Open AccessMutation of a Conserved Hydrophobic Patch Prevents Incorporation of ZP3 into the Zona Pellucida Surrounding Mouse Eggs
Author(s) -
Ming Zhao,
Lyn Gold,
Heidi Dorward,
Li-Fang Liang,
Tanya Hoodbhoy,
Emily S. Boja,
Henry M. Fales,
Jurrien Dean
Publication year - 2003
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.23.24.8982-8991.2003
Subject(s) - zona pellucida , furin , ectodomain , biology , transmembrane domain , zona pellucida glycoprotein , transmembrane protein , microbiology and biotechnology , cleavage (geology) , green fluorescent protein , secretion , secretory pathway , biochemistry , amino acid , endoplasmic reticulum , oocyte , golgi apparatus , gene , embryo , receptor , paleontology , fracture (geology) , enzyme
Three glycoproteins (ZP1, ZP2, and ZP3) are synthesized in growing mouse oocytes and secreted to form an extracellular zona pellucida that mediates sperm binding and fertilization. Each has a signal peptide to direct it into a secretory pathway, a "zona" domain implicated in matrix polymerization and a transmembrane domain from which the ectodomain must be released. Using confocal microscopy and enhanced green fluorescent protein (EGFP), the intracellular trafficking of ZP3 was observed in growing mouse oocytes. Replacement of the zona domain with EGFP did not prevent secretion of ZP3, suggesting the presence of trafficking signals and a cleavage site in the carboxyl terminus. Analysis of linker-scanning mutations of a ZP3-EGFP fusion protein in transient assays and in transgenic mice identified an eight-amino-acid hydrophobic region required for secretion and incorporation into the zona pellucida. The hydrophobic patch is conserved among mouse zona proteins and lies between a potential proprotein convertase (furin) cleavage site and the transmembrane domain. The cleavage site that releases the ectodomain from the transmembrane domain was defined by mass spectrometry of native zonae pellucidae and lies N-terminal to a proprotein convertase site that is distinct from the hydrophobic patch.