Name: detection of ligand-activated g protein-coupled receptor internalization by confocal microscopy
Uploaded: 2017-04-09T14:00:00
Description: Watch this Scientific Journal Video about Detection of Ligand-activated G Protein-coupled Receptor Internalization by Confocal Microscopy at JoVE.com

The authors of this paper would like to thank Prof. Jiayan Xie for technical assistance and equipment usage. This work was financially supported by the National Natural Science Foundation of China (41406137).

1. Cell Preparation
<ol>
	<li>Cell recovery
	<ol>
		<li>Transfer the cryopreserved human embryonic kidney 293 (HEK293) cells from a liquid nitrogen tank to a 37 &#176;C water bath and shake continuously for 1 - 2 min.</li>
		<li>Add 10 mL of equilibrated growth medium (Dulbecco&#39;s modified Eagle&#39;s medium (DMEM), 10% fetal bovine serum (FBS), and 1% penicillin-streptomycin solution) to a 10-cm cell culture dish. Gently add the thawed cells to the equilibrated growth medium.</li>
		<li>Incubate th...

     

<ol>
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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cloning+vectors+for+the+expression+of+green+fluorescent+protein+fusion+proteins+in+transgenic+plants.">Cloning vectors for the expression of green fluorescent protein fusion proteins in transgenic plants.</a> Gene. 221, 35-43 (1998).</li><li>Webb, C. D., Decatur, A., Teleman, A., Losick, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+green+fluorescent+protein+for+visualization+of+cell-specific+gene+expression+and+subcellular+protein+localization+during+sporulation+in+Bacillus+subtilis.">Use of green fluorescent protein for visualization of cell-specific gene expression and subcellular protein localization during sporulation in Bacillus subtilis.</a> J Bacteriol. 177, 5906-5911 (1995).</li><li>Kain, S. R., 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=Green+fluorescent+protein+as+a+reporter+of+gene+expression+and+protein+localization.">Green fluorescent protein as a reporter of gene expression and protein localization.</a> BioTechniques. 19, 650-655 (1995).</li><li>Fukunaga, S., Setoguchi, S., Hirasawa, A., Tsujimoto, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+ligand-mediated+internalization+of+G+protein-coupled+receptor+as+a+novel+pharmacological+approach.">Monitoring ligand-mediated internalization of G protein-coupled receptor as a novel pharmacological approach.</a> Life Sci. 80, 17-23 (2006).</li><li>Yang, 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=Agonist-Activated+Bombyx+Corazonin+Receptor+Is+Internalized+via+an+Arrestin-Dependent+and+Clathrin-Independent+Pathway.">Agonist-Activated Bombyx Corazonin Receptor Is Internalized via an Arrestin-Dependent and Clathrin-Independent Pathway.</a> Biochemistry. 55, 3874-3887 (2016).</li><li>Kohout, T. A., Lefkowitz, 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+G+protein-coupled+receptor+kinases+and+arrestins+during+receptor+desensitization.">Regulation of G protein-coupled receptor kinases and arrestins during receptor desensitization.</a> Mol Pharmacol. 63, 9-18 (2003).</li><li>Ferguson, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+beta-arrestin+in+mediating+agonist-promoted+G+protein-coupled+receptor+internalization.">Role of beta-arrestin in mediating agonist-promoted G protein-coupled receptor internalization.</a> Science. 271, 363-366 (1996).</li><li>Stojilkovic, S. S., Reinhart, J., Catt, K. 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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=Identification+and+Expression+Profile+of+the+Gonadotropin-Releasing+Hormone+Receptor+in+Common+Chinese+Cuttlefish,+Sepiella+japonica.">Identification and Expression Profile of the Gonadotropin-Releasing Hormone Receptor in Common Chinese Cuttlefish, Sepiella japonica.</a> J Exp Zool A Ecol Genet Physiol. , (2016).</li><li>Yang, 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=Specific+activation+of+the+G+protein-coupled+receptor+BNGR-A21+by+the+neuropeptide+corazonin+from+the+silkworm,+Bombyx+mori,+dually+couples+to+the+G(q)+and+G(s)+signaling+cascades.">Specific activation of the G protein-coupled receptor BNGR-A21 by the neuropeptide corazonin from the silkworm, Bombyx mori, dually couples to the G(q) and G(s) signaling cascades.</a> J Biol Chem. 288, 11662-11675 (2013).</li><li>Lu, Z. 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The protocol presented here provides an efficient and easily interpretable method to detect the subcellular localization and internalization of expressed GPCR fusion protein in HEK293 cells. The technique can be easily adapted for many different genes and cell types, such as for the cellular localization and internalization of the corazonin receptor from Bombyx mori in HEK293 and BmN cells16.
The successful application of this powerful assay relies on a few key...

Cells possess cargo trafficking machinery to transport extracellular materials-such as ligands, microorganisms, nutrients, and transmembrane proteins-into the cell for information, energy, and other purposes1,2. It is critical for cellular homeostasis, tissue function, and overall cell survival. The cell-based expression of fluorescent fusion proteins is a powerful way to study the localization and internalization of transmembrane receptors, such as G protein-coupled receptors (GPCR), in signaling pathways3.
The expression of fusion proteins tagged with green fluorescent protein (GFP) from jellyfish Aequorea victoria, combined with direct fluorescence detection techniques, has gained wide acceptance in protein-targeting research4,5,6. GFP-based detection has the advantage of allowing the real-time imaging of living cells while avoiding fixation artifacts7. A series of versatile cloning vectors has been constructed to facilitate the expression of protein fusions to GFP in various cells8,9. The pEGFP-N1 vector is a widely used and commercialized plasmid vector encoding an enhanced green fluorescent protein (EGFP), which has been optimized from wild-type GFP for brighter fluorescence and higher expression in mammalian cells. To observe the fluorescent signal of EGFP expressed in mammalian cells, the fluorescence microscopy should be conducted with the excitation at 488 nm and the emission at 507 nm, preferably with confocal microscopy.
Monitoring the subcellular localization and ligand-mediated internalization of receptors is a common technique to investigate the signal transduction and function of GPCRs10,11. In most cases, internalization leads to desensitization of the GPCRs (the attenuation of the stimulus response in spite of the presence of agonists)12,13. The internalized receptors can be incorporated into the lysosome and degraded, or they can be recycled back to the cell surface, depending on the nature of the receptors and the cell lines used in the experiments.
The gonadotropin-releasing hormone receptors (GnRHRs) belong to the GPCR family and have a typical GPCR protein structure, with an extracellular amino terminal, an intracellular -COOH terminal, and seven transmembrane (TM) domains14. The transfection of recombinant plasmid SjGnRHR-EGFP (with the GnRHR gene from Sepiella japonica) and the confocal microscopy detection of EGFP-tagged SjGnRHR (expressed in HEK293 cells) was reported previously, and GFP fluorescence was established as a reporter for transmembrane protein localization assays15. Now, the internalization of SjGnRHR, activated by S. japonica gonadotropin-releasing hormone (SjGnRH), was demonstrated in time- and dose-dependent manners by confocal microscopy.

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		<tr height="21">
			<td height="21" style="height:21px;width:300px;">HEK293 cell line&#160;</td>
			<td style="width:236px;"></td>
			<td style="width:119px;"></td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">DMEM/High glucose</td>
			<td style="width:236px;">Hyclone</td>
			<td style="width:119px;">SH30022.01</td>
			<td>High glucose 4.0 mM L-glutamine</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Foetal Bovine Serum (FBS)</td>
			<td style="width:236px;">PuFei</td>
			<td style="width:119px;">1101-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Phosphate Buffered Saline (PBS)</td>
			<td style="width:236px;">Genom</td>
			<td style="width:119px;">GNM10010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Penicillin-Streptomycin</td>
			<td style="width:236px;">Genom</td>
			<td style="width:119px;">GNM15140</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">0.25% Trypsin &#38; 0.02% EDTA</td>
			<td style="width:236px;">Genom</td>
			<td style="width:119px;">GNM25200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Opti-MEM (1X)</td>
			<td style="width:236px;">GIBCO, by Life Technologies</td>
			<td style="width:119px;">31985-062</td>
			<td>reduced serum media</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:25px;width:300px;">Lipofectamine 2000 Transfection Reagent</td>
			<td style="width:236px;">Invitrogen</td>
			<td style="width:119px;">11668027</td>
			<td>Reagent 1</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:25px;width:300px;">X-tremeGENE HP DNA Transfection Reagent</td>
			<td style="width:236px;">Roche</td>
			<td style="width:119px;">6366236001</td>
			<td>Reagent 2</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:300px;">DAPI Staining Solution</td>
			<td style="width:236px;">Beyotime</td>
			<td style="width:119px;">C1006</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">DiI</td>
			<td style="width:236px;">Beyotime</td>
			<td style="width:119px;">C1036</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Antifade Mounting Medium</td>
			<td style="width:236px;">Beyotime</td>
			<td style="width:119px;">P0126</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:300px;">Paraformaldehyde</td>
			<td style="width:236px;">Sinopharm Chemical Reagent Co.(SCRC)</td>
			<td style="width:119px;">80096618</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">100 mm cell culture</td>
			<td style="width:236px;">CORNING</td>
			<td style="width:119px;">430167</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">6-well plate&#160;</td>
			<td style="width:236px;">ExCell Bio</td>
			<td style="width:119px;">CS016-0092</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">12-well plate&#160;</td>
			<td style="width:236px;">ExCell Bio</td>
			<td style="width:119px;">CS016-0093</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Cover Glass</td>
			<td style="width:236px;">NEST</td>
			<td style="width:119px;">801007</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Microscope Slides</td>
			<td style="width:236px;">Citoglas</td>
			<td style="width:119px;">10127105P-G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">Thermo Scientific Forma CO2 Incubator</td>
			<td style="width:236px;">Thermo</td>
			<td style="width:119px;">3111</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:300px;">TCS SP5II laser scanning confocal microscope</td>
			<td style="width:236px;">Leica&#160;</td>
			<td style="width:119px;">5100001311</td>
			<td></td>
		</tr>
	</tbody>
</table>

detection of ligand-activated g protein-coupled receptor internalization by confocal microscopy

Confocal laser scanning microscopy (CLSM) is an optical imaging technique for high-contrast imaging. It is a powerful approach to visualize fluorescent fusion proteins, such as green fluorescent protein (GFP), to determine their expression, localization, and function. The subcellular localization of target proteins is important for identification, characterization, and functional analyses. Internalization is one of the predominant mechanisms controlling G protein-coupled receptor (GPCR) signaling to ensure the appropriate cellular responses to stimuli. Here, we describe an experimental method to detect the subcellular localization and internalization of GPCR in HEK293 cells with confocal microscopy. In addition, this experiment provides some details about cell culture and transfection. This protocol is compatible with a variety of widely available fluorescent markers and is applicable to the visualization of the subcellular localization of a majority of proteins, as well as of the internalization of GPCR. This technique should enable researchers to efficiently manipulate GPCR gene expression in mammalian cell lines and should facilitate studies on GPCR subcellular localization and internalization.

Figure 1 shows an example of a confocal microscope system. Figure 2 presents the expression of pEGFP-N1 in HEK293 cells. The GFP signal was detected in the cytoplasm and nucleus. Figure 3 shows the subcellular localization of GnRHR from S. japonica in HEK293 cells, consistent with our previously published results15. The fusion protein with the EGFP tag at the C-terminus of SjGnRHR (SjGnRH...

Watch this Scientific Journal Video about Detection of Ligand-activated G Protein-coupled Receptor Internalization by Confocal Microscopy at JoVE.com

Detection of Ligand-activated G Protein-coupled Receptor Internalization by Confocal Microscopy

This protocol describes confocal microscopy detection of G protein-coupled receptor (GPCR) internalization in mammalian cells. It includes the basic cell culture, transfection, and confocal microscopy procedure and provides an efficient and easily interpretable method to detect the subcellular localization and internalization of fusion-expressed GPCR.

Confocal laser scanning microscopy (CLSM) is an optical imaging technique for high-contrast imaging. It is a powerful approach to visualize fluorescent ...

The overall goal of this experiment is to provide an efficient and easily-interpretable method to detect the subcellular localization and internalization of expressed GPCR fusion proteins in mammalian cells. This method can help answer the key questions in the subcellular protein localization field, such as receptor internalization and recycling. The main advantage of this technique is that it can be used easily and efficiently.So this method can provide insight in monitoring and locating GPCRs. And it can also apply to other systems, such as cytoplasmic and nuclear protein. After recovering and passaging HEK293 cells according to the text protocol, when the cells have grown to near confluence, discard the equilibrated growth medium, add two milliliters of PBS, and swirl the dish to wash the cells.Discard the PBS, and add one milliliter of trypsin EDTA. To completely digest the cells, carefully swirl the dish and aspirate off the solution. Then, put the dish in this 37 degrees Celsius water-jacketed C02 incubator for three minutes.While the cells are incubating, prepare a six well plate by adding two milliliters of equilibrated growth medium to each well. Then, when the cells have lifted from the bottom of the dish, add one milliliter of equilibrated growth medium to the dish. Mix by pipetting and immediately transfer 0.1 milliliters of cell suspension into each well of the prepared six well plate.Gently pipette the suspension in the wells, and incubate the cells at 37 degrees Celsius and 5%CO2. The following day, ensure that the cells are 85-95%confluent. Then, to two sterile microcentrifuge tubes, add three micrograms of plasmid DNA and 100 microliters of reduced serum medium to one tube.Meanwhile, add nine microliters of reagent one and 100 microliters of reduced serum medium to another tube. Incubate the tubes at room temperature for five minutes. Combine the diluted plasmid mixture with diluted reagent one.Then, gently mix the solution, and incubate it at room temperature for 20 minutes. Aspirate the medium of the cells and add 1.5 milliliters of fresh DMEM without FBS. Then, add dropwise 215 microliters of DNA transfection reagent mixture to each well, and gently mix by swirling the plate.Incubate the plate at 37 degrees Celsius and 5%CO2 for four to eight hours. Then, replace the medium with fresh DMEM with 10%FBS. Incubate the cells for another 24 to 48 hours before running any experiments.Transfection efficiency may vary greatly in different cell lines. Therefore, the optimization of the sit and stab in deposition may be necessary depending on the particular cell type used. Remove the growth medium from the six well culture plate.Then, use one milliliter of PBS to wash the cell monolayer. Add 0.5 milliliters of trypsin EDTA, swirl the dish, and aspirate off the solution. Then, incubate the culture plate at 37 degrees Celsius for three minutes.During the incubation, insert 15 millimeter diameter sterile coverslips into each well of a 12 well plate. Resuspend the cells in a small volume of fresh complete growth medium, and transfer the required number of cells to the 12 well plate with coverslips. Then, incubate the cells for 16 to 24 hours.After 16 to 24 hours of incubation, when the cells have grown to near confluence, add five micromolar of the membrane probe dill to each well, and place the cells back in the incubator for 30 minutes. Remove the equilibrated growth medium and use cold PBS to wash the cells twice. Then, add one milliliter of 4%PFA to each well, and agitate the cells for 15 minutes to fix the cells.With PBS, wash the fixed cells twice, then add 200 to 300 microliters of DAPI to each well, and incubate the plate for 10 minutes at room temperature. After washing the cells with PBS twice, carefully remove the coverslips from the plate, and wick off the excess buffer. Invert the coverslips onto microscope slides loaded with one drop of mounting medium.Then, remove the excess mounting medium from the slides. Using cells that have grown to near confluence, remove the equilibrated growth medium and add fresh warmed DMEM. Incubate the cells for one hour.Treat the cells with different concentrations of ligand for 30 minutes. And treat the cells with 10 to the negative six molar ligand for the different times shown here. Use cold PBS to wash the cells twice, then add one milliliter of 4%PFA in PBS to each well, before gently agitating the cells for 15 minutes.After washing the cells twice in PBS, carefully remove the coverslips from the wells of the plate, and mount them as just demonstrated earlier in this video. To carry out confocal microscopy, turn on the hardware of the confocal microscope, including the mercury lamp power, PC microscope, scanner, and laser. Launch the software, then check the configuration and select the laser.Turn on the different units of confocal microscopy system according to the instructions. Place a prepared slide on the microscope stage, and use the stage controller to position the sample over the objective lens. For an oil immersion lens, add one drop of cedar oil on to the coverslip, and orient the slide with a coverslip facing the lens.Under fluorescence, find the cells of interest, then switch to scan mode, and choose the laser power and spectral range of the emission fluorophore. Capture high-quality images by tuning the laser intensity and other parameters. This figure illustrates the expression of pEGFP-N1 in HEK293 cells.The GFP signal was detected in the cytoplasm and the nucleus. The subcellular localization in HEK293 cells of gonadotropin-releasing hormone receptors from S-Japonica, or SjGnRHR, is shown here. EGFP receptors are in green, and Dil staining, which highlights the cell membrane, is in red.The receptors are seen localizing to the plasma membrane. To visualize the internalization of SjGnRHRs, cells were treated with gonadotropin-releasing hormone at different concentrations. As seen here, the internalization of the receptors proceeded in a dose-dependent manner, and the receptor was completely internalized from the cell's surface with the 10 to the minus six molar ligand.When treated with 10 to the minus six molar ligand for different time periods, internalized SjGnRHRs were detectable 10 minutes after agonist simulation, and extreme internalization occurred by 60 minutes. As demonstrated in HEK293 cells, in both experiments, the fluorescent SjGnRHR EGFP fusion protein primarily localized to the plasma membrane, and was dramatically and rapidly internalized into the cells. While attempting this procedure, it's important to remember to keep the cells under the right conditions without bacteria, fungi, and mycoplasma contamination.Following this procedure, and the methods like cell checking and immobilization can be performed in order to answer additional questions like the second in pass V of the protein receptors. After each development, the technology paved the way for researchers in the field of the cell biology and biochemistry to explore the localization and the internalization of transmembrane receptors in various cell lines.

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