Gating of two-pore domain K+ channels by extracellular pH

2006 ◽  
Vol 34 (5) ◽  
pp. 899-902 ◽  
Author(s):  
M.I. Niemeyer ◽  
F.D. González-Nilo ◽  
L. Zúñiga ◽  
W. González ◽  
L.P. Cid ◽  
...  
Keyword(s):  
Extracellular Ph ◽  
Selectivity Filter ◽  
Open Probability ◽  
K Channels ◽  
Task Channels ◽  
Pore Mouth ◽  
Inactivation Gating ◽  
Opening And Closing ◽  
Pore Domain ◽  
And Task

Potassium channels have a conserved selectivity filter that is important in determining which ions are conducted and at what rate. Although K+ channels of different conductance characteristics are known, they differ more widely in the way their opening and closing, the gating, is governed. TASK and TALK subfamily proteins are two-pore region KCNK K+ channels gated open by extracellular pH. We discuss the mechanism for this gating in terms of electrostatic effects on the pore changing the occupancy and open probability of the channels in a way reminiscent of C-type inactivation gating at the selectivity filter. Essential to this proposed mechanism is the replacement of two highly conserved aspartate residues at the pore mouth by asparagine or histidine residues in the TALK and TASK channels.

scholarly journals A unique lower X-gate in TASK channels traps inhibitors within the vestibule

2019 ◽  
Author(s):  
Karin E. J. Rödström ◽  
Aytuğ K. Kiper ◽  
Wei Zhang ◽  
Susanne Rinné ◽  
Ashley C. W. Pike ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Selectivity Filter ◽  
Resting Membrane Potential ◽  
Transmembrane Helices ◽  
Volatile Anaesthetics ◽  
Open Probability ◽  
High Affinity ◽  
Obstructive Sleep ◽  
Task Channels ◽  
Pore Domain

TASK channels are unusual members of the two-pore domain potassium (K2P) channel family, with unique and unexplained physiological and pharmacological characteristics. TASKs are found in neurons1,2, cardiomyocytes3–5 and vascular smooth muscle cells6 where they are involved in regulation of heart rate7, pulmonary artery tone6,8, sleep/wake cycles9 and responses to volatile anaesthetics9–12. K2P channels regulate the resting membrane potential, providing background K+ currents controlled by numerous physiological stimuli13,14. Unlike other K2P channels, TASK channels have the capacity to bind inhibitors with high affinity, exceptional selectivity and very slow compound washout rates. These characteristics make the TASK channels some of the the most easily druggable potassium channels, and indeed TASK-1 inhibitors are currently in clinical trials for obstructive sleep apnea (OSA) and atrial fibrillation (Afib)15 (The DOCTOS and SANDMAN Trials). Generally, potassium channels have an intramembrane vestibule with a selectivity filter above and a gate with four parallel helices below. However, K2P channels studied to date all lack a lower gate. Here we present the structure of TASK-1, revealing a unique lower gate created by interaction of the two crossed C-terminal M4 transmembrane helices at the vestibule entrance, which we designate as an ‟X-gate”. This structure is formed by six residues (V243LRFMT248) that are essential for responses to volatile anaesthetics11, neuro-transmitters16 and G-protein coupled receptors16. Interestingly, mutations within the X-gate and surrounding regions drastically affect both open probability and activation by anaesthetics. Structures of TASK-1 with two novel, high-affinity blockers, shows both inhibitors bound below the selectivity filter, trapped in the vestibule by the X-gate, thus explaining their exceptionally low wash-out rates. Thus, the presence of the X-gate in TASK channels explains many aspects of their unusual physiological and pharmacological behaviour, which is invaluable for future development and optimization of TASK modulators for treatment of heart, lung and sleep disorders.

scholarly journals Mutations reveal voltage gating of CNGA1 channels in saturating cGMP

2009 ◽  
Vol 134 (2) ◽  
pp. 151-164 ◽  
Author(s):  
Juan Ramón Martínez-François ◽  
Yanping Xu ◽  
Zhe Lu
Keyword(s):  
Ion Selectivity ◽  
Selectivity Filter ◽  
Open Probability ◽  
K Channels ◽  
Voltage Gated ◽  
Open Conformation ◽  
Voltage Dependent ◽  
Pore Opening ◽  
Low Probability ◽  
Inherent Voltage

Activity of cyclic nucleotide–gated (CNG) cation channels underlies signal transduction in vertebrate visual receptors. These highly specialized receptor channels open when they bind cyclic GMP (cGMP). Here, we find that certain mutations restricted to the region around the ion selectivity filter render the channels essentially fully voltage gated, in such a manner that the channels remain mostly closed at physiological voltages, even in the presence of saturating concentrations of cGMP. This voltage-dependent gating resembles the selectivity filter-based mechanism seen in KcsA K+ channels, not the S4-based mechanism of voltage-gated K+ channels. Mutations that render CNG channels gated by voltage loosen the attachment of the selectivity filter to its surrounding structure, thereby shifting the channel's gating equilibrium toward closed conformations. Significant pore opening in mutant channels occurs only when positive voltages drive the pore from a low-probability open conformation toward a second open conformation to increase the channels' open probability. Thus, the structure surrounding the selectivity filter has evolved to (nearly completely) suppress the expression of inherent voltage-dependent gating of CNGA1, ensuring that the binding of cGMP by itself suffices to open the channels at physiological voltages.

scholarly journals Study Of Gating Mechanism Of Two Pore Domain K+ Channels Gated By Extracellular Alkalinization: TASK-2 And TASK-3

2009 ◽  
Vol 96 (3) ◽  
pp. 668a
Author(s):  
Fernando D. Gonzalez-Nilo ◽  
Christophe Chipot ◽  
Alex Digenova ◽  
Cristell Navarro ◽  
Wendy Gonzalez-Diaz ◽  
...  
Keyword(s):  
K Channels ◽  
Gating Mechanism ◽  
Pore Domain ◽  
And Task

scholarly journals The gating cycle of a K+ channel at atomic resolution

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Luis G Cuello ◽  
D Marien Cortes ◽  
Eduardo Perozo
Keyword(s):  
Conformational Changes ◽  
Selectivity Filter ◽  
Atomic Resolution ◽  
K Channel ◽  
Allosteric Interactions ◽  
Inactivation Gating ◽  
Pore Domain ◽  
Fine Tune ◽  
Conductive State

C-type inactivation in potassium channels helps fine-tune long-term channel activity through conformational changes at the selectivity filter. Here, through the use of cross-linked constitutively open constructs, we determined the structures of KcsA’s mutants that stabilize the selectivity filter in its conductive (E71A, at 2.25 Å) and deep C-type inactivated (Y82A at 2.4 Å) conformations. These structural snapshots represent KcsA’s transient open-conductive (O/O) and the stable open deep C-type inactivated states (O/I), respectively. The present structures provide an unprecedented view of the selectivity filter backbone in its collapsed deep C-type inactivated conformation, highlighting the close interactions with structural waters and the local allosteric interactions that couple activation and inactivation gating. Together with the structures associated with the closed-inactivated state (C/I) and in the well-known closed conductive state (C/O), this work recapitulates, at atomic resolution, the key conformational changes of a potassium channel pore domain as it progresses along its gating cycle.

scholarly journals A pharmacological master key mechanism that unlocks the selectivity filter gate in K+channels

Science ◽  
2019 ◽  
Vol 363 (6429) ◽  
pp. 875-880 ◽  
Author(s):  
Marcus Schewe ◽  
Han Sun ◽  
Ümit Mert ◽  
Alexandra Mackenzie ◽  
Ashley C. W. Pike ◽  
...  
Keyword(s):  
Selectivity Filter ◽  
Rational Drug Design ◽  
Related Gene ◽  
K Channels ◽  
X Ray ◽  
Voltage Gated ◽  
X Ray Crystallography ◽  
Rational Drug ◽  
Dynamics Simulations ◽  
Pore Domain

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+(K2P) channels, voltage-gated hERG (human ether-à-go-go–related gene) channels and calcium (Ca2+)–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. These results uncover an unrecognized polypharmacology among K+channel activators and highlight a filter gating machinery that is conserved across different families of K+channels with implications for rational drug design.

Na+-induced inward rectification in the two-pore domain K+ channel, TASK-2

2005 ◽  
Vol 288 (1) ◽  
pp. F162-F169 ◽  
Author(s):  
Michael J. Morton ◽  
Sarah Chipperfield ◽  
Abdulrahman Abohamed ◽  
Asipu Sivaprasadarao ◽  
Malcolm Hunter
Keyword(s):  
Single Channel ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Selectivity Filter ◽  
Inward Rectification ◽  
K Channel ◽  
Open Probability ◽  
Whole Cell ◽  
Single Channel Currents ◽  
Pore Domain

TASK-2 is a member of the two-pore domain K+ (K2P) channel family that is expressed at high levels in several epithelia, including the proximal tubule. In common with the other TASK channels, TASK-2 is sensitive to changes in extracellular pH. We have expressed human TASK-2 in Chinese hamster ovary cells and studied whole cell and single-channel activity by patch clamp. The open probability of K2P channels is generally independent of voltage, yielding linear current-voltage ( I- V) curves. Despite these properties, we found that these channels showed distinct inward rectification immediately on the establishment of whole cell clamp, which became progressively less pronounced with time. This rectification was due to intracellular Na+ but was unaffected by polyamines or Mg2+ (agents that cause rectification in Kir channels). Rectification was concentration- and voltage-dependent and could be reversibly induced by switching between Na+-rich and Na+-free bath solutions. In excised inside-out patches, Na+ reduced the amplitude of single-channel currents, indicative of rapid block and unblock of the pore. Mutations in the selectivity filter abolished Na+-induced rectification, suggesting that Na+ binds within the selectivity filter in wild-type channels. This sensitivity to intracellular Na+ may be an additional potential regulatory mechanism of TASK-2 channels.

scholarly journals Targeting two-pore domain K+channels TREK-1 and TASK-3 for the treatment of depression: a new therapeutic concept

2014 ◽  
Vol 172 (3) ◽  
pp. 771-784 ◽  
Author(s):  
M Borsotto ◽  
J Veyssiere ◽  
H Moha ou Maati ◽  
C Devader ◽  
J Mazella ◽  
...  
Keyword(s):  
Therapeutic Concept ◽  
K Channels ◽  
Treatment Of Depression ◽  
Pore Domain ◽  
And Task

scholarly journals Computational study of non-conductive selectivity filter conformations and C-type inactivation in a voltage-dependent potassium channel

2021 ◽  
Vol 153 (9) ◽  
Author(s):  
Jing Li ◽  
Rong Shen ◽  
Ahmed Rohaim ◽  
Ramon Mendoza Uriarte ◽  
Mikolai Fajer ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Computational Study ◽  
Homology Model ◽  
Selectivity Filter ◽  
K Channels ◽  
Activation Gate ◽  
Voltage Dependent ◽  
Signature Sequence ◽  
Dynamics Simulations ◽  
Pore Domain

C-type inactivation is a time-dependent process of great physiological significance that is observed in a large class of K+ channels. Experimental and computational studies of the pH-activated KcsA channel show that the functional C-type inactivated state, for this channel, is associated with a structural constriction of the selectivity filter at the level of the central glycine residue in the signature sequence, TTV(G)YGD. The structural constriction is allosterically promoted by the wide opening of the intracellular activation gate. However, whether this is a universal mechanism for C-type inactivation has not been established with certainty because similar constricted structures have not been observed for other K+ channels. Seeking to ascertain the general plausibility of the constricted filter conformation, molecular dynamics simulations of a homology model of the pore domain of the voltage-gated potassium channel Shaker were performed. Simulations performed with an open intracellular gate spontaneously resulted in a stable constricted-like filter conformation, providing a plausible nonconductive state responsible for C-type inactivation in the Shaker channel. While there are broad similarities with the constricted structure of KcsA, the hypothetical constricted-like conformation of Shaker also displays some subtle differences. Interestingly, those are recapitulated by the Shaker-like E71V KcsA mutant, suggesting that the residue at this position along the pore helix plays a pivotal role in determining the C-type inactivation behavior. Free energy landscape calculations show that the conductive-to-constricted transition in Shaker is allosterically controlled by the degree of opening of the intracellular activation gate, as observed with the KcsA channel. The behavior of the classic inactivating W434F Shaker mutant is also characterized from a 10-μs MD simulation, revealing that the selectivity filter spontaneously adopts a nonconductive conformation that is constricted at the level of the second glycine in the signature sequence, TTVGY(G)D.

scholarly journals Inverted allosteric coupling between activation and inactivation gates in K+ channels

2018 ◽  
Vol 115 (21) ◽  
pp. 5426-5431 ◽  
Author(s):  
Alain J. Labro ◽  
D. Marien Cortes ◽  
Cholpon Tilegenova ◽  
Luis G. Cuello
Keyword(s):  
Selectivity Filter ◽  
K Channels ◽  
Allosteric Coupling ◽  
Allosteric Communication ◽  
Crystallographic Study ◽  
State Dependent ◽  
Activation Gate ◽  
Activation Gating ◽  
Inactivation Gating ◽  
Signature Sequence

The selectivity filter and the activation gate in potassium channels are functionally and structurally coupled. An allosteric coupling underlies C-type inactivation coupled to activation gating in this ion-channel family (i.e., opening of the activation gate triggers the collapse of the channel’s selectivity filter). We have identified the second Threonine residue within the TTVGYGD signature sequence of K+ channels as a crucial residue for this allosteric communication. A Threonine to Alanine substitution at this position was studied in three representative members of the K+-channel family. Interestingly, all of the mutant channels exhibited lack of C-type inactivation gating and an inversion of their allosteric coupling (i.e., closing of the activation gate collapses the channel’s selectivity filter). A state-dependent crystallographic study of KcsA-T75A proves that, on activation, the selectivity filter transitions from a nonconductive and deep C-type inactivated conformation to a conductive one. Finally, we provide a crystallographic demonstration that closed-state inactivation can be achieved by the structural collapse of the channel’s selectivity filter.

269 EXPRESSION OF TANDEM-PORE DOMAIN K+ CHANNELS IN BOVINE OOCYTES AND PRE-IMPLANTATION EMBRYOS

2007 ◽  
Vol 19 (1) ◽  
pp. 251
Author(s):  
C. G. Hur ◽  
D. Kang ◽  
J. Y. Park ◽  
S. G. Hong ◽  
J. Han
Keyword(s):  
Germinal Vesicle ◽  
Human Myometrium ◽  
Resting Membrane Potential ◽  
Rt Pcr ◽  
Cellular Functions ◽  
Cell Stage ◽  
K Channels ◽  
Task Channels ◽  
Pore Domain ◽  
Bovine Oocytes

Tandem-pore domain K+ (K2P) channels that contribute to setting the resting membrane potential of excitable and nonexcitable cells are expressed in many kinds of cells and tissues. Recent studies have shown that TASK [TWIK (Tandem of P domains in Weak Inward rectifying K+ channels)-related acid-sensitive K+ channels] and TREK (TWIK-Related K+ channels), members of K2P channel family that are involved in a variety of cellular functions, are expressed in human myometrium, placenta, and cytotrophoblast cells. However, their expression in bovine oocytes and embryos has not yet been reported. In this study, we examined whether TASK and TREK channels are expressed in bovine immature (germinal vesicle-stage) and mature (metaphase II-stage) oocytes and in pre-implantation (2-cell- and 16-cell-stage) embryos using RT-PCR and immunocytochemistry. RT-PCR data showed that TASK-1, TASK-3, TREK-1, TREK-2, and TRAAK channels were expressed in bovine immature and mature oocytes. Interestingly, the expression levels of TREK channels were 2-fold higher than those of TASK channels as judged by semiquantitative RT-PCR and real-time PCR with cDNA synthesized from 50 individual immature and mature oocytes (P < 0.05, n = 4). Intensity of genes was normalized with respect to that of GAPDH. Consistent with RT-PCR data, immunocytochemical data showed that TASK-1, TASK-3, TREK-1, TREK-2, and TRAAK channels were expressed in bovine immature and mature oocytes. The fluorescence intensity of TREK channels was higher than that of TASK channels (P < 0.05, n = 5). TASK and TREK channels were also expressed in pre-implantation embryos. Of TREK channels, the TREK-2 channel was strongly expressed in immature and mature oocytes and in pre-implantation embryos (P < 0.05, n = 5). For statistics, Student's t-test was used, with P < 0.05 as the criterion for significance. Our results show that TASK-1, TASK-3, TREK-1, TREK-2, and TRAAK channels were expressed in bovine immature and mature oocytes and pre-implantation embryos. These results suggest that TASK and TREK channels could be involved in various physiological processes in mammalian oocytes and embryos.

Sign in / Sign up

Export Citation Format

Share Document