Roles of progesterone receptor membrane component 1 and membrane progestin receptor alpha in regulation of zebrafish oocyte maturation

Abstract

Although previous studies suggest membrane progesterone receptor alpha (mPRα/Paqr7) mediates 17, 20β-dihydroxy-4-pregnen-3-one (DHP) induction of oocyte maturation (OM) in zebrafish, critical information needed to establish mPRα as the receptor mediating OM is lacking. The relative potencies of progestins and specific mPRα agonists in inducing OM matched their relative binding affinities for zebrafish mPRα, supporting its role in OM. Microinjection of pertussis toxin blocked DHP induction of OM and the progestin-induced decrease in cyclic AMP levels, suggesting mPRα activates an inhibitory G protein (Gi). Microinjection of morpholino antisense oligonucleotides to zebrafish pgrmc1 blocked induction of OM by DHP which was accompanied by decreased levels of Pgrmc1 and mPRα on the oocyte plasma membranes. Similarly, treatment of denuded oocytes with a PGRMC1 inhibitor, AG205, blocked the gonadotropin-induced increase in plasma membrane mPRα levels and attenuated DHP induction of OM. Co-incubation with two inhibitors of epidermal growth factor Erbb2, ErbB2 inhibitor II and AG 879, prevented induction of OM by DHP, indicating the likely involvement of Erbb2 in mPRα-mediated signaling. Treatment with AG205 reversed the inhibitory effects of the Erbb2 inhibitors on OM and also inhibited insulin-like growth factor-1 induction of OM. Close associations between Pgrmc1 and mPRα, and between Pgrmc1 and Erbb2 were detected in zebrafish oocytes with in situ proximity ligation assays. The results suggest progestin induction of OM in zebrafish is mediated through an mPRα/Gi/Erbb2 signaling pathway that requires Pgrmc1 for expression of mPRα on oocyte membranes and that Pgrmc1 also is required for induction of OM through Erbb2.

Pgrmc1 Knockout Impairs Oocyte Maturation in Zebrafish

“…Expression of mPRα, the nuclear progesterone receptor (Pgr), and Pgrmc1 in the fully-grown Stage IVa immature follicles was confirmed by Western blot analysis using previously characterized polyclonal zebrafish antibodies ( 8 , 21 , 27 ). In brief, Stage IVa follicles were collected from adult zebrafish following protocols described previously ( 21 , 22 ).…”

PGRMC1 phosphorylation and cell plasticity 2: genomic integrity and CpG methylation

“…Indeed, PGRMC1-associated membrane trafficking determines the cell surface localization of a number of different proteins including e.g., epidermal growth factor receptor (Ahmed et al, 2010a), insulin receptor and glucose transporters GLUT-1 and GLUT-4 in A549 lung cancer cells (Hampton et al, 2018), glucagon-like peptide-1 (GLP-1) receptor complex in pancreatic beta cells , synaptic vesicles in the central nervous system (Izzo et al, 2014), and membrane progestin receptor α (mPRα) in rat granulosa cells (Thomas et al, 2014) and maturing zebrafish oocytes (Aizen et al, 2018). The translocation of transmembrane proteins such as membrane receptors to the cell surface could underlie much of the biology attributed to PGRMC1 (Ahmed et al, 2010b).…”

G protein-coupled estrogen receptor is not required for sex determination or ovary function in zebrafish

“…GPER was shown to regulate oocyte maturation in vitro. In carp (Cyprinus carpio) and zebrafish, maturation of cultured oocytes is regulated by estrogens and progestogens, where pharmacologic and RNA interference approaches demonstrated that estrogens inhibit maturation via GPER while progestogens promote maturation via membrane progesterone receptors [5,[27][28][29][30]. In ovaries cultured from golden hamsters (Mesocricetus auratus), estradiol promoted the formation of primordial follicles in a GPER-dependent manner [31].…”