Hum. Reprod. Advance Access originally published online on July 22, 2009
Human Reproduction 2009 24(11):2856-2867; doi:10.1093/humrep/dep265
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Cumulus-associated 
2-macroglobulin derivative retains proconceptive glycodelin-C in the human cumulus matrix
1 LKS Faculty of Medicine, Department of Obstetrics and Gynaecology, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong SAR, China 2 Centre of Reproduction, Development and Growth, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong SAR, China 3 Department of Obstetrics and Gynaecology, University of Helsinki and Helsinki University Central Hospital 00029 HUS Helsinki, Finland 4 Department of Clinical Chemistry, University of Helsinki and Helsinki University Central Hospital 00029 HUS Helsinki, Finland
5 correspondence address. Fax: +86-852-2855-0947; E-mail: wsbyeung{at}hkucc.hku.hk
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 
2-macroglobulin, confirmed by western blot with anti-2-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 2-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.
CONCLUSION: 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.
Key words:
glycodelin/spermatozoa/cumulus matrix/2-macroglobulin/hyaluronic acid
Contribute equally to the article. Submitted on March 13, 2009; resubmitted on June 4, 2009; accepted on June 22, 2009.