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17β-Estradiol inhibits outward voltage-gated K⁺ currents in human osteoblast-like MG63 cells
Xiantao Li1, Shouchao Zheng, Xuehai Dong
1College of Biomedical Engineering, South-Central University for Nationalities, 708 Minyuan Road, Wuhan 430074, People's Republic of China.
Abstract:
Previous studies have shown that 17β-estradiol has a pivotal function by blocking voltage-gated K⁺ (Kv) channels in several different types of cells such as cardiac myocytes and neurons. Outward Kv currents can also be measured in osteoblasts, although little is known about the effects of 17β-estradiol on these currents. In human osteoblast-like MG63 cells, we found that 17β-estradiol inhibits peak and end Kv currents, with IC₅₀ values of 480 and 325 nM, respectively. To elucidate the mechanism of inhibition, the kinetics of Kv currents were investigated. The half-maximum activation potential (V(½)) was 1.3 mV and was shifted left to -4.4 mV after application of 500 nM 17β-estradiol. For steady-state inactivation, the V(½) was -55.0 mV and weakly shifted left to -58.2 mV. To identify the molecular basis of outward Kv currents in MG63 cells, we performed RT-PCR analyses. The expression of Kv2.1 channels appeared to dominate over that of other Kv channels in MG63 cells. In COS-7 cells with heterologously expressed Kv2.1 channels, 17β-estradiol also inhibits macroscopic currents of Kv2.1. Our data indicate that 17β-estradiol inhibits Kv currents in human osteoblast-like MG63 cells and that Kv2.1 is a potential molecular correlate of outward Kv currents in these cells.
Insights
17β-estradiol inhibits potassium (Kv) channels in human osteoblasts, potentially via Kv2.1 channels. This finding offers insights into hormone action in bone cells.
Area of Science:
- Molecular Biology
- Cell Physiology
- Pharmacology
Background:
- 17β-estradiol is known to block voltage-gated potassium (Kv) channels in various cell types.
- Kv currents are present in osteoblasts, but the effect of 17β-estradiol on these currents is not well understood.
Purpose of the Study:
- To investigate the effects of 17β-estradiol on Kv currents in human osteoblast-like MG63 cells.
- To elucidate the mechanism of inhibition and identify the molecular Kv channel subtypes involved.
Main Methods:
- Patch-clamp electrophysiology was used to measure Kv currents in MG63 cells.
- Kinetic analysis of Kv current activation and inactivation was performed.
- RT-PCR was employed to identify Kv channel gene expression in MG63 cells.
- Heterologous expression of Kv2.1 channels in COS-7 cells was used to confirm channel function.
Main Results:
- 17β-estradiol inhibited peak and sustained Kv currents in MG63 cells with IC₅₀ values of 480 nM and 325 nM, respectively.
- 17β-estradiol shifted the half-maximum activation potential of Kv currents to more negative potentials.
- RT-PCR analysis indicated that Kv2.1 channel expression was dominant in MG63 cells.
- 17β-estradiol inhibited macroscopic currents in COS-7 cells expressing Kv2.1 channels.
Conclusions:
- 17β-estradiol effectively inhibits Kv currents in human osteoblast-like MG63 cells.
- Kv2.1 channels are likely a key molecular component responsible for the outward Kv currents in these cells.
- These findings suggest a potential role for Kv2.1 channels in mediating the effects of 17β-estradiol in osteoblasts.
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