Name: quantitative immunofluorescence assay to measure the variation in protein levels at centrosomes
Uploaded: 2014-12-20T14:00:00
Description: Watch this Scientific Journal Video about Quantitative Immunofluorescence Assay to Measure the Variation in Protein Levels at Centrosomes at JoVE.com

This work was supported by a National Institutes of Health grant (GM77311) and a seed grant from The Ohio Cancer Research Associates (to H.A.F.). SM was partially supported by an Up on the Roof fellowship from the Human Cancer Genetics Program of The Ohio State University Comprehensive Cancer Center.

1. Cell Culture
<ol>
	<li>Use human telomerase reverse transcriptase (hTERT) immortalized retinal pigment epithelial cells (hTERT-RPE1; referred to here as RPE1). 
	NOTE: RPE1 cells are near-diploid, non-transformed human cells that are commonly used to study centriole assembly and ciliogenesis. These cells follow a normal centriole duplication cycle coordinated with a regulated cell cycle.</li>
	<li>Passage a near-confluent 100 mm cell culture dish of RPE1 cells at 1:5 dilution of the original culture into a fres...

<ol>
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Biol. 20, 816-825 (2010).</li><li>Nakazawa, Y., Hiraki, M., Kamiya, R., Hirono, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SAS-6+is+a+cartwheel+protein+that+establishes+the+9-fold+symmetry+of+the+centriole.">SAS-6 is a cartwheel protein that establishes the 9-fold symmetry of the centriole.</a> Curr. Biol. 17, 2169-2174 (2007).</li><li>Strnad, 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=Regulated+HsSAS-6+levels+ensure+formation+of+a+single+procentriole+per+centriole+during+the+centrosome+duplication+cycle.">Regulated HsSAS-6 levels ensure formation of a single procentriole per centriole during the centrosome duplication cycle.</a> Dev. 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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cep97+and+CP110+suppress+a+cilia+assembly+program.">Cep97 and CP110 suppress a cilia assembly program.</a> Cell. 130, 678-690 (2007).</li><li>Salisbury, J., Suino, K., Busby, R., Springett, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Centrin-2+is+required+for+centriole+duplication+in+Mammalian+cells.">Centrin-2 is required for centriole duplication in Mammalian cells.</a> Curr. Biol. 12, 1287 (2002).</li><li>Lukasiewicz, K. B., 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=Control+of+centrin+stability+by+Aurora+A.">Control of centrin stability by Aurora A.</a> PLoS One. 6, e21291 (2011).</li><li>Zhao, J., Ren, Y., Jiang, Q., Feng, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parkin+is+recruited+to+the+centrosome+in+response+to+inhibition+of+proteasomes.">Parkin is recruited to the centrosome in response to inhibition of proteasomes.</a> J. Cell Sci. 116, 4011-4019 (2003).</li><li>Korzeniewski, 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=Cullin+1+functions+as+a+centrosomal+suppressor+of+centriole+multiplication+by+regulating+polo-like+kinase+4+protein+levels.">Cullin 1 functions as a centrosomal suppressor of centriole multiplication by regulating polo-like kinase 4 protein levels.</a> Cancer Res. 69, 6668-6675 (2009).</li><li>Rohatgi, R., Milenkovic, L., Corcoran, R. B., Scott, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hedgehog+signal+transduction+by+Smoothened:+pharmacologic+evidence+for+a+2-step+activation+process.">Hedgehog signal transduction by Smoothened: pharmacologic evidence for a 2-step activation process.</a> Proc. Natl. Acad. Sci. U.S.A. 106, 3196-3201 (2009).</li><li>Majumder, S., Fisk, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=VDAC3+and+Mps1+negatively+regulate+ciliogenesis.">VDAC3 and Mps1 negatively regulate ciliogenesis.</a> Cell Cycle. 12, 849-858 (2013).</li><li>Howell, B. J., Hoffman, D. B., Fang, G., Murray, A. W., Salmon, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualization+of+Mad2+dynamics+at+kinetochores,+along+spindle+fibers,+and+at+spindle+poles+in+living+cells.">Visualization of Mad2 dynamics at kinetochores, along spindle fibers, and at spindle poles in living cells.</a> J. Cell Biol. 150, 1233-1250 (2000).</li><li>Meraldi, P., Nigg, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Centrosome+cohesion+is+regulated+by+a+balance+of+kinase+and+phosphatase+activities.">Centrosome cohesion is regulated by a balance of kinase and phosphatase activities.</a> J. Cell Sci. 114, 3749-3757 (2001).</li><li>Zimmerman, W. C., Sillibourne, J., Rosa, J., Doxsey, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitosis-specific+anchoring+of+gamma+tubulin+complexes+by+pericentrin+controls+spindle+organization+and+mitotic+entry.">Mitosis-specific anchoring of gamma tubulin complexes by pericentrin controls spindle organization and mitotic entry.</a> Mol. Biol. Cell. 15, 3642-3657 (2004).</li><li>Lee, K., Rhee, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PLK1+phosphorylation+of+pericentrin+initiates+centrosome+maturation+at+the+onset+of+mitosis.">PLK1 phosphorylation of pericentrin initiates centrosome maturation at the onset of mitosis.</a> J. Cell Biol. 195, 1093-1101 (2011).</li><li>Lin, Y. 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=Human+microcephaly+protein+CEP135+binds+to+hSAS-6+and+CPAP,+and+is+required+for+centriole+assembly.">Human microcephaly protein CEP135 binds to hSAS-6 and CPAP, and is required for centriole assembly.</a> Embo. J. 32, 1141-1154 (2013).</li><li>Lichtenstein, N., Geiger, B., Kam, Z. <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+cytoskeletal+organization+by+digital+fluorescent+microscopy.">Quantitative analysis of cytoskeletal organization by digital fluorescent microscopy.</a> Cytometry A. 54, 8-18 (2003).</li><li>Keller, 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=Molecular+architecture+of+the+centriole+proteome:+the+conserved+WD40+domain+protein+POC1+is+required+for+centriole+duplication+and+length+control.">Molecular architecture of the centriole proteome: the conserved WD40 domain protein POC1 is required for centriole duplication and length control.</a> Mol. Biol. Cell. 20, 1150-1166 (2009).</li><li>Venoux, 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=Poc1A+and+Poc1B+act+together+in+human+cells+to+ensure+centriole+integrity.">Poc1A and Poc1B act together in human cells to ensure centriole integrity.</a> J. Cell Sci. 126, 163-175 (2013).</li><li>Stevens, N. R., Roque, H., Raff, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DSas-6+and+Ana2+coassemble+into+tubules+to+promote+centriole+duplication+and+engagement.">DSas-6 and Ana2 coassemble into tubules to promote centriole duplication and engagement.</a> Dev. Cell. 19, 913-919 (2010).</li><li>Machiels, B. 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=Detailed+analysis+of+cell+cycle+kinetics+upon+proteasome+inhibition.">Detailed analysis of cell cycle kinetics upon proteasome inhibition.</a> Cytometry. 28, 243-252 (1997).</li><li>Yang, C. H., Kasbek, C., Majumder, S., Yusof, A. M., Fisk, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mps1+phosphorylation+sites+regulate+the+function+of+centrin+2+in+centriole+assembly.">Mps1 phosphorylation sites regulate the function of centrin 2 in centriole assembly.</a> Mol. Biol. Cell. 21, 4361-4372 (2010).</li><li>Tsou, M. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polo+kinase+and+separase+regulate+the+mitotic+licensing+of+centriole+duplication+in+human+cells.">Polo kinase and separase regulate the mitotic licensing of centriole duplication in human cells.</a> Dev. Cell. 17, 344-354 (2009).</li><li>Salic, A., Mitchison, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chemical+method+for+fast+and+sensitive+detection+of+DNA+synthesis+in+vivo.">A chemical method for fast and sensitive detection of DNA synthesis in vivo.</a> Proc. Natl. Acad. Sci. U.S.A. 105, 2415-2420 (2008).</li><li>Buck, S. B., 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=Detection+of+S-phase+cell+cycle+progression+using+5-ethynyl-2'-deoxyuridine+incorporation+with+click+chemistry,+an+alternative+to+using+5-bromo-2'-deoxyuridine+antibodies.">Detection of S-phase cell cycle progression using 5-ethynyl-2'-deoxyuridine incorporation with click chemistry, an alternative to using 5-bromo-2'-deoxyuridine antibodies.</a> Biotechniques. 44, 927-929 (2008).</li><li>Waters, 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=Accuracy+and+precision+in+quantitative+fluorescence+microscopy.">Accuracy and precision in quantitative fluorescence microscopy.</a> J. Cell Biol. 185, 1135-1148 (2009).</li></ol>

Quantitative microscopy in cell biology is commonly associated with live-cell imaging assays such as Fluorescence Resonance Energy Transfer (FRET), Fluorescence Recovery After Photobleaching (FRAP), etc. However, there are growing examples of cell biologists developing different quantitative microscopy assays for fixed cells in recent years27,34-36. Importantly, progress in understanding centrosome biology often requires understanding of the centrosome-specific function of proteins whose centrosomal p...

Centrosomes consist of a pair of centrioles surrounded by pericentriolar material (PCM). Being the major microtubule organizing centers (MTOCs) in mammalian cells, centrosomes serve as the two poles of mitotic spindles in dividing cells, and thus help maintain genomic integrity1. In quiescent cells (e.g., during G0 phase), one of the two centrioles of the centrosome, namely the mother centriole, is transformed into a basal body to assemble the primary cilium, a sensory organelle protruding out from the cell surface2. Once the cells re-enter the cell cycle, primary cilia are disassembled and each centriole directs the assembly of a procentriole at its proximal end that gradually elongates to form a mature centriole3. At the onset of S-phase, a cartwheel-like structure that provides the 9-fold symmetry to the centriole is formed on the surface of each existing centriole and will become the base of each procentriole. Sas6 that is indispensable for centriole assembly is recruited to form the hub of the cartwheel4-6. Other centriolar proteins are then assembled onto the cartwheel in a highly regulated, proximal to distal manner7. After precisely completing centriole duplication, cells assemble additional pericentriolar materials to build two functional centrosomes by the end of G2 phase8. In addition to the core centriolar components9-11, several other proteins including kinases, phosphatases, chaperones, scaffold components, membrane associated proteins and degradation machinery are associated with centrioles, basal bodies and PCM at different times of the cell cycle12-16. It is often noted that the centrosomal levels of many proteins are temporally regulated by centrosomal targeting mechanisms and/or proteasomal degradation at centrosomes. Importantly, the fluctuations in the centrosomal level of several proteins such as Plk4, Mps1, Sas6, and CP110 at different points of the cell cycle appears to be crucial to regulate centriole assembly5,17-22, and in the case of Mps1 preventing this centrosomal degradation leads to the formation of excess centrioles19. On the other hand, the centrosomal fractions of several proteins are less labile compared to cytosolic pools. For example siRNA-mediated down-regulation of Centrin 2 (Cetn2) led to only a moderate decrease of the protein level at the centrioles despite great reduction in its whole cell levels23. It is therefore crucial to measure the changes in the level of centrosomal proteins at the centrosome rather than measuring the whole cell protein levels when assessing their centrosome-specific functions.
In this study we have developed an assay using indirect immunofluorescence (IIF) to quantify the relative level of a protein at centrosomes. This assay is developed particularly to analyze cells that are from different samples and thus can not be imaged at the same time. These samples can be cells that were treated with different reagents (i.e., drug versus control), collected at different time points (i.e., pulse versus chase), or are in different phases of the cell cycle. The principle of this assay lies in measuring the background corrected fluorescent intensity corresponding to a protein at a small region and to normalize that value against the same for another protein whose levels do not vary under the chosen experimental conditions. Several studies in centrosome biology have recently utilized various quantitative microscopy techniques, in both live or fixed cells, to determine the centrosome-specific function of candidate proteins24-27. Similar to those assays, the present technique also measures the background corrected fluorescence intensity of the test protein. However, the inclusion of the normalization using an internal standard in this assay would likely offer greater accuracy and confidence in analyzing two different samples that are on two different coverslips. Moreover, in addition to examining the protein level at centrosomes, with minor adjustments this method can be applied to a diverse set of experimental conditions or at other cellular sites.
Here, we combine our quantitative microscopy assay with a BrdU pulse-chase strategy to compare cells from different cell cycle stages. Instead of using standard cell cycle arrest and release techniques to study various cell cycle time points, asynchronously growing cells are incubated with BrdU to label cells in S-phase, and the labeled cells are chased for various times (typically 4-6 hr). Most of the labeled cells will be in S-phase immediately after the pulse. The length of the chase is chosen so that after the chase, labeled cells will be in late S, G2, or mitosis, which can be verified by morphological characteristics such as- position of centrosomes with respect to nuclei, distance between centrosomes, condensation of chromosomes etc. Thus, the length of the chase depends on the average duration of S, G2 and M phase of a particular cell type. Since this approach avoids cell cycle inhibitors such as hydroxyurea, aphidicolin, nocodazole, etc., it allows a more physiologically relevant cell cycle analysis.
Thus, we demonstrate here that the quantitative fluorescence microscopy assay alone, or in combination with BrdU pulse-chase assay, is a simple yet powerful technique to accurately measure the relative changes in the centrosomal level of a candidate protein during an unperturbed cell cycle. We measured the centrosomal level of VDAC3, a protein that we recently identified at centrosomes in addition to mitochondria16,28, using these assays. Results obtained here verify our previous observation that the centrosomal pool of VDAC3 is regulated by degradation, and also varies in a cell cycle dependent manner16, furthermore validating the applicability of this method.

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			<td height="42" style="height:42px;width:179px;">Name&#160;</td>
			<td style="width:105px;">Company&#160;</td>
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			<td style="width:195px;">Comments</td>
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			<td height="20" style="height:20px;width:179px;">Fibronectin</td>
			<td style="width:105px;">Sigma</td>
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			<td height="20" style="height:20px;width:179px;">MG115</td>
			<td style="width:105px;">Sigma</td>
			<td style="width:99px;">SCP0005</td>
			<td style="width:195px;">Stock of 10 mM in DMSO</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:179px;">BrdU</td>
			<td style="width:105px;">Sigma</td>
			<td style="width:99px;">B5002</td>
			<td style="width:195px;">Stock of 10 mM in DMSO</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:179px;">Anti-g-tubulin (mouse monoclonal, clone GTU 88)</td>
			<td style="width:105px;">Sigma</td>
			<td style="width:99px;">T 6557</td>
			<td style="width:195px;">1:200 in IIF blocking buffer&#160;</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:179px;">Anti-VDAC3 (rabbit polyclonal)&#160;</td>
			<td style="width:105px;">Aviva Systems Biology</td>
			<td style="width:99px;">ARP35180-P050</td>
			<td style="width:195px;">1:50 in IIF blocking buffer, 1:1000 in WB blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Anti-Sas6 (mouse monoclonal)&#160;</td>
			<td style="width:105px;">Santa cruz biotechnology</td>
			<td style="width:99px;">sc-81431</td>
			<td style="width:195px;">1:100 in IIF blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Anti-Cep135 (rabbit polyclonal)</td>
			<td style="width:105px;">Abcam</td>
			<td style="width:99px;">ab-75005</td>
			<td style="width:195px;">1:500 in IIF blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Anti-BrdU (rat monoclonal)&#160;</td>
			<td style="width:105px;">Abcam</td>
			<td style="width:99px;">ab6326</td>
			<td style="width:195px;">1:250 in IIF blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Alexa Fluor 350 Goat Anti-Rat IgG (H+L)</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">A21093</td>
			<td style="width:195px;">1:200 in IIF blocking buffer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:179px;">Alexa Fluor 488 Donkey Anti-Mouse IgG (H+L) Antibody</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">A21202</td>
			<td style="width:195px;">1:1000 in IIF blocking buffer</td>
		</tr>
		<tr height="50">
			<td height="50" style="height:51px;width:179px;">Alexa Fluor 594 Donkey Anti-Mouse IgG (H+L) Antibody</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">A21203</td>
			<td style="width:195px;">1:1000 in IIF blocking buffer</td>
		</tr>
		<tr height="50">
			<td height="50" style="height:51px;width:179px;">Alexa Fluor 488 Donkey Anti-Rabbit IgG (H+L) Antibody</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">A21206</td>
			<td style="width:195px;">1:1000 in IIF blocking buffer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:179px;">Alexa Fluor 594 Donkey Anti-Rabbit IgG (H+L) Antibody</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">A21207</td>
			<td style="width:195px;">1:1000 in IIF blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Anti-g-tubulin (rabbit polyclonal)</td>
			<td style="width:105px;">Sigma</td>
			<td style="width:99px;">T5192</td>
			<td style="width:195px;">1:1000 in WB blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Anti-a-tubulin (mouse monoclonal, DM1A)</td>
			<td style="width:105px;">Sigma</td>
			<td style="width:99px;">T9026</td>
			<td style="width:195px;">1:20000 in WB blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Alexa Fluor 680 Donkey Anti-Rabbit IgG (H+L)</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">A10043</td>
			<td style="width:195px;">1:10000 in WB blocking buffer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:179px;">Mouse IgG (H&#38;L) Antibody IRDye800CW Conjugated</td>
			<td style="width:105px;">Rockland antibodies</td>
			<td style="width:99px;">610-731-002</td>
			<td style="width:195px;">1:10000 in WB blocking buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">SlowFade Gold Antifade Reagent&#160;</td>
			<td style="width:105px;">Life technologies</td>
			<td style="width:99px;">S36936</td>
			<td style="width:195px;">Mounting media</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Round coverslips 12CIR.-1</td>
			<td style="width:105px;">Fisherbrand</td>
			<td style="width:99px;">12-545-80</td>
			<td style="width:195px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Olympus IX-81 microscope</td>
			<td style="width:105px;">Olympus</td>
			<td style="width:99px;"></td>
			<td style="width:195px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Retiga ExiFAST 1394 IR camera</td>
			<td style="width:105px;">QImaging&#160;</td>
			<td style="width:99px;">32-0082B-238</td>
			<td style="width:195px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">100X Plan Apo oil immersion objective</td>
			<td style="width:105px;">Olympus</td>
			<td style="width:99px;"></td>
			<td style="width:195px;">1.4 numerical aperture</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:179px;">Slidebook software package</td>
			<td style="width:105px;">Intelligent Imaging Innovations</td>
			<td style="width:99px;"></td>
			<td style="width:195px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Odyssey IR Imaging System</td>
			<td style="width:105px;">Li-cor Biosciences</td>
			<td style="width:99px;"></td>
			<td style="width:195px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:179px;">Bicinchoninic acid (BCA) assay</td>
			<td style="width:105px;">Thermo Scientific</td>
			<td align="right">23227</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">U-MNU2 Narrow UV cube</td>
			<td style="width:105px;">Olympus</td>
			<td>U-M622</td>
			<td>Filter</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">U-MNU2 Narrow Blue cube</td>
			<td style="width:105px;">Olympus</td>
			<td>U-M643</td>
			<td>Filter</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">U-MNU2 Narrow Green cube</td>
			<td style="width:105px;">Olympus</td>
			<td>U-M663</td>
			<td>Filter</td>
		</tr>
	</tbody>
</table>

quantitative immunofluorescence assay to measure the variation in protein levels at centrosomes

Centrosomes are small but important organelles that serve as the poles of mitotic spindle to maintain genomic integrity or assemble primary cilia to facilitate sensory functions in cells. The level of a protein may be regulated differently at centrosomes than at other .cellular locations, and the variation in the centrosomal level of several proteins at different points of the cell cycle appears to be crucial for the proper regulation of centriole assembly. We developed a quantitative fluorescence microscopy assay that measures relative changes in the level of a protein at centrosomes in fixed cells from different samples, such as at different phases of the cell cycle or after treatment with various reagents. The principle of this assay lies in measuring the background corrected fluorescent intensity corresponding to a protein at a small region, and normalize that measurement against the same for another protein that does not vary under the chosen experimental condition. Utilizing this assay in combination with BrdU pulse and chase strategy to study unperturbed cell cycles, we have quantitatively validated our recent observation that the centrosomal pool of VDAC3 is regulated at centrosomes during the cell cycle, likely by proteasome-mediated degradation specifically at centrosomes.

Our recent studies identified novel centrosomal localization and function of VDAC3, one of the mitochondrial porins16,28. Immunostaining of several mammalian cells including RPE1 cells using a VDAC3-specific antibody showed prominent centrosomal staining and comparatively weak mitochondrial staining. We also showed that centrosomal VDAC3 is preferentially associated with the mother centriole, and the centrosomal pool of both the endogenous and ectopically expressed VDAC3 is regulated by degradation16</sup...

Watch this Scientific Journal Video about Quantitative Immunofluorescence Assay to Measure the Variation in Protein Levels at Centrosomes at JoVE.com

Quantitative Immunofluorescence Assay to Measure the Variation in Protein Levels at Centrosomes

Here, a novel quantitative fluorescence assay is developed to measure changes in the level of a protein specifically at centrosomes by normalizing that protein&#8217;s fluorescence intensity to that of an appropriate internal standard.

Centrosomes are small but important organelles that serve as the poles of mitotic spindle to maintain genomic integrity or assemble primary cilia to ...

Research

JoVE Journal

Biology

Photobleaching Assays (FRAP &amp; FLIP) to Measure Chromatin Protein Dynamics in Living Embryonic Stem Cells

Photobleaching Assays FRAP & FLIP to Measure Chromatin Protein Dynamics in Living Embryonic Stem Cells

Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Loss In Photobleaching (FLIP) enable the study of protein dynamics in living cells with ...

The MultiBac Protein Complex Production Platform at the EMBL

Proteomics  research revealed the impressive complexity of eukaryotic proteomes in  unprecedented detail. It is now a commonly accepted notion that ...

Flow Cytometric Analysis of Bimolecular Fluorescence Complementation: A High Throughput Quantitative Method to Study Protein-protein Interaction

Among methods to study protein-protein interaction inside cells, Bimolecular Fluorescence Complementation (BiFC) is relatively simple and sensitive. BiFC ...

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

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The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

Imaging Centrosomes in Fly Testes

Centrosomes are conserved microtubule-based organelles whose structure and function change dramatically throughout the cell cycle and cell ...

Measurement of Heme Synthesis Levels in Mammalian Cells

Heme serves as the prosthetic group for a wide variety of proteins known as hemoproteins, such as hemoglobin, myoglobin and cytochromes. It is involved in ...

In vitro Methylation Assay to Study Protein Arginine Methylation

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Protein arginine methylation is one of the most abundant post-translational modifications in the nucleus. Protein arginine methylation can be identified ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

In Vitro Assay to Measure Phosphatidylethanolamine Methyltransferase Activity

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Phosphatidylethanolamine methyltransferases are biosynthetic enzymes that catalyze the transfer of one or more methyl group(s) from ...

Using Microfluidic Devices to Measure Lifespan and Cellular Phenotypes in Single Budding Yeast Cells

Budding yeast Saccharomyces cerevisiae is an important model organism in aging research. Genetic studies have revealed many genes with conserved effects ...