This work was supported by an Ellison/AFAR Postdoctoral Fellowship in Aging Research Program to SJK, and a Glenn Foundation Award and NIH grants to PC (1P01AG034906, 1R01GM 090311, 1R01ES 020812). All authors appear in the film.

1. Peptide Treatment to Cells
<ol>
	<li>Plate two million SH-SY5Y or HEK293 cells (2 x 106) into a 10 cm dish and grow them for 2 days</li>
	<li>(Optional) The next day, wash the cells with serum-free Dulbecco&#39;s Modified Eagle Medium (DMEM) media once and incubate with serum free DMEM overnight if the treatment needs to be done in serum free media.</li>
	<li>On day 3, dissolve S14G-humanin peptides in 0.2 &#181;m filtered, distilled water, and reconstitute them as 1mM stock solution. 
	NOTE: The peptides should be dissolved in the appropriate solvent, which can be determined by the sequence characteristics of the peptide (e.g., overall charge) and may be provided by the manufacturer if the peptides are commercially available. For example, S14G-humanin, SHLP2, and SHLP6, and MOTS-c dissolve in water. Aliquot the peptides in an appropriate volume (e.g., 50 &#956;L) to avoid freeze and thaw cycles. Once thawed, do not use them again.</li>
	<li>Aliquot the pre-warmed serum-containing or serum-free media in a 50-mL conical tube and add room temperature 1 mM stock solution to make it into a working concentration (e.g., 1 &#181;M, 10 &#181;M).</li>
	<li>Replace the media with 6 mL peptide solution from step 1.4. and incubate the cells for the appropriate amount of time. 
	NOTE: Choose the incubation time depending on your condition which activates ERK.</li>
</ol>
2. Subcellular Fractionation for Cytosol and Nucleus
<ol>
	<li>Wash the cells twice with 10 mL of ice-cold PBS, scrape the cells off the plate in 5 mL of ice-cold PBS, and transfer the cell suspension into a 15 mL conical tube.</li>
	<li>Centrifuge the cells at 500 x g for 5 min at 4 &#176;C.</li>
	<li>Aspirate the PBS and re-suspend the pellet in 200 &#181;L of ice-cold, fractionation buffer (10 mM HEPES pH = 7.6, 3 mM MgCl2, 10 mM KCl, 5% (v/v) glycerol, 1% non-ionic surfactant (C13H22O(C2H4O)n), protease/phosphatase inhibitors). 
	NOTE: To keep the proteins in their phosphorylation status, the phosphatase inhibitor as well as protease inhibitor should be freshly added and samples should be kept on ice at all times. Repeating freeze and thaw cycles of samples should be avoided. Aliquot samples into small amount (e.g. 50 &#956;g) before freezing them at -80 &#176;C.</li>
	<li>Incubate the re-suspended pellet on ice for 15 min and then centrifuge at 250 x g for 5 min at 4 &#176;C.</li>
	<li>Collect the supernatant as the cytoplasmic fraction and keep the pellet for the nuclear fraction.</li>
	<li>Centrifuge the supernatant to remove cellular debris and other contaminants at 18,000 x g for 10 min at 4 &#176;C and then transfer the supernatant into a new microcentrifuge tube. This is the cytosol fraction.</li>
	<li>Resuspend the pellet in 200 &#956;L ice-cold wash buffer (10 mM HEPES pH = 7.6, 1.5 mM MgCl2, 420 mM NaCl, 25% (v/v) glycerol, 0.2 mM EDTA, protease/phosphatase inhibitors) and centrifuge at 250 x g for 5 min at 4 &#176;C</li>
	<li>Remove the supernatant and resuspend the pellet in 100 &#956;L ice-cold, nuclear extraction buffer (20 mM HEPES pH = 7.6, 1.5 mM MgCl2, 420 mM NaCl, 25% (v/v) glycerol, 0.2 mM EDTA, protease/phosphatase inhibitors) and sonicate 10 times (5 s on, 10 s off, 30% amp.) on ice.</li>
	<li>Centrifuge at 18,000 x g for 10 min at 4 &#176;C.</li>
	<li>Transfer the supernatant to a new microcentrifuge tube. This is the nuclear fraction.</li>
	<li>Quantify the protein amount using a BCA assay</li>
</ol>
3. Crude Mitochondrial Fraction
<ol>
	<li>Wash the cells in each 10 cm dish with 10 mL of ice-cold PBS, add 5 mL ice-cold PBS, and detach the cells using a cell scraper. 
	NOTE: Use three 10 cm dishes of cells to get a good yield of mitochondria for Western Blotting.</li>
	<li>Transfer the cell suspension to a 15 mL conical tube, and combine all from three 10 cm dishes into one 15 ml conical tube.</li>
	<li>Centrifuge the cells at 600 x g for 10 min at 4 &#176;C.</li>
	<li>Aspirate the PBS and re-suspend the pellet in 1 mL of ice-cold mitochondria isolation buffer (10 mM Tris-MOPS, 1 mM EGTA/Tris, 200 mM Sucrose, adjust to pH = 7.4).</li>
	<li>Homogenize the cells with 25 strokes of a 2 mL homogenizer with polytetrafluoroethylene coated pestle on ice. 
	NOTE: This step is critical to maintain mitochondrial integrity and maximize the yield of the mitochondrial fraction. The number of strokes should be optimized for each cell type. Precool the homogenizer before starting the procedure.</li>
	<li>Transfer the homogenate to a microcentrifuge tube and centrifuge it at 600 x g for 10 min at 4 &#176;C to remove nuclei and unbroken cells.</li>
	<li>Collect the supernatant, transfer it to a new microcentrifuge tube, and centrifuge it at 7,000 x g for 10 min at 4 &#176;C. 
	NOTE: The pellet is loose, collect the supernatant with care and try not to disturb the pellet.</li>
	<li>Remove the supernatant, re-suspend the pellet with 200 &#956;L of ice-cold mitochondria isolation buffer, and transfer the solution to a new microcentrifuge tube. Centrifuge the tube at 7,000 x g for 10 min at 4 &#176;C.</li>
	<li>Repeat step 3.8 to wash the pellet. It is not necessary to transfer the supernatant to a new microcentrifuge tube in this step.</li>
	<li>Remove the supernatant from the washed pellet and re-suspend the pellet containing mitochondria with 50 &#956;L of RIPA buffer.</li>
	<li>Incubate the suspension on ice for 10 min.</li>
	<li>Centrifuge the suspension at 16,000 x g for 15 min at 4 &#176;C.</li>
	<li>Transfer the supernatant to a new microcentrifuge tube. This is the mitochondrial fraction.</li>
	<li>Quantify the protein amount using a BCA assay.</li>
</ol>
4. Western Blotting for Phospho-Specific Proteins
<ol>
	<li>Perform an SDS-polyacrylamide gel electrophoresis (8-16% premade gel) and transfer the protein to a PVDF membrane4.</li>
	<li>Incubate the membrane with 5% BSA in TBST (0.1% Polysorbate 20) for 30 min at room temperature to block background non-specific binding sites. 
	NOTE: For phosphorylated protein detection, block the membrane with BSA not Milk. Milk contains casein, an abundant phosphoprotein, which results in high nonspecific signal.</li>
	<li>Incubate the membrane with the primary antibody (anti-phospho-ERK1/2) at 4 &#176;C overnight.</li>
	<li>The next day, wash the membrane with TBST (0.1% polysorbate 20) three times for 5 min at room temperature.</li>
	<li>Incubate the membrane with secondary antibody (anti-rabbit HRP) for 1 h at room temperature.</li>
	<li>Wash the membrane with TBST (0.1% polysorbate 20) three times for 5 min at room temperature.</li>
	<li>Incubate the membrane with ECL solution and image the membrane in the image analyzer.</li>
	<li>Strip the membrane with stripping buffer for 15 min at room temperature and wash the membrane with TBST three times for 5 min.</li>
	<li>Repeat steps 4.2 to 4.7 using the anti-total ERK1/2 antibody.</li>
	<li>To check the purity of each fraction, run SDS-PAGE and perform immunoblots using antibodies recognizing markers for each compartment (e.g., Lamin B1 for nucleus, GAPDH for cytosol, and TOM20 for mitochondria).</li>
</ol>

<ol>
	<li>Yen, K., Lee, C., Mehta, H., Cohen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+emerging+role+of+the+mitochondrial-derived+peptide+humanin+in+stress+resistance.">The emerging role of the mitochondrial-derived peptide humanin in stress resistance.</a> J. Mol. Endocrinol. 50 (1), 11-19 (2013).</li><li>Muzumdar, R. H., Huffman, D. 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=Humanin:+a+novel+central+regulator+of+peripheral+insulin+action.">Humanin: a novel central regulator of peripheral insulin action.</a> PloS one. 4 (7), 6334 (2009).</li><li>Lee, C., Yen, K., Cohen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Humanin:+a+harbinger+of+mitochondrial-derived+peptides.">Humanin: a harbinger of mitochondrial-derived peptides.</a> Trends Endocrinol. Metab. 24 (5), 222-228 (2013).</li><li>Kim, S. J., Guerrero, 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=The+mitochondrial-derived+peptide+humanin+activates+the+ERK1/2,+AKT,+and+STAT3+signaling+pathways+and+has+age-dependent+signaling+differences+in+the+hippocampus.">The mitochondrial-derived peptide humanin activates the ERK1/2, AKT, and STAT3 signaling pathways and has age-dependent signaling differences in the hippocampus.</a> Oncotarget. 7 (30), 46899-46912 (2016).</li><li>Ying, G., Iribarren, P., 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=Humanin,+a+newly+identified+neuroprotective+factor,+uses+the+G+protein-coupled+formylpeptide+receptor-like-1+as+a+functional+receptor.">Humanin, a newly identified neuroprotective factor, uses the G protein-coupled formylpeptide receptor-like-1 as a functional receptor.</a> J. Immunol. 172 (11), 7078-7085 (2004).</li><li>Zhang, W., Liu, H. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MAPK+signal+pathways+in+the+regulation+of+cell+proliferation+in+mammalian+cells.">MAPK signal pathways in the regulation of cell proliferation in mammalian cells.</a> Cell Res. 12 (1), 9-18 (2002).</li><li>Huang, C., Jacobson, K., Schaller, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MAP+kinases+and+cell+migration.">MAP kinases and cell migration.</a> J. Cell Sci. 117, 4619-4628 (2004).</li><li>Cagnol, S., Chambard, J. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ERK+and+cell+death:+mechanisms+of+ERK-induced+cell+death--apoptosis,+autophagy+and+senescence.">ERK and cell death: mechanisms of ERK-induced cell death--apoptosis, autophagy and senescence.</a> FEBS J. 277 (1), 2-21 (2010).</li><li>Raman, M., Chen, W., Cobb, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+regulation+and+properties+of+MAPKs.">Differential regulation and properties of MAPKs.</a> Oncogene. 26 (22), 3100-3112 (2007).</li><li>Morrison, D. K., Davis, R. J. <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+MAP+kinase+signaling+modules+by+scaffold+proteins+in+mammals.">Regulation of MAP kinase signaling modules by scaffold proteins in mammals.</a> Annu. Rev. Cell Dev. 19 (1), 91-118 (2003).</li><li>Wainstein, E., Seger, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+dynamic+subcellular+localization+of+ERK:+mechanisms+of+translocation+and+role+in+various+organelles.">The dynamic subcellular localization of ERK: mechanisms of translocation and role in various organelles.</a> Curr. Opin. Cell Biol. 39, 15-20 (2016).</li><li>Zehorai, E., Yao, Z., Plotnikov, A., Seger, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+subcellular+localization+of+MEK+and+ERK--a+novel+nuclear+translocation+signal+(NTS)+paves+a+way+to+the+nucleus.">The subcellular localization of MEK and ERK--a novel nuclear translocation signal (NTS) paves a way to the nucleus.</a> Mol. Cell. Endocrinol. 314 (2), 213-220 (2010).</li><li>Kolch, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coordinating+ERK/MAPK+signalling+through+scaffolds+and+inhibitors.">Coordinating ERK/MAPK signalling through scaffolds and inhibitors.</a> Nat. Rev. Mol. Cell Biol. 6 (11), 827-837 (2005).</li><li>Horbinski, C., Chu, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinase+signaling+cascades+in+the+mitochondrion:+a+matter+of+life+or+death.">Kinase signaling cascades in the mitochondrion: a matter of life or death.</a> Free Radic. Biol. Med. 38 (1), 2-11 (2005).</li><li>Aebersold, D. M., Shaul, Y. 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=Extracellular+signal-regulated+kinase+1c+(ERK1c),+a+novel+42-kilodalton+ERK,+demonstrates+unique+modes+of+regulation,+localization.">Extracellular signal-regulated kinase 1c (ERK1c), a novel 42-kilodalton ERK, demonstrates unique modes of regulation, localization.</a> Mol Cell Biol. 24 (22), 10000-10015 (2004).</li><li>Zhu, J. -. H., Guo, F., Shelburne, J., Watkins, S., Chu, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localization+of+phosphorylated+ERK/MAP+kinases+to+mitochondria+and+autophagosomes+in+Lewy+body+diseases.">Localization of phosphorylated ERK/MAP kinases to mitochondria and autophagosomes in Lewy body diseases.</a> Brain Pathol. 13 (4), 473-481 (2003).</li><li>Cobb, L. J., Lee, 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=Naturally+occurring+mitochondrial-derived+peptides+are+age-dependent+regulators+of+apoptosis,+insulin+sensitivity,+and+inflammatory+markers.">Naturally occurring mitochondrial-derived peptides are age-dependent regulators of apoptosis, insulin sensitivity, and inflammatory markers.</a> Aging. 8 (4), 796-809 (2016).</li><li>Ihle, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Stat+family+in+cytokine+signaling.">The Stat family in cytokine signaling.</a> Curr. Opin. Cell Biol. 13 (2), 211-217 (2001).</li><li>Xu, Y. S., Liang, J. 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=STAT3+Undergoes+Acetylation-dependent+Mitochondrial+Translocation+to+Regulate+Pyruvate+Metabolism.">STAT3 Undergoes Acetylation-dependent Mitochondrial Translocation to Regulate Pyruvate Metabolism.</a> Sci. Rep. 6 (1), 39517 (2016).</li><li>You, L., Wang, Z., 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+STAT3+in+autophagy.">The role of STAT3 in autophagy.</a> Autophagy. 11 (5), 729-739 (2015).</li><li>Hashimoto, Y., Niikura, T., 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=Detailed+characterization+of+neuroprotection+by+a+rescue+factor+humanin+against+various+Alzheimer's+disease-relevant+insults.">Detailed characterization of neuroprotection by a rescue factor humanin against various Alzheimer's disease-relevant insults.</a> The J Neurosci. 21 (23), 9235-9245 (2001).</li><li>Ying, G., Iribarren, P., 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=Humanin,+a+newly+identified+neuroprotective+factor,+uses+the+G+protein-coupled+formylpeptide+receptor-like-1+as+a+functional+receptor.">Humanin, a newly identified neuroprotective factor, uses the G protein-coupled formylpeptide receptor-like-1 as a functional receptor.</a> J. Immunol. 172 (11), 7078-7085 (2004).</li><li>Hashimoto, Y., Kurita, 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=Humanin+inhibits+apoptosis+in+pituitary+tumor+cells+through+several+signaling+pathways+including+NF-&#954;B+activation.">Humanin inhibits apoptosis in pituitary tumor cells through several signaling pathways including NF-&#954;B activation.</a> Mol. Biol. Cell. 20 (12), 2864-2873 (2009).</li></ol>

Pinchas Cohen is a shareholder and consultant for CohBar, Inc. Kelvin Yen has served as a consultant for CohBar, Inc.

Here, we demonstrated that humanin peptide-mediated ERK1/2 activation occurs in two different cell types, and the subcellular localization of activated ERK1/2 can be different depending on the conditions (e.g., dose of peptide, time point, and cell type). It has been shown that humanin signals through two different receptors22,23, which may explain the differences in signaling between the two cell lines as well as the requirement for different doses of humanin. The physiological implications of this have not been fully studied but it may suggest one possible mechanism for tissue dependent responses to HN. 
Phosphorylation of ERK1/2 plays a crucial role in ERK1/2 signaling and the phosphorylation status of ERK1/2 shows dynamic changes. It is important to optimize the conditions to find when ERK1/2 is phosphorylated under a specific condition/stimulus. To achieve this, try different stimulation conditions (e.g., dose and medium) and conduct time courses to find when the highest level of phosphorylation is achieved. A majority of studies have only focused on ERK1/2 phosphorylation in total cell lysates. However, the results may provide limited functional information as ERK1/2 can interact with different targets and modulate different downstream cascades in specific subcellular compartments. Therefore, examining the subcellular localization of phosphorylated ERK1/2 gives a better understanding of the role of ERK1/2 activation. 
Subcellular fractionation after ERK1/2 activation can be used as a source of further study (e.g., co-immunoprecipitation) to identify novel downstream targets because the subcellular fractionation can enrich for downstream targets of ERK1/2. This method can be applied to other signaling molecules that are translocated into different subcellular compartments upon stimuli after optimization of the conditions. 
Although various methods to isolate mitochondria have been proposed in the past decades, there is partial contamination from other subcellular compartments. The crude mitochondrial isolation method proposed here also contains limited amount of cytoplasm contaminants. As the amount of contamination is small, we consider that it is still a valid method for detecting the localization of ERK1/2 into mitochondria upon activation. As peptides are not necessarily stable in solution, it is sometimes difficult to maintain consistency between experiments. Be sure to make small aliquots of peptide solution to avoid freeze-thaw effects and to improve the consistency of peptide activity.

Emerging studies show that mitochondrial-derived peptides (MDPs) play important roles in cytoprotection and metabolism1,2,3. Understanding the signal transduction pathway in the presence of MDPs gives us insight into the mechanism by which MDPs modulate various functions. The first identified MDP, humanin, has been shown to increase extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation through its receptor binding4,5. However, the downstream effect of ERK1/2 activation is still underexplored.
The ERK1/2 cascade serves as an essential mediator in a variety of cellular processes including proliferation, cell migration, cellular metabolism, survival, and apoptosis6,7,8. To orchestrate all these distinct cellular processes, the activity and subcellular localization of ERK1/2 are tightly regulated by phosphatases and scaffold proteins9,10. In addition to post-translational modification, the dynamic shuttling of ERK1/2 also regulates its signaling function, activity, and specificity11,12. ERK1/2 is primarily localized in the cytosol13. A set of anchoring and scaffold proteins help retain ERK1/2 in cytoskeletal elements, on the surface of organelles, or diffused in the cytoplasm13. Upon stimulation, ERK1/2 is phosphorylated and becomes dissociated from its anchoring proteins, allowing the translocation of ERK1/2 to other subcellular compartments, including the nucleus, mitochondria, Golgi, and lysosomes14,15,16.
Although humanin is known to activate the ERK1/2 signaling pathway, the activation of ERK1/2 is only observed in the total cell lysates. As described previously, since ERK1/2 subcellular localization plays a crucial role in its downstream effect, the analysis of both the subcellular localization and the total levels of phosphorylated ERK1/2 is necessary to provide a comprehensive understanding of humanin-induced ERK1/2 activation and the activation of downstream targets.
To understand the target organelles of activated ERK1/2, subcellular fractionation followed by western blotting for phosphorylated ERK1/2 was performed. This method can be easily implemented as it utilizes standard laboratory equipment and reagents. The isolated subcellular compartments are of high purity, allowing the results to be straightforwardly interpreted. Immunostaining of ERK1/2 may produce similar results. However, certain subcellular compartments are relatively hard to visualize and require special fixation and permeabilization methods. ERK1/2 levels vary in subcellular compartments, and this variation could cause false positive and false negative signals when looking at whole cell lysates. Therefore, an immunoblot using isolated subcellular compartments gives us a better understanding of ERK1/2 localization.
The versatility of the method enables modifications of the protocol to investigate effects of other stimulants including other MDPs or translocation of other signaling molecules such as STAT3. Recently discovered small humanin-like peptides (SHLPs) are encoded from 16S rRNA region where humanin is encoded, and they have similar but distinct properties compared to HN17. For example, SHLP2 and SHLP3 activate ERK1/2 after 8 h although humanin activates ERK1/2 within 5 min. Examining subcellular localization of ERK1/2 in response to different peptides will give us a better understanding of the biology of these peptides. Emerging evidence showed that the subcellular localization of signaling molecules plays a crucial role in their downstream effects. For instance, STAT3 traditionally is known to be primarily localized in the cytosol in resting cells, and then it translocates into the nucleus to activate gene expression in response to cytokines18. STAT3 also translocates to mitochondria and regulates the TCA cycle and ATP production19. Regarding autophagy regulation, different subcellular localization of STAT3 modulates autophagy in various ways20. For example, nuclear STAT3 transcriptionally regulates autophagy-related genes and acts as an autophagy modulator. Cytoplasmic STAT3 constitutively inhibits autophagy by interacting with autophagy signaling molecules. Mitochondrial STAT3 inhibits and prevents mitophagy by suppressing oxidative stress induced autophagy. Therefore, this subcellular compartment isolation method is crucial for understanding the role of other signaling molecules as well as ERK1/2.

<table><tbody><tr><td>p44/42 MAPK (ERK1/2)</td><td>Cell signaling</td><td>9102</td><td>Dilution 1:1,000</td></tr><tr><td>phospho-p44/42 MAPK (ERK1/2)(Thr202/Tyr204)</td><td>Cell signaling</td><td>4370</td><td>Dilution 1:1,000</td></tr><tr><td>Lamin B1</td><td>Cell signaling</td><td>12586</td><td>Nuclear Marker, Dilution 1:1,000</td></tr><tr><td>GAPDH</td><td>Cell signaling</td><td>5174</td><td>Cytoplasmic marker, Dilution 1:2,000</td></tr><tr><td>Tom20</td><td>Santa cruz</td><td>SC-17764</td><td>Mitochondria marker, Dilution 1:2,000</td></tr><tr><td>anti-Rabbit-HRP conjugated</td><td>Cell signaling</td><td>7074</td><td>Dilution 1:30,000</td></tr><tr><td>RIPA Lysis and Extraction Buffer</td><td>ThermoFisher SCIENTIFIC</td><td>89900</td><td></td></tr><tr><td>100 mm Culture Dish</td><td>ThermoFisher SCIENTIFIC</td><td>12556002</td><td></td></tr><tr><td>HNG peptide</td><td>Genescript</td><td></td><td></td></tr><tr><td>25mm sylinge filter</td><td>ThermoFisher SCIENTIFIC</td><td>09-719A</td><td></td></tr><tr><td>HEPES</td><td>Sigma</td><td>H3375</td><td></td></tr><tr><td>MgCl2</td><td>Sigma</td><td>M8266</td><td></td></tr><tr><td>KCl</td><td>Sigma</td><td>P9333</td><td></td></tr><tr><td>Glycerol</td><td>Sigma</td><td>G9012</td><td></td></tr><tr><td>Triton X-100</td><td>ThermoFisher SCIENTIFIC</td><td>BP151-100</td><td></td></tr><tr><td>EDTA</td><td>Sigma</td><td>3609</td><td></td></tr><tr><td>MOPS</td><td>Sigma</td><td>M1254</td><td></td></tr><tr><td>EGTA</td><td>Sigma</td><td>E3889</td><td></td></tr><tr><td>Sucrose</td><td>Sigma</td><td>S7903</td><td></td></tr><tr><td>Tris-base</td><td>ThermoFisher SCIENTIFIC</td><td>BP152-1</td><td></td></tr><tr><td>HCL</td><td>Sigma</td><td>H1758</td><td></td></tr><tr><td>PBS</td><td>Lonza</td><td>17-512F</td><td></td></tr><tr><td>Cell Scraper</td><td>FALCON</td><td>353085</td><td></td></tr><tr><td>Halt&amp;trade; Protease and Phosphatase Inhibitor Cocktail (100X)</td><td>ThermoFisher SCIENTIFIC</td><td>78440</td><td></td></tr><tr><td>Thomas Pestle Tissue Grinder Assemblies with Smooth Pestles</td><td>Thomas Scientific</td><td>3432S90</td><td></td></tr><tr><td>Tween-20</td><td>ThermoFisher SCIENTIFIC</td><td>BP337-500</td><td></td></tr><tr><td>BSA</td><td>ThermoFisher SCIENTIFIC</td><td>BP1600-100</td><td></td></tr><tr><td>8-16% Mini-PROTEAN TGX Precast Protein Gels</td><td>BIO RAD</td><td>4561104</td><td></td></tr><tr><td>Mini Trans-Blot Module</td><td>BIO RAD</td><td>1658030</td><td></td></tr><tr><td>Trans-Blot Turbo Transfer System</td><td>BIO RAD</td><td>1704150</td><td></td></tr><tr><td>Trans-Blot Turbo RTA Mini PVDF Transfer Kit</td><td>BIO RAD</td><td>1704272</td><td></td></tr><tr><td>Clarity Western ECL Blotting Substrates</td><td>BIO RAD</td><td>1705060</td><td></td></tr><tr><td>Restore Western blot stripping buffer</td><td>ThermoFisher SCIENTIFIC</td><td>21059</td><td></td></tr><tr><td>Dulbecco&#039;s Modified Eagle Medium</td><td>ThermoFisher SCIENTIFIC</td><td>11965-092</td><td></td></tr><tr><td>Sonicator, Medel: FB120</td><td>ThermoFisher SCIENTIFIC</td><td>695320-07-12</td><td></td></tr></tbody></table>

subcellular fractionation for erk activation upon mitochondrial-derived peptide treatment

Mitochondrial-derived peptides (MDPs) are a new class of peptides that are encoded by small open reading frames within other known genes of the mitochondrial genome. MDPs have a wide variety of biological effects such as protecting neurons from apoptosis, improving metabolic markers, and protecting cells from chemotherapy. Humanin was the first MDP to be discovered and is the most studied peptide among the MDP family. The membrane receptors and downstream signaling pathways of humanin have been carefully characterized. Additional MDPs such as MOTS-c and SHLP1-6 have been more recently discovered and the signaling mechanisms have yet to be elucidated. Here we describe a cell culture based method to determine the function of these peptides. In particular, cell fractionation techniques in combination with western blotting allow for the quantitative determination of activation and translocation of important signaling molecule. While there are other methods of cell fractionation, the one described here is an easy and straightforward method. These methods can be used to further elucidate the mechanism of action of these peptides and other therapeutic agents.

Using the procedure presented here, we treated HEK293 and SH-SY5Y cells with 1 &#956;M and 100 &#956;M S14G-humanin, a potent humanin analog21, respectively, in complete media for the indicated time periods (Figure 1A and Figure 1B). We then examined the total and phosphorylated form of ERK1/2 at Thr202/Tyr204 from total protein extracts. S14G-humanin treatment showed increase in phosphorylation of ERK1/2 at its regulatory Thr202/Tyr204 Site. The subcellular localization of ERK1/2 plays an important role in its signaling function, particularly in getting its specificity. To understand the target of S14G-humanin-mediated ERK1/2 activation, we analyzed the subcellular localization of total and phosphorylated ERK1/2 following S14G-humanin treatment. In HEK293 cells, the phosphorylated ERK increased in the both cytoplasm and nucleus, but not in the mitochondria (Figure 2A). Interestingly, phosphorylated ERK decreased in the cytoplasm, nucleus, and mitochondria in SH-SY5Y cells (Figure 2B). These results suggest that S14G-humanin-mediated ERK phosphorylation may play a different role in different cell types and different conditions. Therefore, further studies are required to analyze the localization of S14G-humanin-mediated phosphorylation of ERK1/2 in other subcellular compartments, as phosphorylated ERK1/2 translocates into the nucleus, mitochondria, endosomes/lysosomes, and various membranes.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56496/56496fig1.jpg" /> 
Figure 1: S14G-humanin increases the phosphorylation of ERK1/2 in HEK293 and SH-SY5Y cells. Quantification and representative western blots of ERK activation in (A) HEK293 and (B) SH-SY5Y cells. Total cell lysates following (A) 1 &#181;M or (B) 100 &#181;M S14G-humanin treatment in DMEM supplemented with 10% FBS for the indicated time periods were immunoblotted using anti-phospho- and total-ERK 1/2 (Thr202/Tyr204). This figure has been modified from Kim et al.4 <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56496/56496fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56496/56496fig2.jpg" /> 
Figure 2: Phosphorylated ERK1/2 is localized to cytosol, nucleus, and other subcellular compartments upon S14G-humanin treatment in HEK293 and SH-SY5Y cells. Representative western blots showing ERK1/2 subcellular localization (n = 3). (A) HEK293 cells were treated with 1 &#181;M S14G-humanin. Cytosolic (15 &#181;g), nuclear (15 &#181;g and 50 &#181;g), and mitochondrial (15 &#956;g) lysates were immunoblotted using phospho- and total-ERK antibody. (B) SH- SY5Y cells were treated with 100 &#181;M S14G-humanin. Mitochondrial fractions were obtained 30 min after S14G-humanin treatment. Cytosolic, nuclear, and mitochondrial (15 &#181;g) lysates were immunoblotted using phospho- and total-ERK antibody. Anti-GAPDH, Anti-Lamin B, anti-Tom20 antibody were used as the cytosolic, nuclear, mitochondrial fraction markers, respectively. This figure has been modified from Kim et al.4. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56496/56496fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Table 1" src="/files/ftp_upload/56496/56496table1v2.jpg" /> 
Table 1: Buffers for cytosol, nuclear, and Mitochondrial fraction.

Watch this Scientific Journal Video about Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment at JoVE.com

Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment

This protocol describes how to stimulate cells with mitochondrial-derived peptides and assess the signaling cascade and localization of phospho-proteins.

Mitochondrial-derived peptides (MDPs) are a new class of peptides that are encoded by small open reading frames within other known genes of the ...

subcellular-fractionation-for-erk-activation-upon-mitochondrial

Nanyang Technological University

Research

JoVE Journal

Biology

7.8K Views.  University of Southern California. This protocol describes how to stimulate cells with mitochondrial-derived peptides and assess the signaling cascade and localization of phospho-proteins.

Video: Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment

Assaying Protein Kinase Activity with Radiolabeled ATP

Protein kinases are able to govern large-scale cellular changes in response to complex arrays of stimuli, and much effort has been directed at uncovering allosteric details of their regulation. Kinases comprise signaling networks whose defects are often hallmarks of multiple forms of cancer and related diseases, making an assay platform amenable to manipulation of upstream regulatory factors and validation of reaction requirements critical in the search for improved therapeutics. Here, we describe a basic kinase assay that can be easily adapted to suit specific experimental questions including but not limited to testing the effects of biochemical and pharmacological agents, genetic manipulations such as mutation and deletion, as well as cell culture conditions and treatments to probe cell signaling mechanisms. This assay utilizes radiolabeled [&#947;-32P] ATP, which allows for quantitative comparisons and clear visualization of results, and can be modified for use with immunoprecipitated or recombinant kinase, specific or typified substrates, all over a wide range of reaction conditions.

Protein kinases are highly evolved signaling enzymes and scaffolds that are critical for inter- and intracellular signal transduction. We present a protocol for measuring kinase activity through the use of radiolabeled adenosine triphosphate ([&#947;-32P] ATP), a reliable method to aid in elucidation of cellular signaling regulation.

Protein kinases are able to govern large-scale cellular changes in response to complex arrays of stimuli, and much effort has been directed at uncovering ...

Biochemistry

Probing for Mitochondrial Complex Activity in Human Embryonic Stem Cells

Mitochondria are cytoplasmic organelles that have a primary role in cellular metabolism and homeostasis, regulation of the cell signaling network, and programmed cell death. Mitochondria produce ATP, regulate the cytoplasmic redox state and Ca2+ balance, catabolize fatty acids, synthesize heme, nucleotides, steroid hormones, amino acids, and help assemble iron-sulfur clusters in proteins. Mitochondria also have an essential role in heat production. Mutations of the mitochondrial genome cause several types of human disorder. The accumulation of mtDNA mutations correlates with aging and is suspected to have an important role in the development of cancer. Due to their vitally important role in all cell types, the function of mitochondria must also be critical for stem cells. Key advances have been made in our understanding of stem cell viability, proliferation, and differentiation capacity. But the functional activity of stem cells, in particular their energy status, was not yet been studied in detail. Almost nothing is known about the mitochondrial properties of human embryonic stem cells (hESCs) and their differentiated precursor progeny. One way to understand and evaluate the role of mitochondria in hESC function and developmental potential is to directly measure the activity of mitochondrial respiratory complexes. Here, we describe high resolution clear native gel electrophoresis and subsequent in gel activity visualization as a method for analyzing the five respiratory chain complexes of hESCs.

In this video, we will show you how the mitochondrial respiratory chain complexes of human embryonic stem cells can be analyzed using in gel activity assays.

Mitochondria are cytoplasmic organelles that have a primary role in cellular metabolism and homeostasis, regulation of the cell signaling network, and ...

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple cellular and developmental processes principally via activation of ERK, the terminal kinase of the pathway. Tight regulation of ERK activity is essential for normal development and homeostasis; overly active ERK results in excessive cellular proliferation, while underactive ERK causes cell death. C. elegans is a powerful model system that has helped characterize the function and regulation of RTK-RAS-ERK signaling pathway during development. In particular, the RTK-RAS-ERK pathway is essential for C. elegans germline development, which is the focus of this method. Using antibodies specific to the active, diphosphorylated form of ERK (dpERK), the stereotypical localization pattern can be visualized within the germline. Because this pattern is both spatially and temporally controlled, the ability to reproducibly assay dpERK is useful to identify regulators of the pathway that affect dpERK signal duration and amplitude and thus germline development. Here we demonstrate how to successfully dissect, stain, and image dpERK within the C. elegans gonad. This method can be adapted for spatial localization of any signaling or structural protein in the C. elegans gonad, provided an antibody compatible with immunofluorescence is available.

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

We present an immunofluorescence&#160;imaging-based method for spatial and temporal localization of active ERK in the dissected C. elegans gonad. The protocol described here can be adapted for visualization of any signaling or structural protein in the C. elegans gonad, provided a suitable antibody reagent is available.

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple ...

Developmental Biology

Cell Fractionation of U937 Cells in the Absence of High-speed Centrifugation

In this protocol we detail a method to obtain subcellular fractions of U937 cells without the use of ultracentrifugation or indiscriminate detergents. This method utilizes hypotonic buffers, digitonin, mechanical lysis and differential centrifugation to isolate the cytoplasm, mitochondria and plasma membrane. The process can be scaled to accommodate the needs of researchers, is inexpensive and straightforward. This method will allow researchers to determine protein localization in cells without specialized centrifuges and without the use of commercial kits, both of which can be prohibitively expensive. We have successfully used this method to separate cytosolic, plasma membrane and mitochondrial proteins in the human monocyte cell line U937.

Here, we present a protocol to isolate the plasma membrane, cytoplasm and mitochondria of U937 cells without the use of high-speed centrifugation. This technique can be used to purify subcellular fractions for subsequent examination of protein localization via immunoblotting.

In this protocol we detail a method to obtain subcellular fractions of U937 cells without the use of ultracentrifugation or indiscriminate detergents. ...

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae

Despite recent advances in the characterization of yeast mitochondrial proteome, the submitochondrial localization of a significant number of proteins remains elusive. Here, we describe a robust and effective method for determining the suborganellar localization of yeast mitochondrial proteins, which is considered a fundamental step during mitochondrial protein function elucidation. This method involves an initial step that consists of obtaining highly pure intact mitochondria. These mitochondrial preparations are then subjected to a subfractionation protocol consisting of hypotonic shock (swelling) and incubation with proteinase K (protease). During swelling, the outer mitochondrial membrane is selectively disrupted, allowing the proteinase K to digest proteins of the intermembrane space compartment. In parallel, to obtain information about the topology of membrane proteins, the mitochondrial preparations are initially sonicated, and then subjected to alkaline extraction with sodium carbonate. Finally, after centrifugation, the pellet and supernatant fractions from these different treatments are analyzed by SDS-PAGE and western blot. The submitochondrial localization as well as the membrane topology of the protein of interest is obtained by comparing its western blot profile with known standards.

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae

Despite recent advances, many yeast mitochondrial proteins still remain with their functions completely unknown. This protocol provides a simple and reliable method to determine the submitochondrial localization of proteins, which has been fundamental for the elucidation of their molecular functions.

Despite recent advances in the characterization of yeast mitochondrial proteome, the submitochondrial localization of a significant number of proteins ...

A Functional Assay for Gap Junctional Examination; Electroporation of Adherent Cells on Indium-Tin Oxide

In this technique, cells are cultured on a glass slide that is partly coated with indium-tin oxide (ITO), a transparent, electrically conductive material. A variety of molecules, such as peptides or oligonucleotides can be introduced into essentially 100% of the cells in a non-traumatic manner.&#160; Here, we describe how it can be used to study intercellular, gap junctional communication. Lucifer yellow penetrates into the cells when an electric pulse, applied to the conductive surface on which they are growing, causes pores to form through the cell membrane. This is electroporation. Cells growing on the nonconductive&#160;glass surface immediately adjacent to the electroporated region do not take up Lucifer yellow by electroporation but do acquire the fluorescent dye as it is passed to them via gap junctions that link them to the electroporated cells. The results of the transfer of dye from cell to cell can be observed microscopically under fluorescence illumination. This technique allows for precise quantitation of gap junctional communication. In addition, it can be used for the introduction of peptides or other non-permeant molecules, and the transfer of small electroporated peptides via gap junctions to inhibit the signal in the adjacent, non-electroporated cells is a powerful demonstration of signal inhibition.

This presentation demonstrates a method whereby electroporation of adherent, cultured cells is used for the study of intercellular, junctional communication, while the cells grow on a slide coated with conductive and transparent indium-tin oxide.

In this technique, cells are cultured on a glass slide that is partly coated with indium-tin oxide (ITO), a transparent, electrically conductive material. ...

Isolation and Functional Analysis of Mitochondria from Cultured Cells and Mouse Tissue

Comparison between two or more distinct groups, such as healthy vs. disease, is necessary to determine cellular status. Mitochondria are at the nexus of cell heath due to their role in both cell metabolism and energy production as well as control of apoptosis. Therefore, direct evaluation of isolated mitochondria and mitochondrial perturbation offers the ability to determine if organelle-specific (dys)function is occurring. The methods described in this protocol include isolation of intact, functional mitochondria from HEK cultured cells and mouse liver and spinal cord, but can be easily adapted for use with other cultured cells or animal tissues. Mitochondrial function assessed by TMRE and the use of common mitochondrial uncouplers and inhibitors in conjunction with a fluorescent plate reader allow this protocol not only to be versatile and accessible to most research laboratories, but also offers high throughput.

Comparison of mitochondrial membrane potential between samples yields valuable information about cellular status. Detailed steps for isolating mitochondria and assessing response to inhibitors and uncouplers using fluorescence are described. The method and utility of this protocol are illustrated by use of a cell culture and animal model of cellular stress.

Comparison between two or more distinct groups, such as healthy vs. disease, is necessary to determine cellular status. Mitochondria are at the nexus of ...

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1

Although mitochondria possess their own transcriptional machinery, merely 1% of mitochondrial proteins are synthesized inside the organelle. The nuclear-encoded proteins are transported into mitochondria guided by their mitochondria targeting sequences (MTS); however, a majority of mitochondrial localized proteins lack an identifiable MTS. Nevertheless, the fact that MTS can instruct proteins to go into the mitochondria provides a valuable tool for studying mitochondrial functions of normally nuclear and/or cytoplasmic proteins. We have recently identified the cell cycle kinase CyclinB1/Cdk1 complex in the mitochondria. To specifically study the mitochondrial functions of this complex, mitochondrial overexpression and knock-down of this complex without interfering with its nuclear or cytoplasmic functions were essential. By tagging CyclinB1/Cdk1 with MTS, we were able to achieve mitochondrial overexpression of this complex to study its mitochondrial targets as well as functions. Via tagging dominant-negative Cdk1 with MTS, inhibition of Cdk1 activity was accomplished particularly in the mitochondria. Potential mitochondrial targets of CyclinB1/Cdk1 complex were identified using a gel-based proteomics approach. Unlike traditional 2D gel analysis, we employed 2-dimensional difference gel electrophoresis (2D-DIGE) technology followed by phosphoprotein staining to fluorescently label differentially phosphorylated proteins in mitochondrial Cdk1 expressing cells. Identification of phosphoprotein spots that were altered in wild type versus dominant negative Cdk1 bearing mitochondria revealed the identity of mitochondrial targets of Cdk1. Finally, to determine the effect of CyclinB1/Cdk1 mitochondrial localization in cell cycle progression, a cell proliferation assay using a synthetic thymidine analogue EdU (5-ethynyl-2&#8242;-deoxyuridine) was used to monitor the cells as they go through the cell cycle and replicate their DNA. Altogether, we demonstrated a variety of approaches available to study mitochondrial localization and activity of a cell cycle kinase. These are advanced, yet easy to follow methods that will be beneficial to many cell biology researchers.

Here, we outline how to study mitochondrial localization of a (cell cycle) kinase, and how to determine its sub-mitochondrial location as well as potential mitochondrial substrates/targets. Forced expression of proteins into the mitochondria provides a useful tool for studying the functional consequences of mitochondrial localization of a protein of interest.

Although mitochondria possess their own transcriptional machinery, merely 1% of mitochondrial proteins are synthesized inside the organelle. The ...

MATLAB Optimization for Analyzing Mitochondrial Networks in Neuroscience

Optimized Automated Analysis of Live Neuronal Mitochondria Homeostasis Modulation by Isoform-Specific Retinoic Acid Receptors

The complex mitochondrial network makes it very challenging to segment, follow, and analyze live cells. MATLAB tools allow the analysis of mitochondria in timelapse files, considerably simplifying and speeding up the process of image processing. Nonetheless, existing tools produce a large output volume, requiring individual manual attention, and basic experimental setups have an output of thousands of files, each requiring extensive and time-consuming handling. 
To address these issues, a routine optimization was developed, in both MATLAB code and live-script forms, allowing for swift file analysis and significantly reducing document reading and data processing. With a speed of 100 files/min, the optimization allows an overall rapid analysis. The optimization achieves the results output by averaging frame-specific data for individual mitochondria throughout time frames, analyzing data in a defined manner, consistent with those output from existing tools. Live confocal imaging was performed using the dye tetramethylrhodamine methyl ester, and the routine optimization was validated by treating neuronal cells with retinoic acid receptor (RAR) agonists, whose effects on neuronal mitochondria are established in the literature. The results were consistent with the literature and allowed further characterization of mitochondrial network behavior in response to isoform-specific RAR modulation. 
This new methodology allowed rapid and validated characterization of whole-neuron mitochondria network, but it also allows for differentiation between axon and cell body mitochondria, an essential feature to apply in the neuroscience field. Moreover, this protocol can be applied to experiments using fast-acting treatments, allowing the imaging of the same cells before and after treatments, transcending the field of neuroscience.

Author Spotlight: An Optimized Automated Method for Investigating Retinoic Acid Receptors in Neuronal Mitochondria

The mitochondrial network is extremely complex, making it very challenging to analyze. A novel MATLAB tool analyzes live confocal imaged mitochondria in timelapse images but results in a large output volume requiring individual manual attention. To address this issue, a routine optimization was developed, allowing for speedy file analysis.

The complex mitochondrial network makes it very challenging to segment, follow, and analyze live cells. MATLAB tools allow the analysis of mitochondria in ...

Neuroscience

Improved Protein Quantification Using Two-Step Mitochondrial Isolation

Two-Step Tag-Free Isolation of Mitochondria for Improved Protein Discovery and Quantification

Most physiological and disease processes, from central metabolism to immune response to neurodegeneration, involve mitochondria. The mitochondrial proteome is composed of more than 1,000 proteins, and the abundance of each can vary dynamically in response to external stimuli or during disease progression. Here, we describe a protocol for isolating high-quality mitochondria from primary cells and tissues. The two-step procedure comprises (1) mechanical homogenization and differential centrifugation to isolate crude mitochondria, and (2) tag-free immune capture of mitochondria to isolate pure organelles and eliminate contaminants. Mitochondrial proteins from each purification stage are analyzed by quantitative mass spectrometry, and enrichment yields are calculated, allowing the discovery of novel mitochondrial proteins by subtractive proteomics. Our protocol provides a sensitive and comprehensive approach to studying mitochondrial content in cell lines, primary cells, and tissues.

Author Spotlight: Two-Step Tag-Free Isolation of Mitochondria for Improved Protein Discovery and Quantification  

We present a two-step protocol for high-quality mitochondria isolation that is compatible with protein discovery and quantification at a proteome scale. Our protocol does not require genetic engineering and is thus suitable for studying mitochondria from any primary cells and tissues.

Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment

Podsumowanie

Przeglądaj więcej filmów

Rozdziały w tym wideo

Assaying Protein Kinase Activity with Radiolabeled ATP

Probing for Mitochondrial Complex Activity in Human Embryonic Stem Cells

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

Cell Fractionation of U937 Cells in the Absence of High-speed Centrifugation

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae

A Functional Assay for Gap Junctional Examination; Electroporation of Adherent Cells on Indium-Tin Oxide

Isolation and Functional Analysis of Mitochondria from Cultured Cells and Mouse Tissue

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1

Optimized Automated Analysis of Live Neuronal Mitochondria Homeostasis Modulation by Isoform-Specific Retinoic Acid Receptors

Two-Step Tag-Free Isolation of Mitochondria for Improved Protein Discovery and Quantification