Strong cooperativity between subunits in voltage-gated proton channels

González, Carlos; Koch, H.; Drum, Ben M; Larsson, H. Peter

doi:10.1038/nsmb.1739

Cited by 123 publications

(365 citation statements)

References 41 publications

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“…It has been proposed that the gating movement of one monomeric channel subunit affects the gating of the other subunit within the dimeric unit [16][17][18] . We observed, in this study, dimerization by the coiledcoil assembly affected the thermosensitive gating.…”

Section: Coiled-coil Assembly Domain Of Mhv1/vsop and Its Structurementioning

confidence: 99%

“…One characteristic derived from the dimer assembly in the Hv channel is the cooperative channel gating-that is, the gating movement of one monomeric channel subunit affects the gating of the other subunit within the dimeric unit [16][17][18] . However, it remains unclear through which part of the channel the conformational change is transmitted from one subunit to the other during channel gating.…”

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confidence: 99%

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The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

et al. 2012

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Hv1/VsoP is a dimeric voltage-gated H + channel in which the gating of one subunit is reportedly coupled to that of the other subunit within the dimer. The molecular basis for dimer formation and intersubunit coupling, however, remains unknown. Here we show that the carboxy terminus ends downstream of the s4 voltage-sensor helix twist in a dimer coiled-coil architecture, which mediates cooperative gating. We also show that the temperature-dependent activation of H + current through Hv1/VsoP is regulated by thermostability of the coiled-coil domain, and that this regulation is altered by mutation of the linker between s4 and the coiled-coil. Cooperative gating within the dimer is also dependent on the linker structure, which circular dichroism spectrum analysis suggests is α-helical. our results indicate that the cytoplasmic coiled-coil strands form continuous α-helices with s4 and mediate cooperative gating to adjust the range of temperatures over which Hv1/VsoP operates.

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Section: Coiled-coil Assembly Domain Of Mhv1/vsop and Its Structurementioning

confidence: 99%

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confidence: 99%

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

et al. 2012

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“…These structural models will be essential for future investigations of this channel and the development of new pharmacological blockers. (15,16). Accessibility experiments of cysteines introduced into S4 of Hv1 channels suggest that S4 functions as the voltage sensor and that there is an outward movement of S4 upon membrane depolarization (15,16).…”

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confidence: 99%

“…(15,16). Accessibility experiments of cysteines introduced into S4 of Hv1 channels suggest that S4 functions as the voltage sensor and that there is an outward movement of S4 upon membrane depolarization (15,16). The three positively charged residues contribute most, if not all, of the gating charges in Hv1 channels (15,16).…”

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confidence: 99%

Hydrophobic plug functions as a gate in voltage-gated proton channels

Chamberlin

Qiu

Rebolledo

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

150

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Voltage-gated proton (Hv1) channels play important roles in the respiratory burst, in pH regulation, in spermatozoa, in apoptosis, and in cancer metastasis. Unlike other voltage-gated cation channels, the Hv1 channel lacks a centrally located pore formed by the assembly of subunits. Instead, the proton permeation pathway in the Hv1 channel is within the voltage-sensing domain of each subunit. The gating mechanism of this pathway is still unclear. Mutagenic and fluorescence studies suggest that the fourth transmembrane (TM) segment (S4) functions as a voltage sensor and that there is an outward movement of S4 during channel activation. Using thermodynamic mutant cycle analysis, we find that the conserved positively charged residues in S4 are stabilized by countercharges in the other TM segments both in the closed and open states. We constructed models of both the closed and open states of Hv1 channels that are consistent with the mutant cycle analysis. These structural models suggest that electrostatic interactions between TM segments in the closed state pull hydrophobic residues together to form a hydrophobic plug in the center of the voltage-sensing domain. Outward S4 movement during channel activation induces conformational changes that remove this hydrophobic plug and instead insert protonatable residues in the center of the channel that, together with water molecules, can form a hydrogen bond chain across the channel for proton permeation. This suggests that salt bridge networks and the hydrophobic plug function as the gate in Hv1 channels and that outward movement of S4 leads to the opening of this gate.voltage gating | mutagenesis cycle | molecular dynamics | VSOP | blocker T he best-studied function of voltage-gated proton (Hv1) channels is in the immune system, where the activity of Hv1 channels has been shown to play a key role in charge compensation for the electron extrusion by NADPH oxidase during the respiratory burst in phagocytes (1, 2). In addition, this channel is also found in many other cell types including neurons, sperm, and lung airway epithelia cells, where it has been implicated in acid extrusion, male fertility, and the pathology of asthma, respectively (3, 4). During stroke, the activity of Hv1 channels exacerbates neuronal death (5). In 2006, two independent groups identified the genes coding for the Hv1 channel in humans (hHv1) (6) and mice and Ciona intestinalis (voltage-sensing only protein; we call it "Ci-Hv1" in this paper) (7). The sequences of Hv1/(VSOP) are homologous to the sequences of the voltagesensing domain (VSD) of other voltage-gated ion channels, such as voltage-gated sodium, potassium, and calcium channels (Nav, Kv, and Cav channels), and the voltage sensor-containing phosphatase VSP (6, 7). Hydropathy analysis of the Hv1 sequence suggests the existence of four transmembrane (TM) segments (Fig. 1A), designated S1 to S4, similar to the four TM segments of the VSD of Kv channels (Fig. S1). However, Hv1 channels lack the last two TM segments of Kv channels that make up t...

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“…Multiple functions were proposed for proton channels, but these remained speculative until the cloning of the Hv1 protein by two separate laboratories (Ramsey et al, 2006;Sasaki et al, 2006) and the generation of Hv1 knockout mice offered the possibility to test the physiological role of proton channels. Structure-function studies revealed that Hv1 channels are dimers that gate cooperatively (Gonzalez et al, 2010;Musset et al, 2010;Tombola et al, 2010), with each monomer containing a separate conduction pathway and voltage sensor (Koch et al, 2008;Lee et al, 2008;Tombola et al, 2008). Hv1 channels are perfectly selective for protons and are activated by depolarizing voltages and by intracellular acidification, a combination that ensures that the channels only open in conditions that favor proton extrusion from cells.…”

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confidence: 99%

Do Hv1 proton channels regulate the ionic and redox homeostasis of phagosomes?

Chemaly

Demaurex

2012

Molecular and Cellular Endocrinology

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a b s t r a c tRecent work on animal models has revealed the important role played by the voltage-gated proton channel Hv1 during bacterial killing by innate immune cells. Studies from mice lacking Hv1 channels showed that Hv1 proton channels are required for high-level production of reactive oxygen species (ROS) by the NADPH oxidase of phagocytes (NOX2) in two ways. First, Hv1 channels maintain a physiological membrane potential during the respiratory burst of neutrophils by providing a compensating charge for the electrons transferred by NOX2 from NADPH to superoxide. Second, Hv1 channels maintain a physiological cytosolic pH by extruding the acid generated by the NOX2-dependent consumption of NADPH. The two mechanisms directly sustain the activity of the NOX2 enzyme and indirectly sustain other neutrophil functions by enhancing the driving force for the entry of calcium into cells, thereby boosting cellular calcium signals. The increased depolarization of Hv1-deficient neutrophils aborted calcium responses to chemoattractants and revealed adhesion and migration defects that were associated with an impaired depolymerization of the cortical actin cytoskeleton. Current research aims to transpose these findings to phagosomes, the phagocytic vacuoles where bacterial killing takes place. However, the mechanisms that control the phagosomal pH appear to vary greatly between phagocytes: phagosomes rapidly acidify in macrophages but remain neutral for several minutes in neutrophils following ingestion of solid particles, whereas in dendritic cells phagosomes alkalinize, a mechanism thought to promote antigen crosspresentation. In this review, we discuss how the knowledge gained on the role of Hv1 channels at the plasma membrane of neutrophils can be used to study the regulation of the phagosomal pH, ROS, membrane potential, and calcium fluxes in different phagocytic cells.

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Strong cooperativity between subunits in voltage-gated proton channels

Cited by 123 publications

References 41 publications

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

Hydrophobic plug functions as a gate in voltage-gated proton channels

Do Hv1 proton channels regulate the ionic and redox homeostasis of phagosomes?

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