Name: differential labeling of cell-surface and internalized proteins after antibody feeding of live cultured neurons
Uploaded: 2014-02-12T14:30:00
Description: Watch this Scientific Journal Video about Differential Labeling of Cell-surface and Internalized Proteins after Antibody Feeding of Live Cultured Neurons at JoVE.com

The authors thank Teele Palumaa for assistance with the figures. Funded by Project Grant 1008046 from the National Health and Medical Research Council, Australia.

1. Dissociated Hippocampal Neuron Culture
<ol>
	<li>Prepare coverslips (borosilicate glass):
	<ol>
		<li>Wash in 100% ethanol.</li>
		<li>Air dry under UV irradiation.</li>
		<li>Coat with Poly-D-lysine (0.5 mg/ml in 0.15 M borate buffer, overnight at 4 &#176;C).</li>
		<li>On the next day (the day of culture) wash 3x in PBS then coat with laminin (2.5 &#956;g/ml, natural mouse laminin) + 5% v/v heat-inactivated fetal calf serum (FCS) diluted in PBS for 2 hr at 37 &#176;C.</li>
	</ol>
	</li>
	<li>Dissect embryonic day ...

<ol>
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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=Recycling+endosomes+supply+AMPA+receptors+for+LTP.">Recycling endosomes supply AMPA receptors for LTP.</a> Science. 305, 1972-1975 (2004).</li><li>Kennedy, M. J. &. a. m. p. ;., Ehlers, 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=Organelles+and+trafficking+machinery+for+postsynaptic+plasticity.">Organelles and trafficking machinery for postsynaptic plasticity.</a> Annu. Rev. Neurosci. 29, 325-362 (2006).</li><li>Lasiecka, Z. M., Yap, C. C., Caplan, S., Winckler, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+early+endosomes+require+EHD1+for+L1/NgCAM+trafficking.">Neuronal early endosomes require EHD1 for L1/NgCAM trafficking.</a> J. 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The technique described here is complementary to that of cell-surface biotinylation (reviewed by Arancibia-C&#224;rcamo et al.)12 and it is the method of choice for preserving information about the subcellular localization of the internalized protein, provided a suitable primary antibody to an extracellular epitope is available. In addition, quantitation of protein trafficking/internalization over time can be performed (by fixing coverslips at different times throughout the live cell incubation with p...

In establishing the function of newly identified proteins, investigation of the subcellular localization and trafficking of the protein in question can provide important clues about the likely role/s of the protein1,2. Bioinformatic analysis of the transcriptome of the developing neocortex3 provided us with a list of genes exhibiting altered expression during mouse brain corticogenesis. We then adopted a gene knockout approach to ascertain that the protein encoded by one of these genes, sez6, has a key role in neuron development. We observed that the Seizure-related gene 6, or Sez6, protein is located in developing dendrites and is also present in dendritic spines, specialized structures on dendrites that receive and integrate excitatory signals. Furthermore, when this protein is lacking, dendrites and excitatory synapses fail to form correctly4. The probable dominant isoform of the protein has features of a transmembrane receptor although, when the subcellular distribution of immunolabeled protein was examined by confocal microscopy or by immunoelectron microscopy most, if not all, of the signal appeared associated with small vesicles in the somatodendritic compartment with little, or no, protein labeled on the plasma membrane at the cell surface.
In order to definitively show that this putative receptor with a predicted large extracellular domain is trafficked to the plasma membrane, we adopted a live-cell approach using the antiserum we had generated to an extracellular portion of the protein to label protein on the cell surface. By combining this &#8220;antibody feeding&#8221; approach with two applications of differentially-labeled secondary antibody separated by an extensive blocking step and a permeabilization step, we were able to identify two different pools of protein distinguished by binding to fluorescently-labeled secondary antibodies bearing different fluorescent tags. Thus, we were able to distinguish protein that had been internalized by endocytosis during the antibody incubation step from protein that either remained on the cell surface or was trafficked to the surface during this period. Using this method, we established that the protein of interest is trafficked to and from the cell surface in neurons. Therefore, this relatively fast and simple technique proved more informative than traditional immunocytochemistry methods or pre-embedding immunogold electron microscopy, despite the fact that we used the same rabbit polyclonal antiserum for all these techniques. This technique is generally applicable to any transmembrane protein provided a good antibody recognizing extracellular domain epitopes is available. The technique has been used previously to study receptor trafficking of the glutamate receptor GluR1 subunit5.

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		<tr height="21">
			<td height="21" style="height:21px;width:383px;">PBS with Ca and Mg</td>
			<td style="width:269px;">Invitrogen</td>
			<td style="width:119px;">14040182</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Neurobasal medium</td>
			<td style="width:269px;">Invitrogen</td>
			<td style="width:119px;">21103-049</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">B27 supplement</td>
			<td style="width:269px;">Invitrogen</td>
			<td style="width:119px;">17504-044</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">L-glutamine</td>
			<td style="width:269px;">Invitrogen</td>
			<td style="width:119px;">25030-081</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Papain Dissociation System</td>
			<td style="width:269px;">Worthington Biochemical Corporation</td>
			<td style="width:119px;">PDS</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Bovine Serum Albumin&#160;</td>
			<td style="width:269px;">Sigma Aldrich Australia</td>
			<td style="width:119px;">A9418</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:383px;">Hank&#39;s balanced salt solution without calcium, magnesium, phenol red</td>
			<td style="width:269px;">Invitrogen (Gibco)</td>
			<td style="width:119px;">14175-079</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Poly-D-Lysine</td>
			<td style="width:269px;">Sigma Aldrich Australia</td>
			<td style="width:119px;">P0899</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Natural mouse laminin</td>
			<td style="width:269px;">Invitrogen</td>
			<td style="width:119px;">23017-015</td>
			<td>Thaw on ice prior to making aliquots</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Fetal bovine serum HyClone</td>
			<td style="width:269px;">Thermo Fisher</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">fluorodeoxyuridine</td>
			<td style="width:269px;">Sigma Aldrich Australia</td>
			<td style="width:119px;">F0503</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">uridine</td>
			<td style="width:269px;">Sigma Aldrich Australia</td>
			<td style="width:119px;">U3003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">18 mm round glass coverslips</td>
			<td style="width:269px;">Menzel Gl&#228;ser</td>
			<td>CB00180RA1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">VECTASHIELD aqueous mounting medium</td>
			<td style="width:269px;">Vector Laboratories</td>
			<td style="width:119px;">H1400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Donkey anti-rabbit Dylight 649&#160;</td>
			<td>Jackson ImmunoResearch Laboratories</td>
			<td style="width:119px;">711-495-152</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">AffiniPure Fab fragment Goat anti-Rabbit 1gG (H+L)&#160;</td>
			<td>Jackson ImmunoResearch Laboratories</td>
			<td>111-007-003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Paraformaldehyde</td>
			<td style="width:269px;">Sigma Aldrich Australia</td>
			<td style="width:119px;">P6148</td>
			<td>TOXIC - handle in fume hood</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:383px;">Triton-X-100</td>
			<td style="width:269px;">Sigma Aldrich Australia</td>
			<td style="width:119px;">T8787</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alexafluor 488-conjugated donkey anti-rabbit 2&#176; antibody</td>
			<td style="width:269px;">Invitrogen - Molecular Probes</td>
			<td style="width:119px;">A21206</td>
			<td></td>
		</tr>
	</tbody>
</table>

differential labeling of cell-surface and internalized proteins after antibody feeding of live cultured neurons

In order to demonstrate the cell-surface localization of a putative transmembrane receptor in cultured neurons, we labeled the protein on the surface of live neurons with a specific primary antibody raised against an extracellular portion of the protein. Given that receptors are trafficked to and from the surface, if cells are permeabilized after fixation then both cell-surface and internal protein will be detected by the same labeled secondary antibody. Here, we adapted a method used to study protein trafficking (&#8220;antibody feeding&#8221;) to differentially label protein that had been internalized by endocytosis during the antibody incubation step and protein that either remained on the cell surface or was trafficked to the surface during this period. The ability to distinguish these two pools of protein was made possible through the incorporation of an overnight blocking step with highly-concentrated unlabeled secondary antibody after an initial incubation of unpermeabilized neurons with a fluorescently-labeled secondary antibody. After the blocking step, permeabilization of the neurons allowed detection of the internalized pool with a fluorescent secondary antibody labeled with a different fluorophore. Using this technique we were able to obtain important information about the subcellular location of this putative receptor, revealing that it was, indeed, trafficked to the cell-surface in neurons. This technique is broadly applicable to a range of cell types and cell-surface proteins, providing a suitable antibody to an extracellular epitope is available.

The dual-color fluorescent immunostaining technique presented here is useful for labeling extracellular domains of transmembrane proteins in living cells (shown schematically in Figure&#160;1). During the incubation period, the immunoglobulins bind accessible epitopes and a proportion of the population of protein molecules, together with bound antibody, is endocytosed. In addition, newly synthesized protein may reach the cell surface via forward trafficking and recycled protein molecules may be returned ...

Watch this Scientific Journal Video about Differential Labeling of Cell-surface and Internalized Proteins after Antibody Feeding of Live Cultured Neurons at JoVE.com

Differential Labeling of Cell-surface and Internalized Proteins after Antibody Feeding of Live Cultured Neurons

We describe a method to label protein on the surface of living neurons using a specific polyclonal antibody to extracellular epitopes. Protein bound by the antibody on the cell surface and subsequently internalized via endocytosis can be distinguished from protein remaining on, or trafficked to, the surface during the incubation.

In order to demonstrate the cell-surface localization of a putative transmembrane receptor in cultured neurons, we labeled the protein on the surface of ...

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