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The biophysical and molecular basis of TRPV1 proton gating.

ABSTRACT: The capsaicin receptor TRPV1, a member of the transient receptor potential family of non-selective cation channels is a polymodal nociceptor. Noxious thermal stimuli, protons, and the alkaloid irritant capsaicin open the channel. The mechanisms of heat and capsaicin activation have been linked to voltage-dependent gating in TRPV1. However, until now it was unclear whether proton activation or potentiation or both are linked to a similar voltage-dependent mechanism and which molecular determinants underlie the proton gating. Using the whole-cell patch-clamp technique, we show that protons activate and potentiate TRPV1 by shifting the voltage dependence of the activation curves towards more physiological membrane potentials. We further identified a key residue within the pore region of TRPV1, F660, to be critical for voltage-dependent proton activation and potentiation. We conclude that proton activation and potentiation of TRPV1 are both voltage dependent and that amino acid 660 is essential for proton-mediated gating of TRPV1.

SUBMITTER: Aneiros E

PROVIDER: S-EPMC3061026 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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The biophysical and molecular basis of TRPV1 proton gating.

Aneiros Eduardo E Cao Lishuang L Papakosta Marianthi M Stevens Edward B EB Phillips Stephen S Grimm Christian C

The EMBO journal 20110201 6

The capsaicin receptor TRPV1, a member of the transient receptor potential family of non-selective cation channels is a polymodal nociceptor. Noxious thermal stimuli, protons, and the alkaloid irritant capsaicin open the channel. The mechanisms of heat and capsaicin activation have been linked to voltage-dependent gating in TRPV1. However, until now it was unclear whether proton activation or potentiation or both are linked to a similar voltage-dependent mechanism and which molecular determinant ...[more]

PMID: 21285946

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Project description:The Nav1.7 channel critically contributes to the excitability of sensory neurons, and gain-of-function mutations of this channel have been shown to cause inherited erythromelalgia (IEM) with neuropathic pain. In this study, we report a case of a severe phenotype of IEM caused by p.V1316A mutation in the Nav1.7 channel. Mechanistically, we first demonstrate that the Nav?4 peptide acts as a gating modifier rather than an open channel blocker competing with the inactivating peptide to give rise to resurgent currents in the Nav1.7 channel. Moreover, there are two distinct open and two corresponding fast inactivated states in the genesis of resurgent Na+ currents. One is responsible for the resurgent route and practically existent only in the presence of Nav?4 peptide, whereas the other is responsible for the "silent" route of recovery from inactivation. In this regard, the p.V1316A mutation makes hyperpolarization shift in the activation curve, and depolarization shift in the inactivation curve, vividly uncoupling inactivation from activation. In terms of molecular gating operation, the most important changes caused by the p.V1316A mutation are both acceleration of the transition from the inactivated states to the activated states and deceleration of the reverse transition, resulting in much larger sustained as well as resurgent Na+ currents. In summary, the genesis of the resurgent currents in the Nav1.7 channel is ascribable to the transient existence of a distinct and novel open state promoted by the Nav?4 peptide. In addition, S4-5 linker in domain III where V1316 is located seems to play a critical role in activation-inactivation coupling, chiefly via direct modulation of the transitional kinetics between the open and the inactivated states. The sustained and resurgent Na+ currents may therefore be correlatively enhanced by specific mutations involving this linker and relevant regions, and thus marked hyperexcitability in corresponding neural tissues as well as IEM symptomatology.

Project description:As a key cellular sensor, the TRPV1 cation channel undergoes a gating transition from a closed state to an open state in response to various physical and chemical stimuli including noxious heat. Despite years of study, the heat activation mechanism of TRPV1 gating remains enigmatic at the molecular level. Toward elucidating the structural and energetic basis of TRPV1 gating, we have performed molecular dynamics (MD) simulations (with cumulative simulation time of 3 μs), starting from the high-resolution closed and open structures of TRPV1 solved by cryo-electron microscopy. In the closed-state simulations at 30°C, we observed a stably closed channel constricted at the lower gate (near residue I679), while the upper gate (near residues G643 and M644) is dynamic and undergoes flickery opening/closing. In the open-state simulations at 60°C, we found higher conformational variation consistent with a large entropy increase required for the heat activation, and both the lower and upper gates are dynamic with transient opening/closing. Through ensemble-based structural analyses of the closed state versus the open state, we revealed pronounced closed-to-open conformational changes involving the membrane proximal domain (MPD) linker, the outer pore, and the TRP helix, which are accompanied by breaking/forming of a network of closed/open-state specific hydrogen bonds. By comparing the closed-state simulations at 30°C and 60°C, we observed heat-activated conformational changes in the MPD linker, the outer pore, and the TRP helix that resemble the closed-to-open conformational changes, along with partial formation of the open-state specific hydrogen bonds. Some of the residues involved in the above key hydrogen bonds were validated by previous mutational studies. Taken together, our MD simulations have offered rich structural and dynamic details beyond the static structures of TRPV1, and promising targets for future mutagenesis and functional studies of the TRPV1 channel. Proteins 2016; 84:1938-1949. © 2016 Wiley Periodicals, Inc.

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The biophysical and molecular basis of TRPV1 proton gating.

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The biophysical and molecular basis of TRPV1 proton gating.

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