title: Cumulus oophorus-associated glycodelin-C displaces sperm-bound glycodelin-A and -F and stimulates spermatozoa-zona pellucida binding.
abstract: Spermatozoa have to swim through the oviduct and the cumulus oophorus before fertilization in vivo. In the oviduct, spermatozoa are exposed to glycodelin-A and -F that inhibit spermatozoa-zona pellucida binding. In this study, we determined whether these glycodelins would inhibit fertilization. The data showed that the spermatozoa without previous exposure to glycodelin-A and -F acquired glycodelin immunoreactivity during their passage through the cumulus oophorus. On the other hand, when glycodelin-A or -F-pretreated spermatozoa were exposed to the cumulus oophorus, the zona pellucida binding inhibitory activity of glycodelin-A and -F was not only removed, but the spermatozoa acquired enhanced zona pellucida binding ability. These actions of the cumulus oophorus were due to the presence of a cumulus isoform of glycodelin, designated as glycodelin-C. The cumulus cells could convert exogenous glycodelin-A and -F to glycodelin-C, which was then released into the surrounding medium. The protein core of glycodelin-C was identical to that in other glycodelin isoforms, as demonstrated by mass spectrum, peptide mapping, and affinity to anti-glycodelin antibody recognizing the protein core of glycodelin. In addition to having a smaller size and a higher isoelectric point, glycodelin-C also had lectin binding properties different from other isoforms. Glycodelin-C stimulated spermatozoazona pellucida binding in a dose-dependent manner, and it effectively displaced sperm-bound glycodelin-A and -F. In conclusion, the cumulus cells transform glycodelin-A and -F to glycodelin-C, which in turn removes the spermatozoazona binding inhibitory glycodelin isoforms and enhances the zona binding capacity of spermatozoa passing through the cumulus oophorus.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong SAR, China.
authors.forename: Philip C N
authors.initials: PC
authors.lastname: Chiu
authors.forename: Man-Kin
authors.initials: MK
authors.lastname: Chung
authors.forename: Riitta
authors.initials: R
authors.lastname: Koistinen
authors.forename: Hannu
authors.initials: H
authors.lastname: Koistinen
authors.forename: Markku
authors.initials: M
authors.lastname: Seppala
authors.forename: Pak-Chung
authors.initials: PC
authors.lastname: Ho
authors.forename: Ernest H Y
authors.initials: EH
authors.lastname: Ng
authors.forename: Kai-Fai
authors.initials: KF
authors.lastname: Lee
authors.forename: William S B
authors.initials: WS
authors.lastname: Yeung
mesh_terms: D005260:Female; D000071816:Glycodelin; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D011257:Pregnancy Proteins / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000166:cytology / Q000378:metabolism*; D015044:Zona Pellucida / Q000378:metabolism*
chemical_list: D000071816:Glycodelin; D006023:Glycoproteins; C045246:PAEP protein, human; D011257:Pregnancy Proteins; D020033:Protein Isoforms