Investigating the Role of CRAC in FSH Receptor Function and Structure

Abstract

Human infertility is a complex disorder that can often be attributed to a dysfunction of the endocrine system. Follicle‐stimulating hormone (FSH) is one of many hormones that participate in a complex process in both women and men to regulate normal reproduction. The dysfunction of this hormone and its receptor are some of the many causes of infertility. FSH is secreted by the anterior pituitary and, in women, initiates a cascade of biological events that enable ovulation. FSH carries out its function by binding and activating specific receptors. The FSH receptor (FSHR) is a G protein‐coupled receptor (GPCR) that is located in the cell membrane of target cells in the ovaries and testes. GPCRs often interact with a variety of molecules beyond their ligands including, in some cases, cholesterol in the plasma membrane. The Cholesterol Recognition/Interaction Amino Acid Consensus Sequence (CRAC) is one such binding domain and is represented by the sequence LV‐XXXX‐Y‐XXXXX‐K/R. The human FSHR contains a sequence consistent with the CRAC motif in the first intracellular loop L‐TTLQ‐Y‐KLTVP‐R. We hypothesized that mutating this domain will negatively affect the signaling of the receptor upon ligand activation. To test this hypothesis tyrosine 375 was mutated to phenylalanine (Y375F) which should render the CRAC inactive. After establishing a cell line stably expressing the mutant receptor, activation of the p44/42 (ERK1/2) pathway was measured. Preliminary data suggest that signaling of the hFSHR‐Y375F mutant is decreased relative to the wild‐type receptor. As we learn more about this receptor, we continue to gain knowledge about conditions such as infertility. This information can facilitate the development of innovative treatments which can help many families who struggle to conceive.