Phospho-TAU (Ser202/Thr205) cellular kit HTRF®

The Phospho-TAU (Ser202/Thr205) assay measures TAU when phosphorylated at Ser202/Thr205. Unlike Western Blot, the assay is entirely plate-based and does not require gels, electrophoresis, or transfer.

The Phospho-TAU (Ser202/Thr205) assay uses 2 labeled antibodies: one with a donor fluorophore, the other with an acceptor. The first antibody is selected for its specific binding to the phosphorylated motif on the protein, and the second for its ability to recognize the protein independently of its phosphorylation state. Protein phosphorylation enables an immune-complex formation involving both labeled antibodies, and which brings the donor fluorophore into close proximity to the acceptor, thereby generating a FRET signal. Its intensity is directly proportional to the concentration of phosphorylated protein present in the sample, and provides a means of assessing the protein’s phosphorylation state under a no-wash assay format.

50,000 human SH-SY5Y cells were plated in 96-well plates and incubated for 72h at 37 °C - 5% CO2.

After incubation with increasing concentrations of GSK3 inhibitors (CHIR99021 and BIO) for 3 hours, medium was removed and cells were lysed with 50µl of lysis buffer for 30min at RT under gentle shaking. 16 µL of lysate were transferred into a 384-well sv white microplate, and 4 µL of the HTRF phospho-TAU (Ser202/Thr205) detection reagents were added.

The HTRF signal was recorded after an overnight incubation.

50,000 human SH-SY5Y cells were plated in 96-well plates and incubated for 72h at 37 °C - 5% CO2. Medium was removed and cells were lysed with 50µl of lysis buffer for 30min at RT under gentle shaking.

Alcaline phosphatase (25U) was added with the appropriate buffer and removed 1 hour later. 16 µL of lysate were transferred into a 384-well sv white microplate, and 4 µL of the HTRF phospho-TAU (Ser202/Thr205) detection reagents were added. The HTRF signal was recorded after an overnight incubation.

50,000 human SH-SY5Y cells were plated in 96-well plates and incubated for 72h at 37 °C - 5% CO2. The SH-SY5Y cells were then treated with the GSK3 inhibitor, BIO, for 3 hours. After cell culture medium removal, cells were lysed with 50µl of lysis buffer for 30min at RT under gentle shaking. 16 µL of lysate were transferred into a 384-well sv white microplate, and 4 µL of the HTRF phospho-TAU (Ser202/Thr205) and α-tubulin detection reagents were added.

The HTRF signal was recorded after an overnight incubation.

Human SH-SY5Y cells were grown in a T175 flask at 37 °C, 5% CO2 until 80% confluency. Cell culture medium was discarded, and cells were lysed with 3 mL of supplemented lysis buffer for 30 min at room temperature. Soluble fractions were then collected after a 10 min centrifugation. Serial dilutions of the cell lysate were performed in the supplemented lysis buffer, and then 16 µL of each dilution were dispensed and analyzed side-by-side by Western Blot and by HTRF.

Using the HTRF phospho-TAU (Ser202/Thr205) cellular assay, just 2,500 cells were sufficient for minimum signal detection, while 5,000 cells were needed for a Western Blot signal. The HTRF cellular assays are at least 2-fold more sensitive than the Western Blot.

TAU has a prominent role in the pathogenesis of Alzheimer's disease. It becomes hyperphosphorylated and aggregates, forming filaments, which can further condense into neurofibrillary tangles. TAU aggregates may propagate pathology by spreading from cell to cell in a prion-like manner. Drugs modulating TAU hyperphosphorylation and reducing TAU aggregation are viable therapeutic approaches.

The physiological role of TAU protein is to promote assembly and stability of microtubules. Six isoforms of TAU have been described, ranging from 352 to 441 residues coming from exons 2, 3 and 10, that are alternatively spliced. The longest isoform of TAU (TAU-441) contains 85 putative phosphorylation sites, half of which have been confirmed experimentally.