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Protein tyrosine phosphatases in Chaetopterus egg activation
Author(s) -
Hinton Shantá D.,
Yang Dazhi,
Eckberg William R.
Publication year - 2003
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1111/j.1440-169x.2003.00707.x
Subject(s) - oocyte activation , biology , protein tyrosine phosphatase , vanadate , phosphatase , tyrosine phosphorylation , dephosphorylation , tyrosine , biochemistry , phosphorylation , protein phosphatase 2 , microbiology and biotechnology , oocyte , embryo
Changes in protein tyrosine phosphorylation are an essential aspect of egg activation after fertilization. Such changes result from the net contributions of both tyrosine kinases and phosphatases (PTP). This study was conducted to determine what role(s) PTP may have in egg activation. We identified four novel PTP in Chaetopterus pergamentaceus oocytes, cpPTPNT6, cpPTPNT7, cpPTPR2B, and cpPTPR2A, that have significant homology to, respectively, human PTPσ, ‐ρ, ‐D2 and ‐BAS. The first two are cytosolic and the latter two are transmembrane. Several PTP inhibitors were tested to see if they would affect Chaetopterus pergamentaceus fertilization. Eggs treated with β‐bromo‐4‐hydroxyacetophenone (PTP inhibitor 1) exhibited microvillar elongation, which is a sign of cortical changes resulting from activation. Those treated with Na 3 VO 4 underwent full parthenogenetic activation, including polar body formation and pseudocleavage and did so independently of extracellular Ca 2+ , which is required for the Ca 2+ oscillations that initiate development after fertilization. Fluorescence microscopy identified phosphotyrosine‐containing proteins in the cortex and around the nucleus of vanadate‐activated eggs, whereas in fertilized eggs they were concentrated only in the cortex. Immunoblots of vanadate‐activated and fertilized eggs showed tyrosine hyperphosphorylation of approximately140 kDa protein. These results suggest that PTP most likely maintain the egg in an inactive state by dephosphorylation of proteins independent of the Ca 2+ oscillations in the activation process.