Human follicle stimulating hormone receptor signaling is membrane cholesterol and internalization dependent (609.16)

Abstract

Human follicle stimulating hormone (hFSH) is a dimeric glycoprotein secreted by the gonadotropic cells of the anterior pituitary that is essential for reproduction. Its receptor, (hFSHR), is a G protein‐coupled receptor expressed on the surface of granulosa cells in females and Sertoli cells in males. FSH stimulates the maturation of ovarian follicles in females and triggers sperm production in males. Based on previous research in our lab, we proposed that hFSHR resides in lipid rafts and/or caveolae on the cell membrane and that its signaling is cholesterol and internalization dependent. To test this hypothesis, we treated HEK‐293 cells stably transfected with human FSHR cDNA with the cholesterol depleting compound methyl‐beta‐cyclodextrin (MBCD) or the anti‐fungal compound Nystatin which alters the selective permeability of the cell membrane by sequestering cholesterol. Western blotting was used to measure the phosphorylation of map kinases p38 and p42/44 (ERK 1/2). MBCD did not alter FSH dependent activation of p44/42 or p38, but a decrease in activation of both signaling components was observed when the cells were treated with Nystatin. Both treatments decreased cAMP dependent activation of the cAMP response element‐binding protein. These results suggest that FSHR signaling is dependent not on cholesterol alone, but also on internalization, which is blocked by Nystatin. This adds to an increasing body of evidence for multivalent hFSHR signaling with the possibility of selective modulation of the pathways.