新技术：In-Cell Western Assay- 点击： 作者： 来源： 日期：2008-04-24 本站论坛
In-Cell Western Assay
Complete Sample Protocol Detailing the SeedingStimulation, and Detection of the HeLa CellularResponse to Epidermal Growth Factor
I. Required Reagents
Odyssey%26reg; Reagents
IRDye%26#8482; 800CW-labeled secondary antibodies (Rockland Immunochemicals, Inc.)
Alexa Fluor%26reg; 680-labeled secondary antibodies (Molecular Probes, Inc.)
Odyssey%26reg; Blocking Buffer (927-40000)
Additional Reagents
1X PBS wash buffer
Tissue culture reagents (serum, D-MEM, trypsin, 1X PBS)
20% Tween%26reg;-20
Epidermal Growth Factor (Upstate Group Inc., 01-107)
37% formaldehyde
10% Triton%26reg; X-100
Nunc%26#8482; 96 Microwell%26#8482; Plate (Nunc Part Number 167008)
Primary antibodies
Special Note: (1) long passage HeLa cells are not suitable for the assay because of high basal level phosphorylation of ERK. As a result, ordering a new sample of this cell line from ATCC is highly recommended. (2) No starvation is needed or recommended.
II. Sample Protocol
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1. |
Allow HeLa (ATCC; CCL-2) cell growth in a T75 flask using standard tissue culture procedures until cells reach near confluency (~1.5x107 cells; D-MEM, 10% FBS; Gibco%26reg;). |
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2. |
Remove growth media, wash cells with sterile 1X PBS, and trypsinize cells for displacement. |
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3. |
Neutralize displaced cells with culture media and clarify by centrifugation. |
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4. |
Remove supernatant and disrupt the cell pellet manually by hand tapping the collection tube. Avoid use of pipet or vortex during pellet disruption to maintain cell integrity. |
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5. |
Resuspend cells in 20 ml of complete media and count cells using a hemacytometer. |
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6. |
Dilute cells with complete media such that 75,000 cells/ml is achieved. |
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7. |
Manually mix the cell suspension thoroughly. |
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8. |
Under sterile conditions, dispense 200 %26micro;l of the cell suspension per well in a Nunc%26#8482; 96 Microwell%26#8482; Plate (15,000 cells plated per well). |
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9. |
Incubate cells and monitor cell density until confluency is achieved with well to well consistency; approximately two-three days. |
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10. |
Warm serum-free media (D-MEM; Gibco) to 37 °C. Dispense 100 %26micro;l of D-MEM per well in the Nunc 96-well microplate. |
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11. |
Make serial dilutions of EGF in the microplate ranging from 0.2 to 100 ng/ml. Leave the first and second wells without EGF (resting cells as control), as shown in section IV. Experimental Results. |
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12. |
Remove complete media from plate wells by aspiration or manual displacement. |
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13. |
Transfer media from the dilution plate into the experimental plate. |
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14. |
Allow incubation at 37 °C for 7.5 minutes. |
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15. |
Remove activation or stimulation media manually or by aspiration. Immediately fix cells with 4% formaldehyde in 1X PBS for 20 minutes at room temperature.
a. Prepare fresh Fixing Solution as follows:
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| 1X PBS |
45 ml |
| 37% Formaldehyde |
5 ml |
| 3.7% Formaldehyde |
50 ml |
b. Using a multi-channel pipettor, add 150 %26micro;l of fresh Fixing Solution (room temperature solution, RT). Add the Fixing Solution carefully by pipetting down the sides of the wells to avoid detaching the cells from the well bottom.
c. Allow incubation on bench top for 20 minutes at RT with no shaking. |
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16. |
Wash five times with 1X PBS containing 0.1% Triton X-100 (cell permeabilization) for 5 minutes per wash.
a. Prepare Triton Washing Solution as follows:
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| 1X PBS |
495 ml |
| 10% Triton X-100 |
5 ml |
| 1X PBS + 0.1% Triton X-100 |
500 ml |
b. Remove Fixing Solution to an appropriate waste container (contains formaldehyde).
c. Using a multi-channel pipettor, add 200 %26micro;l of Triton Washing Solution (RT). Make sure to carefully add the solution down the sides of the wells to avoid detaching the cells from the well bottom.
d. Allow wash to shake on a rotator for 5 minutes at RT.
e. Repeat washing steps 4 more times after removing wash manually.
b. Using a multi-channel pipettor, add 200 %26micro;l of Tween Washing Solution (RT). Make sure to carefully add the solution down the sides of the wells to avoid detaching the cells from the well bottom.
c. Allow wash to shake on a rotator for 5 minutes at RT.
d. Repeat washing steps 4 more times.
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22. |
Dilute the fluorescently labeled secondary antibody in Odyssey Blocking Buffer as specified below. To lower background, add Tween-20 to the diluted antibody for a final concentration of 0.2%.
Goat anti-rabbit Alexa Fluor 680 (1:200 dilution; Molecular Probes)
Goat anti-mouse IRDye 800CW (1:800 dilution; Rockland Immunochemicals)
Avoid prolonged exposure of the antibody vials to light. |
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23. |
Mix the antibody solutions well and add 50 %26micro;l of the secondary antibody solution to each well. Incubate for 60 minutes with gentle shaking at RT. Protect plate from light during incubation. |
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24. |
Wash the plate five times with 1x PBS + 0.1% Tween-20 for 5 minutes at RT with gentle shaking, using a generous amount of buffer.
a. Using a multi-channel pipettor, add 200 %26micro;l of Tween Washing Solution at RT (see step 21). Make sure to carefully add the solution down the sides of the wells to avoid detaching the cells from the well bottom.
b. Allow wash to shake on a rotator for 5 minutes at RT.
c. Repeat washing steps 4 more times after removing wash manually.
Protect plate from light during washing. |
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25. |
After final wash, remove wash solution completely from wells. Turn the plate upside down and tap or blot gently on paper towels to remove traces of wash buffer. For best results, scan plate immediately; plates may also be stored at 4 °C for up to several weeks (protected from light). |
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26. |
Before plate scanning, clean the bottom plate surface and the Odyssey scanning bed with moist lint free paper to avoid any obstructions during scanning. |
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27. |
Scan the plate with detection in both the 700 and 800 channels using the Odyssey Infrared Imaging System (700 nm detection for Alexa Fluor 680 antibody and 800 nm detection for IRDye 800CW antibody). Use medium quality, 169 %26micro;m resolution, 3.0 mm focus offset, and an intensity setting of 5 for both 700 and 800 nm channels. |
III. Experimental Considerations
Proper selection of microplates can significantly affect the results of your analysis, as each plate has its own characteristics including well depth, plate autofluorescence, and well-to-well signal crossover. Use the general considerations for microplate selection provided below.
In-Cell Western analyses use detection at the well surface with no liquid present. This results in minimal well-to-well signal spread, allowing the use of both clear as well as black-sided plates with clear bottoms. Do not use plates with white wells, since the autofluorescence from the white surface will create significant noise.
In Cell Western assays require sterile plates for tissue culture growth. The following plates are recommended by LI-COR Biosciences:
96 well format Nunc%26#8482; (Part Number 161093, 165305)96 well format Falcon%26#8482; (Part Number 353075, 353948)
384 well format Nunc%26#8482; (Part Number 164688, 164730)384 well format Falcon%26#8482; (Part Number 353961, 353962)
The Odyssey Imager requires that microplates have a maximum 4.0 mm distance from the Odyssey scanning surface to the target detection area of the plate. When using the plates specified above for In-Cell Western assays, the recommended focus offset is 3.0 mm.
If you use plates other than those recommended above, the focus offset can be determined by scanning a plate containing experimental and control samples at 0.5, 1.0, 2.0, 3.0, and 4.0 mm focus offsets. Use the same intensity settings for each scan. After reviewing the collected scans, use the focus offset with the highest signal-to-noise as your focus offset for experiments.
Protect plates from light before imaging to ensure highest sensitivity. When storing plates after imaging, the plates should remain protected from light at room temperature or 4 °C.
Intensity for both 700 and 800 nm channels should be set to 5 for initial scanning. If your image signal is saturated or too high, re-scan using a lower intensity setting (i.e., 2.5). If your image signal is too low, re-scan using a higher intensity setting (i.e., 7.5).
Scan settings of medium to lowest quality, with 169 %26micro;m resolution, provide satisfactory results with minimal scan time. Higher scan quality or resolution may be used, but scan time will increase.
Establish the specificity of your primary antibody by screening lysates through Western blotting and detection on the Odyssey instrument. If significant non-specific banding is present, choose alternative primary antibodies. Non-specific binding of primaries will complicate interpretation of In-Cell Western assay results.
IV. Experimental Results
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| Figure 1. Dose response of HeLa cells to epidermal growth factor (EGF) as measured by specific antibody detecting dual-phosphorylated ERK (Thr202/Tyr204). The image represents a 96-well two color In-Cell Western with the 800 and 700 channels detecting total and phosphorylated ERK, respectively. Background wells were incubated with secondary antibody but no primary antibody. The graph represents normalized quantitative data demonstrating the percent phosphorylation of ERK. |
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