Zona pellucida-induced acrosome reaction in human spermatozoa is potentiated by glycodelin-A via down-regulation of extracellular signal-regulated kinases and up-regulation of zona pellucida-induced calcium influx.
BACKGROUND
Glycodelin-A interacts with spermatozoa before fertilization, but its role in modulating sperm functions is not known. Zona pellucida-induced acrosome reaction is crucial to fertilization and its dysfunction is a cause of male infertility. We hypothesized that glycodelin-A, a glycoprotein found in the female reproductive tract, potentiates human spermatozoa for zona pellucida-induced acrosome reaction.


METHODS
Glycodelin isoforms were immunoaffinity purified. The sperm intracellular cAMP concentration, protein kinase-A (PKA) and extracellular signal-regulated kinase (ERK) activities, and intracellular calcium were measured by ELISA, kinase activity assay kits and Fluo-4AM technique, respectively. The phosphorylation of inositol 1,4,5-trisphosphate type-1 receptor (IP3R1) mediated by ERK was determined by western blotting. Zona pellucida-induced acrosome reaction was detected by Pisum sativum staining.


RESULTS
Pretreatment of spermatozoa with glycodelin-A significantly up-regulated adenylyl cyclase/PKA activity and down-regulated the activity of ERK and its phosphorylation of IP3R1, thereby enhancing zona pellucida-induced calcium influx and zona pellucida-induced acrosome reaction. Glycodelin-F or deglycosylated glycodelin-A did not have these actions. Treatment of spermatozoa with a protein kinase inhibitor abolished the priming activity of glycodelin-A, whilst ERK pathway inhibitors mimic the stimulatory effect of glycodelin-A on zona pellucida-induced acrosome reaction.


CONCLUSIONS
Glycodelin-A in the female reproductive tract sensitizes spermatozoa for zona pellucida-induced acrosome reaction in a glycosylation-specific manner through activation of the adenylyl cyclase/PKA pathway, suppression of extracellular signal-regulated kinase activation and up-regulation of zona pellucida-induced calcium influx. The action of glycodelin-A may be important in vivo to ensure full responsiveness of human spermatozoa to the zona pellucida.
Chiu
Philip C N
PC
Department of Obstetrics and Gynaecology, University of Hong Kong, Pokfulam Road, Hong Kong, China.
Wong
Ben S T
BS
Lee
Cheuk-Lun
CL
Lam
Kevin K W
KK
Chung
Man-Kin
MK
Lee
Kai-Fai
KF
Koistinen
Riitta
R
Koistinen
Hannu
H
Gupta
Satish K
SK
Seppälä
Markku
M
Yeung
William S B
WS
D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000262:Adenylyl Cyclases / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D000071816:Glycodelin; D006023:Glycoproteins / Q000502:physiology*; D006031:Glycosylation; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000187:drug effects / Q000378:metabolism; D008297:Male; D011257:Pregnancy Proteins / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation; D015044:Zona Pellucida / Q000502:physiology*
D000071816:Glycodelin; D006023:Glycoproteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; C045246:PAEP protein, human; D011257:Pregnancy Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D000262:Adenylyl Cyclases; D002118:Calcium