Dataset Information

Dissection of the structure-function relationship of Na_v channels.

ABSTRACT: Voltage-gated sodium channels (Na_v) undergo conformational shifts in response to membrane potential changes, a mechanism known as the electromechanical coupling. To delineate the structure-function relationship of human Na_v channels, we have performed systematic structural analysis using human Na_v1.7 as a prototype. Guided by the structural differences between wild-type (WT) Na_v1.7 and an eleven mutation-containing variant, designated Na_v1.7-M11, we generated three additional intermediate mutants and solved their structures at overall resolutions of 2.9-3.4 Å. The mutant with nine-point mutations in the pore domain (PD), named Na_v1.7-M9, has a reduced cavity volume and a sealed gate, with all voltage-sensing domains (VSDs) remaining up. Structural comparison of WT and Na_v1.7-M9 pinpoints two residues that may be critical to the tightening of the PD. However, the variant containing these two mutations, Na_v1.7-M2, or even in combination with two additional mutations in the VSDs, named Na_v1.7-M4, failed to tighten the PD. Our structural analysis reveals a tendency of PD contraction correlated with the right shift of the static inactivation I-V curves. We predict that the channel in the resting state should have a "tight" PD with down VSDs.

SUBMITTER: Li Z

PROVIDER: S-EPMC10907234 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature

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Publications

Dissection of the structure-function relationship of Nav channels.

Li Zhangqiang Z Wu Qiurong Q Huang Gaoxingyu G Jin Xueqin X Li Jiaao J Pan Xiaojing X Yan Nieng N

Proceedings of the National Academy of Sciences of the United States of America 20240221 9

Voltage-gated sodium channels (Nav) undergo conformational shifts in response to membrane potential changes, a mechanism known as the electromechanical coupling. To delineate the structure-function relationship of human Nav channels, we have performed systematic structural analysis using human Nav1.7 as a prototype. Guided by the structural differences between wild-type (WT) Nav1.7 and an eleven mutation-containing variant, designated Nav1.7 ...[more]

PMID: 38381792

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Project description:Neuronal excitability relies on coordinated action of functionally distinct ion channels. Voltage-gated sodium (NaV) and potassium (KV) channels have distinct but complementary roles in firing action potentials: NaV channels provide depolarizing current while KV channels provide hyperpolarizing current. Mutations and dysfunction of multiple NaV and KV channels underlie disorders of excitability, including pain and epilepsy. Modulating ion channel trafficking may offer a potential therapeutic strategy for these diseases. A fundamental question, however, is whether these channels with distinct functional roles are transported independently or packaged together in the same vesicles in sensory axons. We have used Optical Pulse-Chase Axonal Long-distance (OPAL) imaging to investigate trafficking of NaV and KV channels and other axonal proteins from distinct functional classes in live rodent sensory neurons (from male and female rats). We show that, similar to NaV1.7 channels, NaV1.8 and KV7.2 channels are transported in Rab6a-positive vesicles, and that each of the NaV channel isoforms expressed in healthy, mature sensory neurons - NaV1.6, NaV1.7, NaV1.8, and NaV1.9 - are co-transported in the same vesicles. Further, we show that multiple axonal membrane proteins with different physiological functions - NaV1.7, KV7.2, and TNFR1 - are co-transported in the same vesicles. However, vesicular packaging of axonal membrane proteins is not indiscriminate, since another axonal membrane protein - NCX2 - is transported in separate vesicles. These results shed new light on the development and organization of sensory neuron membranes, revealing complex sorting of axonal proteins with diverse physiological functions into specific transport vesicles.Significance StatementNormal neuronal excitability is dependent on precise regulation of membrane proteins including NaV and KV channels, and imbalance in the level of these channels at the plasma membrane could lead to excitability disorders. Ion channel trafficking could potentially be targeted therapeutically, which would require better understanding of the mechanisms underlying trafficking of functionally diverse channels. Optical Pulse-chase Axonal Long-distance (OPAL) imaging in live neurons permitted examination of the specificity of ion channel trafficking, revealing co-packaging of axonal proteins with opposing physiological functions into the same transport vesicles. This suggests that additional trafficking mechanisms are necessary to regulate levels of surface channels and reveals an important consideration for therapeutic strategies that target ion channel trafficking for the treatment of excitability disorders.

Dataset Information

Dissection of the structure-function relationship of Na_v channels.

Publications

Dissection of the structure-function relationship of Na<sub>v</sub> channels.

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