Mammalian zona pellucida glycoproteins: structure and function during fertilization.
Zona pellucida (ZP) is a glycoproteinaceous translucent matrix that surrounds the mammalian oocyte and plays a critical role in the accomplishment of fertilization. In humans, it is composed of 4 glycoproteins designated as ZP1, ZP2, ZP3 and ZP4, whereas mouse ZP is composed of ZP1, ZP2 and ZP3 (Zp4 being a pseudogene). In addition to a variable sequence identity of a given zona protein among various species, human ZP1 and ZP4 are paralogs and mature polypeptide chains share an identity of 47%. Employing either affinity purified native or recombinant human zona proteins, it has been demonstrated that ZP1, ZP3 and ZP4 bind to the capacitated human spermatozoa and induce an acrosome reaction, whereas in mice, ZP3 acts as the putative primary sperm receptor. Human ZP2 only binds to acrosome-reacted spermatozoa and thus may be acting as a secondary sperm receptor. In contrast to O-linked glycans of ZP3 in mice, N-linked glycans of human ZP3 and ZP4 are more relevant for induction of the acrosome reaction. Recent studies suggest that Sialyl-Lewis(x) sequence present on both N- and O-glycans of human ZP play an important role in human sperm-egg binding. There are subtle differences in the downstream signaling events associated with ZP3 versus ZP1/ZP4-mediated induction of the acrosome reaction. For example, ZP3 but not ZP1/ZP4-mediated induction of the acrosome reaction is dependent on the activation of the Gi protein-coupled receptor. Thus, various studies suggest that, in contrast to mice, in humans more than one zona protein binds to spermatozoa and induces an acrosome reaction.
Reproductive Cell Biology Laboratory, National Institute of Immunology, New Delhi, India. skgupta@nii.res.in
Satish K
SK
Gupta
Beena
B
Bhandari
Abhinav
A
Shrestha
Bichitra K
BK
Biswal
Chetna
C
Palaniappan
Sudha Saryu
SS
Malhotra
Neha
N
Gupta
D020101:Acrosome Reaction / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D004527:Egg Proteins / Q000737:chemistry* / Q000502:physiology*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000502:physiology*; D016415:Sequence Alignment; D015398:Signal Transduction; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology; D013329:Structure-Activity Relationship; D000072216:Zona Pellucida Glycoproteins
D004527:Egg Proteins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C000606514:ZP1 protein, human; C000606515:ZP2 protein, human; C000606517:ZP3 protein, human; D000072216:Zona Pellucida Glycoproteins; C000606519:Zp1 protein, mouse; C000606520:Zp2 protein, mouse; C000606521:Zp3 protein, mouse