Identification of pharmacological chaperones for follicle-stimulating hormone receptor variants

Abstract

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, stabilizing folding and “rescuing” cell surface expression. We previously demonstrated rescue of cell surface expression of luteinizing hormone receptor mutants by an allosteric agonist.

In order to achieve this, a mammalian expression vector encoding epitope-tagged wild-type WT) FSHR was modified to introduce nineteen identified FSHR variants described in patients with reproductive dysfunction. These vectors were transiently transfected into HEK 293-T cells and functionality of the variant receptors in response to FSH was examined by receptor signalling assays, while cell surface and total cellular expression/localisation of the variants was examined by receptor enzyme-linked immunosorbent assay (ELISA) and confocal microscopy, before and after treatment with LHR-Chap and the selection of FSHR small molecule agonists. In all cases, results for the variant receptors were compared to the WT receptor.

In summary, this study demonstrated a cohort of FSHR-selective small-molecules to act as PCs, and gives rise to the idea that employing such substances therapeutically can aid in treating reproductive dysfunction and infertility in patients who harbour class II (and also potentially class II and class IV) variant FSHRs (and also provides further proof-of-principle to support the identification of other therapeutically useful PCs targeting other GPCRs). As a prelude to further therapeutic development, it would also be interesting to see if findings from this in vitro study can be replicated in vivo, using transgenic mouse models harbouring variant FSHRs.