Expression of a novel follicle-stimulating hormone glycoform relating to fertility

Abstract

LH) and follicle-stimulating hormone (FSH), play significant roles in follicular development and maintenance of the estrous cycle. FSH specifically functions to stimulate follicle growth, estrogen synthesis and serve as a selection factor for dominant follicles, which are essential to maintain fertility. FSH exists in two glycoforms: diglycosylated FSH (DiGlycFSH) and tetraglycosylated FSH (TetGlycFSH). The DiGlycFSH contains carbohydrates on the α subunit only, while TetGlycFSH has carbohydrates on both α and β subunits. Pituitary extraction of FSH shows that in young reproductive age women, the DiGlycFSH is more abundant than TetGlycFSH, whereas post menopausal women have more pituitary TetGlycFSH. Bioassay of DiGlycFSH shows that it has greater biological activity than TetGlycFSH. Due to limited availability of DiGlycFSH, bacterial expression of recombinant human (h)FSH (rec hFSH) is needed to provide sufficient glycoform for structural and biological studies. We report our efforts towards synthesis of DiGlycFSH, which involves expression of rec hFSHβ, separation, purification from soluble and insoluble fractions, folding, and reassociation with human chorionic gonadotropin (hCGα). Protein function will be characterized by receptor binding and steroidogenesis assays.