George R. Bousfield

Biography

Done B.S from Saginaw Valley State College, University Center in  Chemistry & Biology and M.A from Indiana University, Bloomington in Zoology, P.H.D FROM Indiana  University, Bloomington IN   Zoology

Research Interest

My laboratory is interested in the structure-function relations of the gonadotropins. These are members of the glycoprotein hormone family, which consists of the three gonadotropins, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and chorionic gonadotropin (CG). The fourth member of this protein family is thyroid stimulating hormone (TSH). Together, the glycoprotein hormones form a unique subset of the cystine knot growth factor superfamily. While most other superfamily members are located at the C-terminal end of a larger precursor from which they are cleaved, and the N-terminal portion then acts as a regulatory factor, the glycoprotein subunits consist of only the cystine knot domains. The subunits are dissimilar proteins, a common alpha subunit that is differentially glycosylated in each hormone, as well as a hormone-specific beta subunit. Another unusual facet of glycoprotein hormone structure-function is these hormones are decorated with N-linked and sometimes O-linked glycans, which are necessary for function. The glycans can determine metabolic clearance rates of the hormones and at least some of them are necessary for biological activity, although the mechanism is unknown. Glycosylation varies in two ways: microheterogeneity and macroheterogeneity. The former results from a population of 2-105 glycans found at each N- or O-glycosylation site, while the latter results from partial glycosylation of the hormone-specific beta subunit. In humans an interesting pattern of glycosylation is found in FSH. The alpha subunit is always N-glycosylated, while the FSHΒ subunit appears to be glycosylated in an all-or-none manner. This produces a FSH glycoform that possesses four N-glycans that we call tetra-glycosylated hFSH and another form that possesses only the alpha subunit N-glycans that we call di-glycosylated hFSH. In young women, di-glycosylated hFSH is the more abundant glycoform present in the pituitary gland, however, there appears to be a progressive loss of this glycoform with increasing age. We are interested in determining if this can be used as a marker for reproductive aging.