Description
The AlphaLISA SureFire Ultra total STAT4 assay is a sandwich immunoassay for quantitative detection of total STAT4 (phosphorylated and non-phosphorylated) in cellular lysates using Alpha Technology.
Formats:
The HV (high volume) kit contains reagents to run 100 wells in 96-well format, using a 60 μL reaction volume.
The 500-point kit contains enough reagents to run 500 wells in 384-well format, using a 20 μL reaction volume.
The 10,000-point kit contains enough reagents to run 10,000 wells in 384-well format, using a 20 μL reaction volume.
The 50,000-point kit contains enough reagents to run 50,000 wells in 384-well format, using a 20 μL reaction volume.
In the AlphaLISA SureFire Ultra assay, Donor beads are coated with streptavidin to capture one of the antibodies, which is biotinylated. Acceptor beads are coated with a proprietary CaptSure™ agent that immobilizes the other antibody, labeled with a CaptSure™ tag. In the presence of target protein, the two antibodies bring the Donor and Acceptor beads close together, generating signal. The amount of light emission is directly proportional to the amount of protein present in the sample.
AlphaLISA SureFire Ultra kits are compatible with:
Cell and tissue lysates
Antibody modulators
Biotherapeutic antibodies
Alpha SureFire kits can be used for:
Cellular kinase assays
Receptor activation studies
Screening
Total-AlphaLISA SureFire Ultra assay principle
The Total-AlphaLISA SureFire Ultra assay measures the expression level of a target protein in a biological sample (e.g. cell lysate).
The Total-AlphaLISA SureFire Ultra assay uses two antibodies which recognize two different distal epitopes on the target protein. AlphaLISA assays require two bead types: Acceptor and Donor Beads. Acceptor Beads are coated with a proprietary CaptSure™ agent to specifically immobilize the assay specific antibody, labeled with a CaptSure tag. Donor Beads are coated with streptavidin to capture one of the detection antibodies, which is biotinylated. In the presence of target protein, the two antibodies bring the Donor and Acceptor Beads in close proximity whereby the singlet oxygen transfers energy to excite the Acceptor Bead, allowing for the generation of a luminescent Alpha signal. The amount of light emission is directly proportional to the quantity of protein present in the sample.
Total-AlphaLISA SureFire Ultra two-plate assay protocol
The two-plate protocol involves culturing and treating the cells in a 96-well plate before lysis, then transferring lysates into a 384-well OptiPlate™ plate before the addition of Total-AlphaLISA SureFire Ultra detection reagents. This protocol enables cell viability and confluence to be monitored. In addition, lysates from a single well can be used to measure multiple targets.
Total-AlphaLISA SureFire Ultra one-plate assay protocol
Detection of Total target protein with AlphaLISA SureFire Ultra reagents can be performed in a single plate used for culturing, treatment, and lysis. No washing steps are required. This HTS designed protocol allows for miniaturization while maintaining robust AlphaLISA SureFire Ultra quality.
Validation of STAT4 Total in NK-92 cells
NK-92 cells were seeded in a T175 flask at 500K/mL in complete MEMα medium deprived of IL-2 and incubated overnight. Cells were resuspended in HBSS + 0.1% BSA, seeded in a 96-well plate (500,000 cells/well) and treated with increasing concentrations of IL-12 for 30 minutes.
After treatment, the cells were lysed with the addition of 5X Lysis Buffer for 10 minutes at RT with shaking (350 rpm). STAT4 Phospho (Tyr693) and Total levels were evaluated using respective AlphaLISA SureFire Ultra assays. For the detection step, 10 µL of cell lysate (approximately 20,000 cells) was transferred into a 384-well white OptiPlate, followed by 5 µL of Acceptor mix and incubated for 1 hour at RT. Finally, 5 µL of Donor mix was then added to each well and incubated for 1 hour at RT in the dark. The plate was read on an Envision using standard AlphaLISA settings.
As expected, IL-12 triggered a dose-dependent increase in the levels of STAT4 Phospho (Tyr693) while Total levels remained unchanged.
Versatility of STAT4 Total assay in various cell lines
Adherent cells were grown to confluency in a T175 flask at 37°C, 5% CO2, and were lysed with Lysis Buffer at a density of 0.5 x 106 cells/mL. Suspension cells were harvested, washed in HBSS and lysed with Lysis Buffer at 1.6 x 106 cells/mL.
Total STAT4 levels were evaluated using the AlphaLISA SureFire Ultra High Specificity assay. For the detection step, 10 µL of cell lysate (5,000 adherent and 16,000 suspension cells) were transferred into a 384-well white OptiPlate, followed by 5 µL of Acceptor Mix and incubated for 1 hour at RT. Finally, 5 µL of Donor Mix was then added to each well and incubated for 1 hour at RT in the dark. The plate was read on an Envision using standard AlphaLISA settings.
STAT4 Total expression was detected highly in NK-92 cells.
STAT4 assay sensitivity - cell lysate dilution
Cell lysate was prepared from NK-92 cells IL-2 starved for 18 hours and stimulated with 200 ng/mL IL-12 for 30 minutes in HBSS + 0.1% BSA. Cells were lysed at 3.2 x 106 with the addition of 5X Lysis Buffer for 10 minutes at RT with shaking.
Lysates were serially diluted in Lysis Buffer and assayed for Phospho (Tyr693) and Total STAT4 levels using respective AlphaLISA SureFire Ultra kits. For the detection step, 10 µL of lysate was transferred into a 384-well white OptiPlate, followed by 5 µL of Acceptor mix and incubated for 1 hour at room temperature. Finally, 5 µL of Donor mix was then added to each well and incubated for 1 hour at RT in the dark. The plate was read on an Envision using standard AlphaLISA settings.
Approximate number of cells/datapoint is indicated on the graph. The dotted line represents assay background. The assay can detect STAT4 expression in less than 200 cells/datapoint.
