Traditional Western blotting is a labor-intensive process that includes gel electrophoresis, protein transfer to a blotting membrane, incubation with primary and secondary antibodies, and chemiluminescent or fluorescent detection of target proteins. (View a typical Western blotting workflow.) Day-to-day reproducibility is poor, because small variations in lysate preparation, gel loading, electrophoresis, transfer, and detection are unavoidable sources of technical variability.
The In-Cell Western™ (ICW) Assay, a quantitative immunofluorescent method, is an alternative to traditional Western blots that increases both reproducibility and sample throughput. (View a typical ICW workflow.)
We recently hosted a webinar called “Rethinking the Traditional Western Blot”, during which John Lyssand, PhD, from LI-COR Biosciences, discussed the In-Cell Western Assay and its use in neuroscience research, in this case, Alzheimer’s Disease. The In-Cell Western Assay enables screening and analysis of many more samples in each experiment, eliminates error-prone protocol steps, and delivers higher reproducibility for biological and technical replicates.
The data presented demonstrated how ICW assays were used in Alzheimer’s Disease research to screen HSP90 inhibitors for their effectiveness in reducing tau activity levels. Dr Lyssand discussed how and why the In-Cell Western Assay is superior to traditional methods for screening of cell samples.
If you didn’t have a chance to join us in September for “Rethinking the Traditional Western blot”, you can view this webinar online and on-demand. Check out the information on In-Cell Western assays on our website. You can also read Professor Dickey’s white paper outlining how he and his group used In-Cell Western Assays to study Alzhemier’s Disease.
Odyssey Infrared Imaging Systems and LI-COR® reagents have been used for research applications in many different disciplines, including neuroscience, neurobiology, Alzheimer’s Disease, Parkinson’s and more.
This week the Society for Neuroscience is holding its annual meeting in New Orleans, LA. LI-COR is there showcasing the Odyssey CLx and the Odyssey Fc, plus the MPX™ Multiplexer Blotting System, and several new products. Stop by Booth 2713 and talk to our LI-COR representatives. Fresh chocolate chip cookies will be available Monday and Tuesday at the booth during certain times – while supplies last! (follow us on Twitter – @licorbio – to find out when to stop by and get a fresh cookie snack!)
Plus pick up your free ‘brain’ pen at the LI-COR Booth (#2713).
Enjoy the conference! We wish you continued success in your research!
Here are a few journal references related to research in the Neurosciences:
Conditional Deletion of Notch1 and Notch2 Genes in Excitatory Neurons of Postnatal Forebrain Does Not Cause Neurodegeneration or Reduction of Notch mRNAs and Proteins
Jin Zheng, Hirotaka Watanabe, Mary Wines-Samuelson, Huailong Zhao, Thomas Gridley, Raphael Kopan, and Jie Shen
J. Biol. Chem., Jun 2012; 287: 20356 – 20368.
Enhancement of Rostral Ventrolateral Medulla Neuronal Nitric-Oxide Synthase–Nitric-Oxide Signaling Mediates the Central Cannabinoid Receptor 1-Evoked Pressor Response in Conscious Rats
Badr Mostafa Ibrahim and Abdel A. Abdel-Rahman
J. Pharmacol. Exp. Ther., Jun 2012; 341: 579 – 586.
Specific Serine-Proline Phosphorylation and Glycogen Synthase Kinase 3β-directed Subcellular Targeting of Stathmin 3/Sclip in Neurons
Sara Devaux, Fabienne E. Poulain, Véronique Devignot, Sylvie Lachkar, Theano Irinopoulou, and André Sobel
J. Biol. Chem., Jun 2012; 287: 22341 – 22353.
For more journal references citing the use of the Odyssey Imagers and LI-COR reagents, see our most recent Publications List.
Molecular profiling reveals diversity of stress signal transduction cascades in highly penetrant Alzheimer’s disease human skin fibroblasts.
Mendonsa, G., et al. PLoS ONE 4(2): e4655. doi:10.1371/journal.pone.0004655
Aberrant signal transduction is associated with Alzheimer’s disease (AD). In skin fibroblasts of AD patients, exaggerated signal transduction occurs in response to bradykinin (BK), an inflammatory neuropeptide. BK-induced PKC signaling causes stimulation of tau phosphorylation on serine residues in AD fibroblasts, but not in normal skin fibroblasts. Quantitative Western blotting with multiplex fluorescent detection (Odyssey Imager; LI-COR Biosciences) was used to monitor protein levels and phosphorylation.
To explore the roles of inflammatory and oxidative stress in AD pathology, this study profiled the effects of these stresses on MAPK signaling cascades in human skin fibroblasts of familial AD patients. AD fibroblasts of different genetic origins express presenilin (PS-1 or PS-2) mutated at a variety of sites. These mutations caused diverse responses to stress induced by BK or H2O2, with unique profiles of stress-induced MAPK activation, caspase-3 cleavage, and survival pathway activation. These results indicate that AD research must consider a broad spectrum of inflammatory, oxidative, and other stress factors and intracellular signaling responses.
Figure 1. Reduced ERK activation in PS-1 (M146L) Alzheimer’s disease fibroblasts stimulated with bradykinin (BK). These fibroblasts carry a mutation in presenilin-1 associated with aberrant signaling. Mutant and control human skin fibroblasts were treated with 250 nM BK and immunoblotted for active and total ERK. Odyssey Imager was used, and fold activation was quantified. Total ERK is shown in green, and phospho-ERK in red; overlapping signals (active ERK) are shown in yellow. ERK activation was greatly reduced in PS-1 (M146L) AD fibroblasts. Graphs show mean + S.E. *p < 0.05 and **p < 0.005; n = 4. doi:10.1371/journal.pone.0004655
What is an On-Cell Western? It’s a cell-based assay that enables quantitative monitoring of cell surface protein expression. The On-Cell Western assay offers the ability to:
- Detect and quantify target proteins localized to the cell surface
- Quantify ligand binding to cell surface receptors
- Monitor receptor internalization and recycling by detecting loss and re-appearance at the cell surface
- Perform and detect cell surface biotinylation assays
- Evaluate the effects of mutations, drugs, and other treatments on protein trafficking
- Analyze many samples quickly and quantitatively
- Avoid use of radioactivity
Figure 1. Cannabinoid receptor 1 (CB1) is internalized after exposure to a specific agonist (Win-2), but the effect is blocked by the antagonist SR1. A) Intensity levels were greatly reduced in wells treated with 1μM of the CB1-specific agonist, Win-2. Cells treated with Win-2 and the specific CB1 antagonist, SR1 displayed no reduction of signal with the treatment. B) Graph displaying results of three independent experiments done in quadruplicate.
Reprinted with permission from Miller, J.W. Tracking G protein-coupled receptor trafficking using Odyssey imaging. LI-COR Biosciences application note (2004).
Visit On-Cell Westerns for more information. We have a sample protocol of On-Cell Western Assay for Targeted Near-infrared-labeled optical imaging agent development. For other scientific publications in which On-Cell Westerns were used, visit our On-Cell Westerns Publications page.
In a previous post, I talked about how In-Cell Western™ assays could be used when studying apoptosis. So, you may be asking yourself, for what other applications can quantitative cell signaling analysis be used? GREAT QUESTION!!
Well, In-Cell ELISAs (as these immunofluorescent assays are also called) have been used successfully in studying protein phosphorylation. Whether you are looking at the effects of drug compounds on signaling pathways, or the timing/kinetics of signal transduction, or trying to determine the IC50 of compounds, In-Cell Western assays are a valuable tool.
Here are two examples of data from IC50 and EC50 determination experiments.
Figure 1. Use of cell labeling for In-Cell Western normalization. A) HeLa cells were treated with increasing amounts of rapamycin in a 384-well format. Fixed cells were stained with phospho-rpS6 antibody and NHS-ester reactive dye (for cell number). Dose dependent inhibition of phospho-rpS6-staining yielded an IC50 of 224 pM (n=4). B) Raw microplate image. For details, see Hoffman, GR et al. Assay Drug Dev Tech 8(2):186-99 (2010).
Figure 2. Dose titration of Wnt3a treatment of mouse L-cells. Half-maximal activation (EC50) of cellular beta-catenin levels occurs at 33 ng/ml ligand. Hannoush, RN. PLoS One. 3(10):e3498 (2008). Creative Commons license 2.5.
To help you get started in designing your experiment, here is a complete sample protocol for measuring IC50 of the inhibitor PD168393 in A431 cells responding to epidermal growth factor (EGF).
Check here for future blog posts on other applications of quantitative cell signaling analysis!