Glycobiology of fertilization in the pig

Abstract

By adopting internal fertilization, the meeting of both gametes -the sperm and the egg -and thus the highly coordinated sequence of interactions leading to fertilization, occur in the female reproductive tract. In mammals, the oviduct has been shown to translate the requirements of the female, coordinating sperm activation (capacitation) and sperm transport with the arrival of the ovulated egg. A hierarchy of carbohydrate-based interactions accompanies these events ranging from the binding of uncapacitated sperm to the oviductal epithelium (establishment of the female sperm reservoir), to the primary and secondary binding processes contributing to gamete recognition and sperm penetration of the oocyte zona pellucida. The current perspective will focus on the carbohydrate-recognition systems in the binding events during fertilization in the pig. The roles of the major carbohydrate-binding proteins, the spermadhesins and the acrosomal serine proteinase, pro/acrosin are discussed under consideration of recent structural data. The glycans and the glycoproteins of the porcine oviduct with a focus on the candidate sperm receptors as well as the zona pellucida N-glycans of prepuberal pigs have been characterized by a mass spectrometric approach. Furthermore, some preliminary data supporting the hypothesis that the zona pellucida has to undergo a maturation process during oocyte development are presented. KEY WORDS: gamete interaction, spermadhesin, acrosin, zona pellucida, glycoprotein, glycan A short review of mammalian fertilizationThe fertilization of an egg by a sperm is the fundamental event in life, as it culminates in the creation of a new individual. In mammals, the meeting of the fertilizing competent sperm and the ovulated egg is the beginning of a highly coordinated sequence of cellular interactions between the haploid gametes, which leads to the formation of the diploid zygote and initiates embryonic development.The first contact between sperm and egg takes place at the outer surface of the surrounding extracellular matrix of the egg, the zona pellucida (ZP). By binding to distinct oligosaccharides of the ZP glycoproteins, the fertilizing sperm recognizes the egg. Upon anchoring the sperm to the egg through the ZP carbohydrates the signaling cascade leading to acrosomal exocytosis of the sperm is activated allowing the sperm to pass through the zona pellucida. The acrosome-reacted sperm in the end interacts and fuses with the egg plasma membrane, which in turn enables the egg to complete meiosis, to initiate the mechanisms to prevent Int.

Sperm arylsulfatase A binds to mZP2 and mZP3 glycoproteins in a nonenzymatic manner

“…Nonetheless, the identity of the ZP glycoproteins to which ASA binds was not known, and this was one specific aim of the current research study. We have postulated that ASA, as a sulfatase, interacts with sulfated sugar residues (Carmona et al 2002a), which are components of the ZP glycans (Shimizu et al 1983, Hirano et al 1993, Noguchi & Nakano 1993, Hokke et al 1994, Takasaki et al 1999, Dell et al 2003, Topfer-Petersen et al 2008, Pang et al 2011. Our computational analyses indicate that the active site pocket of ASA is the positively charged area, which is essential for capturing the sulfated substrate (Lukatela et al 1998, Schenk et al 2009).…”

“…All the results were representative of two or three replicate experiments. Dell et al 2003, Topfer-Petersen et al 2008, Pang et al 2011, it is possible that the interaction between ASA and ZP glycoproteins may be via the binding of ASA to sulfated sugars on the ZP. This prompted us to test whether dextran sulfate, a long-chain polymer of sulfated glucose, could inhibit ASA-ZP binding.…”

“…Mammalian ZP glycans contain sulfated sugar residues, and their significance in sperm binding has been implicated (Shimizu et al 1983, Oehninger et al 1991, Mori et al 1993, Yonezawa et al 1995, Howes et al 2001, Howes & Jones 2002, Moreno et al 2002, Dell et al 2003, Gaboriau et al 2007, Lin et al 2007, Topfer-Petersen et al 2008, Yu et al 2009, Pang et al 2011. A number of sulfatases have desulfation activity on sulfated sugar residues (Hanson et al 2004).…”

Heparin binding analysis of boar sperm and its relation with farrowing capacity

“…In our previous study (Dapino et al, 2009) we proposed that the change of heparin-binding pattern during capacitation may be due to the exposure of HBPs in the acrosomal region upon some spermadhesins shedding from the sperm surface at the beginning of the capacitation process, to the redistribution of anionic phospholipids from the acrosomal to the postacrosomal region, or to a combination of both. Töpfer-Petersen et al (2008) have proposed a model in which some spermadhesins that interact with membrane phospholipids, such as AWN-1, DQH and AQN-3 (all belonging to the family of proteins that bind to heparin), remain bound to sperm after capacitation and may be involved in the union to ZP as primary acceptors (Van Gestel et al, 2007;Monásková et al, 2007). AQN-3 has been identified as a membrane-associated protein that is present in microdomains that emerge during in vitro capacitation at the apical ridge of the plasma membrane of the sperm head .…”

“…It is well known that, in pigs, some spermadhesins are removed from the surface of sperm during capacitation while some HBP, as DQH, remain adsorbed to sperm and interact with components of the zona pellucida (ZP) at fertilisation (Monásková et al, 2007;Töpfer-Petersen et al, 2008). Also, strong evidence indicates that capacitation involves a redesign of the lipid architecture of the sperm plasma membrane (Van Gestel et al, 2007;Leahy and Gadella, 2011a,b), with the consequent redistribution of proteins on the surface .…”