The modulator of nongenomic actions of the estrogen receptor (MNAR) regulates transcription-independent androgen receptor-mediated signaling: evidence that MNAR participates in G protein-regulated meiosis in Xenopus laevis oocytes.
Classical steroid receptors mediate many transcription-independent (nongenomic) steroid responses in vitro, including activation of Src and G proteins. Estrogen-triggered activation of Src can be regulated by the modulator of nongenomic actions of the estrogen receptor (MNAR), which binds to estrogen receptors and Src to create a signaling complex. In contrast, the mechanisms regulating steroid-induced G protein activation are not known, nor are the physiologic responses mediated by MNAR. These studies demonstrate that MNAR regulates the biologically relevant process of meiosis in Xenopus laevis oocytes. MNAR was located throughout oocytes, and reduction of its expression by RNA interference markedly enhanced testosterone-triggered maturation and activation of MAPK. Additionally, Xenopus MNAR augmented androgen receptor (AR)-mediated transcription in CV1 cells through activation of Src. MNAR and AR coimmunoprecipitated as a complex involving the LXXLL-rich segment of MNAR and the ligand binding domain of AR. MNAR and Gbeta also precipitated together, with the same region of MNAR being important for this interaction. Finally, reduction of MNAR expression decreased Gbetagamma-mediated signaling in oocytes. MNAR therefore appears to participate in maintaining meiotic arrest, perhaps by directly enhancing Gbetagamma-mediated inhibition of meiosis. Androgen binding to AR might then release this inhibition, allowing maturation to occur. Thus, MNAR may augment multiple nongenomic signals, depending upon the context and cell type in which it is expressed.
Haas
Derek
D
Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8857, USA.
White
Stacy N
SN
Lutz
Lindsey B
LB
Rasar
Melissa
M
Hammes
Stephen R
SR
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D056970:Co-Repressor Proteins; D004305:Dose-Response Relationship, Drug; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008024:Ligands; D020935:MAP Kinase Signaling System; D008540:Meiosis; D008954:Models, Biological; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D011944:Receptors, Androgen / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism; D015398:Signal Transduction; D013739:Testosterone / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection; D014981:Xenopus; D014982:Xenopus laevis; D019061:src-Family Kinases / Q000378:metabolism
D056970:Co-Repressor Proteins; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D008024:Ligands; C438485:PELP1 protein, human; D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D015534:Trans-Activators; D014157:Transcription Factors; D013739:Testosterone; D019061:src-Family Kinases; D019204:GTP-Binding Proteins; D002118:Calcium