# Structural Mechanisms of Acid Sensing Ion Channels

> **NIH NIH F31** · UNIVERSITY OF COLORADO DENVER · 2020 · $35,029

## Abstract

PROJECT SUMMARY
 Nociception is the process by which sensory neurons detect painful stimuli. Nociceptor activation can
initiate both an acute pain response and produce local inflammation leading to tissue acidosis. This reduction
in pH is associated with a range of pathophysiological responses in the orofacial region including pericoronitis,
pulpitis and migraine. Acid sensing ion channels (ASICs) are molecular proton sensors that are activated in
response to this extracellular acidification. ASICs are widely expressed throughout both the peripheral and
central nervous systems (PNS/CNS). In the PNS, ASICs are found in the trigeminal ganglion (TG) neurons that
innervate tooth pulp, facial skin and periodontal Ruffini endings. There is evidence that ASIC3 expression
correlates with orofacial pain following experimental tooth pain in rats, which could be relieved with ASIC
antagonists, APETx2 and amiloride. ASICs involvement in nociception and mechanosensation within TG
neurons make it a novel analgesic target, but much remains to be elucidated about ASICs molecular
mechanisms before robust and effective drugs can be developed. While structures of ASIC have been solved,
revealing in atomic detail the trimeric nature of this channel, they lack the intracellular termini. Using novel
fluorescence methodologies like specific labeling with an unnatural amino acid and transition metal ion FRET
accompanied by electrophysiology, specific aim 1 seeks to examine intramolecular dynamic rearrangements of
the intracellular domains during channel activation. This set of experiments will fill a void by answering
questions that the ASIC structures do not. I will seek to determine the dynamic rearrangements of the n-
terminus during channel function. I will assign these rearrangements in channel structure to functional states of
the channel using patch clamp electrophysiology. In addition, I will test some hypotheses, put forth by the
crystal structures. There is an unusual domain swapped architecture in the transmembrane domains of ASIC in
some, but not all, crystal structures. I can use my novel approach to test for the presence of this swap in real
membranes. In aim 2, I will seek to understand the heteromeric assembly of ASICs. The literature
overwhelmingly focuses on homomers likely due to the ease of studying one subunit at a time. The
physiological relevance of ASIC heteromers makes them critical to study. However, results from heteromeric
studies are challenging to interpret, often because channel stoichiometry is unknown. Specific aim 2 will try to
delineate the rules of ASIC heteromerization. These experiments will begin to answer questions which should
motivate future studies of heteromers in addition to homomers. Do heteromers form preferentially, whether that
be 2:1 or 1:2, or is it nonspecific? What sites on the channel are responsible for heteromerization? These
findings will help elucidate the molecular mechanisms of ASIC gating and provide a new und...

## Key facts

- **NIH application ID:** 9853622
- **Project number:** 5F31DE028739-02
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Megan Cullinan
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $35,029
- **Award type:** 5
- **Project period:** 2019-02-01 → 2022-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9853622

## Citation

> US National Institutes of Health, RePORTER application 9853622, Structural Mechanisms of Acid Sensing Ion Channels (5F31DE028739-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9853622. Licensed CC0.

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