Enhancement of sperm-zona pellucida (ZP) binding capacity by activation of protein kinase A and C pathways in certain infertile men with defective sperm-ZP binding.
BACKGROUND
Defective sperm-zona pellucida (ZP) binding (DSZPB) is a common cause of failure of fertilization in vitro. This study was to determine if DSZPB is caused by defective pathways upstream of protein kinase A (PKA) and C (PKC), or reduced protein tyrosine phosphorylation (TP).


METHODS
Infertile men with DSZPB and either normal sperm morphology (NSM) > or = 14% (n = 15) or < or =5% (n = 15) were studied. Sperm-ZP binding test was performed by incubation of motile sperm with oocytes for 2 h with or without dibutyryl cyclic AMP (dbcAMP, PKA activator) or phorbol myristate acetate (PMA, PKC activator). TP of capacitated sperm in medium was assessed by immunofluorescence with an anti-phosphotyrosine monoclonal antibody.


RESULTS
For normal sperm with normal sperm-ZP binding, both PMA and dbcAMP significantly enhanced sperm-ZP binding in a dose-response manner. Only dbcAMP, but not PMA, significantly increased TP of capacitated sperm. In DSZPB men with severe teratozoospermia (NSM < or = 5%), neither PMA nor dbcAMP enhanced sperm-ZP binding, despite dbcAMP significantly increasing the TP of capacitated sperm for all samples. In contrast, for DSZPB with NSM > or = 14%, PMA caused significantly increased sperm binding up to normal levels (> or =40 sperm bound/ZP) in five men, and dbcAMP had a similar result in two men. Again TP was significantly enhanced only by dbcAMP, but not by PMA.


CONCLUSIONS
There is defective signalling in pathways upstream of PKC and PKA in some men with DSZPB and normal semen analysis. Stimulation of TP by dbcAMP does not enhance sperm-ZP binding capacity in DSZPB men with low TP, regardless of sperm morphology.
Liu
D Y
DY
Department of Obstetrics and Gynaecology, University of Melbourne, Australia. dyl@unimelb.edu.au
Liu
M L
ML
Baker
H W G
HW
D020101:Acrosome Reaction / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism* / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D007248:Infertility, Male / Q000378:metabolism*; D008297:Male; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D013075:Sperm Capacitation; D013084:Sperm-Ovum Interactions / Q000187:drug effects* / Q000502:physiology; D013094:Spermatozoa / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014443:Tyrosine / Q000378:metabolism
D014443:Tyrosine; D003994:Bucladesine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate