Name: transient expression and cellular localization of recombinant proteins in cultured insect cells
Uploaded: 2017-04-20T15:00:00
Description: Watch this Scientific Journal Video about Transient Expression and Cellular Localization of Recombinant Proteins in Cultured Insect Cells at JoVE.com

We thank Lynn Forlow-Jech and Dannialle LeRoy for technical assistance. This work was supported by base CRIS funding to USDA ARS, National Program 304 - Crop Protection and Quarantine [Project #2020-22620-022-00D] to J.A.F. and J.J.H. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U. S. Department of Agriculture. USDA is an equal opportunity provider and employer.

1. OE-PCR for the Construction of Expression Plasmids
Note: See Table 1 for all primers used in OE-PCR. The use of a high-fidelity DNA polymerase is recommended for all amplifications. However, because these enzymes frequently do not leave a 3&#39; A, it is necessary to perform a brief, non-amplifying incubation with a Taq DNA polymerase to &#34;A-tail&#34; the PCR products prior to cloning them into a TA insect cell expression vector. This protocol demonstrates a method to gene...

<ol>
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Virol. 96 (1), 6-23 (2015).</li><li>Contreras-G&#242;mez, A., 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=Protein+production+using+the+baculovirus-insect+cell+expression+system.">Protein production using the baculovirus-insect cell expression system.</a> Biotechnol. Progr. 30 (1), 1-18 (2014).</li><li>Hunt, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+gene+to+protein:+a+review+of+new+and+enabling+technologies+for+multi-parallel+protein+expression.">From gene to protein: a review of new and enabling technologies for multi-parallel protein expression.</a> Protein Expres. 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Biotechnol. 216, 67-75 (2015).</li><li>Chen, H., 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=Rapid+screening+of+membrane+protein+expression+in+transiently+transfected+insect+cells.">Rapid screening of membrane protein expression in transiently transfected insect cells.</a> Protein Expres. Purif. 88 (1), 134-142 (2013).</li><li>Shen, X., 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=Virus-free+transient+protein+production+in+Sf9+cells.">Virus-free transient protein production in Sf9 cells.</a> J. Biotechnol. 171, 61-70 (2014).</li><li>Loomis, K. 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Heterologous protein expression systems are important tools for the production of recombinant proteins used in numerous downstream applications4. Choosing from the diverse expression systems available depends on the end goal for the protein of interest. Several insect cell expression systems are available that offer flexible alternatives to prokaryotic and eukaryotic cell expression systems5,6. Insect systems requiring baculovirus infectio...

The production of recombinant proteins using insect cell expression systems offers numerous benefits for the study of eukaryotic proteins. Namely, insect cells possess similar post-translational modifications, processing, and sorting mechanisms as those present in mammalian cells, which is advantageous for producing properly folded proteins1,2,3. Insect cell systems also typically require fewer resources and less time and effort for maintenance than mammalian cell lines4,5. The baculovirus expression system is one such insect cell-based system that is now widely used in many disciplines, including the production of recombinant proteins for protein characterization and therapeutics, the immunogenic presentation of foreign peptides and viral proteins for vaccine production, the synthesis of multi-protein complexes, the production of glycosylated proteins, etc.1,2,4,6. There are, however, situations in which baculovirus expression may not be applicable3,7, and the use of nonlytic and transient insect expression systems may be more appropriate. Specifically, transient insect cell expression offers the possibility for the rapid synthesis of recombinant protein, requires less development and maintenance, does not involve viral-imposed cell lysis, and provides a means to better study cellular trafficking during protein synthesis7,8,9,10.
This protocol describes the rapid generation of expression vectors using two-step overlap extension PCR (OE-PCR) 11 and the standard cloning of plasmid DNA in Escherichia coli. Plasmids are used to double-transfect commercially available cultured insect cells and to produce representative proteins. The protocol describes the production and use of two different fluorescently-labeled subcellular marker proteins and demonstrates colocalization with two aquaporin proteins from the insect Bemisia tabaci. The following protocol provides the basic methodology for OE-PCR, insect cell maintenance and transfection, and fluorescence microscopy for the cellular localization of target proteins.

<table border="0" cellpadding="0" cellspacing="0" width="1353">
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		<col />
		<col />
		<col />
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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">KOD DNA Polymerase</td>
			<td style="width:164px;">EMD Millipore</td>
			<td style="width:119px;">71085-3</td>
			<td style="width:645px;">High-fidelity DNA polymerase used for PCR amplification of overlap extension PCR products</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">ExTaq DNA Polymerase</td>
			<td style="width:164px;">TaKaRa-Clontech</td>
			<td style="width:119px;">RR001B</td>
			<td>DNA polymerase used for A-tailing of PCR products</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">EconoTaq PLUS GREEN 2x DNA Polymerase Master Mix</td>
			<td style="width:164px;">Lucigen</td>
			<td style="width:119px;">30033-1</td>
			<td>DNA polymerase used for bacterial colony PCR</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">Biometra TProfessional Gradient Thermocycler</td>
			<td style="width:164px;">Biometra/LABRepCo</td>
			<td style="width:119px;">070-851</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">Agarose LE</td>
			<td style="width:164px;">Benchmark Scientific</td>
			<td style="width:119px;">A1705</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">SYBR Safe DNA Gel Stain</td>
			<td>ThermoFisher</td>
			<td style="width:119px;">S33102</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">Montage DNA Gel Extraction Kit</td>
			<td style="width:164px;">EMD Millipore</td>
			<td style="width:119px;">LSKGEL050</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:425px;">pIB/V5-His TOPO TA Expression Kit</td>
			<td>ThermoFisher</td>
			<td style="width:119px;">K89020</td>
			<td style="width:645px;">Contains components needed to clone overlap extension PCR products, including linearized and topoisomerase I-activated pIB/V5-His-TOPO vector, One Shot TOP10 chemically competent E. coli, and salt solution.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">QIAprep Spin MiniPrep Kit</td>
			<td>Qiagen</td>
			<td style="width:119px;">27104</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">QIAcube Robotic Workstation</td>
			<td>Qiagen</td>
			<td style="width:119px;">9001292</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Purifier Vertical Clean Bench</td>
			<td>Labconco</td>
			<td>3970401</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tni cultured insect cell Line</td>
			<td>Allele Biotech</td>
			<td>ABP-CEL-10005</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sf9 cultured insect cell Line</td>
			<td>Allele Biotech</td>
			<td>ABP-CEL-10002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Serum-Free Insect Culture Medium</td>
			<td>Allele Biotech</td>
			<td>ABP-MED-10002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TNM-FH Insect Culture Medium</td>
			<td>Allele Biotech</td>
			<td>ABP-MED-10001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">IPL-41 Insect Medium</td>
			<td>ThermoFisher</td>
			<td>11405081</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cellfectin II Transfection Reagent</td>
			<td>ThermoFisher</td>
			<td>10362100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">16 cm Disposable Cell Scrapers</td>
			<td>Sarstedt</td>
			<td>83.1832</td>
			<td>Cell scrapers with two-position blade</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">25 cm2 (T25) Tissue Culture Flasks with Vent Filter Caps</td>
			<td>Life Science Products</td>
			<td>CT-229331</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transfer Pipets</td>
			<td>Fisher</td>
			<td>1371120</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sterile, 50 mL Bio-Reaction Tubes</td>
			<td>Life Science Products</td>
			<td>CT-229475</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PipetteBoy</td>
			<td>VWR</td>
			<td>14222-180</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5 mL Serological Pipettes</td>
			<td>Sarstedt</td>
			<td>86.1253.001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.5 mL Flat-Cap PCR Tubes</td>
			<td>Fisher</td>
			<td>14230200</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polypropylene Biohazard Autoclave Bags</td>
			<td>Fisher</td>
			<td>01828C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">35 mm #1.5 Glass Bottom Dishes</td>
			<td>Matsunami Glass</td>
			<td>D35-14-1.5-U</td>
			<td>35 mm dish diameter, 14 mm glass diameter, 1.5 mm glass thickness, uncoated</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Incubator, Model 1510E</td>
			<td>VWR</td>
			<td>35823-961</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Countess II FL Cell Counter</td>
			<td>ThermoFisher</td>
			<td>AMQAF1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Countess Cell Counting Chamber Slides with 0.4% Trypan Blue Reagent</td>
			<td>ThermoFisher</td>
			<td>C10228</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fluoview FV10i-LIV Laser Scanning Confocal Microscope</td>
			<td>Olympus</td>
			<td>FV10i-LIV</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HsPLA2/pCS6 plasmid DNA</td>
			<td>transOMIC Technologies</td>
			<td>TCH1303</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pmCherry Vector</td>
			<td>Clontech</td>
			<td>632522</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:425px;">NucBlue Live ReadyProbes Reagent (Hoechst 33342)</td>
			<td style="width:164px;">ThermoFisher</td>
			<td style="width:119px;">R37605</td>
			<td></td>
		</tr>
	</tbody>
</table>

transient expression and cellular localization of recombinant proteins in cultured insect cells

Heterologous protein expression systems are used for the production of recombinant proteins, the interpretation of cellular trafficking/localization, and the determination of the biochemical function of proteins at the sub-organismal level. Although baculovirus expression systems are increasingly used for protein production in numerous biotechnological, pharmaceutical, and industrial applications, nonlytic systems that do not involve viral infection have clear benefits but are often overlooked and underutilized. Here, we describe a method for generating nonlytic expression vectors and transient recombinant protein expression. This protocol allows for the efficient cellular localization of recombinant proteins and can be used to rapidly discern protein trafficking within the cell. We show the expression of four&#160;recombinant proteins in a commercially available insect cell line, including two aquaporin proteins from the insect Bemisia tabaci, as well as subcellular marker proteins specific for the cell plasma membrane and for intracellular lysosomes. All recombinant proteins were produced as chimeras with fluorescent protein markers at their carboxyl termini, which allows for the direct detection of the recombinant proteins. The double transfection of cells with plasmids harboring constructs for the genes of interest and a known subcellular marker allows for live cell imaging and improved validation of cellular protein localization.

OE-PCR
OE-PCR allows for the synthesis of chimeric DNA products that, once inserted into an expression vector, allow for the production of recombinant chimeric proteins corresponding to any test gene of interest and fluorescent marker protein. Figure 1 represents a general scheme for the production of pIB expression vectors containing B. tabaci aquaporin coding sequences (BtDrip1 and BtDrip2_v1) in-frame w...

Watch this Scientific Journal Video about Transient Expression and Cellular Localization of Recombinant Proteins in Cultured Insect Cells at JoVE.com

Transient Expression and Cellular Localization of Recombinant Proteins in Cultured Insect Cells

Nonlytic insect cell expression systems are underutilized for production, cellular trafficking/localization, and recombinant protein functional analysis. Here, we describe methods to generate expression vectors and subsequent transient protein expression in commercially available lepidopteran cell lines. The co-localization of Bemisia tabaci aquaporins with subcellular fluorescent marker proteins is also presented.

Heterologous protein expression systems are used for the production of recombinant proteins, the interpretation of cellular trafficking/localization, and ...

The overall goal of this procedure is to express fluorescently tagged proteins of interest within commercially available insect cells for the enhanced elucidation of protein function and or cellular trafficking of proteins. This method can help answer key cell biology and biochemistry based questions regarding protein functionality, protein interactions, and or subcellular protein localization. The main advantage of this technique is that constructs can be rapidly generated and expressed proteins functionally assessed in live cells without deleterious effects associated with baculovirus expression, thus improving throughput.Though this method can provide insight in the study of insect proteins, it can also be applied to any system for which the study of protein function or cellular localization is desired. Demonstrating the procedure for insect cell culture and transfection will be Danni LeRoy, a technician from my laboratory. To begin this procedure, remove stock vials of frozen SF9 and Tni cells from the minus 80 degrees celsius freezer and allow them to thaw in a 37 degree celsius water bath.After thawing, decontaminate the vials with 70%ethanol and place them on ice. All cell manipulations requiring the opening of vials and tissue culture flasks must be performed within a laminar flow hood to maintain sterile conditions. Add four milliliters of serum-free insect medium to a new T25 flask and four milliliters of TNM-FH medium to another T25 flask.Transfer one milliliter of thawed Tni cells to the flask with serum-free insect medium and one milliliter of thawed SF9 cells to the flask with TNM-FH medium. Place the flasks in a 28 degree celsius non-humidified incubator and allow the cells to attach for 30 to 45 minutes. Replace the seeding medium with five milliliters of the appropriate medium.And return the flasks to the 28 degree celsius non-humidified incubator. Monitor cell confluence daily. Passage the cells when they reach 90%confluency as shown by these representative images.Tilt the flask containing the confluent cells so that the medium flows toward one corner away from the cell monolayer and use a sterile five milliliter serological pipette to carefully remove the medium without disturbing the cells. For Tni cells, use a new sterile five milliliter serological pipette to gently add four milliliters of serum-free insect medium onto the confluent monolayer. Move the pipette tip across the flask and slowly irrigate to remove cells loosely attached to the flask bottom.To check for the adequate detachment of cells, remove all media, turn the flask over and observe that the bottom of the flask is clear. For SF9 cells, which adhere more tightly, add four milliliters of fresh TNM-FH medium and use a cell scraper to dislodge the attached cells. Use a five milliliter serological pipette to gently mix and reduce cell clumping.After detaching the cells, transfer approximately 0.1 milliliters of each cell and medium mixture to a 1.5 milliliter micro-fuge tube. In a separate 0.5 milliliter micro-fuge tube add 10 microliters of each cell and medium mixture to 10 microliters of trypan blue. Remove the cell counter chamber slide from its packaging and add 10 microliters of the cell medium trypan blue mixture to each side of the counting slide.Insert the slide into an automated cell counter and determine the cell density and viability. Transfer approximately one to 1.5 times 10 to the 6th cells to T25 flasks with fresh media. Label the flasks with the cell line, date, medium used, number of cells added, and passage number.Place the flasks in a 28 degree celsius incubator for up to 72 hours. The procedure for insect cell transfection must also be performed within a laminar flow hood. Seed a T25 flask with up to one times 10 to the 6th Tni or SF9 cells in an appropriate insect cell medium.Tni cells are used in this demonstration. Grow the cells to confluency for 72 hours at 18 degrees celsius. 72 hours later, remove and discard the old medium and dislodge the Tni cells with four milliliters of fresh serum-free insect medium as shown earlier.The most difficult aspect of this procedure is obtaining the appropriate density of cells attached to the glass bottom dishes during transfection. No more than seven times 10 to the 5th cell should be added to each dish. After using an automated cell counter to estimate the cell density, thoroughly but gently mix the cell suspension by inverting the tube and add approximately seven times 10 to the 5th cells to individual 35 millimeter glass bottom dishes.Allow the cells to attach for 20 to 25 minutes at 28 degrees celsius. For each transfection, add two micrograms of plasmid DNA to 0.1 milliliters of serum-free insect medium without FBS in a sterile 1.5 milliliter micro-fuge tube. In a separate tube, mix eight microliters of transfection reagent with 0.1 milliliters of serum-free insect medium.Then transfer the solution to the tube containing the plasmid DNA of interest. Lightly vortex and incubate at room temperature for 20 to 30 minutes. Next, dilute the plasmid transfection mixture with 0.8 milliliters of serum-free insect medium, bringing the total volume up to one milliliter.Carefully remove the media from the glass dish containing attached cells. Overlay the attached cells with the diluted plasmid transfection medium. Incubate the cells at 28 degrees celsius for five hours.After five hours, remove and discard the transfection medium and gently wash the cells with one milliliter of serum-free insect medium, being careful not to dislodge the cells. Add two milliliters of fresh serum-free insect cell medium and incubate at 28 degrees celsius for 48 to 72 hours. 48 to 72 hours after transfection of the insect cells, wash the cells once with one milliliter of IPL-41 insect medium and then cover with two milliliters of IPL-41 for imaging.Add four drops of Hoechst live cell staining reagent to the medium and incubate at 28 degrees celsius for 20 to 25 minutes. Place the 35 millimeter dish into the self enclosed laser scanning confocal microscope. Although many glass dishes are commercially available, it's important that they fit the microscope stage and it may be necessary to empirically determine which glassware is most compatible with cell attachment.Adjust the microscope for Hoechst, EGFP and mCherry observation conditions. 359 nanometers and 461 nanometers for Hoechst excitation and emission. 489 nanometers and 510 nanometers for EGFP excitation and emission.And 580 nanometers and 610 nanometers for mCherry excitation and emission. Using a 10X objective, perform an initial scan to confirm fluorescent expression. After that, switch to scanning mode using a 60X phase contrast water immersion objective.Adjust the laser power, detector sensitivity, scanning speed, Z-axis depth, and digital zoom to optimize the image contrast and resolution. Image the cells at 1.5X digital zoom to give a total of 90X amplification. Save and export the raw data as TIFF image files for later analysis.Tni cells were transfected with the indicated plasmids and the expression of recombinant proteins was visualized using confocal fluorescence microscopy. Successful transfection and expression of recombinant BtDrip1-EGFP is evident by the presence of green fluorescence on the cell's surface. Cells transfected with BtDrip2 version one EGFP show green fluorescence within indicating the intracellular expression of BtDrip2 version one.Likewise, cells transfected with PIB DmSPR-mCherry or PIB PLA2G15-mCherry show red fluorescence indicating the expression of the respective chimeras. In the merged images, the orange or yellow areas indicate expression of both EGFP and mCherry which suggests that the proteins are co-localized within the same subcellular structures. An overlay of cells double transfected with PIB BtDrip1-EGFP and PIB DmSPR-mCherry suggests co-localization of BtDrip1-EGFP and DmSPR-mCherry on the cell's surface.Cells double transfected with BtDrip2 version one EGFP and PIB DmSPR-mCherry show little co-localization of green and red fluorescence signals confirming the intracellular expression of BtDrip2 version one. In contrast the co-expression of PIB BtDrip2 version one EGFP and the PIB PLA2G15-mCherry lysosomal marker resulted in a significant overlap in the cytoplasmic green and red fluorescent signals. This strongly suggests that BtDrip2 is traffic to intercellular lysosomes.After watching this video, you should have a good understanding of how to express fluorescent protein chimeras within cultured insect cells. This system offers rapid vector construction in protein synthesis, avoids challenges of virus based expression systems, and provides a robust means to observe cellular trafficking proteins.

transient-expression-cellular-localization-recombinant-proteins

Research

JoVE Journal

Biology

A Method For Production of Recombinant mCD1d Protein in Insect Cells.

CD1 proteins constitute a third class of antigen-presenting molecules. They are cell surface glycoproteins, expressed as approximately 50-kDa glycosylated heavy chains that are noncovalently associated with beta2-microglobulin. They bind lipids rather than peptides. Although their structure confirms the similarity of CD1 proteins to MHC class I and class II antigen presenting molecules, the mCD1d groove is relatively narrow, deep, and highly hydrophobic and it has two binding pockets instead of the several shallow pockets described for the classical MHC-encoded antigen-presenting molecules. Based upon their amino acid sequences, such a hydrobphobic groove provides an ideal environment for the binding of lipid antigens. The Natural Killer T (NKT) cells use their TCR to recognize glycolipids bound to or presented by CD1d. T cells reactive to lipids presented by CD1 have been involved in the protection against autoimmune and infectious diseases and in tumor rejection. Thus, the ability to identify, purify , and track the response of CD1-reactive NKT cell is of great importance . The generation of tetramers of alpha Galactosyl ceramide (a-Galcer) with CD1d has significant insight into the biology of NKT cells. Tetramers constructed from other CD1 molecules have also been generated and these new reagents have greatly expanded the knowledge of the functions of lipid-reactive T cells, with potential use in monitoring the response to lipid-based vaccines and in the diagnosis of autoimmune diseases and other treatments.

A Method to prepare Insect cells and infect them with baculovirus for the the purpose of production of recombinant mCD1d proteinand generating mCD1d tetramers.

CD1 proteins constitute a third class of antigen-presenting molecules. They are cell surface glycoproteins, expressed as approximately 50-kDa glycosylated ...

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Expression of Recombinant Proteins in the Methylotrophic Yeast Pichia pastoris

Protein expression in the microbial eukaryotic host Pichia pastoris offers the possibility to generate high amounts of recombinant protein in a fast and easy to use expression system.
As a single-celled microorganism P. pastoris is easy to manipulate and grows rapidly on inexpensive media at high cell densities. Being a eukaryote, P. pastoris is able to perform many of the post-translational modifications performed by higher eukaryotic cells and the obtained recombinant proteins undergo protein folding, proteolytic processing, disulfide bond formation and glycosylation [1].
As a methylotrophic yeast P. pastoris is capable of metabolizing methanol as its sole carbon source. The strong promoter for alcohol oxidase, AOX1, is tightly regulated and induced by methanol and it is used for the expression of the gene of interest. Accordingly, the expression of the foreign protein can be induced by adding methanol to the growth medium [2; 3].
Another important advantage is the secretion of the recombinant protein into the growth medium, using a signal sequence to target the foreign protein to the secretory pathway of P. pastoris. With only low levels of endogenous protein secreted to the media by the yeast itself and no added proteins to the media, a heterologous protein builds the majority of the total protein in the medium and facilitates following protein purification steps [3; 4].
The vector used here (pPICZ&alpha;A) contains the AOX1 promoter for tightly regulated, methanol-induced expression of the gene of interest; the &alpha;-factor secretion signal for secretion of the recombinant protein, a Zeocin resistance gene for selection in both E. coli and Pichia and a C-terminal peptide containing the c-myc epitope and a polyhistidine (6xHis) tag for detection and purification of a recombinant protein. We also show western blot analysis of the recombinant protein using the specific Anti-myc-HRP antibody recognizing the c-myc epitope on the parent vector.

Expression of Recombinant Proteins in the Methylotrophic Yeast Pichia pastoris

The protocol describes protein expression using the methylotrophic yeast Pichia pastoris. The preparation of electrocompetent yeast cells, transformation of the vector with the gene of interest into P. pastoris and yeast DNA purification are also performed. Western blot analysis and protein purification build the last steps in this protein expression protocol.

Protein expression in the microbial eukaryotic host Pichia pastoris offers the possibility to generate high amounts of recombinant protein in a fast and ...

Efficient Agroinfiltration of Plants for High-level Transient Expression of Recombinant Proteins

Mammalian cell culture is the major platform for commercial production of human vaccines and therapeutic proteins. However, it cannot meet the increasing worldwide demand for pharmaceuticals due to its limited scalability and high cost. Plants have shown to be one of the most promising alternative pharmaceutical production platforms that are robust, scalable, low-cost and safe. The recent development of virus-based vectors has allowed rapid and high-level transient expression of recombinant proteins in plants. To further optimize the utility of the transient expression system, we demonstrate a simple, efficient and scalable methodology to introduce target-gene containing Agrobacterium into plant tissue in this study. Our results indicate that agroinfiltration with both syringe and vacuum methods have resulted in the efficient introduction of Agrobacterium into leaves and robust production of two fluorescent proteins; GFP and DsRed. Furthermore, we demonstrate the unique advantages offered by both methods. Syringe infiltration is simple and does not need expensive equipment. It also allows the flexibility to either infiltrate the entire leave with one target gene, or to introduce genes of multiple targets on one leaf. Thus, it can be used for laboratory scale expression of recombinant proteins as well as for comparing different proteins or vectors for yield or expression kinetics. The simplicity of syringe infiltration also suggests its utility in high school and college education for the subject of biotechnology. In contrast, vacuum infiltration is more robust and can be scaled-up for commercial manufacture of pharmaceutical proteins. It also offers the advantage of being able to agroinfiltrate plant species that are not amenable for syringe infiltration such as lettuce and Arabidopsis. Overall, the combination of syringe and vacuum agroinfiltration provides researchers and educators a simple, efficient, and robust methodology for transient protein expression. It will greatly facilitate the development of pharmaceutical proteins and promote science education.

Plants offer a novel system for the production of pharmaceutical proteins on a commercial scale that is more scalable, cost-efficient and safe than current expression paradigms. In this study, we report a simple and convenient, yet scalable approach to introduce target-gene containing Agrobacterium tumefaciens into plants for protein transient expression.

Mammalian cell culture is the major platform for commercial production of human vaccines and therapeutic proteins. However, it cannot meet the increasing ...

Efficient Production and Purification of Recombinant Murine Kindlin-3 from Insect Cells for Biophysical Studies

Kindlins are essential coactivators, with talin, of the cell surface receptors&#160;integrins and also participate in integrin outside-in signalling, and the control of gene transcription in the cell nucleus. The kindlins are ~75 kDa multidomain proteins and bind to an NPxY motif and upstream T/S cluster of the integrin &#946;-subunit cytoplasmic tail. The hematopoietically-important kindlin isoform, kindlin-3, is critical for platelet aggregation during thrombus formation, leukocyte rolling in response to infection and inflammation and osteoclast podocyte formation in bone resorption. Kindlin-3&#39;s role in these processes has resulted in extensive cellular and physiological studies. However, there is a need for an efficient method of acquiring high quality milligram quantities of the protein for further studies. We have developed a protocol, here described, for the efficient expression and purification of recombinant murine kindlin-3 by use of a baculovirus-driven expression system in Sf9 cells yielding sufficient amounts of high purity full-length protein to allow its biophysical characterization. The same approach could be taken in the study of the other mammalian kindlin isoforms.

Kindlins are fundamental to cell adhesion through integrins but studies of them have been hampered by the difficulty encountered in expressing them recombinantly in bacterial hosts. We describe here methods for their efficient production in baculovirus-infected insect cells.

Kindlins are essential coactivators, with talin, of the cell surface receptors&#160;integrins and also participate in integrin outside-in signalling, and ...

High Throughput Quantitative Expression Screening and Purification Applied to Recombinant Disulfide-rich Venom Proteins Produced in E. coli

Escherichia coli (E. coli) is the most widely used expression system for the production of recombinant proteins for structural and functional studies. However, purifying proteins is sometimes challenging since many proteins are expressed in an insoluble form. When working with difficult or multiple targets it is therefore recommended to use high throughput (HTP) protein expression screening on a small scale (1-4&#160;ml cultures) to quickly identify conditions for soluble expression. To cope with the various structural genomics programs of the lab, a quantitative (within a range of 0.1-100 mg/L culture of recombinant protein) and HTP protein expression screening protocol was implemented and validated on thousands of proteins. The protocols were automated with the use of a liquid handling robot but can also be performed manually without specialized equipment.
Disulfide-rich venom proteins are gaining increasing recognition for their potential as therapeutic drug leads. They can be highly potent and selective, but their complex disulfide bond networks make them challenging to produce. As a member of the FP7 European Venomics project (<a href="http://www.venomics.eu">www.venomics.eu</a>), our challenge is to develop successful production strategies with the aim of producing thousands of novel venom proteins for functional characterization. Aided by the redox properties of disulfide bond isomerase DsbC, we adapted our HTP production pipeline for the expression of oxidized, functional venom peptides in the E. coli cytoplasm. The protocols are also applicable to the production of diverse disulfide-rich proteins. Here we demonstrate our pipeline applied to the production of animal venom proteins. With the protocols described herein it is likely that soluble disulfide-rich proteins will be obtained in as little as a week. Even from a small scale, there is the potential to use the purified proteins for validating the oxidation state by mass spectrometry, for characterization in pilot studies, or for sensitive micro-assays.

High Throughput Quantitative Expression Screening and Purification Applied to Recombinant Disulfide-rich Venom Proteins Produced in E. coli

A protocol for the quantitative, high throughput expression screening and analytical purification of fusion proteins from small-scale Escherichia coli cultures is described and applied to the expression of disulfide-rich animal venom protein targets.

Escherichia coli (E. coli) is the most widely used expression system for the production of recombinant proteins for structural and functional studies. ...

Transient Expression of Proteins by Hydrodynamic Gene Delivery in Mice

Efficient expression of transgenes in vivo is of critical importance in studying gene function and developing treatments for diseases. Over the past years, hydrodynamic gene delivery (HGD) has emerged as a simple, fast, safe and effective method for delivering transgenes into rodents. This technique relies on the force generated by the rapid injection of a large volume of physiological solution to increase the permeability of cell membranes of perfused organs and thus deliver DNA into cells. One of the main advantages of HGD is the ability to introduce transgenes into mammalian cells using naked plasmid DNA (pDNA). Introducing an exogenous gene using a plasmid is minimally laborious, highly efficient and, contrary to viral carriers, remarkably safe. HGD was initially used to deliver genes into mice, it is now used to deliver a wide range of substances, including oligonucleotides, artificial chromosomes, RNA, proteins and small molecules into mice, rats and, to a limited degree, other animals. This protocol describes HGD in mice and focuses on three key aspects of the method that are critical to performing the procedure successfully: correct insertion of the needle into the vein, the volume of injection and the speed of delivery. Examples are given to show the application of this method to the transient expression of two genes that encode secreted, primate-specific proteins, apolipoprotein L-I (APOL-I) and haptoglobin-related protein (HPR).

In vivo transfection of naked DNA by hydrodynamic gene delivery introduces genes into the tissue of an animal with minimal inflammatory response. Sufficient amounts of gene product are generated such that gene function and regulation as well as protein structure and function can be analyzed.

Efficient expression of transgenes in vivo is of critical importance in studying gene function and developing treatments for diseases. Over the past ...

siRNA Screening to Identify Ubiquitin and Ubiquitin-like System Regulators of Biological Pathways in Cultured Mammalian Cells

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that regulates diverse biological pathways including the hypoxia response, proteostasis, the DNA damage response and transcription.&#160; To better understand how UBLs regulate pathways relevant to human disease, we have compiled a human siRNA &#8220;ubiquitome&#8221; library consisting of 1,186 siRNA duplex pools targeting all known and predicted components of UBL system pathways. This library can be screened against a range of cell lines expressing reporters of diverse biological pathways to determine which UBL components act as positive or negative regulators of the pathway in question.&#160; Here, we describe a protocol utilizing this library to identify ubiquitome-regulators of the HIF1A-mediated cellular response to hypoxia using a transcription-based luciferase reporter.&#160; An initial assay development stage is performed to establish suitable screening parameters of the cell line before performing the screen in three stages: primary, secondary and tertiary/deconvolution screening. &#160;The use of targeted over whole genome siRNA libraries is becoming increasingly popular as it offers the advantage of reporting only on members of the pathway with which the investigators are most interested.&#160; Despite inherent limitations of siRNA screening, in particular false-positives caused by siRNA off-target effects, the identification of genuine novel regulators of the pathways in question outweigh these shortcomings, which can be overcome by performing a series of carefully undertaken control experiments.

Here, we describe a methodology to perform a targeted siRNA &#8220;ubiquitome&#8221; screen to identify novel ubiquitin and ubiquitin-like regulators of the HIF1A-mediated cellular response to hypoxia.&#160; This can be adapted to any biological pathway where a robust read out of reporter activity is available.

Post-translational modification of proteins with ubiquitin and ubiquitin-like molecules (UBLs) is emerging as a dynamic cellular signaling network that ...

A Comparative Analysis of Recombinant Protein Expression in Different Biofactories: Bacteria, Insect Cells and Plant Systems

Plant-based systems are considered a valuable platform for the production of recombinant proteins as a result of their well-documented potential for the flexible, low-cost production of high-quality, bioactive products.
In this study, we compared the expression of a target human recombinant protein in traditional fermenter-based cell cultures (bacterial and insect) with plant-based expression systems, both transient and stable.
For each platform, we described the set-up, optimization and length of the production process, the final product quality and the yields and we evaluated provisional production costs, specific for the selected target recombinant protein.
Overall, our results indicate that bacteria are unsuitable for the production of the target protein due to its accumulation within insoluble inclusion bodies. On the other hand, plant-based systems are versatile platforms that allow the production of the selected protein at lower-costs than Baculovirus/insect cell system. In particular, stable transgenic lines displayed the highest-yield of the final product and transient expressing plants the fastest process development. However, not all recombinant proteins may benefit from plant-based systems but the best production platform should be determined empirically with a case-by-case approach, as described here.

In this study the expression of a target human recombinant protein in different production platforms was compared. We focused on traditional fermenter-based cultures and on plants, describing the set-up of each system and highlighting, on the basis of the reported results, the inherent limits and advantages for each platform.

Plant-based systems are considered a valuable platform for the production of recombinant proteins as a result of their well-documented potential for the ...

High Yield Expression of Recombinant Human Proteins with the Transient Transfection of HEK293 Cells in Suspension

The art of producing recombinant proteins with complex post-translational modifications represents a major challenge for studies of structure and function. The rapid establishment and high recovery from transiently-transfected mammalian cell lines addresses this barrier and is an effective means of expressing proteins that are naturally channeled through the ER and Golgi-mediated secretory pathway. Here is one protocol for protein expression using the human HEK293F and HEK293S cell lines transfected with a mammalian expression vector designed for high protein yields. The applicability of this system is demonstrated using three representative glycoproteins that expressed with yields between 95-120 mg of purified protein recovered per liter of culture. These proteins are the human Fc&#947;RIIIa and the rat &#945;2-6 sialyltransferase, ST6GalI, both expressed with an N-terminal GFP fusion, as well as the unmodified human immunoglobulin G1 Fc. This robust system utilizes a serum-free medium that is adaptable for expression of isotopically enriched proteins and carbohydrates for structural studies using mass spectrometry and nuclear magnetic resonance spectroscopy. Furthermore, the composition of the N-glycan can be tuned by adding a small molecule to prevent certain glycan modifications in a manner that does not reduce yield.

Laboratory-scale production of eukaryotic proteins with appropriate post-translational modification represents a significant barrier. Here is a robust protocol with rapid establishment and turnaround for protein expression using a mammalian expression system. This system supports selective amino acid, selective labeling of proteins and small molecule modulators of glycan composition.