Estrogen Receptor α Rapidly Activates the IGF-1 Receptor Pathway

Abstract

Estrogen and insulin-like-growth factor 1 (IGF-1) are potent mitogenic stimuli that share important properties in the control of cellular proliferation. However, the coupling between the signaling cascades of estrogen receptors ␣ and ␤ and the IGF-1 receptor (IGF-1R) is poorly understood. Therefore, we selectively transfected estrogen receptor ␣ or ␤ in COS7 and HEK293 cells, which contain IGF-1R. In presence of estrogen receptor ␣ but not ␤, 17␤-estradiol (E2) rapidly induces phosphorylation of the IGF-1R and the extracellular signal-regulated kinases 1/2. Furthermore, upon stimulation with E2, estrogen receptor ␣ but not ␤ bound rapidly to the IGF-1R in COS7 as well as L6 cells, which express all investigated receptors endogenously. Control experiments in the IGF-1R-deficient fibroblast cell line R ؊ showed that after stimulation with E2 only estrogen receptor ␣ bound to the transfected IGF-1R. Overexpression of dominant negative mitogen-activated protein kinases kinase inhibited this effect. Finally, estrogen receptor ␣ but not ␤ is required to induce the activation of the estrogen receptor-responsive reporter ERE-LUC in IGF-1-stimulated cells. Taken together, these data demonstrate that ligand bound estrogen receptor ␣ is required for rapid activation of the IGF-1R signaling cascade.Estrogen as well as insulin-like growth factor 1 (IGF-1) 1 are potent mitogens that are involved in a large array of processes that control proliferation and differentiation in mammalian cells (1, 2). Both mitogens act through receptor-mediated signaling pathways. The cross-talk between these two signaling pathways is currently under investigation (3-6). Estrogen is a steroid hormone that binds to members of the nuclear receptor superfamily (7), whereas IGF-1 as a peptide-growth factor binds to a transmembrane tyrosine kinase receptor, which signals via a series of phosphorylation events (2).Two different estrogen receptors, ER␣ and ER␤, which are encoded by genes located on different chromosomes, have been identified so far (8,9). Sequence analysis demonstrates a high degree of homology between ER␣ and ER␤ in the DNA-binding domain and the ligand-binding domain. However, there are significant differences in regions that would be expected to influence transcriptional activity. The ability of estrogen receptors to activate target gene transcription has been attributed to two regions: the N-terminal activation function 1 (AF-1) and the ligand-dependent AF-2, which is localized in the C-terminal hormone-binding domain (10, 11). AF-1 and AF-2 can activate transcription independently and synergistically, and they act in a promoter-and cell-specific manner (12, 13). Phosphorylation of a serine residue at position 118 is required for full action of the AF-1 (14). Both AF-1 and AF-2 are required to enhance transcription of target genes through AP-1 sites (15). Interestingly, ER␣ and ER␤ act differently at AP-1 sites (16), which may be due to differences in their AF domains (17). ER␣ and ER␤ can form homo-and heterodimers (18), and thus t...

Estrogens stimulate the proliferation of human cholangiocarcinoma by inducing the expression and secretion of vascular endothelial growth factor

“…This cell line markedly proliferated when exposed to 17β-estradiol or IGF1, which also inhibited apoptosis with additive effects [12]. Estrogens exerted their proliferative effects by acting on both ER and IGF1-R with a sort of functional coupling of the two receptors, specifically ER-α and IGF1-R, and this was previously shown in different neoplastic and non-neoplastic cell types [18][19]. In the present study we evaluated the involvement of VEGF and related receptors in the estrogen-indu0ced proliferation of HuH-28 cells.…”

“…Cell extracts (10 μg) were diluted in 6× LSB (Laemly sample buffer) containing 0.3 M 2-mercaptoethanol and resolved by 10% SDS-polyacrylamide gel electrophoresis. Western blotting was performed as described [18,19] by using the following primary antibodies: (1) anti-PCNA, specific mouse monoclonal antibody (1:350 dilution; Santa Cruz); (2) anti-VEGF-A (1:200 dilution; Santa Cruz); (3) anti-VEGF-C; rabbit polyclonal antibody (1:2000 dilution; Zymed); (4) anti-VEGFR-1 mouse monoclonal antibody (1:100 dilution; Sigma); (5) anti-VEGFR-2 rabbit polyclonal antibody (1:1250 dilution: Upstate Biotechnology); (6) anti-VEGFR-3 rabbit polyclonal antibody (1:200 dilution; Santa Cruz); (7) anti-β actin, mouse monoclonal antibody (1:1500 dilution; Sigma). As secondary antibodies, anti-mouse IgG peroxidase conjugated (Sigma; 1:2000) or anti-rabbit IgG peroxidase conjugated (1:10,000; Sigma) or anti-goat IgG peroxidase conjugated (1:10,000; Sigma) were used.…”

Nuclear insulin receptor substrate 1 interacts with estrogen receptor α at ERE promoters

“…ERa association with cytoplasmic signaling molecules is not unusual. Recently, ERa has been shown to bind the PI-3K/Akt complex (Simoncini et al, 2000;Sun et al, 2001), and to interact with growth factor receptor docking protein Shc (Song et al, 2002) as well as with IGF-IR (Kahlert et al, 2000). Similarly, we reported that unliganded ERa can associate with cytoplasmic IRS-1 in MDA-MB-231/ER cells (Morelli et al, 2003).…”

A Novel Taspine Derivative, HMQ1611, Inhibits Breast Cancer Cell Growth via Estrogen Receptor α and EGF Receptor Signaling Pathways

“…In addition to this genomic mechanism of ERa, increasing experimental evidence has showed its nongenomic effect, which can be rapidly activated by estrogen (8)(9)(10)(11)(12). The membrane ERa can also transactivate insulin-like growth factor 1 receptor (IGF-1R) and EGF receptor (EGFR)/HER2, which leads to the activation of the downstream extracellular signal-regulated kinases (ERK) signaling cascade (13)(14)(15). For ERapositive breast cancer, anti-ER treatment strategies involve selective estrogen receptor modulators (SERMs), selective estrogen receptor downregulators, and disruption of estrogen synthesis (16)(17)(18).…”