The Membrane Cholesterol Modulates the Interaction Between 17-βEstradiol and the BK Channel.

Sara T Granados,Ramon Latorre,Yolima P Torres

doi:10.3389/fphar.2021.687360

Sara T Granados, Ramon Latorre + Show 1 more

Open Access

https://doi.org/10.3389/fphar.2021.687360

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Abstract

BK channels are composed by the pore forming α subunit and, in some tissues, is associated with different accessory β subunits. These proteins modify the biophysical properties of the channel, amplifying the range of BK channel activation according to the physiological context. In the vascular cells, the pore forming BKα subunit is expressed with the β1 subunit, where they play an essential role in the modulation of arterial tone and blood pressure. In eukaryotes, cholesterol is a structural lipid of the cellular membrane. Changes in the ratio of cholesterol content in the plasma membrane (PM) regulates the BK channel activation altering its open probability, and hence, vascular contraction. It has been shown that the estrogen 17β-Estradiol (E2) causes a vasodilator effect in vascular cells, inducing a leftward shift in the V0.5 of the GV curve. Here, we evaluate whether changes in the membrane cholesterol concentration modify the effect that E2 induces on the BKα/β1 channel activity. Using binding and electrophysiology assays after cholesterol depletion or enrichment, we show that the cholesterol enrichment significantly decreases the expression of the α subunit, while cholesterol depletion increased the expression of that α subunit. Additionally, we demonstrated that changes in the membrane cholesterol cause the loss of the modulatory effect of E2 on the BKα/β1 channel activity, without affecting the E2 binding to the complex. Our data suggest that changes in membrane cholesterol content could affect channel properties related to the E2 effect on BKα/β1 channel activity. Finally, the results suggest that an optimal membrane cholesterol content is essential for the activation of BK channels through the β1 subunit.

Highlights

The large-conductance, Ca2+- and voltage-activated K+ (BK) channel is a transmembrane protein formed by four α subunits (Latorre et al, 2017)
If changes in membrane cholesterol content affected cell viability and we found that it was not affected after cholesterol depletion (HEK 293: from 100 to 97.6% ± 11.6; BKα/ β1-HEK 293: 100 to 84.2% ± 4) or enrichment (HEK 293: from 100 to 94.7% ± 3.7; BKα/β1-HEK 293: 100 to 84% ± 10.5) in any of the evaluated cells (Figure 1D)
To evaluate if changes in the membrane cholesterol content affect the modulation that E2 induces in BK channel activity, we evaluate the effect of E2 in biophysical properties of BKα/β1 channel expressed in cells after cholesterol depletion or enrichment

Summary

Introduction

The large-conductance, Ca2+- and voltage-activated K+ (BK) channel is a transmembrane protein formed by four α subunits (Latorre et al, 2017). The α subunit is ubiquitously expressed in mammalian tissues. BK channels can be modulated by estrogens such as 17β-Estradiol (E2), when α subunit is co-expressed with the β1 subunit (Valverde et al, 1999; De Wet et al, 2006; Granados et al, 2019). E2 increases the open probability of the BK channel (Valverde et al, 1999; De Wet et al, 2006; Granados et al, 2019), which can regulate the vascular tone, causing a protector effect on the vascular tissue (Plüger et al, 2000; Löhn et al, 2001)

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