Sperm surface fibronectin. Expression following capacitation.
The Arg-Gly-Asp (RGD) amino acid sequence plays a role in many cell-to-cell and cell-to-matrix adhesion systems, as a recognition sequence for cell membrane receptors termed integrins. Receptors of the VLA subfamily of integrins recognize fibronectin, laminin, and collagen. Given the authors' findings that fibronectin-derived, RDG-containing peptides competitively inhibit sperm-oolemmal adhesion and penetration in both heterologous (human-hamster) and homologous (hamster-hamster) gamete interactions, the expression of fibronectin on the surface of fresh, capacitated, and acrosome-reacted human spermatozoa was studied. The majority of fresh spermatozoa did not display fibronectin on their plasma membrane (0 to 16% positive), as demonstrated by the lack of binding of both monoclonal and polyclonal anti-fibronectin antibodies. In contrast, a significantly greater proportion of spermatozoa (varying between 18% to 100% for different donors) incubated overnight under capacitating conditions reacted with anti-fibronectin antibodies. The induction of an acrosome reaction with progesterone did not alter the proportion of sperm displaying fibronectin or its distribution on the sperm surface. A physiologic role of fibronectin in sperm-oolemmal interaction was suggested by the effects of anti-fibronectin antibodies on sperm oolemmal adhesion and penetration of hamster eggs by human spermatozoa, which were both significantly reduced (P less than 0.001).
Fusi
F M
FM
Department of Obstetrics and Gynecology, State University of New York, Stony Brook 11794-8091.
Bronson
R A
RA
D000177:Acrosome / Q000502:physiology; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D006224:Cricetinae; D005260:Female; D005353:Fibronectins / Q000032:analysis* / Q000276:immunology / Q000502:physiology; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D008647:Mesocricetus; D013075:Sperm Capacitation / Q000502:physiology*; D013084:Sperm-Ovum Interactions / Q000276:immunology / Q000502:physiology; D013094:Spermatozoa / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure
D000906:Antibodies; D005353:Fibronectins