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Assay Method Information

Assay Name:  CHO GLP-1R Clone H6-Assay 1
Description:  GLP-1R-mediated agonist activity was determined with a cell-based functional assay utilizing an HTRF (Homogeneous Time-Resolved Fluorescence) cAMP detection kit (cAMP HI Range Assay Kit; CisBio cat #62AM6PEJ) that measures cAMP levels in the cell. The method is a competitive immunoassay between native cAMP produced by the cells and exogenous cAMP labeled with the dye d2. The tracer binding is visualized by a mAb anti-cAMP labeled with Cryptate. The specific signal (i.e. energy transfer) is inversely proportional to the concentration of cAMP in either standard or experimental sample.The human GLP-1R coding sequence (NCBI Reference Sequence NP_002053.3, including naturally-occurring variant Gly168Ser) was subcloned into pcDNA3 (Invitrogen) and a cell line stably expressing the receptor was isolated (designated Clone H6). Saturation binding analyses (filtration assay procedure) using 125I-GLP-17-36 (Perkin Elmer) showed that plasma membranes derived from this cell line express a high GLP-1R density (Kd: 0.4 nM, Bmax: 1900 fmol/mg protein).Cells were removed from cryopreservation, re-suspended in 40 mL of Dulbecco's Phosphate Buffered Saline (DPBS-Lonza Cat #17-512Q) and centrifuged at 800g for 5 min at 22 C. The cell pellet was then re-suspended in 10 mL of growth medium [DMEM/F12 1:1 Mixture with HEPES, L-Gln, 500 mL (DMEM/F12 Lonza Cat #12-719F), 10% heat inactivated fetal bovine serum (Gibco Cat #16140-071), 5 mL of 100 Pen-Strep (Gibco Cat #15140-122), 5 mL of 100 L-Glutamine (Gibco Cat #25030-081) and 500 μg/mL Geneticin (G418) (Invitrogen #10131035)]. A 1 mL sample of the cell suspension in growth media was counted on a Becton Dickinson ViCell to determine cell viability and cell count per mL. The remaining cell suspension was then adjusted with growth media to deliver 2000 viable cells per well using a Matrix Combi Multidrop reagent dispenser, and the cells were dispensed into a white 384 well tissue culture treated assay plate (Corning 3570). The assay plate was then incubated for 48 hours at 37 C. in a humidified environment in 5% carbon dioxide.Varying concentrations of each compound to be tested (in DMSO) were diluted in assay buffer (HBSS with Calcium/Magnesium (Lonza/BioWhittaker cat #10-527F)/0.1% BSA (Sigma Aldrich cat #A7409-1L)/20 mM HEPES (Lonza/BioWhiftaker cat #17-737E) containing 100 μM 3-isobutyl-1-methylxanthin (IBMX; Sigma cat #15879). The final DMSO concentration is 1%.After 48 hours, the growth media was removed from the assay plate wells, and the cells were treated with 20 μL of the serially diluted compound in assay buffer for 30 minutes at 37 C. in a humidified environment in 5% carbon dioxide. Following the 30 minute incubation, 10 μL of labeled d2 cAMP and 10 μL of anti-cAMP antibody (both diluted 1:20 in cell lysis buffer; as described in the manufacturer's assay protocol) were added to each well of the assay plate. The plates were then incubated at room temperature and after 60 minutes, changes in the HTRF signal were read with an Envision 2104 multi-label plate reader using excitation of 330 nm and emissions of 615 and 665 nm. Raw data were converted to nM cAMP by interpolation from a cAMP standard curve (as described in the manufacturer's assay protocol) and the percent effect was determined relative to a saturating concentration of the full agonist GLP-17-36 (1 μM) included on each plate. EC50 determinations were made from agonist dose-response curves analyzed with a curve fitting program using a 4-parameter logistic dose response equation.
Affinity data for this assay
 

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Last update November 1, 2007
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