C/EBP Homologous Protein (CHOP), also known as DDIT3, is a stress-inducible transcription factor primarily activated during endoplasmic reticulum (ER) stress. It is primarily activated through the unfolded protein response (UPR), particularly downstream of the PERK–eIF2α–ATF4 signaling axis. CHOP promotes apoptosis when ER stress is severe or prolonged, by upregulating pro-apoptotic genes, repressing anti-apoptotic factors such as BCL2, and modulating oxidative stress pathways. Elevated CHOP expression is implicated in various diseases, including neurodegeneration, metabolic disorders, and cancer. In tumors, CHOP can either suppress or promote tumorigenesis depending on the context, making it a nuanced target for therapeutic intervention.
The AlphaLISA SureFire Ultra Human and Mouse Total CHOP Detection Kit is a sandwich immunoassay for the quantitative detection of total CHOP 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.
AlphaLISA SureFire Ultra kits are compatible with:
Cell and tissue lysates
Antibody modulators
Biotherapeutic antibodies
AlphaLISA SureFire Ultra kits can be used for:
Cellular kinase assays
Receptor activation studies
High-throughput screening for preclinical studies
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.
Induction of CHOP expression in Thapsigargin treated cells
A549 cells were seeded in a 96-well plate (40,000 cells/well) in complete medium and incubated overnight at 37°C, 5% CO2. The cells were treated with increasing concentrations of Thapsigargin for 4 hours.
After treatment, the cells were lysed with 100 µL of Lysis Buffer for 10 minutes at RT with shaking (350 rpm). CHOP and Cofilin Total levels were evaluated using respective AlphaLISA SureFire Ultra assays. For the detection step, 10 µL of cell lysate (approximately 4,000 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, Thapsigargin triggered a dose-dependent increase in the levels of CHOP while Cofilin levels remained unchanged.
Induction of CHOP expression in Thapsigargin treated cells
RAW 264.7 cells were seeded in a 96-well plate (40,000 cells/well) in complete medium and incubated overnight at 37°C, 5% CO2. The cells were treated with increasing concentrations of Thapsigargin for 4 hours.
After treatment, the cells were lysed with 100 µL of Lysis Buffer for 10 minutes at RT with shaking (350 rpm). CHOP and Cofilin Total levels were evaluated using respective AlphaLISA SureFire Ultra assays. For the detection step, 10 µL of cell lysate (approximately 4,000 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, Thapsigargin triggered a dose-dependent increase in the levels of CHOP, while Cofilin levels remained unchanged.
Induction of CHOP expression in Tunicamycin treated cells
A549 cells were seeded in a 96-well plate (40,000 cells/well) in complete medium and incubated overnight at 37°C, 5% CO2. The cells were treated with increasing concentrations of Tunicamycin for 4 hours.
After treatment, the cells were lysed with 100 µL of Lysis Buffer for 10 minutes at RT with shaking (350 rpm). CHOP and Cofilin Total levels were evaluated using respective AlphaLISA SureFire Ultra assays. For the detection step, 10 µL of cell lysate (approximately 4,000 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, Tunicamycin triggered a dose-dependent increase in the levels of CHOP, while Cofilin levels remained unchanged.
Induction of CHOP expression in Tunicamycin treated cells
RAW 264.7 cells were seeded in a 96-well plate (40,000 cells/well) in complete medium and incubated overnight at 37°C, 5% CO2. The cells were treated with increasing concentrations of Tunicamycin for 4 hours.
After treatment, the cells were lysed with 100 µL of Lysis Buffer for 10 minutes at RT with shaking (350 rpm). CHOP and Cofilin Total levels were evaluated using respective AlphaLISA SureFire Ultra assays. For the detection step, 10 µL of cell lysate (approximately 4,000 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, Tunicamycin triggered a dose-dependent increase in the levels of CHOP while Cofilin levels remained unchanged.
Expression of CHOP in various cell lines
Adherent cells were seeded at 40,000 cells/well in a 96-well culture plate in complete medium and incubated overnight at 37°C, 5% CO2. Cells were lysed with 100 µL of Lysis Buffer.
Suspension cells were seeded at 400,000 cells/well in a 96-well culture plate in HBSS + 0.1% BSA, cells were spun down and lysed with 100 µL of Lysis Buffer.
CHOP Total levels were evaluated by AlphaLISA SureFire Ultra. For the detection step, 10 µL of cell lysate (approximately 4,000 adherent cells or 40,000 suspension 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.
High CHOP expression was observed in THP-1, Caco-2 and NIH/3T3 cells.
