33P-Based Assay: The biochemical EC50 (half-maximal concentration required for full activation) of compounds for the activation of AMPK was evaluated by 33P-based assay using SAMS peptide (commercially available) derived from ACC-1. Twenty μl of phosphorylated AMPK diluted in assay buffer, (50 mM HEPES, 1 mM EGTA, 10 mM MgCl2, 0.25 mM DTT, 0.01% Tween-20, 0.01% BSA (pH 7.5)) was added to 384 well plates containing 1 μL of test compound. Following a fifteen minute room temperature incubation, 10 μL of protein phosphatase PP2A was added to the plate to dephosphorylate pThr172 of AMPK. After incubation for 90 minutes, 10 μL of substrate mixture containing 41 nM okadaic acid, 82 μM SAMS peptide, 82 μM ATP and tracer amounts (6.8 nM) of 33P-containing ATP was added to the plate. The reaction was terminated after 60 minutes incubation at room temperature by the addition of 15 μL of 2% H3PO4. Subsequently, 45 μl of reaction mix was transferred to 384 well Millipore MZPH filter plates (MZPHNO50) pre-treated with 25 μL of 2% H3PO4 and the plates were washed three times with assay buffer. 20 μL of Ready Safe scintillation fluid was added to dried plates followed by detection on the Trilux detector.
Substrate activity at human OAT3 expressed in HEK293 cells assessed as ratio of compound uptake in human OAT3 transfected HEK293 cells to uptake in vector-treated HEK293 cells at 1 uM after 3 mins by LC-MS analysis
Substrate activity at rat OAT3 expressed in HEK293 cells assessed as ratio of compound uptake in rat OAT3 transfected HEK293 cells to uptake in vector-treated HEK293 cells at 1 uM after 3 mins by LC-MS analysis
Substrate activity at human OAT1 expressed in HEK293 cells assessed as ratio of compound uptake in human OAT1 transfected HEK293 cells to uptake in vector-treated HEK293 cells at 1 uM after 3 mins by LC-MS analysis