| Modification Notes |
The steroid progesterone induces the resumption of maturation in oocytes via a nongenomic pathway through binding to a novel membrane progestin receptor (mPR). This pathway inhibits adenylyl cyclase and reduces intracellular cAMP, and also activates mitogen-activated protein kinase to effect signal transduction pathways. Five distinct groups, designated å, ∫, ©, ∂ and ´, comprise the mPR gene family. mPRå, also designated progestin and adipoQ receptor family member VII (PAQR7), consists of an extracellular N-terminus, an intracellular C-terminus and seven transmembrane domains. mPRå is expressed in ovary, testis, placenta, uterus and bladder. mPR∫, or progestin and adipoQ receptor family member VIII (PAQR8), consists of eight putative transmembrane regions and an intracellular N-terminus that contains a leucine-rich motif. mPR∫ is a 354 amino acid protein expressed in brain and spinal cord. Both mPRå and mPR∫ may be G protein-coupled receptors and may be involved in oocyte maturation. |