Date of Award

6-2019

Document Type

Open Access

Degree Name

Bachelor of Science

Department

Biochemistry

First Advisor

Brian Cohen

Keywords

FSH, GPCR, Infertility, Endocrinology, Caveolin, Lipid Rafts, CANDLES

Abstract

Over twelve percent of women aged fifteen to forty-five in America suffer from infertility and/or impaired fecundity and over seven million women have used infertility services, such as intrauterine insemination and in vitro fertilization. Some cases of infertility may be due to dysfunctional human follicle stimulating hormone (hFSH) signaling. hFSH plays a role in spermatogenesis in males, as well as follicle maturation and estrogen production in females. Problems with either hFSH or the hFSH receptor (hFSHR) decrease fertility in males and cause complete infertility in females. As part of the hypothalamic-pituitary-gonadal axis, hFSH is released from the pituitary gland and binds to hFSHR in the ovaries and testes.

It has been shown that hFSHR interacts with lipid rafts, stiffer regions of the plasma membrane with higher sphingolipid and cholesterol concentrations, and with caveolin, a protein found in certain lipid rafts. This interaction may occur through a specific sequence of amino acids in the 4th transmembrane domain of the hFSHR consistent with a caveolin interaction motif (CIM). Previous work from our lab also suggested that hFSHR signaling is regulated through residency in lipid rafts, such that hFSHR signaling is inhibited as a result of recruitment into lipid rafts.

The current study investigated the effect of mutations of the CBM and of MBCD treatment on hFSHR signaling. It was hypothesized that complex mutation of the CBM would cause increased hFSHR signaling by disrupting interactions with caveolin, preventing inhibition via residency in lipid rafts. Mutants were created using site-directed mutagenesis and expression vectors were transiently transfected into HEK293 cells and hFSHR signaling was qualitatively compared between mutants via western blot. Mutation of two sites in the CBM resulted in increased basal and induced hFSHR signaling. It was also hypothesized that MBCD treatment would lead to increased signaling, but an EPAC-based FRET assay found that cholesterol depletion decreased hFSHR signaling to near nothing. Further understanding of hFSHR signaling regulation would allow for development of new fertility treatments for men and women.

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