The authors wish to acknowledge support from Dr. Lavoisier Ramos-Espiritu at the Rockefeller High Throughput and Spectroscopy Resource Center.

Sperm are collected from 8-16-week-old CD-1 male mice. Animal experiments were approved by Weill Cornell Medicine&#39;s Institutional Animal Care and Use Committee (IACUC).
1. Day prior to assay
<ol>
	<li>Preparation of sensor cartridge and extracellular flux analyzer calibrant
	<ol>
		<li>To hydrate the sensor cartridge, remove the sensor cartridge from the XFe96 Extracellular Flux Assay Kit and place the sensor cartridge upside down next to the utility plate.</li>
		<li>Fill a solution reservoir with 25 mL of double-distilled H2O using a multichannel pipette, add 200 &#181;L of H2O to each well of the utility plate. Place the sensor cartridge back into the utility plate and incubate overnight in a 37 &#176;C non-CO2 incubator. 
		NOTE: Cartridge needs to be hydrated for at least 4 h.</li>
		<li>Aliquot 25 mL of the extracellular flux analyzer calibrant into a 50 mL conical tube and incubate it overnight in a 37 &#176;C non-CO2 incubator.</li>
	</ol>
	</li>
	<li>Preparation of ConA-coated microplates
	<ol>
		<li>Dissolve 2.5 mg of ConA in 5 mL of double-distilled H2O to prepare a 0.5 mg/mL (w/v) stock.</li>
		<li>Using a multichannel pipette, fill each well of an extracellular flux analyzer 96-well plate with 50 &#181;L of the 0.5 mg/mL Con A solution. Leave the lid open and let the plate dry overnight at room temperature. 
		NOTE: Multiple plates can be coated at once and stored at 4 &#176;C for up to four weeks until ready for use.</li>
	</ol>
	</li>
	<li>Preparation of sperm buffer
	<ol>
		<li>Prepare 250 mL of extracellular flux analyzer TYH buffer with low HEPES containing 138 mM NaCl, 4.7 mM KCl, 1.7 mM CaCl2, 1.2 mM KH2PO4, 1.2 mM MgSO4, 5.6 mM glucose, and 1 mM HEPES. Heat the buffer to 37 &#176;C and adjust the pH to 7.4.</li>
	</ol>
	</li>
</ol>
2. Day of the assay
<ol>
	<li>Preparation for cartridge calibration
	<ol>
		<li>Replace the H2O in the utility plate with 200 &#181;L of XF calibrant per well and incubate for at least 1 h in a non-CO2 37 &#176;C incubator. 
		NOTE: Instead of calibrant, sterile-filtered PBS, pH 7.4 can be used.</li>
		<li>Heat 50 mL of TYH buffer at 37 &#176;C.</li>
	</ol>
	</li>
	<li>Generating a wave template for the extracellular flux analyzer
	<ol>
		<li>Turn the extracellular flux analyzer on and allow the temperature to stabilize to 37 &#176;C.</li>
		<li>Open the wave software and design a new template by opening a blank template (see Supplemental File 1, wave template).</li>
		<li>Open the Group definitions tab. Define assay media as TYH; pH 7.4 and cell type as mouse sperm, leave injection strategies and pretreatments blank. Create different groups for each assay condition; in this example, there are 6 different groups (TYH, TYH + db-cAMP/IBMX, 2-DG, 2-DG + db-cAMP/IBMX, Ant/Rot, Ant/Rot + db-cAMP/IBMX); dibutyryl cAMP (db-cAMP) and 3-Isobutyl-1-methylxanthine (IBMX) to induce capacitation, 2-deoxyglucose (2-DG) as glycolysis inhibitor, antimycin A (antA) and rotenone (rot) as inhibitor of complex III and complex I of the electron transport chain. 
		NOTE: To account for variability between wells, at least 7-8 wells per condition should be measured in parallel.</li>
		<li>Open the Plate map tab and define the plate map by assigning groups to specific wells. 
		NOTE: The four corner wells (A1, A12, H1, H12) will be filled with TYH buffer (no sperm) and will later be used for background subtraction.</li>
		<li>Open the Protocol tab, add 4 different measurement cycles, select the respective port and edit the measurement details (Figure 2, Table 1). Highlight measure after injection and do not highlight equilibrate.</li>
		<li>Save the assay template, fill out the project summary and define the saving location for the results file.</li>
	</ol>
	</li>
	<li>Preparation of compounds to load into sensor cartridge
	<ol>
		<li>Prepare 2 mL of 50 mM db-cAMP by dissolving 9.8 mg of compound in TYH buffer and add IBMX to a final concentration of 5 mM. 
		NOTE: IBMX has the tendency to precipitate after being diluted in TYH buffer. Precipitates can be dissolved by vortexing and incubating the TYH/db-cAMP/IBMX solution in a 37 &#176;C heat block for 5 min.</li>
		<li>Prepare 1 mL of 500 mM 2-DG by dissolving 82.1 mg of compound in TYH buffer.</li>
		<li>Prepare 1 mL of 5 &#181;M of AntA/Rot by diluting both drugs in TYH buffer. 
		NOTE: Compounds are diluted 10-fold by injection into the extracellular flux analyzer cartridge; therefore, be sure that injection solutions are 10x more concentrated.</li>
	</ol>
	</li>
	<li>Isolation of mouse sperm
	<ol>
		<li>Anesthetize 3 male mice between 8 and 16 weeks by isoflurane and sacrifice the mice by cervical dislocation after no response to toe pinching was detected. Remove the cauda epididymides and vasa deferentia.</li>
		<li>Place each cauda in 500 &#181;L of prewarmed TYH buffer in 24-well plate well, immobilize the cauda to the bottom of the plate using a pair of forceps and open the tissue by making 5-7 small incisions with feather scissors.</li>
		<li>Transfer the plate immediately into a non-CO2 37 &#176;C incubator and let the sperm disperse for 15 min.</li>
	</ol>
	</li>
	<li>Loading of the sensor cartridge
	<ol>
		<li>Two port-loading guides for port A and D and port B and C are provided in the Extracellular Flux kit. For loading a specific port, remove the lid from the sensor cartridge and align the letter of the respective port loading guide with the upper left corner of the cartridge. While injecting, use the fingertips of the non-injecting hand to hold the port loading guide in place and insert the pipette tips vertically into the port loading guide holes.</li>
		<li>Port A: Using a multichannel pipette, inject 20 &#181;L of the TYH buffer into every column.</li>
		<li>Port B: Inject 22 &#181;L of TYH buffer into column 1-4, inject 22 &#181;L of 500 mM 2-DG into column 5-8, and 25 &#181;L of 5 &#181;M AntA/Rot into column 9-12.</li>
		<li>Port C: Inject 25 &#181;L of TYH buffer into every column with odd numbers, inject 25 &#181;L of 10 mM db-cAMP/ 500 &#181;M IBMX into every column with even numbers.</li>
		<li>Place the sensor cartridge with the calibration plate into the extracellular flux analyzer and start the assay. Calibration takes 10 - 15 min.</li>
	</ol>
	</li>
	<li>Preparation of sperm plates
	<ol>
		<li>Dissolve 45 mg of BSA in 15 mL of TYH buffer (3 mg/mL w/v) and prepare three aliquots of 3 mL BSA/TYH solution each in 5 mL centrifuge tubes.</li>
		<li>Combine two sperm wells each in one 1.5 mL centrifuge tube, count the sperm using a hematocytometer and dilute the sperm to a concentration of 2 x 107 sperm/mL. 
		NOTE: Use cut pipette tips for pipetting sperm to avoid damaging the cells.</li>
		<li>Centrifuge the sperm for 3 min at 700 x g, remove the supernatant and add 1 mL of TYH buffer. Repeat the centrifugation step, remove the supernatant, and transfer each sperm suspension aliquot into one 5 mL centrifuge tube with 3 mL of BSA/TYH.</li>
		<li>Place 180 &#181;L of TYH buffer into each corner well (A1, A12, H1, H12) of a ConA-coated plate. Place 180 &#181;L of sperm suspension into each empty well of the ConA-coated plate (1.2 x 106 sperm/well).</li>
		<li>Centrifuge the sperm plate at 250 x g for 1 min, rotate the plate by 180&#176;, and centrifuge again at 250 x g for 1 min (lowest braking rate 1).</li>
		<li>Remove the calibration plate from the extracellular flux analyzer and add the sperm plate. Continue the assay.</li>
	</ol>
	</li>
	<li>Data extraction and analysis
	<ol>
		<li>After finishing the assay, remove the cartridge, open the results file, click the Export tab and export the completed run as a GraphPad Prism file (Supplemental File 2: Primary example data used for Figure 3).</li>
		<li>Duplicate the ECAR and OCR file by clicking on the New tab and then the Duplicate Family&#8230; tab (Figure 3A).</li>
		<li>Delete the first 7 rows of data (Figure 3B).</li>
		<li>Normalize to the data point before the cAMP/IBMX injection by baseline subtracting row 1. Click on the Analyze tab, then on the Remove baseline and column math tab. Highlight Selected row(s): First Row, Calculation: Ratio:Value/Baseline, and Subcolumns: Ignore Subcolumn. Click OK (Figure 3C).</li>
	</ol>
	</li>
</ol>

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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=Increased+OXPHOS+activity+precedes+rise+in+glycolytic+rate+in+H-RasV12/E1A+transformed+fibroblasts+that+develop+a+Warburg+phenotype.">Increased OXPHOS activity precedes rise in glycolytic rate in H-RasV12/E1A transformed fibroblasts that develop a Warburg phenotype.</a> Molecular Cancer. 8, 54 (2009).</li><li>Chao, L. 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=Insulin+resistance+and+altered+systemic+glucose+metabolism+in+mice+lacking+Nur77.">Insulin resistance and altered systemic glucose metabolism in mice lacking Nur77.</a> Diabetes. 58 (12), 2788-2796 (2009).</li><li>Chang, M. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+analysis+of+flagellar+movement+in+hyperactivated+and+acrosome-reacted+golden+hamster+spermatozoa.">Quantitative analysis of flagellar movement in hyperactivated and acrosome-reacted golden hamster spermatozoa.</a> Molecular Reproduction and Development. 61 (3), 376-384 (2002).</li><li>Suarez, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+hyperactivation+in+sperm.">Control of hyperactivation in sperm.</a> Human Reproduction Update. 14 (6), 647-657 (2008).</li><li>Goodson, S. G., Qiu, Y., Sutton, K. A., Xie, G., Jia, W., O'Brien, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolic+substrates+exhibit+differential+effects+on+functional+parameters+of+mouse+sperm+capacitation.">Metabolic substrates exhibit differential effects on functional parameters of mouse sperm capacitation.</a> Biology of Reproduction. 87 (3), 75 (2012).</li><li>Travis, A. 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=Functional+relationships+between+capacitation-dependent+cell+signaling+and+compartmentalized+metabolic+pathways+in+murine+spermatozoa.">Functional relationships between capacitation-dependent cell signaling and compartmentalized metabolic pathways in murine spermatozoa.</a> Journal of Biological Chemistry. 276 (10), 7630-7636 (2001).</li><li>Urner, F., Leppens-Luisier, G., Sakkas, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+tyrosine+phosphorylation+in+sperm+during+gamete+interaction+in+the+mouse:+the+influence+of+glucose.">Protein tyrosine phosphorylation in sperm during gamete interaction in the mouse: the influence of glucose.</a> Biology of Reproduction. 64 (5), 1350-1357 (2001).</li><li>Danshina, P. 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=Phosphoglycerate+kinase+2+(PGK2)+is+essential+for+sperm+function+and+male+fertility+in+mice.">Phosphoglycerate kinase 2 (PGK2) is essential for sperm function and male fertility in mice.</a> Biology of Reproduction. 82 (1), 136-145 (2010).</li><li>Miki, K., 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=Glyceraldehyde+3-phosphate+dehydrogenase-S,+a+sperm-specific+glycolytic+enzyme,+is+required+for+sperm+motility+and+male+fertility.">Glyceraldehyde 3-phosphate dehydrogenase-S, a sperm-specific glycolytic enzyme, is required for sperm motility and male fertility.</a> Proceedings of the National Academy of Sciences. 101 (47), 16501-16506 (2004).</li><li>Mori, 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=Mouse+spermatogenic+cell-specific+type+1+hexokinase+(mHk1-s)+transcripts+are+expressed+by+alternative+splicing+from+the+mHk1+gene+and+the+HK1-S+protein+is+localized+mainly+in+the+sperm+tail.">Mouse spermatogenic cell-specific type 1 hexokinase (mHk1-s) transcripts are expressed by alternative splicing from the mHk1 gene and the HK1-S protein is localized mainly in the sperm tail.</a> Molecular Reproduction and Development. 49 (4), 374-385 (1998).</li><li>Westhoff, D., Kamp, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glyceraldehyde+3-phosphate+dehydrogenase+is+bound+to+the+fibrous+sheath+of+mammalian+spermatozoa.">Glyceraldehyde 3-phosphate dehydrogenase is bound to the fibrous sheath of mammalian spermatozoa.</a> Journal of Cell Science. 110 (15), 1821-1829 (1997).</li><li>Nevo, A. C., Rikmenspoel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diffusion+of+ATP+in+sperm+flagella.">Diffusion of ATP in sperm flagella.</a> Journal of Theoretical Biology. 26 (1), 11-18 (1970).</li><li>Adam, D. E., Wei, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mass+transport+of+ATP+within+the+motile+sperm.">Mass transport of ATP within the motile sperm.</a> Journal of Theoretical Biology. 49 (1), 125-145 (1975).</li><li>Tombes, R. M., Shapiro, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzyme+termini+of+a+phosphocreatine+shuttle.+Purification+and+characterization+of+two+creatine+kinase+isozymes+from+sea+urchin+sperm.">Enzyme termini of a phosphocreatine shuttle. Purification and characterization of two creatine kinase isozymes from sea urchin sperm.</a> Journal of Biological Chemistry. 262 (33), 16011-16019 (1987).</li><li>Gomendio, M., Tourmente, M., Roldan, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Why+mammalian+lineages+respond+differently+to+sexual+selection:+metabolic+rate+constrains+the+evolution+of+sperm+size.">Why mammalian lineages respond differently to sexual selection: metabolic rate constrains the evolution of sperm size.</a> Proceedings of the Royal Society of Biological Sciences. 278 (1721), 3135-3141 (2011).</li><li>Tourmente, M., Villar-Moya, P., Rial, E., Roldan, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+ATP+generation+via+glycolysis+and+oxidative+phosphorylation+and+relationships+with+sperm+motility+in+mouse+species.">Differences in ATP generation via glycolysis and oxidative phosphorylation and relationships with sperm motility in mouse species.</a> Journal of Biological Chemistry. 290 (33), 20613-20626 (2015).</li><li>Visconti, P. 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=Capacitation+of+mouse+spermatozoa.+II.+Protein+tyrosine+phosphorylation+and+capacitation+are+regulated+by+a+cAMP-dependent+pathway.">Capacitation of mouse spermatozoa. II. Protein tyrosine phosphorylation and capacitation are regulated by a cAMP-dependent pathway.</a> Development. 121 (4), 1139-1150 (1995).</li><li>Buck, J., Sinclair, M. L., Schapal, L., Cann, M. J., Levin, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytosolic+adenylyl+cyclase+defines+a+unique+signaling+molecule+in+mammals.">Cytosolic adenylyl cyclase defines a unique signaling molecule in mammals.</a> PNAS. 96 (1), 79-84 (1999).</li><li>Visconti, P. E., Bailey, J. L., Moore, G. D., Pan, D., Olds-Clarke, P., Kopf, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capacitation+of+mouse+spermatozoa.+I.+Correlation+between+the+capacitation+state+and+protein+tyrosine+phosphorylation.">Capacitation of mouse spermatozoa. I. Correlation between the capacitation state and protein tyrosine phosphorylation.</a> Development. 121 (4), 1129-1137 (1995).</li><li>Morgan, D. 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=Tissue-specific+PKA+inhibition+using+a+chemical+genetic+approach+and+its+application+to+studies+on+sperm+capacitation.">Tissue-specific PKA inhibition using a chemical genetic approach and its application to studies on sperm capacitation.</a> PNAS. 105 (52), 20740-20745 (2008).</li><li>Lybaert, P., Danguy, A., Leleux, F., Meuris, S., Lebrun, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+methodology+for+the+detection+and+quantification+of+the+acrosome+reaction+in+mouse+spermatozoa.">Improved methodology for the detection and quantification of the acrosome reaction in mouse spermatozoa.</a> Histology and Histopathology. 24 (8), 999-1007 (2009).</li></ol>

The authors have nothing to disclose.

The loss of sperm capacitation in the absence of certain metabolic substrates or critical metabolic enzymes revealed energy metabolism as a key factor supporting successful fertilization. A metabolic switch during cell activation is a well-established concept in other cell types, however, we are just beginning to understand how sperm adapt their metabolism to the increasing energy demand during capacitation. Using an extracellular flux analyzer, we developed an easily applicable tool to monitor changes in glycolysis and ...

The application of mass spectrometry has revolutionized the study of metabolism. Targeted metabolic profiling and metabolomic tracing allow precise monitoring of changes in energy metabolism. However, performing metabolomics successfully requires extensive training, experienced staff, and expensive, highly sensitive mass spectrometers not readily available to every laboratory. In recent years, using an extracellular flux analyzer, such as the Seahorse XFe96 has grown popular as a surrogate method for measuring changes in energy metabolism in various cell types1,2,3,4,5.
Sperm are highly specialized motile cells; whose task is to deliver the paternal genome to the oocyte. Sperm leaving the male reproductive tract after ejaculation are still functionally immature and cannot fertilize the oocyte because they are unable to penetrate the oocytes&#39; vestments. Sperm acquire fertilization competence as they transit through the female reproductive tract in a maturation process known as capacitation6,7. Freshly ejaculated sperm or sperm dissected from the cauda epididymis can be capacitated in vitro by incubation in defined capacitation media containing Ca2+, bicarbonate (HCO3-) or a cell-permeable cAMP analog (e.g., dibutyryl-cAMP), a cholesterol acceptor (e.g., bovine serum albumin, BSA), and an energy source (e.g., glucose). During capacitation, sperm modify their motility pattern into an asymmetric flagellar beat, representing a swimming mode called hyperactivation8,9, and they become competent to undergo the acrosome reaction7, where proteolytic enzymes are released that digest the oocytes&#39; vestments. These processes require energy, and similar to somatic cells, sperm generate ATP and other high energy compounds via glycolysis as well as mitochondrial TCA cycle and oxidative phosphorylation (oxphos)10. While multiple studies demonstrate that glycolysis is necessary and sufficient to support sperm capacitation11,12,13,14, the contribution of oxphos is less clear. Contrary to other cell types where glycolysis is physically coupled to the TCA cycle, sperm are highly compartmentalized and are thought to maintain these processes in separate flagellar compartments: the midpiece concentrates the mitochondrial machinery, whereas the key enzymes of glycolysis appear to be restricted to the principal piece15,16. This compartmentalization results in an ongoing debate about whether pyruvate produced in the principal piece by glycolysis can support mitochondrial oxphos in the midpiece, and whether ATP produced by oxphos in the midpiece would be able to diffuse sufficiently rapidly along the length of the flagellum to support the energy requirements in distal parts of the principal piece17,18,19. There is also support of a role for oxphos in sperm capacitation. Not only is oxphos more energetically favorable than glycolysis, generating 16 times more ATP than glycolysis, but midpiece volume and mitochondrial content are directly correlated with reproductive fitness in mammalian species which exhibit greater degrees of competition between males for mates20. Addressing these questions requires methods for examining the relative contributions of glycolysis and oxphos during sperm capacitation.
Tourmente et al. applied a 24-well extracellular flux analyzer to compare the energy metabolism of closely related mouse species with significantly different sperm performance parameters21. Instead of reporting the basal ECAR and OCR values of non-capacitated sperm, here, we adapt their method using a 96-well extracellular flux analyzer to monitor changes in energy metabolism during mouse sperm capacitation in real-time. We developed a method that allows simultaneously monitoring glycolysis and oxphos in real-time in sperm with beating flagella in up to twelve different experimental conditions by measuring the flux of oxygen (O2) and protons (H+) (Figure 1A). Due to the breakdown of pyruvate to lactate during glycolysis and the production of CO2 via the TCA-cycle, non-capacitated and capacitated sperm extrude H+ into the assay media which are detected by the extracellular flux analyzer via H+-sensitive fluorophores immobilized to the probe tip of a sensor cartridge. In parallel, O2 consumption by oxidative phosphorylation is detected via O2-sensitive fluorophores immobilized to the same probe tip (Figure 1B). Effective detection of the released H+ and consumed O2 requires a modified sperm buffer with low buffering capacity without bicarbonate or phenol red. Thus, to induce capacitation in the absence of bicarbonate, we adopted the use of a cell-permeable cAMP analog injected together with the broad-range PDE inhibitor IBMX22. Three additional independent injection ports allow the injection of pharmacological activators and/or inhibitors, which facilitates real-time detection of changes in cellular respiration and glycolysis rate due to experimental manipulation.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2-Deoxy-D-glucose</td>
			<td>Sigma-Aldrich</td>
			<td>D8375</td>
			<td>2-DG</td>
		</tr>
		<tr>
			<td>3-Isobutyl-1-methylxanthine</td>
			<td>Sigma-Aldrich</td>
			<td>I7018</td>
			<td>IBMX; prepare a 500 mM stock solution in DMSO (111.1 mg/ml) and store in small aliquots</td>
		</tr>
		<tr>
			<td>Antimycin A</td>
			<td>Sigma-Aldrich</td>
			<td>A8674</td>
			<td>AntA; prepare a 5 mM stock solution in DMSO (2.7 mg/ml) and store in small aliquots</td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A1470</td>
			<td>BSA</td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>C1016</td>
			<td>CaCl2</td>
		</tr>
		<tr>
			<td>Concanacalin A, Lectin from Arachis hypogaea (peanut)</td>
			<td>Sigma-Aldrich</td>
			<td>L7381</td>
			<td>ConA</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G7528</td>
			<td></td>
		</tr>
		<tr>
			<td>Hepes</td>
			<td>Sigma-Aldrich</td>
			<td>H0887</td>
			<td></td>
		</tr>
		<tr>
			<td>Isothesia</td>
			<td>Henry Schein Animal Health</td>
			<td>1169567761</td>
			<td>Isoflurane</td>
		</tr>
		<tr>
			<td>Magnesium sulfate</td>
			<td>Sigma-Aldrich</td>
			<td>M2643</td>
			<td>MgSO4</td>
		</tr>
		<tr>
			<td>N6,2&#39;-O-Dibutyryladenosine 3&#39;,5&#39;-cyclic monophosphate sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>D0627</td>
			<td>db-cAMP</td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>P9333</td>
			<td>KCl</td>
		</tr>
		<tr>
			<td>Potassium dihydrogen phosphate</td>
			<td>Sigma-Aldrich</td>
			<td>P5655</td>
			<td>KH2PO4</td>
		</tr>
		<tr>
			<td>Rotenone</td>
			<td>Cayman Chemical Company</td>
			<td>13995</td>
			<td>Rot; prepare a 5 mM stock solution in DMSO (2mg/ml) and store in small aliquots</td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Sigma-Aldrich</td>
			<td>S5761</td>
			<td>NaHCO3-</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>S9888</td>
			<td>NaCl</td>
		</tr>
		<tr>
			<td>Equipment and materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>12 channel pipette 10-100 &#956;L</td>
			<td>eppendorf</td>
			<td>ES-12-100</td>
			<td></td>
		</tr>
		<tr>
			<td>12 channel pipette 50-300 &#956;L</td>
			<td>vwr</td>
			<td>613-5257</td>
			<td></td>
		</tr>
		<tr>
			<td>37 &#176;C, non-CO2 incubator</td>
			<td>vwr</td>
			<td>1545</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL cetrifuge tubes</td>
			<td>eppendorf</td>
			<td>30119380</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL conical centrifuge tubes</td>
			<td>vwr</td>
			<td>76211-286</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge with plate adapter</td>
			<td>Thermo Scientific</td>
			<td>IEC FL40R</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection kit</td>
			<td>World Precision Instruments</td>
			<td>MOUSEKIT</td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted phase contrast microscope with 40X objective</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>OctaPool Solution Reservoirs, 25 ml, divided</td>
			<td>Thomas Scientific</td>
			<td>1159X93</td>
			<td></td>
		</tr>
		<tr>
			<td>OctaPool Solution Reservoirs, 25 mL, divided</td>
			<td>Thomas Scientific</td>
			<td>1159X95</td>
			<td></td>
		</tr>
		<tr>
			<td>Seahorse XFe96 Analyzer</td>
			<td>Agilent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Seahorse XFe96 FluxPak</td>
			<td>Agilent</td>
			<td>102416-100</td>
			<td>Also sold as XFe96 FluxPak mini (102601-100) with 6 instead of 18 cartidges.</td>
		</tr>
	</tbody>
</table>

using an extracellular flux analyzer to measure changes in glycolysis and oxidative phosphorylation during mouse sperm capacitation

Mammalian sperm acquire fertilization capacity in the female reproductive tract in a process known as capacitation. Capacitation-associated processes require energy. There remains an ongoing debate about the sources generating the ATP which fuels sperm progressive motility, capacitation, hyperactivation, and acrosome reaction. Here, we describe the application of an extracellular flux analyzer as a tool to analyze changes in energy metabolism during mouse sperm capacitation. Using H+- and O2- sensitive fluorophores, this method allows monitoring glycolysis and oxidative phosphorylation in real-time in non-capacitated versus capacitating sperm. Using this assay in the presence of different energy substrates and/or pharmacological activators and/or inhibitors can provide important insights into the contribution of different metabolic pathways and the intersection between signaling cascades and metabolism during sperm capacitation.

This method uses an extracellular flux analyzer to monitor real-time changes in the rate of glycolysis and oxphos during mouse sperm capacitation. Figure 4 shows an exemplary experiment where sperm were capacitated in the presence of glucose as the only energy substrate and 2-DG and antimycin and rotenone as pharmacological modulators. The energy substrate in the extracellular flux analyzer TYH buffer and the pharmacological modulators can be freely selected ...

Watch this Scientific Journal Video about Using an Extracellular Flux Analyzer to Measure Changes in Glycolysis and Oxidative Phosphorylation during Mouse Sperm Capacitation at JoVE.com

Using an Extracellular Flux Analyzer to Measure Changes in Glycolysis and Oxidative Phosphorylation during Mouse Sperm Capacitation

We describe the application of an extracellular flux analyzer to monitor real-time changes in glycolysis and oxidative phosphorylation during mouse sperm capacitation.

Mammalian sperm acquire fertilization capacity in the female reproductive tract in a process known as capacitation. Capacitation-associated processes ...

using-an-extracellular-flux-analyzer-to-measure-changes-glycolysis

Research

JoVE Journal

Biochemistry

7.7K Views.  Weill Cornell Medical College. We describe the application of an extracellular flux analyzer to monitor real-time changes in glycolysis and oxidative phosphorylation during mouse sperm capacitation.

Video: Using an Extracellular Flux Analyzer to Measure Changes in Glycolysis and Oxidative Phosphorylation during Mouse Sperm Capacitation

Oligopeptide Competition Assay for Phosphorylation Site Determination

Protein phosphorylation at specific sites determines its conformation and interaction with other molecules. Thus, protein phosphorylation affects biological functions and characteristics of the cell. Currently, the most common method for discovering phosphorylation sites is by liquid chromatography/mass spectrometry (LC/MS) analysis, a rapid and sensitive method. However, relatively labile phosphate moieties are often released from phosphopeptides during the fragmentation step, which often yields false-negative signals. In such cases, a traditional in vitro kinase assay using site-directed mutants would be more accurate, but this method is laborious and time-consuming. Therefore, an alternative method using peptide competition may be advantageous. The consensus recognition motif of 5&#39; adenosine monophosphate-activated protein kinase (AMPK) has been established1 and was validated using a positional scanning peptide library assay2. Thus, AMPK phosphorylation sites for a novel substrate could be predicted and confirmed by the peptide competition assays. In this report, we describe the detailed steps and procedures for the in vitro oligopeptide-competing kinase assay by illustrating AMPK-mediated nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation. To authenticate the phosphorylation site, we carried out a sequential in vitro kinase assay using a site-specific mutant. Overall, the peptide competition assay provides a method to screen multiple potential phosphorylation sites and to identify sites for validation by the phosphorylation site mutants.

Peptide competition assays are widely used in a variety of molecular and immunological experiments. This paper describes a detailed method for an in vitro oligopeptide-competing kinase assay and the associated validation procedures, which may be useful to find specific phosphorylation sites.

Protein phosphorylation at specific sites determines its conformation and interaction with other molecules. Thus, protein phosphorylation affects ...

Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been shown to be linked with familial Parkinson&#39;s disease (FPD). Since abnormal activation of the kinase activity of LRRK2 has been implicated in the pathogenesis of PD, it is essential to establish a method to evaluate the physiological levels of the kinase activity of LRRK2. Recent studies revealed that LRRK2 phosphorylates members of the Rab GTPase family, including Rab10, under physiological conditions. Although the phosphorylation of endogenous Rab10 by LRRK2 in cultured cells could be detected by mass spectrometry, it has been difficult to detect it by immunoblotting due to the poor sensitivity of currently available phosphorylation-specific antibodies for Rab10. Here, we describe a simple method of detecting the endogenous levels of Rab10 phosphorylation by LRRK2 based on immunoblotting utilizing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) combined with a phosphate-binding tag (P-tag), which is N-(5-(2-aminoethylcarbamoyl)pyridin-2-ylmetyl)-N,N&#39;,N&#39;-tris(pyridin-2-yl-methyl)-1,3-diaminopropan-2-ol. The present protocol not only provides an example of the methodology utilizing the P-tag but also enables the assessment of how mutations as well as inhibitor treatment/administration or any other factors alter the downstream signaling of LRRK2 in cells and tissues.

The present study describes a simple method of detecting endogenous levels of Rab10 phosphorylation by leucine-rich repeat kinase 2.

Mutations in leucine-rich repeat kinase 2 (LRRK2) have been shown to be linked with familial Parkinson&#39;s disease (FPD). Since abnormal activation of ...

The Determination of Protease Specificity in Mouse Tissue Extracts by MALDI-TOF Mass Spectrometry: Manipulating PH to Cause Specificity Changes

Proteases have several biological functions, including protein activation/inactivation and food digestion. Identifying protease specificity is important for revealing protease function. The method proposed in this study determines protease specificity by measuring the molecular weight of unique substrates using Matrix-assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) mass spectrometry. The substrates contain iminobiotin, while the cleaved site consists of amino acids, and the spacer consists of polyethylene glycol. The cleaved substrate will generate a unique molecular weight using a cleaved amino acid. One of the merits of this method is that it may be carried out in one pot using crude samples, and it is also suitable for assessing multiple samples. In this article, we describe a simple experimental method optimized with samples extracted from mouse lung tissue, including tissue extraction, placement of digestive substrates into samples, purification of digestive substrates under different pH conditions, and measurement of the substrates&#39; molecular weight using MALDI-TOF mass spectrometry. In summary, this technique allows for the identification of protease specificity in crude samples derived from tissue extracts using MALDI-TOF mass spectrometry, which may easily be scaled up for multiple sample processing.

Here, we present a protocol to determine protease specificity in crude mouse tissue extracts using MALDI-TOF spectrometry.

Proteases have several biological functions, including protein activation/inactivation and food digestion. Identifying protease specificity is important ...

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Cyclin-dependent kinase 1 (Cdk1) is a master controller for the cell cycle in all eukaryotes and phosphorylates an estimated 8 - 13% of the proteome; however, the number of identified targets for Cdk1, particularly in human cells is still low. The identification of Cdk1-specific phosphorylation sites is important, as they provide mechanistic insights into how Cdk1 controls the cell cycle. Cell cycle regulation is critical for faithful chromosome segregation, and defects in this complicated process lead to chromosomal aberrations and cancer.
Here, we describe an in vitro kinase assay that is used to identify Cdk1-specific phosphorylation sites. In this assay, a purified protein is phosphorylated in vitro by commercially available human Cdk1/cyclin B. Successful phosphorylation is confirmed by SDS-PAGE, and phosphorylation sites are subsequently identified by mass spectrometry. We also describe purification protocols that yield highly pure and homogeneous protein preparations suitable for the kinase assay, and a binding assay for the functional verification of the identified phosphorylation sites, which probes the interaction between a classical nuclear localization signal (cNLS) and its nuclear transport receptor karyopherin &#945;. To aid with experimental design, we review approaches for the prediction of Cdk1-specific phosphorylation sites from protein sequences. Together these protocols present a very powerful approach that yields Cdk1-specific phosphorylation sites and enables mechanistic studies into how Cdk1 controls the cell cycle. Since this method relies on purified proteins, it can be applied to any model organism and yields reliable results, especially when combined with cell functional studies.

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Cyclin-dependent kinase 1 (Cdk1) is activated in the G2 phase of the cell cycle and regulates many cellular pathways. Here, we present a protocol for an in vitro kinase assay with Cdk1, which allows the identification of Cdk1-specific phosphorylation sites for establishing cellular targets of this important kinase.

Cyclin-dependent kinase 1 (Cdk1) is a master controller for the cell cycle in all eukaryotes and phosphorylates an estimated 8 - 13% of the proteome; ...

Examining the Dynamics of Cellular Adhesion and Spreading of Epithelial Cells on Fibronectin During Oxidative Stress

The adhesion and spreading of cells onto the extracellular matrix (ECM) are essential cellular processes during organismal development and for the homeostasis of adult tissues. Interestingly, oxidative stress can alter these processes, thus contributing to the pathophysiology of diseases such as metastatic cancer. Therefore, understanding the mechanism(s) of how cells attach and spread on the ECM during perturbations in redox status can provide insight into normal and disease states. Described below is a step-wise protocol that utilizes an immunofluorescence-based assay to specifically quantify cell adhesion and spreading of immortalized fibroblast cells on fibronectin (FN) in vitro. Briefly, anchorage-dependent cells are held in suspension and exposed to the ATM kinase inhibitor Ku55933 to induce oxidative stress. Cells are then plated on FN-coated surface and allowed to attach for predetermined periods of time. Cells that remain attached are fixed and labeled with fluorescence-based antibody markers of adhesion (e.g., paxillin) and spreading (e.g., F-actin). Data acquisition and analysis are performed using commonly available laboratory equipment, including an epifluorescence microscope and freely available Fiji software. This procedure is highly versatile and can be modified for a variety of cell lines, ECM proteins, or inhibitors in order to examine a broad range of biological questions.

This method is useful for quantifying the early dynamics of cellular adhesion and spreading of anchorage-dependent cells onto the fibronectin. Furthermore, this assay can be used to investigate the effects of altered redox homeostasis on cell spreading and/or cell adhesion-related intracellular signaling pathways.

The adhesion and spreading of cells onto the extracellular matrix (ECM) are essential cellular processes during organismal development and for the ...

Nonradioactive Assay to Measure Polynucleotide Phosphorylation of Small Nucleotide Substrates

Polynucleotide kinases (PNKs) are enzymes that catalyze the phosphorylation of the 5&#39; hydroxyl end of DNA and RNA oligonucleotides. The activity of PNKs can be quantified using direct or indirect approaches. Presented here is a direct, in vitro approach to measure PNK activity that relies on a fluorescently-labeled oligonucleotide substrate and polyacrylamide gel electrophoresis. This approach provides resolution of the phosphorylated products while avoiding the use of radiolabeled substrates. The protocol details how to set up the phosphorylation reaction, prepare and run large polyacrylamide gels, and quantify the reaction products. The most technically challenging part of this assay is pouring and running the large polyacrylamide gels; thus, important details to overcome common difficulties are provided. This protocol was optimized for Grc3, a PNK that assembles into an obligate pre-ribosomal RNA processing complex with its binding partner, the Las1 nuclease. However, this protocol can be adapted to measure the activity of other PNK enzymes. Moreover, this assay can also be modified to determine the effects of different components of the reaction, such as the nucleoside triphosphate, metal ions, and oligonucleotides.

This protocol describes a nonradioactive assay to measure kinase activity of polynucleotide kinases (PNKs) on small DNA and RNA substrates.

Polynucleotide kinases (PNKs) are enzymes that catalyze the phosphorylation of the 5&#39; hydroxyl end of DNA and RNA oligonucleotides. The activity of ...

DetectSyn: A Rapid, Unbiased Fluorescent Method to Detect Changes in Synapse Density

Synapses are the site of communication between neurons. Neuronal circuit strength is related to synaptic density, and the breakdown of synapses is characteristic of disease states like major depressive disorder (MDD) and Alzheimer's disease. Traditional techniques to investigate synapse numbers include genetic expression of fluorescent markers (e.g., green fluorescent protein (GFP)), dyes that fill a neuron (e.g., carbocyanine dye, DiI), and immunofluorescent detection of spine markers (e.g., postsynaptic density 95 (PSD95)). A major caveat to these proxy techniques is that they only identify postsynaptic changes. Yet, a synapse is a connection between a presynaptic terminal and a postsynaptic spine. The gold standard for measuring synapse formation/elimination requires time-consuming electron microscopy or array tomography techniques. These techniques require specialized training and costly equipment. Further, only a limited number of neurons can be assessed and are used to represent changes to an entire brain region. DetectSyn is a rapid fluorescent technique that identifies changes to synapse formation or elimination due to a disease state or drug activity. DetectSyn utilizes a rapid proximity ligation assay to detect juxtaposed pre- and postsynaptic proteins and standard fluorescent microscopy, a technique readily available to most laboratories. Fluorescent detection of the resulting puncta allows for quick and unbiased analysis of experiments. DetectSyn provides more representative results than electron microscopy because larger areas can be analyzed than a limited number of fluorescent neurons. Moreover, DetectSyn works for in vitro cultured neurons and fixed tissue slices. Finally, a method is provided to analyze the data collected from this technique. Overall, DetectSyn offers a procedure for detecting relative changes in synapse density across treatments or disease states and is more accessible than traditional techniques.

DetectSyn is an unbiased, rapid fluorescent assay that measures changes in relative synapse (pre- and postsynaptic engagement) number across treatments or disease states. This technique utilizes a proximity ligation technique that can be used both in cultured neurons and fixed tissue.

Synapses are the site of communication between neurons. Neuronal circuit strength is related to synaptic density, and the breakdown of synapses is ...

An Optimized Single-Molecule Pull-Down Assay for Quantification of Protein Phosphorylation

Phosphorylation is a necessary posttranslational modification that regulates protein function and directs cell signaling outcomes. Current methods to measure protein phosphorylation cannot preserve the heterogeneity in phosphorylation across individual proteins. The single-molecule pull-down (SiMPull) assay was developed to investigate the composition of macromolecular complexes via immunoprecipitation of proteins on a glass coverslip followed by single-molecule imaging. The current technique is an adaptation of SiMPull that provides robust quantification of the phosphorylation state of full-length membrane receptors at the single-molecule level. Imaging thousands of individual receptors in this way allows for quantifying protein phosphorylation patterns. The present protocol details the optimized SiMPull procedure, from sample preparation to imaging. Optimization of glass preparation and antibody fixation protocols further enhances data quality. The current protocol provides code for the single-molecule data analysis that calculates the fraction of receptors phosphorylated within a sample. While this work focuses on phosphorylation of the epidermal growth factor receptor (EGFR), the protocol can be generalized to other membrane receptors and cytosolic signaling molecules.

The present protocol describes sample preparation and data analysis to quantify protein phosphorylation using an improved single-molecule pull-down (SiMPull) assay.

Phosphorylation is a necessary posttranslational modification that regulates protein function and directs cell signaling outcomes. Current methods to ...

Extracellular Glucose Depletion as an Indirect Measure of Glucose Uptake in Cells and Tissues Ex Vivo

The ongoing worldwide epidemic of diabetes increases the demand for the identification of environmental, nutritional, endocrine, genetic, and epigenetic factors affecting glucose uptake. The measurement of intracellular fluorescence is a widely used method to test the uptake of fluorescently-labeled glucose (FD-glucose) in cells in vitro, or for imaging glucose-consuming tissues in vivo. This assay assesses glucose uptake at a chosen time point. The intracellular analysis assumes that the metabolism of FD-glucose is slower than that of endogenous glucose, which participates in catabolic and anabolic reactions and signaling. However, dynamic glucose metabolism also alters uptake mechanisms, which would require kinetic measurements of glucose uptake in response to different factors. This article describes a method for measuring extracellular FD-glucose depletion and validates its correlation with intracellular FD-glucose uptake in cells and tissues ex vivo. Extracellular glucose depletion may be potentially applicable for high-throughput kinetic and dose-dependent studies, as well as identifying compounds with glycemic activity and their tissue-specific effects.

Extracellular Glucose Depletion as an Indirect Measure of Glucose Uptake in Cells and Tissues Ex Vivo

Extracellular depletion of fluorescently labeled glucose correlates with glucose uptake and could be used for high-throughput screening of glucose uptake in excised organs and cell cultures.

The ongoing worldwide epidemic of diabetes increases the demand for the identification of environmental, nutritional, endocrine, genetic, and epigenetic ...

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 ...