title: Cumulus-associated alpha2-macroglobulin derivative retains proconceptive glycodelin-C in the human cumulus matrix.
abstract: BACKGROUND
  Glycodelin-C is a glycodelin isoform isolated from the cumulus matrix. It stimulates spermatozoa-zona pellucida binding. Here, we report the isolation and characterization of a novel glycodelin interacting protein (GIP) from human cumulus matrix.
  
  
  METHODS
  GIP was purified by liquid chromatograph and identified by mass spectrometry. The interaction of GIP with glycodelin, matrix molecule and spermatozoa were investigated.
  
  
  RESULTS
  Mass spectrometry analysis suggested that GIP contained the N-terminal region of alpha2-macroglobulin, confirmed by western blot with anti-alpha2-macroglobulin antibody. GIP bound to native but not deglycosylated glycodelin-C in native gel electrophoresis, suggesting that the binding was glycosylation-dependent. GIP did not bind to capacitated and uncapacitated human spermatozoa. The cumulus cells could convert exogenous labeled alpha2-macroglobulin into GIP in vitro. GIP interacted with hyaluronic acid, a major component of the cumulus matrix. Glycodelin-C bound to hyaluronic acid-coated agarose beads in the presence of GIP. Human spermatozoa acquired the hyaluronic acid-GIP-bound glycodelin-C during incubation in vitro.
  
  
  CONCLUSIONS
  The hyaluronic acid-GIP complex formed in the cumulus matrix retains and concentrates glycodelin-C in the cumulus matrix for displacing sperm-bound glycodelin-A and -F and stimulating the zona binding activity of the spermatozoa traversing through the cumulus mass.
authors.affiliation: LKS Faculty of Medicine, Department of Obstetrics and Gynaecology, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China.
authors.forename: Man-Kin
authors.initials: MK
authors.lastname: Chung
authors.forename: Philip C N
authors.initials: PC
authors.lastname: Chiu
authors.forename: Cheuk-Lun
authors.initials: CL
authors.lastname: Lee
authors.forename: Ronald T K
authors.initials: RT
authors.lastname: Pang
authors.forename: E H Y
authors.initials: EH
authors.lastname: Ng
authors.forename: Kai-Fai
authors.initials: KF
authors.lastname: Lee
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: William S B
authors.initials: WS
authors.lastname: Yeung
mesh_terms: D002853:Chromatography, Liquid; D054885:Cumulus Cells / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005260:Female; D000071816:Glycodelin; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D011257:Pregnancy Proteins / Q000378:metabolism*; D020033:Protein Isoforms / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000378:metabolism*
chemical_list: D016326:Extracellular Matrix Proteins; D000071816:Glycodelin; D006023:Glycoproteins; C045246:PAEP protein, human; D011257:Pregnancy Proteins; D020033:Protein Isoforms; D000511:alpha-Macroglobulins; D006820:Hyaluronic Acid