Role of glycosylation in function of follicle-stimulating hormone

The oligosaccharide structures of heterodimeric glycoprotein hormones, such as follicle-stimulating hormone (FSH), have been shown to play an importan t role in the biosynthesis, secretion, metabolic fate, and regulation of po tency of the hormone. The oligosaccharide structures attached to each subun it of the protein seem to exhibit distinct roles in some of these functions , Glycans attached to the alpha-subunit are critical for dimer assembly, in tegrity, and secretion, as well as for signal transduction; although beta-s ubunit glycans are also important for dimer assembly and secretion, they pl ay a crucial role in clearance of the dimer from the circulation. Alternati ve glycosylation on FSH and other glycoprotein hormones not only may affect the metabolic clearance and net in vivo biopotency of the hormone, but als o offers the interesting possibility that some glycosylation variants of th e hormone may provoke differential or even unique effects at the target cel l level. Glycosylation of FSH is regulated by hypothalamic and/or end produ cts from the glands under the control of this hormone. In particular, estro gens regulate terminal sialylation and thus some functional properties of t he gonadotropin influenced by sialic acid. Through these extrapituitary inp uts, the gonadotroph may regulate not only the amount but also the intensit y of the gonadotropin signal to be secreted by the pituitary in a given phy siological condition.