Therapeutic rescue of misfolded/mistrafficked mutants: automation-friendly high-throughput assays for identification of pharmacoperone drugs of GPCRs.

Mutations cause protein folding defects that result in cellular misrouting of otherwise functional proteins. Such mutations are responsible for a wide range of disease states, especially among G-protein coupled receptors. Drugs which serve as chemical templates and promote the proper folding of these proteins are valuable therapeutic molecules since they return functional proteins to the proper site of action. Small molecules have been identified that are able to function as pharmacological chaperones or "pharmacoperones" and stabilize the correct conformations of their target proteins with high specificity. Most of these are also agonists or antagonists of the proteins of interest, complicating potential therapeutic use. This is due, in part, to the fact that the majority of these were discovered during high-throughput screening campaigns using assays designed to detect agonists and antagonists, rather than compounds which improve the trafficking of misrouted mutants. The assays described in this report are designed specifically to identify compounds which result in the reactivation and correct trafficking of misfolded gonadotropin releasing hormone receptor and vasopressin type 2 receptor mutants, rather than those which act as agonists directly. The system reported is a generalizable approach amenable to use in automated (robotic) high-throughput screening efforts and can be used to identify compounds which affect protein conformation without necessarily acting as direct agonists or antagonists.