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Assay Method Information

Assay Name:  G-402 cell line assay
Description:  Herein we identified the use of the G-402 cell line as a host cell to ectopically express (transiently or stably) enzymes of the CYP11 family. Specifically we developed stable G-402 cells expressing ectopically human CYP11B1, human CYP11B2, human CYP11A1, cynmolgus CYP11B1 or cynomolgus CYP11B2 enzyme activity. Importantly the identified cell line G-402 expresses co-factors (adrenodoxin and adrenodoxin reductase) important for the activity of the CYP11 family and no relevant enzyme activity of the CYP11 family (in comparison to H295R cells) was detected in these cells. Therefore the G-402 cell line is uniquely suited as a host cell for the ectopic expression of enzymes from the CYP11 family.G-402 cells can be obtained from ATCC (CRL-1440) and were originally derived from a renal leiomyoblastoma.The expression plasmids contains the ORF for either human/cyno CYP11B1 or CYP11B2 under the control of a suitable promoter (CMV-promoter) and a suitable resistance marker (neomycin). Using standard techniques the expression plasmid is transfected into G-402 cells and these cells are then selected for expressing the given resistance markers. Individual cell-clones are then selected and assessed for displaying the desired enzymatic activity using 11-Deoxycorticosterone (Cyp11B2) or 11-Deoxycortisol (Cyp11B1) as a substrate.G-402 cells expressing CYP11 constructs were established as described above and maintained in McCoy's 5a Medium Modified, ATCC Catalog No. 30-2007 containing 10% FCS and 400 μg/ml G418 (Geneticin) at 37 C. under an atmosphere of 5% CO2/95% air. Cellular enzyme assays were performed in DMEM/F12 medium containing 2.5% charcoal treated FCS and appropriate concentration of substrate (0.3-10 uM 11-Deoxycorticosterone, 11-Deoxycortisol or Corticosterone). For assaying enzymatic activity, cells were plated onto 96 well plates and incubated for 16 h. An aliquot of the supernatant is then transferred and analyzed for the concentration of the expected product (Aldosterone for CYP11B2; Cortisol for CYP11B1). The concentrations of these steroids can be determined using HTRF assays from CisBio analyzing either Aldosterone or Cortisol.Inhibition of the release of produced steroids can be used as a measure of the respective enzyme inhibition by test compounds added during the cellular enzyme assay. The dose dependent inhibition of enzymatic activity by a compound is calculated by means of plotting added inhibitor concentrations (x-axes) vs. measured steroid/product level (y-axes). The inhibition is then calculated by fitting the following 4-parameter sigmoidal function (Morgan-Mercer-Flodin (MMF) model) to the raw data points using the least squares method:y = AB + Cx D B + x D wherein, A is the maximum y value, B is the EC50 factor determined using XLFit, C is the minimum y value and D is the slope value.
Affinity data for this assay
 

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Last update November 1, 2007
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