Levels of semenogelin in human spermatozoa decrease during capacitation: involvement of reactive oxygen species and zinc.
BACKGROUND
Semenogelin (Sg), the main protein of human semen coagulum, prevents sperm capacitation. The objective of this study was to examine the role of Sg and its mechanism of action.


RESULTS
Sg blocked sperm capacitation triggered by various stimuli, via inhibition of superoxide anion (O(2)*-; luminescence assay) and nitric oxide (NO*; tested using diaminofluorescein) generation. Triton-soluble and -insoluble sperm fractions contained Sg and Sg peptides (immunoblotting), the level of which decreased with initiation of capacitation. This drop was prevented by superoxide dismutase and NO* synthase inhibitor and was reproduced by addition of O(2)*- and NO*. Zinc (Zn(2+)) blocked and a zinc chelator (TPEN) promoted the decline in Sg levels. There was a decreased labelling of Sg on the head in capacitating spermatozoa with the two fixation techniques tested (immunocytochemistry). Reactive oxygen species (ROS) (O(2)*- and NO*) caused, these changes, and zinc prevented them. Spermatozoa quickly internalized Sg upon incubation and Sg was then rapidly degraded in a zinc-inhibitable manner.


CONCLUSIONS
Sg blocked capacitation mainly via inhibition of ROS generation. Spermatozoa appeared permeable to Sg and processed Sg in a zinc-inhibitable fashion. ROS themselves could promote sperm disposal of Sg which maybe one of the mechanisms that allows initiation of capacitation.
de Lamirande
E
E
Urology Research Laboratory, H6.47, McGill University Health Centre at Royal Victoria Hospital, 687 Ave des Pins ouest, Montréal, QC, Canada H3A 1A1. edelamirande@yahoo.com
Lamothe
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G
D002614:Chelating Agents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005029:Ethylenediamines / Q000494:pharmacology; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D021381:Protein Transport; D017382:Reactive Oxygen Species / Q000378:metabolism*; D029607:Seminal Vesicle Secretory Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D013075:Sperm Capacitation / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology / Q000502:physiology*
D002614:Chelating Agents; D004791:Enzyme Inhibitors; D005029:Ethylenediamines; D017382:Reactive Oxygen Species; D029607:Seminal Vesicle Secretory Proteins; C424482:seminal vesicle-specific antigen; D013481:Superoxides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D015032:Zinc; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine