Binding of a murine proteinase inhibitor to the acrosome region of the human sperm head

Abstract

Proteinase inhibitors are present in the various glands, tissues, and secretions of the male reproductive tract. Some of these inhibitors bind to the acrosomal region of the sperm, and their release during in vitro or in utero incubation suggests that they may play a role in capacitation. In the mouse, the binding site for a trypsin-acrosin inhibitor, the acceptor, has been implicated in capacitation, zona binding, and the acrosome reaction. This presentation demonstrates that a component, molecular weight approximately 20,000, on the human sperm head may recognize the murine inhibitor. Furthermore, the acrosome reaction can be induced in capacitated human sperm by immunoaggregation of bound murine inhibitor. The data indicate that the proteinase inhibitor binding site on the human sperm head may, as with a similar site on murine sperm, play a role in the early events of fertilization.

The mode of reproductive‐derived Spink (serine protease inhibitor Kazal‐type) action in the modulation of mammalian sperm activity

“…Like human Spink2, mouse SVI/Spink3 can bind to the human sperm head (Boettger‐Tong et al. , 1993), showing the similarity of the Spink3‐binding site on mouse spermatozoa to the Spink2‐binding site on human spermatozoa.…”

Mouse sperm patch‐clamp recordings reveal single Cl− channels sensitive to niflumic acid, a blocker of the sperm acrosome reaction

“…Inhibition was studied with the same procedure except that the blocker was added 5 min prior to the agonist. At the end of the experiment AR was determined by established procedures [17, 18]. A minimum of 100 sperm were counted under light field microscopy and expressed as the fraction of reacted sperm induced by the agonist vs. a maximum of reacted sperm obtained with the Ca 2+ ionophore A‐23187 (AR/ARA‐23) at 15 μM.…”

Developmental sperm contributions: fertilization and beyond

“…In earlier work performed in nonhuman models, diverse candidates were postulated as primary sperm receptors for ZP3: [1] a 95 kd tyrosine-kinase (8); [2] sp56 (9); [3] trypsine-like protein (10); [4] b1-4 galactosyltransferase (11); and [5] spermadhesins (12). However, none of these molecules has been unequivocally established as an active receptor, and the physiological relevance of these candidates is still under debate.…”