Assay methods and compositions useful for measuring the transduction of an intracellular signal

A method for identifying compounds that modulate cell surface protein-mediated activity by detecting intracellular transduction of a signal generated upon interaction of the compound with the cell surface protein, comprising:

• comparing the amount of transcription of a reporter gene or the amount of reporter gene product expressed in a first recombinant cell in the presence of the compound with the amount of transcription or product in the absence of the compound, or with the amount of transcription or product in a second recombinant cell;
• and
• selecting compounds that change the amount of transcription of a reporter gene or the amount of reporter gene product expressed in the first recombinant cell in the presence of the compound compared to the amount of transcription or product in the absence of the compound, or compared to the amount of transcription or product in the second recombinant cell, wherein:
• the cell surface protein is a surface receptor or ion channel;
• the first recombinant cell contains a reporter gene Construct and expresses the cell surface protein;
• the second recombinant cell is identical to the first recombinant cell, except that it does not express the cell surface protein;
• and
• the reporter gene constructs contains:
• (a) a transcriptional control element that is responsive to the intracellular signal that is generated by the interaction of an agonist with the cell surface protein;
• and
• (b) a reporter gene that encodes a detectable transcriptional or translational product and that is in operative association with the transcriptional control element.