# Mechanisms of Permeation and Gating of Voltage-Sensing Domains

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA-IRVINE · 2020 · $320,618

## Abstract

Project Summary
Voltage-gated ion channels are a diverse group of membrane proteins that play significant roles in a
variety of physiological and pathological processes, from neuronal excitability and muscle contraction,
to autoimmunity, stroke, and cancer. They all share a common structural module, the voltage-sensing
domain (VSD), responsible for turning on and off an effector domain in response to changes in
membrane potential. Previous studies from us and other groups have shown that, while most VSDs do
not conduct ions, they can become leaky as a result of mutations. Mutated VSDs permeable to ions or
protons are responsible for serious genetic disorders, such as hypokalemic periodic paralysis, and
cardiac arrhythmias with dilated cardiomyopathy. The VSD of the voltage-gated channel Hv1, on the
other hand, is inherently proton-conductive and this property is key to the channel's many
physiological functions. The long-term goal of this study is to elucidate how VSDs conduct ions and
protons, how their activity is regulated, and how they can be blocked pharmacologically for therapeutic
purposes. Here, we will focus on the Hv1 channel, an emerging drug target for a variety of diseases,
including cancer and stroke. The mechanism underlying VSD-mediated proton conduction in Hv1 is
poorly understood and there is an unmet need for small-molecule inhibitors of Hv1 activity. We have
previously discovered a class of compounds that act as Hv1 blockers and characterized their binding
environment. We identified aromatic interactions within the core of the channel's VSD that could be
harnessed to create better drugs to suppress Hv1 activity. In aim 1, we propose to use
electrophysiological measurements and unnatural amino acid substitutions to examine how these
interactions contribute to Hv1 block and voltage-dependent activation. One of the main problems
limiting our understanding of proton-selective permeation is the inadequate description of channel-
proton interactions by simulation methods based on classic mechanics. In aim 2, we will use quantum
mechanics/molecular mechanics simulations on a validated Hv1 structural model in combination with
the rational design of a proton-conducting VSD to obtain detailed information on how protons move
within the Hv1 permeation pathway. Hv1 function is known to be tightly regulated in the cell. But, little
is known about how this regulation is achieved. We have recently identified a new modality of channel
regulation mediated by mechanical stress, which can provide an explanation for the hyperactivity of
Hv1 previously described in microglia under conditions of ischemic stroke. In aim 3, we will use
electrophysiology, high-speed pressure clamp stimulation, and targeted mutagenesis to determine the
mechanism of Hv1 mechanosensitivity.

## Key facts

- **NIH application ID:** 9821208
- **Project number:** 5R01GM098973-09
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **Principal Investigator:** Francesco Tombola
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $320,618
- **Award type:** 5
- **Project period:** 2011-07-01 → 2022-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9821208

## Citation

> US National Institutes of Health, RePORTER application 9821208, Mechanisms of Permeation and Gating of Voltage-Sensing Domains (5R01GM098973-09). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9821208. Licensed CC0.

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