Rescue of cell surface expression and signalling of mutant follicle-stimulating hormone receptors

Mutations in G protein-coupled receptors (GPCRs) underlie numerous diseases. Many cause receptor misfolding and failure to reach the cell surface. Pharmacological chaperones are cell-permeant small-molecules that engage nascent mutant GPCRs in the endoplasmic reticulum, stabilising folding and ‘rescuing’ cell surface expression. We previously demonstrated rescue of cell surface expression of luteinising hormone receptor mutants by an allosteric agonist. Here we demonstrate that a similar approach can be employed to rescue mutant follicle-stimulating hormone receptors (FSHRs) with poor cell surface expression using a small-molecule FSHR agonist, CAN1404. Seventeen FSHR mutations described in patients with reproductive dysfunction were expressed in HEK 293T cells and cell surface expression was determined by ELISA of epitope-tagged FSHRs before/after treatment with CAN1404. Cell surface expression was severely reduced to ≤18% of wild-type (WT) for eleven, modestly reduced to 66–84% of WT for four and was not reduced for two. Of the eleven with severely reduced cell surface expression, restoration to ≥57% of WT levels was achieved for six by treatment with 1 µM CAN1404 for 24 h and a corresponding increase in FSH-induced signalling was observed for four of these, indicating restored functionality. Therefore, CAN1404 acts as a pharmacological chaperone and can rescue cell surface expression and function of certain mutant FSHRs with severely reduced cell surface expression. These findings aid in advancing the understanding of the effects of genetic mutations on GPCR function and provide a proof of therapeutic principle for FSHR PCs.