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Naked mole-rat acid-sensing ion channel 3 forms nonfunctional homomers, but functional heteromers

Published version
Peer-reviewed

Type

Article

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Authors

Schuhmacher, Laura-Nadine 
Callejo, Gerard 
Srivats, Shyam 
Smith, Ewan St John  ORCID logo  https://orcid.org/0000-0002-2699-1979

Abstract

ABSTRACT

Acid-sensing ion channels (ASICs) form both homotrimeric and heterotrimeric ion channels that are activated by extracellular protons and are involved in a wide range of physiological and pathophysiological processes, including pain and anxiety. ASIC proteins can form both homotrimeric and heterotrimeric ion channels. The ASIC3 subunit has been shown to be of particular importance in the peripheral nervous system with pharmacological and genetic manipulations demonstrating a role in pain. Naked mole-rats, despite having functional ASICs, are insensitive to acid as a noxious stimulus and show diminished avoidance of acidic fumes, ammonia and carbon dioxide. Here we cloned naked mole-rat ASIC3 (nmrASIC3) and used a cell surface biotinylation assay to demonstrate that it traffics to the plasma membrane, but using whole-cell patch-clamp electrophysiology we observed that nmrASIC3 is insensitive to both protons and the non-proton ASIC3 agonist 2-Guanidine-4-methylquinazoline (GMQ). However, in line with previous reports of ASIC3 mRNA expression in dorsal root ganglia (DRG) neurons, we found that the ASIC3 antagonist APETx2 reversibly inhibits ASIC-like currents in naked mole-rat DRG neurons. We further show that like the proton-insensitive ASIC2b and ASIC4, nmrASIC3 forms functional, proton sensitive heteromers with other ASIC subunits. An amino acid alignment of ASIC3s between 9 relevant rodent species and human identified unique sequence differences that might underlie the proton insensitivity of nmrASIC3. However, introducing nmrASIC3 differences into rat ASIC3 (rASIC3) produced only minor differences in channel function, and replacing nmrASIC3 sequence with that of rASIC3 did not produce a proton-sensitive ion channel. Our observation that nmrASIC3 forms nonfunctional homomers may reflect a further adaptation of the naked mole-rat to living in an environment with high-carbon dioxide levels.

Description

Keywords

32 Biomedical and Clinical Sciences, 3208 Medical Physiology, 3209 Neurosciences, 3202 Clinical Sciences, Neurosciences, Biotechnology, Genetics, Pain Research, Chronic Pain, 1 Underpinning research, 1.1 Normal biological development and functioning

Journal Title

Journal of Biological Chemistry

Conference Name

Journal ISSN

1083-351X

Volume Title

Publisher

American Society for Biochemistry and Molecular Biology Inc.
Sponsorship
ARTHRITIS RESEARCH UK (20930)
Biotechnology and Biological Sciences Research Council (BB/J014540/1)
Biotechnology and Biological Sciences Research Council Doctoral Training Programme Grant BB/J014540/1 Arthritis Research UK Grant 20930. Cambridge International and European Trust. Royal Society Research Grant RG130110.