Zona-Binding Inhibitory Factor-1 from Human Follicular Fluid Is an Isoform of Glycodelin1

Abstract

Zona-binding inhibitory factor-1 (ZIF-1), a glycoprotein in human follicular fluid, reduces the binding of spermatozoa to the zona pellucida. ZIF-1 has a number of properties similar to those of glycodelin-A from human follicular fluid. The objective of this study was to compare the biochemical characteristics of these two glycoproteins. N-terminal sequencing and protease-digested peptide mapping showed that ZIF-1 and glycodelin-A have the same protein core. However, these glycoproteins differ in their oligosaccharide chains, as demonstrated by fluorophore-assisted carbohydrate electrophoresis, lectin-binding ability, and isoelectric focusing. ZIF-1 inhibited spermatozoa-zona pellucida binding slightly more than did glycodelin-A and significantly suppressed progesterone-induced acrosome reaction of human spermatozoa. Indirect immunofluorescence staining revealed specific binding of glycodelin-A and ZIF-1 to the acrosome region of human spermatozoa, where ZIF-1 produced a stronger signal than did glycodelin-A at the same protein concentration. These data suggest that ZIF-1 is a differentially glycosylated isoform of glycodelin that potently inhibits human sperm-egg interaction. Future study on the function role of ZIF-1 would provide a better understanding of the regulation of fertilization in humans.

Glycodelin-S in Human Seminal Plasma Reduces Cholesterol Efflux andInhibits Capacitation ofSpermatozoa

“…There are two binding sites for GdS; a low and a high affinity binding site. Three observations indicate that, on human spermatozoa, these binding sites are different from those of GdA and GdF (8,12). First, the affinity of GdS to spermatozoa is much lower than that of GdF.…”

“…The concentration of GdS used was physiological in human seminal plasma (13). Monoclonal anti-glycodelin antibody (clone F43-7F9) recognizing the protein core of glycodelins was used to determine glycodelin immunoreactivity in the spermatozoa from the three aliquots as described (8). The staining was observed with an excitation filter BP 450 -490, chromatic beam splitter FT510, and barrier filter LP520.…”

“…Its absence in the endometrium in the periovulatory period is related to the presence of a fertilization window (6). GdF also inhibits spermatozoa-ZP binding (8). GdF, but not the other glycodelin isoforms, suppresses progesterone-induced acrosome reaction (8,12), suggesting that it may protect spermatozoa from premature acrosome reaction before binding to the ZP.…”

“…GdF also inhibits spermatozoa-ZP binding (8). GdF, but not the other glycodelin isoforms, suppresses progesterone-induced acrosome reaction (8,12), suggesting that it may protect spermatozoa from premature acrosome reaction before binding to the ZP. Glycodelin-S does not adversely affect spermatozoa-zona binding (6), and its action on spermatozoa is not clear.…”

“…There are three putative N-glycosylation sites at Asn-28, Asn-63, and Asn-85, of which the first two are glycosylated (7). There are three known isoforms of glycodelin, amniotic fluid glycodelin (glycodelin-A, GdA), follicular fluid glycodelin (glycodelin-F, GdF) and seminal plasma glycodelin (glycodelin-S, GdS) (6,8). The three isoforms have an identical protein backbone, but their glycosylation profiles are different (6,8).…”