Activation of a G protein complex by aggregation of beta-1,4-galactosyltransferase on the surface of sperm.
Fertilization is initiated by the species-specific binding of sperm to the extracellular coat of the egg. One sperm receptor for the mouse egg is beta-1,4-galactosyltransferase (GalTase), which binds O-linked oligosaccharides on the egg coat glycoprotein ZP3. ZP3 binding induces acrosomal exocytosis through the activation of a pertussis toxin-sensitive heterotrimeric guanine nucleotide-binding protein (G protein). The cytoplasmic domain of sperm surface GalTase bound to and activated a heterotrimeric G protein complex that contained the Gi alpha subunit. Aggregation of GalTase by multivalent ligands elicited G protein activation. Sperm from transgenic mice that overexpressed GalTase had higher rates of G protein activation than did wild-type sperm, which rendered transgenic sperm hypersensitive to their ZP3 ligand. Thus, the cytoplasmic domain of cell surface GalTase appears to enable it to function as a signal-transducing receptor for extracellular oligosaccharide ligands.
Gong
X
X
Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Dubois
D H
DH
Miller
D J
DJ
Shur
B D
BD
D000177:Acrosome / Q000502:physiology; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D004527:Egg Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009237:N-Acetyllactosamine Synthase / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D037342:Pertussis Toxin; D011956:Receptors, Cell Surface; D015398:Signal Transduction; D013094:Spermatozoa / Q000201:enzymology / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D015044:Zona Pellucida / Q000737:chemistry*; D000072216:Zona Pellucida Glycoproteins
D004527:Egg Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D010566:Virulence Factors, Bordetella; D000072216:Zona Pellucida Glycoproteins; C000606521:Zp3 protein, mouse; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009237:N-Acetyllactosamine Synthase; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins