Disease relevance of ZP2

• We produced in Escherichia coli a recombinant human ZP2 protein (rec-hZP2) corresponding to amino acid sequence 1-206 of the mature protein [1].
• Zona pellucida proteins are secreted to form a filamentous zona matrix in which ZP2 and ZP3 complex into co-polymers cross-linked by ZP1 [2].
• To facilitate our understanding of the role of zona pellucida glycoproteins during fertilization in humans, recombinant human zona pellucida glycoprotein-A (hZPA), -B (hZPB) and -C (hZPC) were obtained by using Escherichia coli and baculovirus expression systems [3].
• However, only a few of these knockout of genes such as encoding oocyte glycoprotein coat comprised of zona pellucida (ZP) 1, ZP2 and ZP3 and oocute plasma membrane specific proteins showed a specific and exclusive target infertility effect without concomitant effects on the non-reproductive organ system [4].

High impact information on ZP2

• Here, we report that the ZP domain of ZP2, ZP3 and THP is responsible for polymerization of these proteins into filaments of similar supramolecular structure [5].
• The amino acid sequence of the receptor is closely related to that of the mouse zona pellucida protein ZP2 [6].
• Taken together, these observations indicate that ZP2 and ZP3 traffic independently through the oocyte prior to assembly into the zona pellucida [7].
• ZP2 and ZP3 Traffic Independently within Oocytes prior to Assembly into the Extracellular Zona Pellucida [7].
• ZP2 and ZP3 colocalize in the endoplasmic reticulum and in 1- to 5-mum post-Golgi structures comprising multivesicular aggregates (MVA), but a coimmunoprecipitation assay does not detect physical interactions [7].

Biological context of ZP2

• The N-terminal polypeptide portion of human ZP2 was shown to contain a binding site for acrosome-reacted spermatozoa and to play an important role in secondary sperm binding and penetration into the ZP [1].
• The goals of this study were to determine the effects of recombinant human ZP2, ZP3, and ZP4 on human sperm acrosomal exocytosis and sperm motility [8].
• Furthermore, AS ZP2-20 identifies a ZP2 epitope that is possibly of functional relevance for sperm-egg interaction [2].
• The rZP1 also showed a sequence homology to mouse ZP1, known as a mouse orthologue of ZPB family, suggesting that the rZP2 and rZP1 are members of ZPA and ZPB families, respectively [9].
• The ZP2-specific protease may be released during cortical granule exocytosis which occurs during meiotic maturation and following sperm-egg fusion as part of the block to polyspermy [10].

Anatomical context of ZP2

• The mouse zona pellucida contains three glycoproteins, ZP1, ZP2, and ZP3, which are conserved in rat and human [11].
• We investigated the status of ZP2 in the oocytes used in the functional tests, and demonstrated that sperm binding and acrosome reaction induction, but not ZP penetration, occurred whether or not ZP2 was cleaved [12].
• The three glycoproteins, ZP1, ZP2, and ZP3, that comprise the zp have been characterized from many species and assigned different roles in gamete interaction [13].
• Neither ZP2 nor suramin bind to acrosome intact sperm and can, therefore, only exert their effects after exposure of the acrosomal contents [14].
• Recombinant human zona pellucida proteins ZP1, ZP2 and ZP3 co-expressed in a human cell line [15].

Associations of ZP2 with chemical compounds

• Rec-hZPA interaction was disturbed by dextran sulphate (75% inhibition with 10 microM), fucose (67% inhibition with 1.5 microM), and mannose (69% inhibition with 333 mM) [16].
• Interactions between mouse ZP2 glycoprotein and proacrosin; a mechanism for secondary binding of sperm to the zona pellucida during fertilization [17].
• A mouse acrosomal cortical matrix protein, MC41, has ZP2-binding activity and forms a complex with a 75-kDa serine protease [18].
• Results presented suggest that ZP2-proteinase readily diffuses through the zona pellucida within 5 min of activation of eggs by ionophore A23187 and carries out limited proteolysis of ZP2 [19].
• In one form, cystatin, ZP2, fibroin-like substance (FLS), and cathepsin-like substance (CLS) are conjugated, which is extracted by sodium dodecyl sulfate [20].

Other interactions of ZP2

• CONCLUSION(S): The rec-hZPA is the major ZP ligand for human proacrosin/acrosin [16].
• Cross-linking of ZP2 and ZP3 by transglutaminase is required for the formation of the outer layer of fertilization envelope of carp egg [21].
• Appearance of ZP2-proteinase is completely dependent upon activation of eggs, consistent with it being present in cortical granule exudate [19].

Analytical, diagnostic and therapeutic context of ZP2

• Recombinant expression of human (h) ZP1, ZP2, and ZP3 produces glycoproteins that are secreted and have migration patterns in SDS-PAGE identical to those of native human zona pellucida proteins [22].
• A model in which the zona block to polyspermy is caused by direct titration of zona pellucida binding sites is suggested as an alternative to the explanation that relies on enzyme cleavage of ZP2 to ZP2f [23].
• Far Western blotting technique indicated that MC41 bound to both ZP2 and ZP2(f) in the presence of high-salt-soluble sperm proteins [18].
• Immuno-electron microscopy demonstrated an equal distribution of ZP2 throughout the human zona pellucida [24].
• Using transgenesis to replace mouse ZP2 and/or ZP3 with human homologs, mouse lines with human-mouse chimeric zonae pellucidae have been established [25].

References