HTRF Human & Mouse Total VASP Detection Kit, 500 Assay Points

Total-VASP assay principle

The Total-VASP assay quantifies the expression level of VASP in a cell lysate. Contrary to Western Blot, the assay is entirely plate-based and does not require gels, electrophoresis or transfer. The Total-VASP assay uses two labeled antibodies: one coupled to a donor fluorophore, the other to an acceptor. Both antibodies are highly specific for a distinct epitope on the protein. In presence of VASP 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.

Total-VASP 2-plate assay protocol

The 2 plate protocol involves culturing cells in a 96-well plate before lysis then transferring lysates to a 384-well low volume detection plate before adding Total-VASP HTRF detection reagents. This protocol enables the cells' viability and confluence to be monitored.

Total-VASP 1-plate assay protocol

Detection of total VASP 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.

HTRF assay compared to western blot using total VASP assay on mouse NIH3T3 cells

Validation on A431cells treated with forskolin

Human A431 cells were plated at 100,000 cells/well in a 96 well plate, and incubated for 24h at 37°C, 5% CO2. After treatment for 30 min with increasing concentrations of Forskolin, the medium was removed and the cells were lysed with 60 µL of lysis buffer for 30min at RT under gentle shaking. 16 µL of lysate were transferred into a 384-well low volume white microplate and 4 µL of the HTRF phospho-VASP (Ser157), phosphor-VASP (S239) or total VASP detection reagents were added. The HTRF signal was recorded after an overnight incubation.

Validation on NIH3T3 cells treated with forskolin

Mouse NIH3T3 cells were plated at 100,000 cells/well in a 96 well plate, and incubated for 24h at 37°C, 5% CO2. After treatment for 30 min with increasing concentrations of Forskolin, the medium was removed and the cells were lysed with 60 µL of lysis buffer for 30 min at RT under gentle shaking. 16 µL of lysate were transferred into a 384-well low volume white microplate and 4 µL of the HTRF phospho-VASP (Ser157), phosphor-VASP (S239) or total VASP detection reagents were added. The HTRF signal was recorded after an overnight incubation.

Function and regulation of VASP

Vasodilator-stimulated phosphoprotein (VASP) is an actin-associated protein and a member of the Ena-VASP family. VASP stimulates actin filament elongation, and is involved in cytoskeleton remodeling and cell polarity. VASP proteins are involved in axon guidance, platelet activation and cell migration. In platelets, VASP is a major substrate for cAMP-dependent protein kinase A (PKA) and cGMP-dependent protein kinase G (PKG). Whereas the preferred site for PKA is Ser-157, the preferred site for PKG is Ser-239. Phosphorylation modulates F-actin binding, actin filament elongation and platelet activation. VASP phosphorylation is often used to monitor the effect of drugs that reduce platelet reactivity in cardiovascular diseases.