Total-cRaf assay principle

The Total cRaf assay quantifies the expression level of cRaf in a cell lysate. Unlike Western Blot, the assay is entirely plate-based and does not require gels, electrophoresis, or transfer. The Total cRaf assay uses two labeled antibodies, one coupled to a donor fluorophore and the other to an acceptor. Both antibodies are highly specific for a distinct epitope on the protein. In the presence of eNOS in a cell extract, the addition of these conjugates brings the donor fluorophore into close proximity with the acceptor and thereby generates a FRET signal. Its intensity is directly proportional to the concentration of the protein present in the sample, and provides a means of assessing the protein's expression under a no-wash assay format.

TotalcRaf two-plate assay protocol

The two-plate protocol involves culturing cells in a 96-well plate before lysis. Then lysates are transferred into a 384-well low volume detection plate before the addition of HTRF Total cRaf detection reagents. This protocol enables the cells' viability and confluence to be monitored.

Total cRaf one-plate assay protocol

Detection of Total eNOS with HTRF reagents can be performed in a single plate used for culturing, stimulation, and lysis. No washing steps are required. This HTS designed protocol enables miniaturization while maintaining robust HTRF quality.

Total and phospho c-RAF (S43) detection in TPA-stimulated HeLa cells

HeLa cells were plated under 100 µl in a 96-well plates (100,000 cells/well) in complete culture medium and incubated overnight at 37°C, 5% CO2. The day after, medium was removed and 50 µl of serum-free culture medium was added to starve cells for 5h at 37°C, 5% CO2. Then cells were treated with 50 µl of increasing concentrations of TPA for 15 min at 37°C, 5% CO2.

After medium removal, cells were then lysed with 50 µL of supplemented lysis buffer #2 for 30 minutes at RT under gentle shaking, and 16 µL of lysate were transferred into a low volume white microplate before the addition of 4 µL of the premixed HTRF phospho-cRaf (Ser43) or Total-cRaf detection reagents. The HTRF signal was recorded after ON incubation.

Total and phospho c-RAF (S43) detection in TPA-stimulated HEK293T cells

HEK293T cells were plated under 100 µl in a 96-well plates (100,000 cells/well) in complete culture medium and incubated overnight at 37°C, 5% CO2. The day after, medium was removed and 50 µl of serum-free culture medium was added to starve cells for 5h at 37°C, 5% CO2. Then cells were treated with 50 µl of increasing concentrations of TPA for 15 min at 37°C, 5% CO2.

After medium removal, cells were then lysed with 50 µL of supplemented lysis buffer #2 for 30 minutes at RT under gentle shaking, and 16 µL of lysate were transferred into a low volume white microplate before the addition of 4 µL of the premixed HTRF phospho-cRaf (Ser43) or Total-cRaf detection reagents. The HTRF signal was recorded after ON incubation.

Function and regulation of RSK1

RAF proto-oncogene serine/threonine-protein kinase (c-RAF) is par of the MAP kinases pathway where it links the upstream effector Ras to the downstream MAPK/ERK cascade. It therefore pays roles in cell fate decisions including proliferation, differentiation, apoptosis, survival and oncogenic transformation.

c-RAF is activated by Ser338 phosphorylation as a direct or indirect effect of PKC, or by GTP-bound Ras directly. Inactivation is ensured by the phosphorylation at Ser43 via MAPK/ERK-dependent feedback.