Novel Cell-Based Phosphodiesterase Assays

A method for identifying a compound that modulates phosphodiesterase (PDE) activity, comprising:

• (a) providing a cell that expresses:
• a phosphodiesterase (PDE) protein;
• a cyclic nucleotide gated (CNG) channel protein;
• and
• an exogenous G protein coupled receptor (GPCR) protein that increases the level of cyclic nucleotide production in the absence of external stimulation of intracellular cyclic nucleotide production;
• wherein the increased level of cyclic nucleotide produced by the said exogenous GPCR protein does not activate said CNG channel in the absence of either external stimulation of intracellular cyclic nucleotide production, an inhibitor of said PDE, or both;
• (b) contacting said cell, in the absence of external stimulation of intracellular cyclic nucleotide production, with a compound that putatively modulates the activity of said PDE;
• and
• (c) measuring activity of said CNG channel, wherein the activity of said CNG channel is indicative of changes in cellular concentration of a cyclic nucleotide;
• thereby identifying whether said compound modulates the activity of said PDE.

A cell comprising:

• a phosphodiesterase (PDE) protein;
• a cyclic nucleotide gated (CNG) channel;
• and
• an exogenous G protein coupled receptor (GPCR) protein that increases the level of intracellular cyclic nucleotide production in the absence of external stimulation of intracellular cyclic nucleotide production,
• wherein activation of said CNG channel is not detected in the absence of an inhibitor of said PDE and wherein activation of said CNG channel is detected in the presence of an inhibitor of said PDE.