Voltage-gating and cytosolic Ca2+ activation mechanisms of Arabidopsis two-pore channel AtTPC1

2021 ◽  
Vol 118 (49) ◽  
pp. e2113946118
Author(s):  
Fan Ye ◽  
Lingyi Xu ◽  
Xiaoxiao Li ◽  
Weizhong Zeng ◽  
Ninghai Gan ◽  
...  
Keyword(s):  
Voltage Gating ◽  
Pore Channel ◽  
Voltage Gated ◽  
Gating Mechanism ◽  
Ef Hand ◽  
Activation Mechanisms ◽  
Voltage Gated Ion Channels ◽  
Structural Mechanisms ◽  
Voltage Sensing Domain ◽  
Insight Into

Arabidopsis thaliana two-pore channel AtTPC1 is a voltage-gated, Ca2+-modulated, nonselective cation channel that is localized in the vacuolar membrane and responsible for generating slow vacuolar (SV) current. Under depolarizing membrane potential, cytosolic Ca2+ activates AtTPC1 by binding at the EF-hand domain, whereas luminal Ca2+ inhibits the channel by stabilizing the voltage-sensing domain II (VSDII) in the resting state. Here, we present 2.8 to 3.3 Å cryoelectron microscopy (cryo-EM) structures of AtTPC1 in two conformations, one in closed conformation with unbound EF-hand domain and resting VSDII and the other in a partially open conformation with Ca2+-bound EF-hand domain and activated VSDII. Structural comparison between the two different conformations allows us to elucidate the structural mechanisms of voltage gating, cytosolic Ca2+ activation, and their coupling in AtTPC1. This study also provides structural insight into the general voltage-gating mechanism among voltage-gated ion channels.

scholarly journals Resting state structure of the hyperdepolarization activated two-pore channel 3

2020 ◽  
Vol 117 (4) ◽  
pp. 1988-1993
Author(s):  
Miles Sasha Dickinson ◽  
Alexander Myasnikov ◽  
Jacob Eriksen ◽  
Nicole Poweleit ◽  
Robert M. Stroud
Keyword(s):  
Resting State ◽  
Action Potentials ◽  
Pore Channel ◽  
Activation Threshold ◽  
Voltage Gated ◽  
Bona Fide ◽  
Voltage Gated Ion Channels ◽  
Voltage Sensing Domain ◽  
Voltage Activation ◽  
Closed Pore

Voltage-gated ion channels endow membranes with excitability and the means to propagate action potentials that form the basis of all neuronal signaling. We determined the structure of a voltage-gated sodium channel, two-pore channel 3 (TPC3), which generates ultralong action potentials. TPC3 is distinguished by activation only at extreme membrane depolarization (V50 ∼ +75 mV), in contrast to other TPCs and NaV channels that activate between −20 and 0 mV. We present electrophysiological evidence that TPC3 voltage activation depends only on voltage sensing domain 2 (VSD2) and that each of the three gating arginines in VSD2 reduces the activation threshold. The structure presents a chemical basis for sodium selectivity, and a constricted gate suggests a closed pore consistent with extreme voltage dependence. The structure, confirmed by our electrophysiology, illustrates the configuration of a bona fide resting state voltage sensor, observed without the need for any inhibitory ligand, and independent of any chemical or mutagenic alteration.

scholarly journals Hydrophobic gasket mutation produces gating pore currents in closed human voltage-gated proton channels

2019 ◽  
Vol 116 (38) ◽  
pp. 18951-18961 ◽  
Author(s):  
Richard Banh ◽  
Vladimir V. Cherny ◽  
Deri Morgan ◽  
Boris Musset ◽  
Sarah Thomas ◽  
...  
Keyword(s):  
Proton Channel ◽  
Voltage Gated ◽  
Closed State ◽  
Channel Opening ◽  
Proton Current ◽  
Voltage Dependent ◽  
Current Flows ◽  
Voltage Gated Ion Channels ◽  
Dynamics Simulations ◽  
Voltage Sensing Domain

The hydrophobic gasket (HG), a ring of hydrophobic amino acids in the voltage-sensing domain of most voltage-gated ion channels, forms a constriction between internal and external aqueous vestibules. Cationic Arg or Lys side chains lining the S4 helix move through this “gating pore” when the channel opens. S4 movement may occur during gating of the human voltage-gated proton channel, hHV1, but proton current flows through the same pore in open channels. Here, we replaced putative HG residues with less hydrophobic residues or acidic Asp. Substitution of individuals, pairs, or all 3 HG positions did not impair proton selectivity. Evidently, the HG does not act as a secondary selectivity filter. However, 2 unexpected functions of the HG in HV1 were discovered. Mutating HG residues independently accelerated channel opening and compromised the closed state. Mutants exhibited open–closed gating, but strikingly, at negative voltages where “normal” gating produces a nonconducting closed state, the channel leaked protons. Closed-channel proton current was smaller than open-channel current and was inhibited by 10 μM Zn2+. Extreme hyperpolarization produced a deeper closed state through a weakly voltage-dependent transition. We functionally identify the HG as Val109, Phe150, Val177, and Val178, which play a critical and exclusive role in preventing H+ influx through closed channels. Molecular dynamics simulations revealed enhanced mobility of Arg208 in mutants exhibiting H+ leak. Mutation of HG residues produces gating pore currents reminiscent of several channelopathies.

scholarly journals Gating mechanism of human N-type voltage-gated calcium channel

2021 ◽  
Author(s):  
Yanli Dong ◽  
Yiwei Gao ◽  
Shuai Xu ◽  
Yuhang Wang ◽  
Zhuoya Yu ◽  
...  
Keyword(s):  
Resting State ◽  
Complex Structure ◽  
The Other ◽  
Nociceptive Transmission ◽  
Voltage Gated ◽  
Gating Mechanisms ◽  
Cryo Electron Microscopy ◽  
Gating Mechanism ◽  
Voltage Sensing Domain ◽  
Structural Insights

N-type voltage-gated calcium (CaV) channels mediate Ca2+ influx at the presynaptic terminals in response to action potential and play vital roles in synaptogenesis, neurotransmitter releasing, and nociceptive transmission. Here we elucidate a cryo-electron microscopy (cryo-EM) structure of the human CaV2.2 complex at resolution of 2.8 Å. This complex structure reveals how the CaV2.2, β1, and α2δ1 subunits are assembled. In our structure, the second voltage-sensing domain (VSD) is stabilized at a resting-state conformation, which is distinct from the other three VSDs of CaV2.2 as well as activated VSDs observed in previous structures of CaV channels. The structure also shows that the intracellular gate formed by S6 helices is closed, and a W-helix from the DII-III linker is determined to act as a blocking-ball that causes closed-state inactivation in CaV2.2. Collectively, our structure provides previously unseen structural insights into fundamental gating mechanisms of CaV channels.

scholarly journals Voltage-Gated Proton Channels Find Their Dream Job Managing the Respiratory Burst in Phagocytes

Physiology ◽  
2010 ◽  
Vol 25 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Thomas E. DeCoursey
Keyword(s):  
Reactive Oxygen Species ◽  
Nadph Oxidase ◽  
Respiratory Burst ◽  
Proton Channel ◽  
Oxygen Species ◽  
Proton Extrusion ◽  
Proton Channels ◽  
Voltage Gated ◽  
Voltage Gated Ion Channels ◽  
Voltage Sensing Domain

The voltage-gated proton channel bears surprising resemblance to the voltage-sensing domain (S1–S4) of other voltage-gated ion channels but is a dimer with two conduction pathways. The proton channel seems designed for efficient proton extrusion from cells. In phagocytes, it facilitates the production of reactive oxygen species by NADPH oxidase.

Voltage gating of ion channels

1994 ◽  
Vol 27 (1) ◽  
pp. 1-40 ◽  
Author(s):  
F. J. Sigworth
Keyword(s):  
Ion Channels ◽  
Action Potential ◽  
Sodium Channels ◽  
Calcium Ions ◽  
Neurotransmitter Release ◽  
Voltage Gating ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Voltage Gated Sodium Channels ◽  
Voltage Gated Ion Channels

Voltage-gated ion channels are membrane proteins that play a central role in the propagation and transduction of cellular signals (Hille, 1992). Calcium ions entering cells through voltage-gated calcium channels serve as the trigger for neurotransmitter release, muscle contraction, and the release of hormones. Voltage-gated sodium channels initiate the nerve action potential and provide for its rapid propagation because the ion fluxes through these channels regeneratively cause more channels to open.

scholarly journals The isolated voltage sensing domain of the Shaker potassium channel forms a voltage-gated cation channel

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Juan Zhao ◽  
Rikard Blunck
Keyword(s):  
Transmembrane Helix ◽  
Voltage Sensing ◽  
Shaker Potassium Channel ◽  
Voltage Gated ◽  
Kv Channel ◽  
C Terminus ◽  
Ion Conducting ◽  
Voltage Gated Ion Channels ◽  
Voltage Sensing Domain ◽  
Pore Domain

Domains in macromolecular complexes are often considered structurally and functionally conserved while energetically coupled to each other. In the modular voltage-gated ion channels the central ion-conducting pore is surrounded by four voltage sensing domains (VSDs). Here, the energetic coupling is mediated by interactions between the S4-S5 linker, covalently linking the domains, and the proximal C-terminus. In order to characterize the intrinsic gating of the voltage sensing domain in the absence of the pore domain, the Shaker Kv channel was truncated after the fourth transmembrane helix S4 (Shaker-iVSD). Shaker-iVSD showed significantly altered gating kinetics and formed a cation-selective ion channel with a strong preference for protons. Ion conduction in Shaker-iVSD developed despite identical primary sequence, indicating an allosteric influence of the pore domain. Shaker-iVSD also displays pronounced 'relaxation'. Closing of the pore correlates with entry into relaxation suggesting that the two processes are energetically related.

scholarly journals Role of the Fourth Transmembrane Segment in TRAAK Channel Mechanosensitivity

2018 ◽  
Author(s):  
Mingfeng Zhang ◽  
Fuqiang Yao ◽  
Chengfang Pan ◽  
Zhiqiang Yan
Keyword(s):  
Ion Channels ◽  
Transmembrane Domain ◽  
Mechanical Force ◽  
Dynamic Interactions ◽  
Functional Roles ◽  
Physiological Processes ◽  
Gating Mechanism ◽  
Voltage Gated Ion Channels ◽  
Voltage Sensing Domain

AbstractMechanosensitive ion channels such as Piezo, TRAAK, TRPs and OSCA are important transmembrane proteins that are involved in many physiological processes such as touch, hearing and blood pressure regulation. Unlike ligand-gated channels or voltage-gated ion channels, which have a canonical ligand-binding domain or voltage-sensing domain, the mechanosensitive domain and related gating mechanism remain elusive. TRAAK channels are mechanosensitive channels that convert a physical mechanical force into a flow of potassium ions. The structures of TRAAK channels have been solved, however, the functional roles of the structural domains associated with channel mechanosensitivity remains unclear. Here, we generated a series of chimeric mutations between TRAAK and a non-mechanosensitive silent TWIK-1 K2P channel. We found that the selectivity filter region functions as the major gate of outward rectification and found that lower part of fourth transmembrane domain (M4) is necessary for TRAAK channel mechanosensitivity. We further demonstrated that upper part of M4 can modulate the mechanosensitivity of TRAAK channel. Furthermore, we found that hydrophilic substitutions of W262 and F121 facing each other, and hydrophobic substitutions of Q258 and G124, which are above and below W262 and F121, respectively, greatly increase mechanosensitivity, which suggests that dynamic interactions in the upper part of M4 and PH1 domain are involved in TRAAK channel mechanosensitivity. Interestingly, these gain-of-function mutations are sensitive to cell-poking stimuli, indicating that cell-poking stimuli generate a low membrane mechanical force that opens TRAAK channels. Our results thus showed that fourth transmembrane domain of TRAAK is critical for the gating of TRAAK by mechanical force and suggested that multiple dynamic interactions in the upper part of M4 and PH1 domain are involved in this process.

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