scholarly journals Enhancement of TWIK-related Acid-sensitive Potassium Channel 3 (TASK3) Two-pore Domain Potassium Channel Activity by Tumor Necrosis Factor α

2013 ◽  
Vol 289 (3) ◽  
pp. 1388-1401 ◽  
Author(s):  
Mickael-F El Hachmane ◽  
Kathryn A. Rees ◽  
Emma L. Veale ◽  
Vadim V. Sumbayev ◽  
Alistair Mathie
Keyword(s):  
Potassium Channel ◽  
Cell Voltage ◽  
Cell Types ◽  
Resting Membrane Potential ◽  
Channel Activity ◽  
Inflammatory Conditions ◽  
C Terminus ◽  
K2p Channels ◽  
Factor Α ◽  
Pore Domain

TASK3 two-pore domain potassium (K2P) channels are responsible for native leak K channels in many cell types which regulate cell resting membrane potential and excitability. In addition, TASK3 channels contribute to the regulation of cellular potassium homeostasis. Because TASK3 channels are important for cell viability, having putative roles in both neuronal apoptosis and oncogenesis, we sought to determine their behavior under inflammatory conditions by investigating the effect of TNFα on TASK3 channel current. TASK3 channels were expressed in tsA-201 cells, and the current through them was measured using whole cell voltage clamp recordings. We show that THP-1 human myeloid leukemia monocytes, co-cultured with hTASK3-transfected tsA-201 cells, can be activated by the specific Toll-like receptor 7/8 activator, R848, to release TNFα that subsequently enhances hTASK3 current. Both hTASK3 and mTASK3 channel activity is increased by incubation with recombinant TNFα (10 ng/ml for 2–15 h), but other K2P channels (hTASK1, hTASK2, hTREK1, and hTRESK) are unaffected. This enhancement by TNFα is not due to alterations in levels of channel expression at the membrane but rather to an alteration in channel gating. The enhancement by TNFα can be blocked by extracellular acidification but persists for mutated TASK3 (H98A) channels that are no longer acid-sensitive even in an acidic extracellular environment. TNFα action on TASK3 channels is mediated through the intracellular C terminus of the channel. Furthermore, it occurs through the ASK1 pathway and is JNK- and p38-dependent. In combination, TNFα activation and TASK3 channel activity can promote cellular apoptosis.

scholarly journals Two-Pore-Domain Potassium (K2P-) Channels: Cardiac Expression Patterns and Disease-Specific Remodelling Processes

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2914
Author(s):  
Felix Wiedmann ◽  
Norbert Frey ◽  
Constanze Schmidt
Keyword(s):  
Action Potential ◽  
Cardiac Fibrosis ◽  
Cardiac Tissue ◽  
Therapeutic Potential ◽  
Expression Patterns ◽  
Cell Types ◽  
Resting Membrane Potential ◽  
K2p Channel ◽  
K2p Channels ◽  
Pore Domain

Two-pore-domain potassium (K2P-) channels conduct outward K+ currents that maintain the resting membrane potential and modulate action potential repolarization. Members of the K2P channel family are widely expressed among different human cell types and organs where they were shown to regulate important physiological processes. Their functional activity is controlled by a broad variety of different stimuli, like pH level, temperature, and mechanical stress but also by the presence of lipids or pharmacological agents. In patients suffering from cardiovascular diseases, alterations in K2P-channel expression and function have been observed, suggesting functional significance and a potential therapeutic role of these ion channels. For example, upregulation of atrial specific K2P3.1 (TASK-1) currents in atrial fibrillation (AF) patients was shown to contribute to atrial action potential duration shortening, a key feature of AF-associated atrial electrical remodelling. Therefore, targeting K2P3.1 (TASK-1) channels might constitute an intriguing strategy for AF treatment. Further, mechanoactive K2P2.1 (TREK-1) currents have been implicated in the development of cardiac hypertrophy, cardiac fibrosis and heart failure. Cardiovascular expression of other K2P channels has been described, functional evidence in cardiac tissue however remains sparse. In the present review, expression, function, and regulation of cardiovascular K2P channels are summarized and compared among different species. Remodelling patterns, observed in disease models are discussed and compared to findings from clinical patients to assess the therapeutic potential of K2P channels.

scholarly journals A “Target Class” Screen to Identify Activators of Two-Pore Domain Potassium (K2P) Channels

2020 ◽  
pp. 247255522097612
Author(s):  
David McCoull ◽  
Emma Ococks ◽  
Jonathan M. Large ◽  
David C. Tickle ◽  
Alistair Mathie ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Point Of View ◽  
Resting Membrane Potential ◽  
Small Molecule Activation ◽  
Target Class ◽  
Index Set ◽  
Diverse Range ◽  
K2p Channels ◽  
Additional Approach ◽  
Pore Domain

Two-pore domain potassium (K2P) channels carry background (or leak) potassium current and play a key role in regulating resting membrane potential and cellular excitability. Accumulating evidence points to a role for K2Ps in human pathophysiologies, most notably in pain and migraine, making them attractive targets for therapeutic intervention. However, there remains a lack of selective pharmacological tools. The aim of this work was to apply a “target class” approach to investigate the K2P superfamily and identify novel activators across all the described subclasses of K2P channels. Target class drug discovery allows for the leveraging of accumulated knowledge and maximizing synergies across a family of targets and serves as an additional approach to standard target-based screening. A common assay platform using baculovirus (BacMam) to transiently express K2P channels in mammalian cells and a thallium flux assay to determine channel activity was developed, allowing the simultaneous screening of multiple targets. Importantly, this system, by allowing precise titration of channel function, allows optimization to facilitate the identification of activators. A representative set of channels (THIK-1, TWIK-1, TREK-2, TASK-3, and TASK-2) were screened against a library of Food and Drug Administration (FDA)-approved compounds and the LifeArc Index Set. Activators were then analyzed in concentration–response format across all channels to assess selectivity. Using the target class approach to investigate the K2P channels has enabled us to determine which of the K2Ps are amenable to small-molecule activation, de-risk multiple channels from a technical point of view, and identify a diverse range of previously undescribed pharmacology.

Tandem Pore Domain Potassium Channels

2019 ◽  
Author(s):  
Douglas A. Bayliss
Keyword(s):  
Single Channel ◽  
Resting Membrane Potential ◽  
K2p Channel ◽  
Physiological Processes ◽  
System A ◽  
Wide Range ◽  
K2p Channels ◽  
To Come ◽  
A Site ◽  
Pore Domain

The KCNK gene family encodes two-pore-domain potassium (K2P) channels, which generate the background (“leak”) K+ currents that establish a negative resting membrane potential in cells of the nervous system. A pseudotetrameric K+-selective pore is formed by pairing channel subunits, each with two pore-domains, in homo- or heterodimeric conformations. Unique features apparent from high-resolution K2P channel structures include a domain-swapped extracellular cap domain, a lateral hydrophobic-lined fenestration connecting the lipid bilayer to the channel vestibule, and an antiparallel proximal C-terminal region that links the paired subunits and provides a site for polymodal channel modulation. Individual channels transition between open and closed states, with the channel gate located at the selectivity filter. In general, K2P channels display relatively modest voltage- and time-dependent gating, together with distinct single-channel rectification properties, that conspire to yield characteristic weakly rectifying macroscopic currents over a broad range of membrane potentials (i.e., background K+ currents). Of particular note, K2P channel activity can be regulated by a wide range of physicochemical factors, neuromodulators, and clinically useful drugs; a distinct repertoire of activators and inhibitors for different K2P channel subtypes endows each with unique modulatory potential. Thus, by mediating background currents and serving as targets for multiple modulators, K2P channels are able to dynamically regulate key determinants of cell-intrinsic electroresponsive properties. The roles of specific K2P channels in various physiological processes and pathological conditions are now beginning to come into focus, and this may portend utility for these channels as potential therapeutic targets.

scholarly journals Structures of the human two-pore domain potassium channels TREK-1 and TREK-2

2014 ◽  
Vol 70 (a1) ◽  
pp. C1489-C1489
Author(s):  
Ashley Pike ◽  
Yin Dong ◽  
Alexandra Mackenzie ◽  
Conor McClenaghan ◽  
Shubhashish Mukhopadhyay ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Channel Gating ◽  
Resting Membrane Potential ◽  
Transmembrane Helices ◽  
Ion Conductance ◽  
K2p Channels ◽  
Extracellular Stimuli ◽  
Structural Mechanisms ◽  
Pore Domain ◽  
Pore Lining

TREK-1/2 are members of the mechano-gated subfamily of two-pore (K2P) domain potassium channels leaking K+ out of the cell and contributing to the resting membrane potential. In contrast to the classical tetrameric potassium channels, K2P channels are dimeric with an atypical architecture and the structural mechanisms underlying their channel gating are poorly understood. Here we present the crystal structures of human TREK-1 and TREK-2 at resolutions of 2.7 and 3.4Å which provide insights into the basis of intracellular and extracellular gating in this unique family of ion channels. We have solved the structure of TREK-2 in two distinct conformations differing in the orientation of the pore-lining transmembrane helices. The C-terminal M4 helix is hinged at a conserved glycine residue so that it adopts one of two distinct orientations. The M4 helix is either kinked towards the membrane, packing against the M2 inner helix of the adjacent subunit ("M4 up") or straightens and interacts with the M2/M3 helices from the same subunit ("M4 down"). In the M4 down state, a hydrophobic lateral opening runs perpendicular to the ion conductance pathway between M2 and M4 and links the inner vestibule to the membrane-exposed face of the channel. Transition between the "M4 down" and "M4 up" conformations may play a role in channel activation and gating. Cocrystallisation with a TREK-1/2 channel inhibitor promotes the "M4 down" state. The structure of TREK-1 exhibits an "M4-up" conformation but is unusual in that the selectivity filter is significantly distorted with only two correctly-formed potassium sites. The structure also reveals a divalent ion binding site between the extracellular cap and the pore domain loop. The TREK-1 structure illustrates how changes at an extracellular site can affect the pore structure. The structures will be described in detail along with their implications for channel gating in response to intracellular and extracellular stimuli.

scholarly journals Molecular Background of Leak K+ Currents: Two-Pore Domain Potassium Channels

2010 ◽  
Vol 90 (2) ◽  
pp. 559-605 ◽  
Author(s):  
Péter Enyedi ◽  
Gábor Czirják
Keyword(s):  
Intracellular Signaling ◽  
Molecular Mechanisms ◽  
Cell Types ◽  
Detailed Examination ◽  
Resting Membrane Potential ◽  
Membrane Stretch ◽  
Physiological Processes ◽  
Pore Domain ◽  
K Currents

Two-pore domain K+ (K2P) channels give rise to leak (also called background) K+ currents. The well-known role of background K+ currents is to stabilize the negative resting membrane potential and counterbalance depolarization. However, it has become apparent in the past decade (during the detailed examination of the cloned and corresponding native K2P channel types) that this primary hyperpolarizing action is not performed passively. The K2P channels are regulated by a wide variety of voltage-independent factors. Basic physicochemical parameters (e.g., pH, temperature, membrane stretch) and also several intracellular signaling pathways substantially and specifically modulate the different members of the six K2P channel subfamilies (TWIK, TREK, TASK, TALK, THIK, and TRESK). The deep implication in diverse physiological processes, the circumscribed expression pattern of the different channels, and the interesting pharmacological profile brought the K2P channel family into the spotlight. In this review, we focus on the physiological roles of K2P channels in the most extensively investigated cell types, with special emphasis on the molecular mechanisms of channel regulation.

Two-Pore Domain Potassium Channels as Drug Targets: Anesthesia and Beyond

2021 ◽  
Vol 61 (1) ◽  
pp. 401-420 ◽  
Author(s):  
Alistair Mathie ◽  
Emma L. Veale ◽  
Kevin P. Cunningham ◽  
Robyn G. Holden ◽  
Paul D. Wright
Keyword(s):  
Small Molecule ◽  
Drug Targets ◽  
Cell Activity ◽  
Therapeutic Benefit ◽  
Resting Membrane Potential ◽  
Screening Programs ◽  
K2p Channel ◽  
K2p Channels ◽  
Pharmacological Regulation ◽  
Pore Domain

Two-pore domain potassium (K2P) channels stabilize the resting membrane potential of both excitable and nonexcitable cells and, as such, are important regulators of cell activity. There are many conditions where pharmacological regulation of K2P channel activity would be of therapeutic benefit, including, but not limited to, atrial fibrillation, respiratory depression, pulmonary hypertension, neuropathic pain, migraine, depression, and some forms of cancer. Up until now, few if any selective pharmacological regulators of K2P channels have been available. However, recent publications of solved structures with small-molecule activators and inhibitors bound to TREK-1, TREK-2, and TASK-1 K2P channels have given insight into the pharmacophore requirements for compound binding to these sites. Together with the increasing availability of a number of novel, active, small-molecule compounds from K2P channel screening programs, these advances have opened up the possibility of rational activator and inhibitor design to selectively target K2P channels.

scholarly journals Negative Influence by the Force: Mechanically Induced Hyperpolarization via K2P Background Potassium Channels

2021 ◽  
Vol 22 (16) ◽  
pp. 9062
Author(s):  
Miklós Lengyel ◽  
Péter Enyedi ◽  
Gábor Czirják
Keyword(s):  
Membrane Potential ◽  
Ion Channels ◽  
Potassium Channels ◽  
Cell Types ◽  
Negative Influence ◽  
Phospholipid Bilayer ◽  
Cellular Functions ◽  
K2p Channels ◽  
K Current ◽  
Pore Domain

The two-pore domain K2P subunits form background (leak) potassium channels, which are characterized by constitutive, although not necessarily constant activity, at all membrane potential values. Among the fifteen pore-forming K2P subunits encoded by the KCNK genes, the three members of the TREK subfamily, TREK-1, TREK-2, and TRAAK are mechanosensitive ion channels. Mechanically induced opening of these channels generally results in outward K+ current under physiological conditions, with consequent hyperpolarization and inhibition of membrane potential-dependent cellular functions. In the past decade, great advances have been made in the investigation of the molecular determinants of mechanosensation, and members of the TREK subfamily have emerged among the best-understood examples of mammalian ion channels directly influenced by the tension of the phospholipid bilayer. In parallel, the crucial contribution of mechano-gated TREK channels to the regulation of membrane potential in several cell types has been reported. In this review, we summarize the general principles underlying the mechanical activation of K2P channels, and focus on the physiological roles of mechanically induced hyperpolarization.

scholarly journals Retigabine holds KV7 channels open and stabilizes the resting potential

2016 ◽  
Vol 147 (3) ◽  
pp. 229-241 ◽  
Author(s):  
Aaron Corbin-Leftwich ◽  
Sayeed M. Mossadeq ◽  
Junghoon Ha ◽  
Iwona Ruchala ◽  
Audrey Han Ngoc Le ◽  
...  
Keyword(s):  
Voltage Dependence ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Xenopus Laevis Oocytes ◽  
Channel Activity ◽  
Pore Region ◽  
Threshold Potential ◽  
Kv7 Channels ◽  
Open States ◽  
Pore Domain

The anticonvulsant Retigabine is a KV7 channel agonist used to treat hyperexcitability disorders in humans. Retigabine shifts the voltage dependence for activation of the heteromeric KV7.2/KV7.3 channel to more negative potentials, thus facilitating activation. Although the molecular mechanism underlying Retigabine’s action remains unknown, previous studies have identified the pore region of KV7 channels as the drug’s target. This suggested that the Retigabine-induced shift in voltage dependence likely derives from the stabilization of the pore domain in an open (conducting) conformation. Testing this idea, we show that the heteromeric KV7.2/KV7.3 channel has at least two open states, which we named O1 and O2, with O2 being more stable. The O1 state was reached after short membrane depolarizations, whereas O2 was reached after prolonged depolarization or during steady state at the typical neuronal resting potentials. We also found that activation and deactivation seem to follow distinct pathways, suggesting that the KV7.2/KV7.3 channel activity displays hysteresis. As for the action of Retigabine, we discovered that this agonist discriminates between open states, preferentially acting on the O2 state and further stabilizing it. Based on these findings, we proposed a novel mechanism for the therapeutic effect of Retigabine whereby this drug reduces excitability by enhancing the resting potential open state stability of KV7.2/KV7.3 channels. To address this hypothesis, we used a model for action potential (AP) in Xenopus laevis oocytes and found that the resting membrane potential became more negative as a function of Retigabine concentration, whereas the threshold potential for AP firing remained unaltered.

Molecular and functional properties of two-pore-domain potassium channels

2000 ◽  
Vol 279 (5) ◽  
pp. F793-F801 ◽  
Author(s):  
Florian Lesage ◽  
Michel Lazdunski
Keyword(s):  
Salient Feature ◽  
Cell Types ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
General Anesthetics ◽  
Transmembrane Segments ◽  
Kinase C ◽  
Pore Domain ◽  
Recent Demonstration ◽  
External Ph

The two-pore-domain K+ channels, or K2P channels, constitute a novel class of K+channel subunits. They have four transmembrane segments and are active as dimers. The tissue distribution of these channels is widespread, and they are found in both excitable and nonexcitable cells. K2P channels produce currents with unusual characteristics. They are quasi-instantaneous and noninactivating, and they are active at all membrane potentials and insensitive to the classic K+ channel blockers. These properties designate them as background K+ channels. They are expected to play a major role in setting the resting membrane potential in many cell types. Another salient feature of K2P channels is the diversity of their regulatory mechanisms. The weak inward rectifiers TWIK-1 and TWIK-2 are stimulated by activators of protein kinase C and decreased by internal acidification, the baseline TWIK-related acid-sensitive K+ (TASK)-1 and TASK-2 channels are sensitive to external pH changes in a narrow range near physiological pH, and the TWIK-related (TREK)-1 and TWIK-related arachidonic acid-stimulated K+ (TRAAK) channels are the first cloned polyunsaturated fatty acids-activated and mechanogated K+ channels. The recent demonstration that TASK-1 and TREK-1 channels are activated by inhalational general anesthetics, and that TRAAK is activated by the neuroprotective agent riluzole, indicates that this novel class of K+ channels is an interesting target for new therapeutic developments.

TASK, TREK & Co.: a mutable potassium channel family for diverse tasks in the brain

e-Neuroforum ◽  
2015 ◽  
Vol 21 (2) ◽  
Author(s):  
P. Ehling ◽  
Stefan Bittner ◽  
Sven G. Meuth ◽  
Thomas Budde
Keyword(s):  
Neurological Diseases ◽  
Outward Current ◽  
Resting Membrane Potential ◽  
K2p Channel ◽  
Membrane Pores ◽  
Open Questions ◽  
K2p Channels ◽  
In The Beginning ◽  
Pore Domain ◽  
The Brain

AbstractDiscovered during the 1990s and in the beginning regarded as passive membrane pores, the family of two-pore domain potassium (K2P)-channels initially received only little attention. Today the view on this channel family comprising 15 ubiquitously expressed members in mammals has greatly changed. K2P-channels carry potassium outward current that counterbalances membrane depolarization and stabilizes the resting membrane potential. Thereby they are important regulators for the excitability and the firing behaviour especially in neurons. The long list of modulating mechanisms underlines the channels’ relevance. K2P-channels in the thalamus contribute to the regulation of the sleep-wake cycle. They also mediate the effect of volatile anaesthetics by supporting the thalamic activity mode that is also typical for sleep. This review summarizes our knowledge about K2P-channel physiology in the brain, provides an idea of the role of these channels in neurological diseases and lists open questions as well as technical challenges in K2P-channel research.

Sign in / Sign up

Export Citation Format

Share Document