Protein Kinase A(PKA)-Restrictcive and PKA-Permissive Phases of Oocyte Maturation

Substantial evidence has indicated that cAMP-dependent protein kinase (protein kinase A orPKA) plays a critical role in maintaining meiotic prophase arrest in vertebrate oocytes.However, PKA activity dynamic and its physiological substrate profile remain poorly defined.We have recently developed a novel PKA substrate construct which we employ to monitor PKAactivity in live oocytes. In the current study, we have employed biochemical and imaginganalyses of single cells to determine PKA activity dynamics during oocyte maturation and toinvestigate the consequence of re-activation of PKA during oocyte maturation. Wedemonstrated here that progesterone caused a rapid and permanent inhibition of PKA during theentire maturation process. However, artificial reactivation of endogenous PKA had differentialconsequences, depending on the timing of PKA reactivation. Reactivation of endogenous PKAat any time prior to GVBD inhibited progesterone-induced GVBD. PKA reactivation at GVBD,or thereafter, did not interfere with meiosis I to meiosis II transition, nor did it interfere withmetaphase II arrest. These results demonstrate for the first time a PKA-restricted phase and aPKA-permissive phase during oocyte maturation.