Lipid-dependent gating of a voltage-gated potassium channel

Abstract

Recent studies hypothesized that phospholipids stabilize two voltage-sensing arginine residues of certain voltage-gated potassium channels in activated conformations. It remains unclear how lipids directly affect these channels. Here, by examining the conformations of the KvAP in different lipids, we showed that without voltage change, the voltage-sensor domains switched from the activated to the resting state when their surrounding lipids were changed from phospholipids to nonphospholipids. Such lipid-determined conformational change was coupled to the ion-conducting pore, suggesting that parallel to voltage gating, the channel is gated by its annular lipids. Our measurements recognized that the energetic cost of lipid-dependent gating approaches that of voltage gating, but kinetically it appears much slower. Our data support that a channel and its surrounding lipids together constitute a functional unit, and natural nonphospholipids such as cholesterol should exert strong effects on voltage-gated channels. Our first observation of lipid-dependent gating may have general implications to other membrane proteins.

bSUM: A bead-supported unilamellar membrane system facilitating unidirectional insertion of membrane proteins into giant vesicles

“…Under such conditions, the channels with their intracellular side facing outside (the opposite of what we (Fig. 5 C, black arrow; Zheng et al, 2011). As a positive control, we showed that the L125C KvAP in bSUMs treated with detergents was reactive, probably because of the mobility of the voltage-sensor domains in the detergents (Fig.…”

“…the proteinaceous parts are solely responsible for voltagedependent function. Recent studies, however, recognize that lipids play critically important roles in the controlled opening or closing (gating) of these ion channels (Ramu et al, 2006;Schmidt et al, 2006;Schmidt and MacKinnon, 2008;Xu et al, 2008;Zheng et al, 2011;Jiang and Gonen, 2012;Brohawn et al, 2014;Hite et al, 2014). Compelling evidence from these studies suggests that lipids surrounding a voltage-gated potassium (Kv) channel exert strong gating effects on the channels by directly affecting the energetics behind the conformational changes of the voltage-sensor domains.…”

“…Such a membrane would allow the control of lipid composition and the predefined orientation of protein incorporation in membranes. It will enable us to quantitatively gating" effect (Schmidt et al, 2006;Zheng et al, 2011) to reflect the slower steady-state changes in the gating property of a channel. These studies suggest that many of the lipid molecules in eukaryotic cell membranes, which lack phosphate groups in their headgroup regions, for example, cholesterol, may exert specific gating effects on voltage-gated ion channels using a similar mechanism.…”

Amphipathic antenna of an inward rectifier K + channel responds to changes in the inner membrane leaflet

“…Data have been reported on the functionally modifying effects of membrane lipids on channel proteins that result in the gating equilibrium being altered (6,(9)(10)(11)(12)(13). In voltage-gated channels, the voltage-sensor domain (VSD) primarily senses changes in the membrane electric field, but this sensing is modulated by the lipid composition (9,11,13).…”

“…In voltage-gated channels, the voltage-sensor domain (VSD) primarily senses changes in the membrane electric field, but this sensing is modulated by the lipid composition (9,11,13). For the non-voltage-gated (the twotransmembrane-helix inward-rectifier type) channels, such as the KcsA potassium channel from Streptomyces lividans, the underlying mechanism of the effect exerted by lipids is still undergoing extensive investigation, even though the structural information on the channel proteins cocrystallized with lipid molecules has already been reported (14)(15)(16)).…”