Involvement of annexin 5 in G protein mediated signal transduction

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A new G protein mediated signal transduction mechanism was studied. It was clarified that annexin 5 took part in the G protein coupled signal transduction process. Annexin is a member of newly identified calcium-phospholipid binding proteins. The outline of the results is brought together as follows.1.From GnRH receptor to annexin 5 synthesisIt was clarified that the MAPK system lay between the GnRH receptor and annexin 5 mRNA synthesis in the pituitary gonadotropes. In addition, it was observed that annexin 5 was indispensable to the process that GnRH promotes the gonadotrophin secretion, and clarified that annexin 5 was a new signal factor of the GnRH receptor signal transduction.2.Annexin 5 in the ovaryChanges in ovarian annexin 5 were analyzed. The synthesis of annexin 5 was demonstrated to start after luteinization and the expression of annexin 5 was inhibited by prolactin. It was clarified that annexin 5 appeared in corpus luteum by the inhibition of prolactin secretion and those cells were in apoptosis. In addition, it was clarified that local GnRH enhanced annexin 5 expression and induced apoptosis.3.Annexin 5 in the testisAnnexin 5 was demonstrated to distribute to various testicular cells. Among these, endotherial cells and Leydig dells were intensely stained with anti-annexin 5. It was clarified that annexin 5 of Leydig cells was increased by the administration of human chorinic gonadotropin. This effect was shown to be mediated by the local GnRH action.Getting together, annexin 5 was shown to be under the control of GnRH receptor in the anterior pituitary gonadotropes, luteal cells and Leydig cells. Annexin 5 is a biomarker of GnRH receptor. GnRH receptor-annexin 5 system seems to be utilized in various cell species.