Molecular Human Reproduction, Vol. 6, No. 11, 977-982,
November 2000
© 2000 European Society of Human Reproduction and Embryology
Testis and spermatogenesis |
Vitronectin is sequestered within human spermatozoa and liberated following the acrosome reaction
1 Department of Obstetrics and Gynecology 2 Department of Pathology, State University of New York at Stony Brook, New York, USA 3 Institute of Biochemistry and Justus-Leibig-Universitat, Giessen, Germany
Abstract
Vitronectin plays a role in the regulation of complement and thrombin activities and in cell surface proteolysis. Vitronectin is also an intrinsic protein of human spermatozoa. Vitronectin message has been detected in whole testis poly-A mRNA and localized by in-situ reverse transcription-polymerase chain reaction to spermatocytes. The proportion of spermatozoa that express vitronectin increases following their capacitation. In this study, spermatozoa from a man of proven fertility were probed with an anti-vitronectin monoclonal antibody (VN7) before and after their permeabilization with 0.1% Triton X-100. Of fresh spermatozoa observed by confocal microscopy, 0–8% showed vitronectin staining. However, 75% of those observed displayed vitronectin following permeabilization. Serial confocal sections through the sperm head confirmed the internal localization of vitronectin. The acrosomal status of capacitated spermatozoa that expressed vitronectin was then determined. Dual colour microscopy with rhodamine-conjugated anti-vitronectin antibody and a fluorescein-conjugated antibody directed against CD46 (a complement regulatory protein expressed on the inner acrosomal membrane) revealed that only acrosome-reacted (CD46-positive) spermatozoa displayed vitronectin. Two populations of these spermatozoa were observed. Fifty-seven of 260 (22%) were CD46-positive/vitronectin-positive and 72 of 260 (28%) were CD46-positive/vitronectin-negative. No spermatozoa were CD46-negative/vitronectin-positive. These results confirm that vitronectin is released from a sequestered location within the spermatozoon following the acrosome reaction.
acrosome reaction/capacitation/integrins/spermatozoa/vitronectin
Notes
4 To whom correspondence should be addressed at: Department of Obstetrics and Gynecology, Health Sciences Center, State University of New York, Stony Brook, New York 11794–8091, USA. E-mail: rbronson{at}notes.cc.sunysb.edu
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