Phosphorylation of MNAR promotes estrogen activation of phosphatidylinositol 3-kinase.
Estrogen actions are mediated by a complex interface of direct control of gene expression (the so-called "genomic action") and by regulation of cell signaling/phosphorylation cascades, referred to as the "nongenomic," or extranuclear, action. We have previously described the identification of MNAR (modulator of nongenomic action of estrogen receptor) as a novel scaffold protein that regulates estrogen receptor alpha (ERalpha) activation of cSrc. In this study, we have investigated the role of MNAR in 17beta-estradiol (E2)-induced activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Consistent with our previous results, a direct correlation was established between MNAR expression levels and E2-induced activation of PI3 and Akt kinases. Endogenous MNAR, ERalpha, cSrc, and p85, the regulatory subunit of PI3 kinase, interacted in MCF7 cells treated with E2. The interaction between p85 and MNAR required activation of cSrc and MNAR phosphorylation on Tyr 920. Consequently, the mutation of this tyrosine to alanine (Y920A) abrogated the interaction between MNAR and p85 and the E2-induced activation of the PI3K/Akt pathway, which was required for the E2-induced protection of MCF7 cells from apoptosis. Nonetheless, the Y920A mutant potentiated the E2-induced activation of the Src/MAPK pathway and MCF7 cell proliferation, as observed with the wild-type MNAR. These results provide new and important insights into the molecular mechanisms of E2-induced regulation of cell proliferation and apoptosis.
Greger
James G
JG
Women's Health and Musculoskeletal Biology, Wyeth Research, Nuclear Receptors, 500 Arcola Road, Collegeville, PA 19426, USA.
Fursov
Natalie
N
Cooch
Neil
N
McLarney
Sean
S
Freedman
Leonard P
LP
Edwards
Dean P
DP
Cheskis
Boris J
BJ
D000409:Alanine / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004789:Enzyme Activation / Q000187:drug effects; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D020935:MAP Kinase Signaling System; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism*; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D000409:Alanine; D004958:Estradiol; D047628:Estrogen Receptor alpha; D004967:Estrogens; D049452:Green Fluorescent Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D011960:Receptors, Estrogen; D014443:Tyrosine; D019061:src-Family Kinases