Estrogen-related receptor alpha1 transcriptional activities are regulated in part via the ErbB2/HER2 signaling pathway.
We previously showed that (a) estrogen-related receptor alpha1 (ERRalpha1) down-modulates estrogen receptor (ER)-stimulated transcription in low ErbB2-expressing MCF-7 mammary carcinoma cells, and (b) ERRalpha and ErbB2 mRNA levels positively correlate in clinical breast tumors. We show here that ERRalpha1 represses ERalpha-mediated activation in MCF-7 cells because it failed to recruit the coactivator glucocorticoid receptor interacting protein 1 (GRIP1) when bound to an estrogen response element. In contrast, ERRalpha1 activated estrogen response element- and ERR response element-mediated transcription in ERalpha-positive, high ErbB2-expressing BT-474 mammary carcinoma cells, activation that was enhanced by overexpression of GRIP1. Likewise, regulation of the endogenous genes pS2, progesterone receptor, and ErbB2 by ERRalpha1 reflected the cell type-specific differences observed with our reporter plasmids. Importantly, overexpression of activated ErbB2 in MCF-7 cells led to transcriptional activation, rather than repression, by ERRalpha1. Two-dimensional PAGE of radiophosphate-labeled ERRalpha1 indicated that it was hyperphosphorylated in BT-474 relative to MCF-7 cells; incubation of these cells with anti-ErbB2 antibody led to reduction in the extent of ERRalpha1 phosphorylation. Additionally, mitogen-activated protein kinases (MAPK) and Akts, components of the ErbB2 pathway, phosphorylated ERRalpha1 in vitro. ERRalpha1-activated transcription in BT-474 cells was inhibited by disruption of ErbB2/epidermal growth factor receptor signaling with trastuzumab or gefitinib or inactivation of downstream components of this signaling, MAPK kinase/MAPK, and phosphatidylinositol-3-OH kinase/Akt, with U0126 or LY294002, respectively. Thus, ERRalpha1 activities are regulated, in part, via ErbB2 signaling, with ERRalpha1 likely positively feedback-regulating ErbB2 expression. Taken together, we conclude that ERRalpha1 phosphorylation status shows potential as a biomarker of clinical course and antihormonal- and ErbB2-based treatment options, with ERRalpha1 serving as a novel target for drug development.
Ariazi
Eric A
EA
McArdle Laboratory for Cancer Research, University of Wisconsin-Madison, Madison, WI 53706, USA.
Kraus
Richard J
RJ
Farrell
Michael L
ML
Jordan
V Craig
VC
Mertz
Janet E
JE
D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D024202:Electrophoretic Mobility Shift Assay; D066246:ErbB Receptors / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000378:metabolism; D004967:Estrogens / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D051958:Nuclear Receptor Coactivator 2 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D053766:Presenilin-2 / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000235:genetics* / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D000097983:ERRalpha Estrogen-Related Receptor
D066246:ErbB Receptors; D047628:Estrogen Receptor alpha; D004967:Estrogens; D020929:Mitogen-Activated Protein Kinase Kinases; D051958:Nuclear Receptor Coactivator 2; D019869:Phosphatidylinositol 3-Kinases; D053766:Presenilin-2; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D000097983:ERRalpha Estrogen-Related Receptor; C508861:PSEN2 protein, human