The Two-Pore Domain Potassium Channel KCNK5: Induction by Estrogen Receptor α and Role in Proliferation of Breast Cancer Cells

Abstract

The growth of many human breast tumors requires the proliferative effect of estrogen acting via the estrogen receptor α (ERα). ERα signaling is therefore a clinically important target for breast cancer prevention and therapeutics. Although extensively studied, the mechanism by which ERα promotes proliferation remains to be fully established. We observed an up-regulation of transcript encoding the pH-sensitive two-pore domain potassium channel KCNK5 in a screen for genes stimulated by 17β-estradiol (E2) in the ERα(+) breast cancer cell lines MCF-7 and T47D. KCNK5 mRNA increased starting 1 h after the onset of E2 treatment, and protein levels followed after 12 h. Estrogen-responsive elements are found in the enhancer region of KCNK5, and chromatin immunoprecipitation assays revealed binding of ERα to the KCNK5 enhancer in E2-treated MCF-7 cells. Cells treated with E2 also showed increases in the amplitude of pH-sensitive potassium currents, as assessed by whole-cell recordings. These currents are blocked by clofilium. Although confocal microscopy suggested that most of the channels are located in intracellular compartments, the increase in macroscopic currents suggests that E2 treatment increases the number of active channels at the cell surface. Application of small interfering RNA specific for KCNK5 decreased pH-sensitive potassium currents and also reduced the estrogen-induced proliferation of T47D cells. We conclude that E2 induces the expression of KCNK5 via ERα(+) in breast cancer cells, and this channel plays a role in regulating proliferation in these cell lines. KCNK5 may therefore represent a useful target for treatment, for example, of tamoxifen-resistant breast cancer.

Estradiol-activated estrogen receptor α does not regulate mature microRNAs in T47D breast cancer cells

“…1, significant differences were observed between time points. Whereas the KCNK5 gene had its maximum response at 1 h [15], all three genes showed a strong and significant response at 24 h; at this time point, genes were shown to be upregulated between 10-and 57-fold. ICI induced ER␣ depletion resulted in inhibition of expression, demonstrating the key role of this receptor in their regulation.…”

“…The pS2 (TFF1), KCNK5, and SPINK4 genes, which have been shown to be regulated by ER␣ [10], were used to confirm ER␣ transcriptional activation by qPCR. These are involved in a range of cellular processes: PS2 is similar in function to some growth factors, KCNK5 is a potassium ion channel involved in breast cancer proliferation [15], and SPINK4 is a serine peptidase inhibitor. PS2 has a classical ERE in its promoter sequence, and KCNK5 has a binding site for ER␣ and is directly regulated through ER␣ DNA binding [15].…”

“…These are involved in a range of cellular processes: PS2 is similar in function to some growth factors, KCNK5 is a potassium ion channel involved in breast cancer proliferation [15], and SPINK4 is a serine peptidase inhibitor. PS2 has a classical ERE in its promoter sequence, and KCNK5 has a binding site for ER␣ and is directly regulated through ER␣ DNA binding [15]. We expected that 24 h treatment would result in a marked response of these genes, and that regulation would occur solely through ER␣.…”

The two-pore domain potassium channel KCNK5 deteriorates outcome in ischemic neurodegeneration

“…Interestingly, KCNK5 was recently described to be present in two estrogen receptor α-positive (EFα + ) tumor cell lines where it was further upregulated by 17β-estradiol treatment [2]. Notably, ischemic stroke increases expression of ERα, and this receptor is not suggested to be involved in estrogen-mediated neuroprotection in female mice [59].…”

ecancermedicalscience

“…These insights have resulted in candidate markers and target mechanisms in endocrine therapy. For example, gene expression profiling studies using microarrays have identified hundreds of oestrogen responsive genes, both transcriptional targets as well as those downstream of ER-regulated signalling pathways, which can be exploited as both markers of oestrogen responsiveness in tumour cells and as targetable genes and gene networks, which specifically regulate tumour cell proliferation [82–84]. Comparative analysis of sensitive and resistant cells may further elucidate markers and mechanisms of resistance.…”