| Assay Method Information | |
| | High Throughput Screening Assay |
| Description: | The commercially available HEK293/TREx line (Invitrogen) was stably transfected with a TRPC5 construct and screened by conventional calcium imaging to find clones with TRPC5 expression following stimulation with 1 μg/ml tetracycline. These cells were maintained in the growth medium recommended by the manufacturer supplemented with 100 μg/ml hygromycin to promote retention of the TRPC5 construct. After growing to near confluency, cells were plated at a density of 35,000 cells/well in 384 well CellBind plates (Corning) in the presence of 1 μg/ml tetracycline, and allowed to grow for 20-30 hrs. A nearly confluent monolayer resulted. Cells were then loaded with Ca2+ dye: Fura-2/AM or Fluo4/AM was added to the wells to a final concentration of 4 μM or 0.5 μM, respectively, and incubated for 80 min or 60 min, respectively, at room temperature. Supernatant was then removed from the cells by inverting plates with a sharp flick, and 25 μl Hank's Balanced Salt Solution (HBSS; 0.185 g/l D-glucose, 0.9767 g/l MgS04 (anhydrous), 0.4 g/l KCl, 0.06 g/l KH2PO4 (anhydrous), 0.35 g/l NaHCO3, 8.0 g/l NaCl, and 0.04788 g/l Na2HPO4 (anhydrous); pH 7.4) was then added to each well. Following 0.5 hour for recovery from loading, cells were assayed using the Hamamatsu FDSS 6000 system, which permitted illumination alternately at 340 nm and 380 nm for Fura-2 experiments, or at 485 nm for Fluo4 experiments. Frames were acquired at a rate of 0.2 Hz. During the assay, the plates were continuously vortexed, with pipette mixing of wells following addition of each reagent. For the screening assay, 26 μl of a diluted compound stock (at 50 μM) was added to each well for 2 minutes following the collection of a short (4 frame) baseline. 13 μl 62 mM high-Ca2+Ringer solution (4.17 ml of normal ringer (with 2 mM Ca2+) plus 5.83 ml of isotonic calcium ringer (105 mM Ca2+; in this ringer all sodium has been replaced with calcium)) was then added to each well, achieving a final concentration of 14 mM Ca2+ and 10 μM test compound. Data was collected for 3 minutes following addition of high Ca2+Ringer, where the fluorescent intensity (for Fluo4) and the F340/F380 ratio (for Fura-2) were proportional to the [Ca2+]i Negative controls consisted of HEK293/TREx TRPC5 cells exposed to high Ca2+ solution, but no compound. Positive control conditions consisted of addition of 2-APB, a promiscuous blocker of TRPC5 and other channels, to columns 23 and 24 of the plates, to a final concentration of 200 μM. The Fluo4 cell-based fluorescence assay was used to determine the intracellular Ca2+ concentration in the presence of varying drug concentration. Final concentrations of compounds tested were 20 μM, 6.667 μM, 2.222 μM, 0.741 μM, 0.247 μM, 0.082 μM, and 0.027 μM. Compounds were tested in triplicate at all concentrations. |
| Affinity data for this assay | |
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