海星卵母細胞成熟期間PRK2調節機制之探討﹝1/3﹞
Date Issued
2002-07-31
Date
2002-07-31
Author(s)
DOI
902313B002320
Abstract
Animal oocytes grow and acquire all the
required mRNA and proteins for the early
embryonic development. After growth
oocytes arrest in the prophase of meiosis I
until the stimulation of maturation hormone.
In starfish, maturation hormone,
1-methyladenine (1-MA), triggers the
activation of maturation promoting factor,
which is a major driving force for the
resumption of meiosis. At the mean time,
the protein synthesis machinery is also
activated for translating stored mRNA. 1-MA
is known to induce the activation of
inhibitory G protein that leads to a bifurcate
pathway including the activation of PI3
kinase and inactivation of adenylyl cyclase.
Although, we know both the increase in PI3
kinase and the decrease in adenylyl cyclase
activities are required for activation of MPF
and protein synthesis, the downstream
effectors of these signaling pathways are
unclear. Shortly after the induction of
1-MA, there is an increase in protein kinase
C like activity, which precedes the activation
of MPF and initiation of protein synthesis.
Later, this PKC-like activity is proved to be
mainly due to the protein kinase C-related
kinase 2 (PRK2). The initiation of protein
synthesis is activated by phosphorylation of
eukaryotic initiation factor 4E (eIF4E).
Recently, I further demonstrated that PRK2
phosphoryaltes eIF4E in vitro. (Lee et al.,
2000. Dev Biol. 228, 166-180.). In addition,
PRK2 activity is regulated by 1-MA-induced
PI3 kinase and adenylyl cyclase-dependent
pathway. These observations suggest PRK2
is the key molecule mediating this
G-protein-induced event during meiotic
maturation in starfish. However, the definite proof awaits PRK2 functional study
in vivo. This study aims to elucidate the
role and regulation of PRK2 during meiotic
maturation in starfish oocytes. Specifically,
I will ask whether the role of PRK2 in vivo
can be determined using known PRK2
activators and inhibitors, including a
constitutively active and a dominant-negative
PRK2. Due to the lack of the same starfish
species used in previous studies, our
laboratory is trying to use a native starfish,
Archaster typicus, collected at the beach of
PenHu and Asterias amurensis from
Tasmania, Australia. We have established a
system for testing the responses of Archaster
typicus and oocytes to maturation hormone.
We also demonstrated the presence of PRK2
protein in Asterias amurensis and possibly
Archaster typicus oocytes by Western
blotting or immunoprecipitation against
Pisaster ochraceus PRK2 antibody. In
addition, we also generated (1) a
constitutively active PRK2 by removing the
regulatory domain and (2) a
dominant-negative mutant by changing
PRK2 amino acid 666 from a lysine to an
arginine. The effects of PRK2 mutants
described on the maturation responses of
Archaster typicus and Asterias amurensis
oocytes are underway.
Subjects
starfish
oocyte maturation
PRK2
eIF4E, PI3 kinase and adenylyl
cyclase
cyclase
Publisher
臺北市：國立臺灣大學漁業科學研究所
Type
journal article
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