Atomistic mechanism of noncanonical voltage gating in K channels.

In classical voltage-gated cation channels, the movement of a voltage-sensing domain (VSD) opens a gate in the pore domain. However, two-pore domain K (K) channels lack a VSD and instead rely on K movement within the selectivity filter (SF) to convert voltage changes into pore opening. To uncover the atomistic basis of voltage gating in TREK K channels, we integrated large-scale atomistic molecular dynamics simulations with extensive mutagenesis and patch-clamp electrophysiology, including sucrose-based experiments.

Cryo-EM structure of the human THIK-1 K2P K channel reveals a lower Y gate regulated by lipids and anesthetics.

THIK-1 (KCNK13) is a halothane-inhibited and anionic-lipid-activated two-pore domain (K2P) K channel implicated in microglial activation and neuroinflammation, and a current target for the treatment of neurodegenerative disorders, for example Alzheimer's disease and amyothropic lateral sclerosis (ALS). However, compared to other K2P channels, little is known about the structural and functional properties of THIK-1. Here we present a 3.

Structures of TASK-1 and TASK-3 K2P channels provide insight into their gating and dysfunction in disease.

TASK-1 and TASK-3 are pH-sensitive two-pore domain (K2P/KCNK) K channels. Their functional roles make them promising targets for treatment of multiple disorders including sleep apnea, pain, and atrial fibrillation. Mutations in these channels are also associated with neurodevelopmental and hypertensive disorders.

Ion occupancy of the selectivity filter controls opening of a cytoplasmic gate in the K channel TALK-2.

Two-pore domain K (K) channel activity was previously thought to be controlled primarily via a selectivity filter (SF) gate. However, recent crystal structures of TASK-1 and TASK-2 revealed a lower gate at the cytoplasmic pore entrance. Here, we report functional evidence of such a lower gate in the K channel K2P17.

Atomistic mechanism of coupling between cytosolic sensor domain and selectivity filter in TREK K2P channels.

The two-pore domain potassium (K) channels TREK-1 and TREK-2 link neuronal excitability to a variety of stimuli including mechanical force, lipids, temperature and phosphorylation. This regulation involves the C-terminus as a polymodal stimulus sensor and the selectivity filter (SF) as channel gate. Using crystallographic up- and down-state structures of TREK-2 as a template for full atomistic molecular dynamics (MD) simulations, we reveal that the SF in down-state undergoes inactivation via conformational changes, while the up-state structure maintains a stable and conductive SF.

Extracellular modulation of TREK-2 activity with nanobodies provides insight into the mechanisms of K2P channel regulation.

Potassium channels of the Two-Pore Domain (K2P) subfamily, KCNK1-KCNK18, play crucial roles in controlling the electrical activity of many different cell types and represent attractive therapeutic targets. However, the identification of highly selective small molecule drugs against these channels has been challenging due to the high degree of structural and functional conservation that exists not only between K2P channels, but across the whole K channel superfamily. To address the issue of selectivity, here we generate camelid antibody fragments (nanobodies) against the TREK-2 (KCNK10) K2P K channel and identify selective binders including several that directly modulate channel activity.

Validation of TREK1 ion channel activators as an immunomodulatory and neuroprotective strategy in neuroinflammation.

Modulation of two-pore domain potassium (K) channels has emerged as a novel field of therapeutic strategies as they may regulate immune cell activation and metabolism, inflammatory signals, or barrier integrity. One of these ion channels is the TWIK-related potassium channel 1 (TREK1). In the current study, we report the identification and validation of new TREK1 activators.

Gain-of-function mutations in KCNK3 cause a developmental disorder with sleep apnea.

Sleep apnea is a common disorder that represents a global public health burden. KCNK3 encodes TASK-1, a K channel implicated in the control of breathing, but its link with sleep apnea remains poorly understood. Here we describe a new developmental disorder with associated sleep apnea (developmental delay with sleep apnea, or DDSA) caused by rare de novo gain-of-function mutations in KCNK3.

The versatile regulation of K2P channels by polyanionic lipids of the phosphoinositide and fatty acid metabolism.

Work over the past three decades has greatly advanced our understanding of the regulation of Kir K+ channels by polyanionic lipids of the phosphoinositide (e.g., PIP2) and fatty acid metabolism (e.

An otopetrin family proton channel promotes cellular acid efflux critical for biomineralization in a marine calcifier.

Otopetrins comprise a family of proton-selective channels that are critically important for the mineralization of otoliths and statoconia in vertebrates but whose underlying cellular mechanisms remain largely unknown. Here, we demonstrate that otopetrins are critically involved in the calcification process by providing an exit route for protons liberated by the formation of CaCO Using the sea urchin larva, we examined the otopetrin ortholog , which is exclusively expressed in the calcifying primary mesenchymal cells (PMCs) that generate the calcitic larval skeleton. expression is stimulated during skeletogenesis, and knockdown of impairs spicule formation.

Norfluoxetine inhibits TREK-2 K2P channels by multiple mechanisms including state-independent effects on the selectivity filter gate.

The TREK subfamily of two-pore domain K+ (K2P) channels are inhibited by fluoxetine and its metabolite, norfluoxetine (NFx). Although not the principal targets of this antidepressant, TREK channel inhibition by NFx has provided important insights into the conformational changes associated with channel gating and highlighted the role of the selectivity filter in this process. However, despite the availability of TREK-2 crystal structures with NFx bound, the precise mechanisms underlying NFx inhibition remain elusive.

Selectivity filter instability dominates the low intrinsic activity of the TWIK-1 K2P K channel.

Two-pore domain K (K2P) channels have many important physiological functions. However, the functional properties of the TWIK-1 (K2P1.1/) K2P channel remain poorly characterized because heterologous expression of this ion channel yields only very low levels of functional activity.

The molecular basis for an allosteric inhibition of K-flux gating in K channels.

Two-pore-domain potassium (K) channels are key regulators of many physiological and pathophysiological processes and thus emerged as promising drug targets. As for other potassium channels, there is a lack of selective blockers, since drugs preferentially bind to a conserved binding site located in the central cavity. Thus, there is a high medical need to identify novel drug-binding sites outside the conserved lipophilic central cavity and to identify new allosteric mechanisms of channel inhibition.

A pharmacological master key mechanism that unlocks the selectivity filter gate in K channels.

Potassium (K) channels have been evolutionarily tuned for activation by diverse biological stimuli, and pharmacological activation is thought to target these specific gating mechanisms. Here we report a class of negatively charged activators (NCAs) that bypass the specific mechanisms but act as master keys to open K channels gated at their selectivity filter (SF), including many two-pore domain K (K) channels, voltage-gated hERG (human ether-à-go-go-related gene) channels and calcium (Ca)-activated big-conductance potassium (BK)-type channels. Functional analysis, x-ray crystallography, and molecular dynamics simulations revealed that the NCAs bind to similar sites below the SF, increase pore and SF K occupancy, and open the filter gate.

The VAMP-associated protein VAPB is required for cardiac and neuronal pacemaker channel function.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels encode neuronal and cardiac pacemaker currents. The composition of pacemaker channel complexes in different tissues is poorly understood, and the presence of additional HCN modulating subunits was speculated. Here we show that vesicle-associated membrane protein-associated protein B (VAPB), previously associated with a familial form of amyotrophic lateral sclerosis 8, is an essential HCN1 and HCN2 modulator.

Bilayer-Mediated Structural Transitions Control Mechanosensitivity of the TREK-2 K2P Channel.

The mechanosensitive two-pore domain (K2P) K channels (TREK-1, TREK-2, and TRAAK) are important for mechanical and thermal nociception. However, the mechanisms underlying their gating by membrane stretch remain controversial. Here we use molecular dynamics simulations to examine their behavior in a lipid bilayer.

Sodium permeable and "hypersensitive" TREK-1 channels cause ventricular tachycardia.

In a patient with right ventricular outflow tract (RVOT) tachycardia, we identified a heterozygous point mutation in the selectivity filter of the stretch-activated K potassium channel TREK-1 ( or K2.1). This mutation introduces abnormal sodium permeability to TREK-1.

Polymodal activation of the TREK-2 K2P channel produces structurally distinct open states.

The TREK subfamily of two-pore domain (K2P) K(+) channels exhibit polymodal gating by a wide range of physical and chemical stimuli. Crystal structures now exist for these channels in two main states referred to as the "up" and "down" conformations. However, recent studies have resulted in contradictory and mutually exclusive conclusions about the functional (i.

A Non-canonical Voltage-Sensing Mechanism Controls Gating in K2P K(+) Channels.

Two-pore domain (K2P) K(+) channels are major regulators of excitability that endow cells with an outwardly rectifying background "leak" conductance. In some K2P channels, strong voltage-dependent activation has been observed, but the mechanism remains unresolved because they lack a canonical voltage-sensing domain. Here, we show voltage-dependent gating is common to most K2P channels and that this voltage sensitivity originates from the movement of three to four ions into the high electric field of an inactive selectivity filter.