Abstract
Aldosterone induces relevant effects binding to the mineralcorticoid receptor (MR), which acts as a ligand-gated transcription factor. Alternate mechanisms can mediate the action of aldosterone such as the activation of epidermal growth factor receptor (EGFR), MAPK/ERK, transcription factors and ion channels. The G-protein estrogen receptor (GPER) has been involved in the stimulatory effects of estrogenic signalling in breast cancer. GPER has been also shown to contribute to certain responses to aldosterone, however the role played by GPER and the molecular mechanisms implicated remain to be fully understood. Here, we evaluated the involvement of GPER in the stimulatory action exerted by aldosterone in breast cancer cells and breast tumor derived endothelial cells (B-TEC). Competition assays, gene expression and silencing studies, immunoblotting and immunofluorescence experiments, cell proliferation and migration were performed in order to provide novel insights into the role of GPER in the aldosterone-activated signalling. Our results demonstrate that aldosterone triggers the EGFR/ERK transduction pathway in a MR- and GPER-dependent manner. Aldosterone does not bind to GPER, it however induces the direct interaction between MR and GPER as well as between GPER and EGFR. Next, we ascertain that the up-regulation of the Na+/H+ exchanger-1 (NHE-1) induced by aldosterone involves MR and GPER. Biologically, both MR and GPER contribute to the proliferation and migration of breast and endothelial cancer cells mediated by NHE-1 upon aldosterone exposure. Our data further extend the current knowledge on the molecular mechanisms through which GPER may contribute to the stimulatory action elicited by aldosterone in breast cancer.
Highlights
Aldosterone elicits multiple biological effects binding to the mineralcorticoid receptor (MR), which acts as a ligand-gated transcription factor [1]
We began our study evaluating whether aldosterone could be able to activate the epidermal growth factor receptor (EGFR)/ERK transduction signalling in SkBr3 breast cancer cells and breast tumor derived endothelial cells (B-TEC) breast tumor-derived endothelial cells, which were used as model systems
We performed saturation curves and scatchard plot analyses using as radiotracers the G-protein estrogen receptor (GPER) ligand [3H]E2 [28, 31,32, 34,35,36] and the MR ligand [3H]aldosterone. [3H]E2 showed an estimated Bmax corresponding to 6799 ± 707.8 cpm/1 × 105 SkBr3 cells and an estimated Kd corresponding to 8.16 ± 1.70 nM (Figure 2A), whereas [3H]aldosterone showed an estimated Bmax corresponding to 2159 ± 229.2 cpm/1 × 105 SkBr3 cells and an estimated Kd corresponding to 0.42 ± 0.08 nM (Figure 2B)
Summary
Aldosterone elicits multiple biological effects binding to the mineralcorticoid receptor (MR), which acts as a ligand-gated transcription factor [1]. Rapid aldosterone signalling involves alternate mechanisms that include the activation of transduction pathways like tyrosine kinase c-Src, epidermal growth factor receptor (EGFR) and MAPK/ERK cascade [2,3,4]. Aldosterone activates ionic membrane transporters as the Na+/H+ exchanger (NHE1) and Na+/HCO3- cotransporter (NBC), which regulate the cellular pH and volume [6,7]. It has been shown that aldosterone stimulates www.impactjournals.com/oncotarget the survival and proliferation of renal carcinoma cells by upregulating K-RAS and the activation of the Akt and Raf pathways [12]. An aldosterone blocker inhibited the growth of hepatocellular carcinoma and angiogenesis both in vitro and in vivo [13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
