Cell glycosaminoglycans content modulates human voltage‐gated proton channel (H_V1) gating

Abstract

Voltage‐gated proton channels (HV1) have been found in many mammalian cells and play a crucial role in the immune system, male fertility, and cancer progression. Glycosaminoglycans play a significant role in various aspects of cell physiology, including the modulation of membrane receptors and ion channel function. We present here evidence that mechanosensitivity of the dimeric HV1 channel transduce changes on cell membrane fluidity related to the defective biosynthesis of chondroitin sulfate and heparan sulfate in Chinese Hamster Ovary (CHO‐745) cells into a leftward shift in the activation voltage dependence. This effect was accompanied by an increase in the H+ current, and an acceleration of the activation kinetics, under symmetrical or asymmetrical pH gradient (ΔpH) conditions. Similar gating alterations were evoked by two naturally occurring HV1 N‐terminal truncated isoforms expressed in wild‐type CHO‐K1 and CHO‐745 cells. On three different monomeric HV1 constructs, no alterations in the biophysical parameters were observed. Moreover, we have shown that HV1 gating can be modulated by manipulating CHO‐K1 cell membrane fluidity. Our results suggest that the defective biosynthesis of chondroitin sulfate and heparan sulfate on CHO‐745 cell increases membrane fluidity and allosterically modulates the coupling between voltage‐ and ΔpH‐sensing through the dimeric HV1 channel.

A synthetic flavonoid derivate in the plasma membrane transforms the voltage‐clamp fluorometry signal of CiHv1

“…This hypothesis is in accordance with previous studies demonstrating that altered packing in the cell membrane can modulate the gating process of various voltagegated channels [15]. It was previously reported that increased membrane fluidity increases the proton current through Hv1 measured at a given membrane potential, since the activation of the proton current is accelerated and the G-V function is shifted to the left indicating that Hv1 opens at a more negative membrane potential [16]. This is in good agreement with our results, since decreased membrane fluidity induced by Oxophench resulted in a slight inhibitory effect on the Hv1 current in a dose-dependent manner at a given membrane potential (Fig.…”

“…4G). This altered membrane fluidity results in an altered function of membrane proteinsand thus of the H V 1 ion channel [16] as observed in other voltagegated ion channels [15]. Consistently, it is reasonable to assume that in this more rigid medium, the conformational change of the H V 1 ion channel requires more energy as we previously showed in the case of K V 1.3 [30].…”

“…More specifically, they can increase the packing order of lipid heads and decrease membrane fluidity depending on their exact structure and functional groups [14]. This altered fluidity may have a pronounced effect on the activity of transmembrane proteins, e.g., ion channels [15] as demonstrated for the Hv1 ion channel [16]. Moreover, flavonoids can have a direct impact on ion channels.…”