Loss of Zona Pellucida Binding Proteins in the Acrosomal Matrix Disrupts Acrosome Biogenesis and Sperm Morphogenesis

The remarkable complexity of the molecular events governing adhesion and fusion of the male and female gametes is becoming apparent. Novel research suggests that these highly specific cellular interactions are facilitated by multiprotein complexes that are delivered to and/or assembled on the surface of the gametes by molecular chaperones in preparation for sperm-egg interaction. While the activation of these molecular chaperones and the mechanisms by which they shuttle proteins to the surface of the cell remain the subject of ongoing investigation, a compelling suggestion is that these processes are augmented by dynamic membrane microdomains or lipid rafts that migrate to the apical region of the sperm head after capacitation. Preliminary studies of the oocyte plasma membrane have also revealed the presence of lipid rafts comprising several molecular chaperones, raising the possibility that similar mechanisms may be involved in the activation of maternal fusion machinery and the regulation of oocyte plasma membrane integrity. Despite these findings, the analysis of oocyte surface multiprotein complexes is currently lacking. Further analyses of the intermediary proteins that facilitate the expression of key players in sperm-egg fusion are likely to deliver important insights into this unique event, which culminates in the cytoplasmic continuity of the male and female gametes.Reproduction (2013) 145 R31-R42

Section: Multiprotein Complexes In Sperm Capacitation and Zp Interactionmentioning

confidence: 99%

The function of chaperone proteins in the assemblage of protein complexes involved in gamete adhesion and fusion processes

Bromfield

Nixon

2013

“…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).…”

Section: Wtmentioning

confidence: 99%

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

Xu¹,

Liu²,

Srakaew³

et al. 2012

We have shown previously that sperm surface arylsulfatase A (ASA) of mouse, pig, and human is involved in sperm-egg zona pellucida (ZP) binding. By treating capacitated mouse sperm with A23187 to induce the acrosome reaction, we demonstrated by immunoblotting that ASA also existed in the acrosomal content and on the inner acrosomal membrane. Since mZP2 and mZP3 are known as sperm receptors, whereas mZP1 as a cross-linker of mZP2/mZP3, we determined whether purified ASA bound to mZP2 and mZP3 selectively. The three mZP glycoproteins were purified from solubilized ovarian ZP by size exclusion column chromatography. Immuno-dot blot analyses revealed that purified sperm ASA bound to mZP2 at the highest level followed by mZP3, whereas the binding of ASA to mZP1 was minimal. The results confirmed the physiological significance of sperm ASA in the ZP binding process. The binding of ASA to mZP2 and mZP3 was, however, not dependent on the active site pocket amino acids, Cys69, Lys123, and Lys302, which are pertinent to the capturing of an arylsulfate substrate, since ASA mutant with Ala substitution at these three residues still bound to mZP2 and mZP3. The availability of the active site pocket of ASA bound to the ZP suggested that ASA would still retain enzymatic activity, which might be important for subsequent sperm penetration through the ZP.

“…Genetic manipulations of sperm have often led to unpredictable morphological and physiological changes (Baba et al 1994, Lu & Shur 1997, Nishimura et al 2001, Ensslin et al 2007, Lin et al 2007). Because of these previous problems, some skepticism is warranted about the findings with these in vivo fluorescently tagged sperm (Jin et al 2011).…”

Section: An Alternate Model For Mouse Sperm-zp Binding That Fits the mentioning

confidence: 99%

The molecular basis of mouse sperm–zona pellucida binding: a still unresolved issue in developmental biology

Clark¹

2011

During murine fertilization, sperm bind to the specialized extracellular matrix of the egg, known as the zona pellucida (ZP). This matrix is composed of three major glycoproteins designated ZP1, ZP2, and ZP3. Three models for sperm-ZP binding are now under consideration. The domain-specific model posits that adhesion relies primarily on interactions between N-glycans located within the C-terminal domain of ZP3 and a lectin-like egg-binding protein in the sperm plasma membrane. However, this model does not explain recent results obtained in studies with ZP2 mut mice. In the supramolecular structure model, sperm bind to a three-dimensional zona matrix that depends on the cleavage status of ZP2. This paradigm does not explain the potent inhibitory effect of specific carbohydrate sequences or a C-terminal glycopeptide (gp55) derived from ZP3. Recently, O-glycans linked at Thr 155 and Thr 162 of ZP3 were implicated as potential ligands that mediate initial sperm-ZP binding. This novel model will be reviewed. A major challenge is to develop an alternate model for sperm-ZP binding that fits as much of the data as possible. Such a model is presented in this review. This paradigm could explain how the inability to cleave ZP2 mut in ZP2 mut mice could result in continued sperm binding to two-cell stage embryos without the formation of a supramolecular binding complex. These novel insights should guide future experiments that will eventually determine the molecular basis underlying gamete binding in the mouse and other eutherian mammals.