Major Proteins of Bovine Seminal Vesicles Bind to Spermatozoa1

Abstract

Bovine seminal vesicles synthesize a family of closely related proteins, namely BSP-A1, BSP-A2, BSP-A3, and BSP-30-kDa (collectively called BSP proteins). Recently, we showed that these proteins bind specifically to choline phospholipids. Since this class of phospholipids is the major phospholipid fraction of the spermatozoan membrane, we investigated the binding of BSP proteins to spermatozoa. Polyclonal antibodies against purified BSP proteins raised in rabbits were used to detect these antigens in bovine epididymal and ejaculated spermatozoa as well as in bovine seminal plasma. Comparison of spermatozoa taken from the caudae epididymides with ejaculated spermatozoa through use of various techniques, namely, surface labeling followed by immunoprecipitation and immunoblotting, showed that epididymal spermatozoa are devoid of BSP proteins whereas ejaculated spermatozoa possess membrane-bound BSP proteins. Through use of the indirect immunofluorescence technique, the ejaculated spermatozoa of bull were characterized by an immunoreaction restricted to the midpiece, acrosome, and postacrosomal region, but no specific immunostaining could be found on the surface of epididymal spermatozoa. Surface-labeled BSP proteins on spermatozoa could not be displaced with buffers containing high salt concentration (1 M NaCl), but could be displaced specifically with phosphorylcholine (alone or in combination with urea). The data indicate that the BSP proteins that are secretory products of the seminal vesicles bind to the sperm surface upon ejaculation.

Binding patterns of seminal plasma plasma proteins on bovine epididymal and ejaculated sperm membrane

“…In the present study a similar binding pattern for BSP-A3 was detected, confirming prior reports that BSP-A3 binds to different regions of ejaculated bovine sperm, but it is not found on epididymal sperm membrane (Manjunath et al, 1993). This protein originates from the vesicular glands (Manjunath et al, 1988) and interacts with the sperm during ejaculation, more specifically with membrane choline-containing phospholipids (Desnoyers and Manjunath, 1992), a step that initiates sperm capacitation (Thérien et al, 1995).…”

V-ATPase upregulation during early pregnancy: a possible link to establishment of an inflammatory response during preimplantation period of pregnancy

“…It has been previously reported that male semen contributes to the events through which maternal tolerance is established at the outset of pregnancy (Manjunath et al 1994, Robertson et al 2009. We have previously shown that the a2V expression was significantly higher in the preimplantation embryos and placentas of nonabortion-prone (\BALB/c!_BALB/c and \ CBA!_BALB/c) matings compared with the abortion-prone (\ CBA!_DBA) matings.…”

“…These molecules target the cells of the cervix, uterus, and oviduct and induce early inflammatory responses important for the establishment of successful implantation (Manjunath et al 1994, Robertson et al 2006.…”

Detection of osteopontin on Holstein bull spermatozoa, in cauda epididymal fluid and testis homogenates, and its potential role in bovine fertilization

“…In support of this notion, OPN has been described as a sperm surface molecule in rats (Siiteri et al 1995), as associated with sperm during development in the testis (Luedtke et al 2002), and while sperm are transported and stored in the epididymis (Siiteri et al 1995, Luedtke et al 2002, and is present in AGF (Cancel et al 1999) at ejaculation. In addition, proteins from AGF are known to bind to sperm during ejaculation (Manjunath et al 1994).…”