Structural insights into the mechanisms of CNBD channel function

James, Zachary M.; Zagotta, William N.

doi:10.1085/jgp.201711898

Cited by 94 publications

(138 citation statements)

References 139 publications

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“…The three-dimensional protein structures of many ion channels, including some EAG subfamily channels and other members of the structurally-related CNBD family have been elucidated, initially using X-ray crystallography and NMR spectroscopy, and currently, by the spectacular improvements in single particle cryo-EM (reviewed in Vandenberg et al, 2017;Lau et al, 2018;James and Zagotta, 2018;Okamura and Okochi, 2019;Barros et al, 2019). The discovery that, despite their shared common primary organization, the EAG channels and other members of the Kv family can adopt two main architectural patterns in their transmembrane core (Figure 3), caused an essential breakthrough in our view of the structural basis of the molecular mechanism(s) involved in the voltage-triggered gating of these entities.…”

Section: Eag Channels: Prototypic Examples Of Non-domain-swapped Chanmentioning

confidence: 99%

“…Indeed, pioneer studies with Kv10.1 and Kv11.1 channels in which the separate N-and C-terminal halves of the protein were expressed after breaking the covalent continuity of the S4-S5 linker (S4-S5 split channels), demonstrated the production of voltage-gated channels exhibiting voltage-sensing and permeation properties similar to those of the complete protein (Lorinczi et al, 2015). Thus, both structural and functional evidences point to the existence of a new mechanism in this type of Kv channels, different to the classical lever one proposed for the Shaker-like Kv channels (Whicher and MacKinnon, 2016;Wang and MacKinnon, 2017;Tao et al, 2017;Flynn and Zagotta, 2018;Zhao et al, 2017;Lee and MacKinnon, 2018;James and Zagotta, 2018).…”

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confidence: 94%

“…c. a voltage-dependent activation with so-called "inverted" gating polarity, as in the HCN channels, in which, unlike the typical depolarization-dependent activation exhibited by the Kv channels, membrane depolarization causes channel closing while activation is triggered by membrane hyperpolarization. In this case, an increased activity is also elicited upon binding of cyclic nucleotides to their intracellular CNBDs (Lee and MacKinnon, 2017;James and Zagotta, 2018). d. a pure voltage-and depolarization-dependent activation gating, as in the genuine Kv channels of the EAG subfamily.…”

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confidence: 99%

“…It is interesting to note that although the EAG subfamily channels and other members of the so-called CNBD channel group share some common structural features, such as the presence of a VSD and PD arrangement and a non-swapped architecture, this group includes entities exhibiting quite divergent functional and/or gating properties (reviewed in James and Zagotta, 2018;Barros et al, 2019). These divergences are even more evident when other non-domainswapped channels are considered.…”

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confidence: 99%

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The EAG Voltage-Dependent K+ Channel Subfamily: Similarities and Differences in Structural Organization and Gating

et al. 2020

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EAG (ether-à-go-go or KCNH) are a subfamily of the voltage-gated potassium (Kv) channels. Like for all potassium channels, opening of EAG channels drives the membrane potential toward its equilibrium value for potassium, thus setting the resting potential and repolarizing action potentials. As voltage-dependent channels, they switch between open and closed conformations (gating) when changes in membrane potential are sensed by a voltage sensing domain (VSD) which is functionally coupled to a pore domain (PD) containing the permeation pathway, the potassium selectivity filter, and the channel gate. All Kv channels are tetrameric, with four VSDs formed by the S1-S4 transmembrane segments of each subunit, surrounding a central PD with the four S5-S6 sections arranged in a square-shaped structure. Structural information, mutagenesis, and functional experiments, indicated that in "classical/Shaker-type" Kv channels voltagetriggered VSD reorganizations are transmitted to PD gating via the a-helical S4-S5 sequence that links both modules. Importantly, these Shaker-type channels share a domain-swapped VSD/PD organization, with each VSD contacting the PD of the adjacent subunit. In this case, the S4-S5 linker, acting as a rigid mechanical lever (electromechanical lever coupling), would lead to channel gate opening at the cytoplasmic S6 helices bundle. However, new functional data with EAG channels split between the VSD and PD modules indicate that, in some Kv channels, alternative VSD/PD coupling mechanisms do exist. Noticeably, recent elucidation of the architecture of some EAG channels, and other relatives, showed that their VSDs are non-domain swapped. Despite similarities in primary sequence and predicted structural organization for all EAG channels, they show marked kinetic differences whose molecular basis is not completely understood. Thus, while a common general architecture may establish the gating system used by the EAG channels and the physicochemical coupling of voltage sensing to gating, subtle changes in that common structure, and/or allosteric influences of protein domains relatively distant from the central gating machinery, can crucially influence the gating Frontiers in Pharmacology | www.frontiersin.org

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Section: Eag Channels: Prototypic Examples Of Non-domain-swapped Chanmentioning

confidence: 99%

mentioning

confidence: 94%

mentioning

confidence: 99%

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confidence: 99%

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The EAG Voltage-Dependent K+ Channel Subfamily: Similarities and Differences in Structural Organization and Gating

et al. 2020

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“…The HCN channel is one of the most well characterized hyperpolarization-activated ion channels. They belong to cyclic nucleotide-binding domain (CNBD) family of ion channels which also includes depolarization activated EAG (ether-à-go go) and hERG (human ether-à-go go related) channels, and a prototypical cyclic nucleotide-activated (CNG) ion channel (Craven and Zagotta, 2006;James and Zagotta, 2018;Yu et al, 2005). EAG channels behave like canonical depolarization-activated ion channels (Warmke et al, 1991;Wu et al, 1983;Zhong and Wu, 1991) but hERG channels are functionally unique.…”

Section: Introductionmentioning

confidence: 99%

Bipolar Switching by HCN Voltage Sensor Underlies Hyperpolarization Activation

Cowgill

Klenchin

Alvarez-Baron

et al. 2018

Preprint

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Despite sharing a common architecture with archetypal voltage-gated ion channels (VGIC), the hyperpolarization-and cyclic AMP-activated ion (HCN) channels open upon hyperpolarization rather than depolarization. The basic motions of voltage sensor and pore gates are conserved implying that these domains are inversely coupled in HCN channels. Using structure-guided protein engineering, we systematically assembled an array of mosaic channels that display the full complement of voltage-activation phenotypes observed in the VGIC superfamily. Our studies reveal that the voltage-sensing S3b-S4 transmembrane segment of the HCN channel has an intrinsic ability to drive pore opening in either direction. Specific contacts at the pore-voltage sensor interface and unique interactions near the pore gate forces the HCN channel into a hERG-like inactivated state, thereby obscuring their opening upon depolarization. Our findings reveal an unexpected common principle underpinning voltage gating in the VGIC superfamily and identify the essential determinants of gating polarity.3

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Fluorophore‐Labeled Cyclic Nucleotides as Potent Agonists of Cyclic Nucleotide‐Regulated Ion Channels

et al. 2020

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High‐affinity fluorescent derivatives of cyclic adenosine and guanosine monophosphate are powerful tools for investigating their natural targets. Cyclic nucleotide‐regulated ion channels belong to these targets and are vital for many signal transduction processes, such as vision and olfaction. The relation of ligand binding to activation gating is still challenging, and there is a need for fluorescent probes that enable the process to be broken down to the single‐molecule level. This inspired us to prepare fluorophore‐labeled cyclic nucleotides, which are composed of a bright dye and a nucleotide derivative with a thiophenol motif at position 8 that has already been shown to enable superior binding affinity. These bioconjugates were prepared by a novel cross‐linking strategy that involves substitution of the nucleobase with a modified thiophenolate in good yield. Both fluorescent nucleotides are potent activators of different cyclic nucleotide‐regulated ion channels with respect to the natural ligand and previously reported substances. Molecular docking of the probes excluding the fluorophore reveals that the high potency can be attributed to additional hydrophobic and cation‐π interactions between the ligand and the protein. Moreover, the introduced substances have the potential to investigate related target proteins, such as cAMP‐ and cGMP‐dependent protein kinases, exchange proteins directly activated by cAMP or phosphodiesterases.

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Structural insights into the mechanisms of CNBD channel function

Abstract: James and Zagotta discuss how recent cryoEM structures inform our understanding of cyclic nucleotide–binding domain channels.

Cited by 94 publications

References 139 publications

The EAG Voltage-Dependent K+ Channel Subfamily: Similarities and Differences in Structural Organization and Gating

The EAG Voltage-Dependent K+ Channel Subfamily: Similarities and Differences in Structural Organization and Gating

Bipolar Switching by HCN Voltage Sensor Underlies Hyperpolarization Activation

Fluorophore‐Labeled Cyclic Nucleotides as Potent Agonists of Cyclic Nucleotide‐Regulated Ion Channels

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