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Tyrosyl‐phosphorylated proteins are involved in regulation of meiosis in the rat egg
Author(s) -
BenYosef Dalit,
Talmor Anat,
Shwartz Lior,
Granot Yosef,
Shalgi Ruth
Publication year - 1998
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199802)49:2<176::aid-mrd8>3.0.co;2-m
Subject(s) - biology , phosphorylation , ionomycin , tyrosine , protein kinase a , human fertilization , kinase , protein tyrosine phosphatase , protein phosphorylation , oocyte activation , phosphatase , microbiology and biotechnology , tyrosine phosphorylation , tyrosine kinase , biochemistry , signal transduction , oocyte , embryo , genetics , intracellular
Fertilization in invertebrates results in tyrosine (Tyr) phosphorylation of several egg proteins. However, the involvement of Tyr phosphorylation in mediating mammalian egg activation has not yet been investigated. Using an antibody specific for phosphotyrosine (P‐Tyr), immunoblotting, and densitometric analysis, we found that maturation of the oocyte is accompanied by a generalized increase in the P‐Tyr content of almost all egg proteins detected. After sperm penetration, 5 of the 17 protein bands detected demonstrated a small increase in their P‐Tyr content, while at the pronuclear (PN) stage the signal was markedly reduced. Ionomycin emulated the changes observed at fertilization in most protein bands detected, demonstrating a small increase in their P‐Tyr content within 15 min of exposure. Analysis of the involvement of the tyrosyl‐phosphorylated, mitogen‐activated protein (MAP) kinase during meiosis revealed comigration of the phosphotyrosyl bands with the protein and a good correlation with its enzyme activity. Maturation was accompanied by an increase in MAP kinase activity. The activity dropped partially after sperm penetration and furthermore later at the PN stage. A larger quantity accompanied by a more significant change in the P‐Tyr content implies for extracellular regulated kinase (ERK) 2 being the dominant isoform present in the rat egg. Our results indicate that fertilization in mammals involves changes in activity of protein tyrosine kinases (PTKs) or in the balance between PTKs and protein tyrosine phosphatases. The single, ionomycin‐induced Ca 2+ rise is sufficient to imitate fertilization‐induced changes in MAP kinase activity, as well as in tyrosine phosphorylation of other proteins within the egg. Mol. Reprod. Dev. 49:176–185, 1998. © 1998 Wiley‐Liss, Inc.