Calyculin A, protein phosphatase inhibitor, enhances capacitation of human sperm.
OBJECTIVE
To examine the effects of protein phosphatase inhibitors on capacitation and protein phosphorylation in human sperm.


METHODS
The chlortetracycline (CTC) fluorescence assay was used to monitor capacitated sperm treated with or without protein phosphatase inhibitors. Capacitation was confirmed by the ability of sperm to undergo the acrosome reaction in response to Ca++ ionophore A23187 or mouse zonae pellucidae. 32P-labeled sperm phosphoproteins were analyzed by one-dimensional gel electrophoresis to detect the effects of protein phosphatase inhibitors on protein phosphorylation.


RESULTS
The treatment of sperm with calyculin A resulted in the following: [1] the rapid appearance of the clear perimeter pattern, specifically, distribution of fluorescence over the entire head exhibiting a bright perimeter and bright midpiece, in a dose-dependent manner in the 1 to 100 nM range; [2] an accelerated ability to undergo the acrosome reaction; and [3] an enhanced phosphorylation of sperm phosphoproteins in a dose-related fashion in the 1 to 100 nM range. A similar stimulatory effect was observed only with a 100-fold higher concentrations of okadaic acid, another protein phosphatase inhibitor.


CONCLUSIONS
Our results strongly suggest that protein phosphorylation and dephosphorylation may be involved in the regulation of human sperm capacitation.
Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo, Japan.
S
S
Furuya
Y
Y
Endo
K
K
Osumi
M
M
Oba
S
S
Nozawa
S
S
Suzuki
D000177:Acrosome / Q000502:physiology; D002751:Chlortetracycline; D004988:Ethers, Cyclic / Q000494:pharmacology; D005453:Fluorescence; D006801:Humans; D008297:Male; D008387:Marine Toxins; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation / Q000187:drug effects; D011506:Proteins / Q000378:metabolism; D013075:Sperm Capacitation / Q000187:drug effects*; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology
D004988:Ethers, Cyclic; D008387:Marine Toxins; D010080:Oxazoles; D011506:Proteins; D019319:Okadaic Acid; C059041:calyculin A; D010749:Phosphoprotein Phosphatases; D002751:Chlortetracycline