Nj. Winston et B. Maro, Changes in the activity of type 2A protein phosphatases during meiotic maturation and the first mitotic cell cycle in mouse oocytes, BIO CELL, 91(3), 1999, pp. 175-183
We have established an assay to measure protein phosphatase activity in mou
se oocytes using [P-32]-radiolabeled phosphorylase a as the substrate. Remo
val of the radiolabel from the substrate in vitro was linear with time and
could be inhibited totally by the addition of okadaic acid (inhibitor of ty
pe 1 and type 2 protein phosphatases), or partially by protein inhibitor 2
(inhibitor of type 1 protein phosphatases). We performed a detailed study o
f the activity of type 2A protein phosphatases in mouse oocytes undergoing
meiotic maturation and after parthenogenetic activation of mature oocytes a
rrested in metaphase II. Significant changes in the activity of type 2A pro
tein phosphatases were observed during the first meiotic and the first mito
tic cell cycles. These alterations in type 2A protein phosphatase activity
occurred in the absence of changes in the quantity of the catalytic subunit
and can be correlated with changes in the activity of protein kinases and
rearrangement of the cellular cytoskeleton. Our observations support a role
for type 2A protein phosphatases in cell cycle regulation and demonstrate
that, like the protein kinases, the type 2A phosphatases also undergo chang
es in their activity during early mammalian development. (C) Elsevier, Pari
s.