Name: assaying surface expression of chemosensory receptors in heterologous cells
Uploaded: 2011-02-23T17:30:00
Description: Watch this Scientific Journal Video about Assaying Surface Expression of Chemosensory Receptors in Heterologous Cells at JoVE.com

We thank the members of Matsunami laboratory for critical reading of this manuscript.

1. Procedure:
The procedure comprises of three parts completed over a total time of 3 days: transferring cells, transfection and immunocytochemistry, one step carried out per day. Transfer and transfection of cells over the first two days must be carried out in sterile conditions in a laminar flow chamber.
Day 1: Transfer of HEK293T cells for surface expression assay.
<ol>
<li>Transfer medium (M10): Mix minimum essential medium supplemented with 10% (by volume) feta...

<ol>
	<li>Buck, L., Axel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+multigene+family+may+encode+odorant+receptors:+a+molecular+basis+for+odor+recognition.">A novel multigene family may encode odorant receptors: a molecular basis for odor recognition.</a> Cell. 65, 175-187 (1991).</li><li>Malnic, B., Hirono, J., Sato, T., Buck, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combinatorial+receptor+codes+for+odors.">Combinatorial receptor codes for odors.</a> Cell. 96, 713-723 (1999).</li><li>Saito, H., Kubota, M., Roberts, R. W., Chi, Q., Matsunami, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RTP+family+members+induce+functional+expression+of+mammalian+odorant+receptors.">RTP family members induce functional expression of mammalian odorant receptors.</a> Cell. 119, 679-691 (2004).</li><li>Zhuang, H., Matsunami, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+cell-surface+expression+and+measuring+activation+of+mammalian+odorant+receptors+in+heterologous+cells.">Evaluating cell-surface expression and measuring activation of mammalian odorant receptors in heterologous cells.</a> Nat Protoc. 3, 1402-1413 (2008).</li></ol>

Each step must be carried out carefully to ensure prominent and distinctive surface staining. The entire staining process must be carried out in cold (on ice), and the tray on which cover slips are laid must be cooled prior to use to ensure cells stay alive. Moreover fixation is done at the end of the surface staining process. This is in sharp contrast with internal staining where fixation precedes staining to permeabilize the cell membrane to primary and secondary antibodies. Time of exposure of cover slips to air must ...

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		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Cover slip 22 X 22 mm (#1)</td>
<td>&nbsp;</td>
<td>Thermo Scientific</td>
<td>72200-11</td>
<td>&nbsp;</td>
<tr>
<td>Fetal bovine serum</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>16000</td>
<td>&nbsp;</td>
<tr>
<td>Lipofectamine 2000</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>11668-019</td>
<td>&nbsp;</td>
<tr>
<td>Minimal essential medium</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>M4655</td>
<td>With L glutamate, Earle&#x2019;s salt and bicarbonate</td>
</tr>
<tr>
<td>Mowiol</td>
<td>&nbsp;</td>
<td>Calbiochem</td>
<td>475904</td>
<td>&nbsp;</td>
<tr>
<td>Paraformaldehyde</td>
<td>&nbsp;</td>
<td>EMS</td>
<td>19208</td>
<td>&nbsp;</td>
<tr>
<td>Hanks Balanced Salt Solution (HBSS) 1X </td>
<td>&nbsp;</td>
<td>Gibco </td>
<td>14025</td>
<td>With calcium chloride and magnesium chloride</td>
</tr>
<tr>
<td>HEPES Buffer Solution</td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>15630</td>
<td>&nbsp;</td>
<tr>
<td>Phosphate Buffer Saline (PBS)</td>
<td>&nbsp;</td>
<td>Cellgro</td>
<td>21-040-CV</td>
<td>Without calcium and magnesium</td>
</tr>
<tr>
<td>Poly D Lysine Hydrobromide</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>P7280</td>
<td>&nbsp;</td>
<tr>
<td>Sodium Azide</td>
<td>&nbsp;</td>
<td>EM Science</td>
<td>SX0299-1</td>
<td>&nbsp;</td>
<tr>
<td>Tissue culture dish 35 X 10 mm</td>
<td>&nbsp;</td>
<td>Falcon</td>
<td>353801</td>
<td>&nbsp;</td>
<tr>
<td>Trypsin-EDTA </td>
<td>&nbsp;</td>
<td>Gibco</td>
<td>25300</td>
<td>0.05%</td>
</tr>		</tbody>
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assaying surface expression of chemosensory receptors in heterologous cells

The vivid world of odors is recognized by the sense of olfaction. Olfaction in mice is mediated by a repertoire of about 1200 G Protein Coupled Receptors (GPCRs) 1 that are postulated to bind volatile odorant molecules and converting the extracellular signal into an intracellular signal by coupling with G protein G&alpha;olf. Binding of the odorants to the receptors is thought to follow a combinatorial rule, that is, one odorant may bind several receptors and one receptor may bind several odorants to varying degrees 2. Biochemical, signaling and ligand binding studies have been conveniently carried out for most GPCRs using heterologous cells. However use of heterologous cells for study of odorant receptors, was precluded for a long time since on transfection they failed to export to the surface. Saito et al have demonstrated single membrane pass Receptor Transporting Protein (RTP) family chaperones show enhanced expression in the olfactory sensory neurons and act as chaperones to traffic odorant receptors to the surface in heterologous cells, when co transfected together 3. To carry out biochemical assays for receptors using heterologous cells, one must first determine if the receptor shows robust surface expression in the cell line. This can be assayed by overexpressing the receptors with the chaperone RTP1S followed by live cell staining to fluorescently label the extracellular domain or a tag in the extracellular domain exclusively. Here we demonstrate a protocol to carry out live cell staining that can be used to detect odorant receptors on the surface of HEK293T cells conveniently. In addition, it may also be used to assay for surface expression of other chemosensory receptors or GPCRs.

Watch this Scientific Journal Video about Assaying Surface Expression of Chemosensory Receptors in Heterologous Cells at JoVE.com

Assaying Surface Expression of Chemosensory Receptors in Heterologous Cells

Here we demonstrate a protocol to carry out live cell staining that can be used to detect odorant receptors on the surface of HEK293T cells conveniently. In addition, it may also be used to assay for surface expression of other chemosensory receptors or GPCRs.

The vivid world of odors is recognized by the sense of olfaction. Olfaction in mice is mediated by a repertoire of about 1200 G Protein Coupled Receptors ...

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