tr>
			<td>Succinate</td>
			<td>Sigma-Aldrich</td>
			<td>S 2378</td>
			<td>Sodium succinate dibasic hexahydrate (CAS number 6106-21-4); &#8805;99%</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Merck</td>
			<td>107,651,000</td>
			<td>Sucrose for microbiology use (CAS number 57-50-1)</td>
		</tr>
		<tr>
			<td>Taurine</td>
			<td>Sigma-Aldrich</td>
			<td>T0625</td>
			<td>CAS number 107-35-7</td>
		</tr>
	</tbody>
</table>

analyzing mitochondrial function in a drosophila melanogaster pink1b9-null mutant using high-resolution respirometry

Neurodegenerative diseases, including Parkinson&#39;s Disease (PD), and cellular disturbances such as cancer are some of the disorders that disrupt energy metabolism with impairment of mitochondrial functions. Mitochondria are organelles that control both energy metabolism and cellular processes involved in cell survival and death. For this reason, approaches to evaluate mitochondrial function can offer important insights into cellular conditions in pathological and physiological processes. In this regard, high-resolution respirometry (HRR) protocols allow evaluation of the whole mitochondrial respiratory chain function or the activity of specific mitochondrial complexes. Furthermore, studying mitochondrial physiology and bioenergetics requires genetically and experimentally tractable models such as Drosophila melanogaster.
This model presents several advantages, such as its similarity to human physiology, its rapid life cycle, easy maintenance, cost-effectiveness, high throughput capabilities, and a minimized number of ethical concerns. These attributes collectively establish it as an invaluable tool for dissecting complex cellular processes. The present work explains how to analyze mitochondrial function using the Drosophila melanogaster PINK1B9-null mutant. The pink1 gene is responsible for encoding PTEN-induced putative kinase 1, through a process recognized as mitophagy, which is crucial for the removal of dysfunctional mitochondria from the mitochondrial network. Mutations in this gene have been associated with an autosomal recessive early-onset familial form of PD. This model can be used to study mitochondrial dysfunction involved in the pathophysiology of PD.

Here, we that O2 flux in OXPHOS CI (P = 0.0341) and OXPHOS CI&#38;II (P = 0.0392) states is reduced in PINK1B9&#160;null flies when compared to control flies (Figure 4). This result was also observed in previous findings from our group29,30.
CI and CII are key components of the electron transport system (ETS), in which CI is responsible for the transfer of el...

Watch this Scientific Journal Video about Exploring Mitochondrial Function and Chemical Toxicity Using Drosophila melanogaster at JoVE.com

Author Spotlight: Exploring Mitochondrial Function and Chemical Toxicity Using Drosophila melanogaster 

Here we present a high-resolution respirometry protocol to analyze bioenergetics in PINK1B9-null mutant fruit flies. The method uses the Substrate-Uncoupler-Inhibitor-Titration (SUIT) protocol.

Analyzing Mitochondrial Function in a Drosophila melanogaster PINK1B9-Null Mutant Using High-resolution Respirometry

Neurodegenerative diseases, including Parkinson&#39;s Disease (PD), and cellular disturbances such as cancer are some of the disorders that disrupt energy ...

analyzing-mitochondrial-function-drosophila-melanogaster-pink1b9-null

Research

JoVE Journal

Biochemistry

837 Views.  Federal University of Santa Maria. Here we present a high-resolution respirometry protocol to analyze bioenergetics in PINK1B9-null mutant fruit flies. The method uses the Substrate-Uncoupler-Inhibitor-Titration (SUIT) protocol.

Video: Author Spotlight: Exploring Mitochondrial Function and Chemical Toxicity Using Drosophila melanogaster 

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 ...

High-resolution Single Particle Analysis from Electron Cryo-microscopy Images Using SPHIRE

SPHIRE (SPARX for High-Resolution Electron Microscopy) is a novel open-source, user-friendly software suite for the semi-automated processing of single particle electron cryo-microscopy (cryo-EM) data. The protocol presented here describes in detail how to obtain a near-atomic resolution structure starting from cryo-EM micrograph movies by guiding users through all steps of the single particle structure determination pipeline. These steps are controlled from the new SPHIRE graphical user interface and require minimum user intervention. Using this protocol, a 3.5 &#197; structure of TcdA1, a Tc toxin complex from Photorhabdus luminescens, was derived from only 9500 single particles. This streamlined approach will help novice users without extensive processing experience and a priori structural information, to obtain noise-free and unbiased atomic models of their purified macromolecular complexes in their native state.

This paper presents a protocol for processing cryo-EM images using the software suite SPHIRE. The present protocol can be applied for nearly all single particle EM projects that target near-atomic resolution.

SPHIRE (SPARX for High-Resolution Electron Microscopy) is a novel open-source, user-friendly software suite for the semi-automated processing of single ...

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 Colorimetric Assay of Citrate Synthase Activity in Drosophila Melanogaster

Mitochondria play the most prominent roles in cellular metabolism by producing ATP through oxidative phosphorylation and regulating a variety of physiological processes. Mitochondrial dysfunction is a primary cause of a number of metabolic and neurodegenerative diseases. Intact mitochondria are critical for their proper functioning. The enzyme citrate synthase is localized in the mitochondrial matrix and thus can be used as a quantitative enzyme marker of intact mitochondrial mass. Given that many molecules and pathways that have important functions in mitochondria are highly conserved between humans and Drosophila, and that an array of powerful genetic tools are available in Drosophila, Drosophila serves as a good model system for studying mitochondrial function. Here, we present a protocol for fast and simple measurement of citrate synthase activity in tissue homogenate from adult flies without isolating mitochondria. This protocol is also suitable for measuring citrate synthase activity in larvae, cultured cells, and mammalian tissues.

A Colorimetric Assay of Citrate Synthase Activity in Drosophila Melanogaster

We present a protocol for a colorimetric assay of citrate synthase activity for quantification of intact mitochondrial mass in Drosophila tissue homogenates.

Mitochondria play the most prominent roles in cellular metabolism by producing ATP through oxidative phosphorylation and regulating a variety of ...

Routine Collection of High-Resolution cryo-EM Datasets Using 200 KV Transmission Electron Microscope

Cryo-electron microscopy (cryo-EM) has been established as a routine method for protein structure determination during the past decade, taking an ever-increasing share of published structural data. Recent advances in TEM technology and automation have boosted both the speed of data collection and quality of acquired images while simultaneously decreasing the required level of expertise for obtaining cryo-EM maps at sub-3 &#197; resolutions. While most of such high-resolution structures have been obtained using state-of-the-art 300 kV cryo-TEM systems, high-resolution structures can be also obtained with 200 kV cryo-TEM systems, especially when equipped with an energy filter. Additionally, automation of microscope alignments and data collection with real-time image quality assessment reduces system complexity and assures optimal microscope settings, resulting in increased yield of high-quality images and overall throughput of data collection. This protocol demonstrates the implementation of recent technological advances and automation features on a 200 kV cryo-transmission electron microscope and shows how to collect data for the reconstruction of 3D maps that are sufficient for de novo atomic model building. We focus on best practices, critical variables, and common issues that must be considered to enable the routine collection of such high-resolution cryo-EM datasets. Particularly the following essential topics are reviewed in detail: i) automation of microscope alignments, ii) selection of suitable areas for data acquisition, iii) optimal optical parameters for high-quality, high-throughput data collection, iv) energy filter tuning for zero-loss imaging, and v) data management and quality assessment. Application of the best practices and improvement of achievable resolution using an energy filter will be demonstrated on the example of apo-ferritin that was reconstructed to 1.6 &#197;, and Thermoplasma acidophilum 20S proteasome reconstructed to 2.1-&#197; resolution using a 200 kV TEM equipped with an energy filter and a direct electron detector.

High-resolution cryo-EM maps of macromolecules can be also achieved by using 200 kV TEM microscopes. This protocol shows the best practices for setting accurate optics alignments, data acquisition schemes, and selection of imaging areas that are all essential for the successful collection of high-resolution datasets using a 200 kV TEM.

Cryo-electron microscopy (cryo-EM) has been established as a routine method for protein structure determination during the past decade, taking an ...

Assessing Mitochondrial Function in Sciatic Nerve by High-Resolution Respirometry

Mitochondrial dysfunction in peripheral nerves accompanies several diseases associated with peripheral neuropathy, which can be triggered by multiple causes, including autoimmune diseases, diabetes, infections, inherited disorders, and tumors. Assessing mitochondrial function in mouse peripheral nerves can be challenging due to the small sample size, a limited number of mitochondria present in the tissue, and the presence of a myelin sheath. The technique described in this work minimizes these challenges by using a unique permeabilization protocol adapted from one used for muscle fibers, to assess sciatic nerve mitochondrial function instead of isolating the mitochondria from the tissue. By measuring fluorimetric reactive species production with Amplex Red/Peroxidase and comparing different mitochondrial substrates and inhibitors in saponin-permeabilized nerves, it was possible to detect mitochondrial respiratory states, reactive oxygen species (ROS), and the activity of mitochondrial complexes simultaneously. Therefore, the method presented here offers advantages compared to the assessment of mitochondrial function by other techniques.

High-resolution respirometry coupled to fluorescence sensors determines mitochondrial oxygen consumption and reactive oxygen species (ROS) generation. The present protocol describes a technique to assess mitochondrial respiratory rates and ROS production in the permeabilized sciatic nerve.

Mitochondrial dysfunction in peripheral nerves accompanies several diseases associated with peripheral neuropathy, which can be triggered by multiple ...

Advancing High-Resolution Imaging of Virus Assemblies in Liquid and Ice

Interest in liquid-electron microscopy (liquid-EM) has skyrocketed in recent years as scientists can now observe real-time processes at the nanoscale. It is extremely desirable to pair high-resolution cryo-EM information with dynamic observations as many events occur at rapid timescales - in the millisecond range or faster. Improved knowledge of flexible structures can also assist in the design of novel reagents to combat emerging pathogens, such as SARS-CoV-2. More importantly, viewing biological materials in a fluid environment provides a unique glimpse of their performance in the human body. Presented here are newly developed methods to investigate the nanoscale properties of virus assemblies in liquid and vitreous ice. To accomplish this goal, well-defined samples were used as model systems. Side-by-side comparisons of sample preparation methods and representative structural information are presented. Sub-nanometer features are shown for structures resolved in the range of ~3.5-&#197;-10 &#197;. Other recent results that support this complementary framework include dynamic insights of vaccine candidates and antibody-based therapies imaged in liquid. Overall, these correlative applications advance our ability to visualize molecular dynamics, providing a unique context for their use in human health and disease.

Here protocols are described to prepare virus assemblies suitable for liquid-EM and cryo-EM analysis at the nanoscale using transmission electron microscopy.

Interest in liquid-electron microscopy (liquid-EM) has skyrocketed in recent years as scientists can now observe real-time processes at the nanoscale. It ...

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 ...