Dataset Information

Gain-of-Function Mutation W493R in the Epithelial Sodium Channel Allosterically Reconfigures Intersubunit Coupling.

ABSTRACT: Sodium absorption in epithelial cells is rate-limited by the epithelial sodium channel (ENaC) activity in lung, kidney, and the distal colon. Pathophysiological conditions, such as cystic fibrosis and Liddle syndrome, result from water-electrolyte imbalance partly due to malfunction of ENaC regulation. Because the quaternary structure of ENaC is yet undetermined, the bases of pathologically linked mutations in ENaC subunits ?, ?, and ? are largely unknown. Here, we present a structural model of heterotetrameric ENaC ?1??2? that is consistent with previous cross-linking results and site-directed mutagenesis experiments. By using this model, we show that the disease-causing mutation ?W493R rewires structural dynamics of the intersubunit interfaces ?1? and ?2?. Changes in dynamics can allosterically propagate to the channel gate. We demonstrate that cleavage of the ?-subunit, which is critical for full channel activation, does not mediate activation of ENaC by ?W493R. Our molecular dynamics simulations led us to identify a channel-activating electrostatic interaction between ?2Arg-493 and ?Glu-348 at the ?2? interface. By neutralizing a sodium-binding acidic patch at the ?1? interface, we reduced ENaC activation of ?W493R by more than 2-fold. By combining homology modeling, molecular dynamics, cysteine cross-linking, and voltage clamp experiments, we propose a dynamics-driven model for the gain-of-function in ENaC by ?W493R. Our integrated computational and experimental approach advances our understanding of structure, dynamics, and function of ENaC in its disease-causing state.

SUBMITTER: Shobair M

PROVIDER: S-EPMC4759151 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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Gain-of-Function Mutation W493R in the Epithelial Sodium Channel Allosterically Reconfigures Intersubunit Coupling.

Shobair Mahmoud M Dagliyan Onur O Kota Pradeep P Dang Yan L YL He Hong H Stutts M Jackson MJ Dokholyan Nikolay V NV

The Journal of biological chemistry 20151214 8

Sodium absorption in epithelial cells is rate-limited by the epithelial sodium channel (ENaC) activity in lung, kidney, and the distal colon. Pathophysiological conditions, such as cystic fibrosis and Liddle syndrome, result from water-electrolyte imbalance partly due to malfunction of ENaC regulation. Because the quaternary structure of ENaC is yet undetermined, the bases of pathologically linked mutations in ENaC subunits α, β, and γ are largely unknown. Here, we present a structural model of ...[more]

PMID: 26668308

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Project description:Small fiber neuropathy (SFN) is a common condition affecting thinly myelinated Aδ and unmyelinated C fibers, often resulting in excruciating pain and dysautonomia. SFN has been associated with several conditions, but a significant number of cases have no discernible cause. Recent genetic studies have identified potentially pathogenic gain-of-function mutations in several pore-forming voltage-gated sodium channel α subunits (NaV) in a subset of patients with SFN, but the auxiliary sodium channel β subunits have been less implicated in the development of the disease. β subunits modulate NaV trafficking and gating, and several mutations have been linked to epilepsy and cardiac dysfunction. Recently, we provided the first evidence for the contribution of a mutation in the β2 subunit to pain in human painful diabetic neuropathy. Here, we provide the first evidence for the involvement of a sodium channel β subunit mutation in the pathogenesis of SFN with no other known causes. We show, through current-clamp analysis, that the newly identified Y69H variant of the β2 subunit induces neuronal hyperexcitability in dorsal root ganglion neurons, lowering the threshold for action potential firing and allowing for increased repetitive action potential spiking. Underlying the hyperexcitability induced by the β2-Y69H variant, we demonstrate an upregulation in tetrodotoxin-sensitive, but not tetrodotoxin-resistant sodium currents. This provides the first evidence for the involvement of β2 subunits in SFN and strengthens the link between sodium channel β subunits and the development of neuropathic pain in humans.NEW & NOTEWORTHY Small fiber neuropathy (SFN) often has no discernible cause, although mutations in the voltage-gated sodium channel α subunits have been implicated in some cases. We identify a patient suffering from SFN with a mutation in the auxiliary β2 subunit and no other discernible causes for SFN. Functional assessment confirms this mutation renders dorsal root ganglion neurons hyperexcitable and upregulates tetrodotoxin-sensitive sodium currents. This study strengthens a newly emerging link between sodium channel β2 subunit mutations and human pain disorders.

Dataset Information

Gain-of-Function Mutation W493R in the Epithelial Sodium Channel Allosterically Reconfigures Intersubunit Coupling.

Publications

Gain-of-Function Mutation W493R in the Epithelial Sodium Channel Allosterically Reconfigures Intersubunit Coupling.

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