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Comparison of N-helix and IFM-motif mediated inactivation a, b Cartoon representation of the IFM-motif mediated allosteric inactivation of human NaV1.7 (PDB: 6j8j) and the N-helix mediated inactivation of NaVEh. IFM-motif shown in spheres and colored in yellow. Dashed black circle indicates the gate size. c, d Fast inactivation time course of NaV1.7 (n = 7) and NaVEh (n = 12). The time constant was plotted to the test voltages. e, f The time course for recovery from fast inactivation of NaV1.7 (n = 7) and NaVEh (n = 9). For each point, data are means +/−SEM. Source data are provided.
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Voltage-gated sodium (NaV) channels initiate action potentials. Fast inactivation of NaV channels, mediated by an Ile-Phe-Met motif, is crucial for preventing hyperexcitability and regulating firing frequency. Here we present cryo-electron microscopy structure of NaVEh from the coccolithophore Emiliania huxleyi, which reveals an unexpected molecula...
Citations
... Extensive functional and structural studies have elucidated the molecular mechanism of Na V channel fast inactivation, that is, a triple hydrophobic residue motif Ile-Phe-Met (IFM) located in the intracellular loop between domain III (DIII) and DIV serves as a hydrophobic latch closing the activation gate 5,[12][13][14][15] . Interestingly, we have recently described an unexpected N-terminal helix (N-helix) mediated N-type fast inactivation of Na V Eh from the coccolithophore Emiliania huxleyi 16 , which is mechanistically distinct from the IFM-motif mediated fast inactivation but similar to the ball-and-chain inactivation of potassium channels 17 . ...
... Lipid molecules and local anesthetic drugs are thought to act as reversible inhibitors, which slowly penetrate the fenestrations into the pore and block the channel 28,32,33 . However, lipid molecules were not consistently found within the fenestrations of Na V channels 16,27 . Taken as a whole, none of these proposed mechanisms can satisfactorily explain the phenomenon of slow inactivation. ...
... The resulting mutants turned out to be non-functional (Supplementary Fig. 3a-g). Alternatively, we mutated 15 AAAA 18 of Na V Eh ΔN to 15 EEEE 18 , which would increase the repulsion of the N-terminal loop with the negatively charged outer mouth of the activation gate 16 . The resulting construct Na V Eh ΔN18E exhibited almost complete ablation of fast inactivation ( Supplementary Fig. 3a, d). ...
Voltage-gated sodium (NaV) channels mediate a plethora of electrical activities. NaV channels govern cellular excitability in response to depolarizing stimuli. Inactivation is an intrinsic property of NaV channels that regulates cellular excitability by controlling the channel availability. The fast inactivation, mediated by the Ile-Phe-Met (IFM) motif and the N-terminal helix (N-helix), has been well-characterized. However, the molecular mechanism underlying NaV channel slow inactivation remains elusive. Here, we demonstrate that the removal of the N-helix of NaVEh (NaVEhΔN) results in a slow-inactivated channel, and present cryo-EM structure of NaVEhΔN in a potential slow-inactivated state. The structure features a closed activation gate and a dilated selectivity filter (SF), indicating that the upper SF and the inner gate could serve as a gate for slow inactivation. In comparison to the NaVEh structure, NaVEhΔN undergoes marked conformational shifts on the intracellular side. Together, our results provide important mechanistic insights into NaV channel slow inactivation.
... These sodium channels are targeted by various natural and synthetic insecticides, including DDT (dichlorodiphenyltrichloroethane), pyrethroids, and sodium channel blocker insecticides (SCBI), which demonstrate high selectivity for insects [14]. Some peptide venom toxins found in scorpions and sea anemones selectively affect insect sodium channels while sparing their mammalian counterparts [15,16]. ...
Purpose: This research aimed to assess the underlying cause behind the in vitro acaricidal impact of proparacaine HCl on Demodex Folliculorum. Methods: In accordance with Gao's suggestion we epilated a total of 8 eyelashes 4 from the lower and 4 from the upper eyelid of a patient who applied for blepharitis symptoms to the ophthalmology clinic. We fixated 4 of these eyelashes with classical immersion oil and covered them with a coverslip. We wetted 4 of them with Proparacaine Hydrochloride 5 mg (0.5%) and painted them with Na-fluorescein, and covered them with a coverslip. Results: When we examined the eyelashes that were wetted with Proparacaine Hydrochloride under the light microscope there was no difference in mobility in the Demodex of the eyelashes at first 15 minutes. After 30 minutes we saw that the creamy lipid-like structure which is seen normally in the middle of the Demodex was saponified in Demodex. The other Demodex samples that were in the immersion oil were still alive. Conclusions: In this case report, we wanted to evaluate the reason for the acaricidal effect of Proparacaine Hydrochloride a local anesthetic agent on Demodex folliculorum. The idea came true while trying to demonstrate Na-fluorescein uptake of Demodex folliculorum under the microscope Short Research Article 33 after using Proparacaine Hydrochloride5 mg (0.5%) to wet the Na-fluorescein paper and surprisingly we obtained these findings suggesting that it is a substance that may have an anti-acaricidal, anti-demodex effect potential to be a new player for treatment of demodicosis in the future.
... The channel kinetics such as C-type inactivation, N-type inactivation, delayed rectifier activation, etc. may largely plastic the cellular ion homeostasis. The mechanism of C-type inactivation [24][25][26] and N-type inactivation 27,28 has some examples. However, the delayed rectifier activation coupled with the Cole-Moore effects remains elusive 3 . ...
The transmembrane voltage gradient is a general physico-chemical cue that regulates diverse biological function through voltage-gated ion channels. How voltage sensing mediates ion flows remains unknown at the molecular level. Here, we report six conformations of the human Eag2 (hEag2) ranging from closed, pre-open, open, and pore dilation but non-conducting states captured by cryo-electron microscopy (cryo-EM). These multiple states illuminate dynamics of the selectivity filter and ion permeation pathway with delayed rectifier properties and Cole-Moore effect at the atomic level. Mechanistically, a short S4-S5 linker is coupled with the constrict sites to mediate voltage transducing in a non-domain-swapped configuration, resulting transitions for constrict sites of F464 and Q472 from gating to open state stabilizing for voltage energy transduction. Meanwhile, an additional potassium ion occupied at positions S6 confers the delayed rectifier property and Cole-Moore effects. These results provide insight into voltage transducing and potassium current across membrane, and shed light on the long-sought Cole-Moore effects.
... Zhang et al. reported that an N-terminal helix of Na v Eh could plug into the open activation gate and block the fast inactivation. 34 Thus, the mechanism of fast inactivation is still worth exploring deeply. When APs occur, VSD senses the voltage change and S4 moves to the active position. ...
Voltage‐gated sodium channels (VGSCs/Na v s), which control the flow of Na ⁺ and affect the generation of action potentials (APs), have been regarded as essential targets for many diseases. The biological and pharmacological functions of VGSCs have been extensively studied and many efforts have been made to discover and design ligands of VGSCs as potential therapies. Here, we summarize the recent and representative studies of VGSCs from the perspective of computer‐aided drug design (CADD) and molecular modeling, including the structural biology of VGSCs, virtual screening and drug design toward VGSCs based on CADD, and functional studies using molecular modeling technologies. Furthermore, we conclude the achievements that have been made in the field of VGSCs and discuss the shortcomings found in previous studies. We hope that this review can provide some inspiration and reference for future investigations of VGSCs and drug design.
This article is categorized under: Structure and Mechanism > Computational Biochemistry and Biophysics
Voltage gradient is a general physical cue that regulates diverse biological function through voltage-gated ion channels. How voltage sensing mediates ion flows remains unknown at the molecular level. Here, we report six conformations of the human Eag2 (hEag2) ranging from closed, pre-open, open, and pore dilation but non-conducting states captured by cryo-electron microscopy (cryo-EM). These multiple states illuminate dynamics of selectivity filter and ion permeating pathway with delayed rectifier property and Cole-Moore effect at the atomic level. Mechanistically, a short S4-S5 linker is coupled with the constrict sites to mediate voltage transducing in a non-domain-swapped configuration, resulting transitions for constrict sites of F464s and Q472s from gating to open state stabilizing for voltage energy transduction. Meanwhile, an additional ion occupied at positions S6 potassium ion confers the delayed rectifier property and Cole-Moore effects. These results provide novel insight into voltage transducing and potassium current across membrane, and shed light on the long-sought Cole-Moore effects.
Voltage-gated sodium channel NaV1.7 plays essential roles in pain and odor perception. NaV1.7 variants cause pain disorders. Accordingly, NaV1.7 has elicited extensive attention in developing new analgesics. Here we present cryo-EM structures of human NaV1.7/β1/β2 complexed with inhibitors XEN907, TC-N1752 and NaV1.7-IN2, explaining specific binding sites and modulation mechanism for the pore blockers. These inhibitors bind in the central cavity blocking ion permeation, but engage different parts of the cavity wall. XEN907 directly causes α- to π-helix transition of DIV-S6 helix, which tightens the fast inactivation gate. TC-N1752 induces π-helix transition of DII-S6 helix mediated by a conserved asparagine on DIII-S6, which closes the activation gate. NaV1.7-IN2 serves as a pore blocker without causing conformational change. Electrophysiological results demonstrate that XEN907 and TC-N1752 stabilize NaV1.7 in inactivated state and delay the recovery from inactivation. Our results provide structural framework for NaV1.7 modulation by pore blockers, and important implications for developing subtype-selective analgesics.
The Venus flytrap possesses modified leaves that can snap shut fast enough to catch a fly. A new study identifies the major components of the toolkit that allows the flytrap to fire action potentials, illustrating how different ion channels and transporters are recruited to give rise to this unique plant behavioural response.
