Journal Article

Pain-enhancing mechanism through interaction between TRPV1 and anoctamin 1 in sensory neurons

Takayama, Yasunori, Furue, Hidemasa, Uta, Daisuke, Tominaga, Makoto

2015

Overview

The capsaicin receptor transient receptor potential cation channel vanilloid 1 (TRPV1) is activated by various noxious stimuli, and the stimuli are converted into electrical signals in primary sensory neurons. It is believed that cation influx through TRPV1 causes depolarization, leading to the activation of voltage-gated sodium channels, followed by the generation of action potential. Here we report that the capsaicin-evoked action potential could be induced by two components: a cation influx-mediated depolarization caused by TRPV1 activation and a subsequent anion efflux-mediated depolarization via activation of anoctamin 1 (ANO1), a calcium-activated chloride channel, resulting from the entry of calcium through TRPV1. The interaction between TRPV1 and ANO1 is based on their physical binding. Capsaicin activated the chloride currents in an extracellular calcium-dependent manner in HEK293T cells expressing TRPV1 and ANO1. Similarly, in mouse dorsal root ganglion neurons, capsaicin-activated inward currents were inhibited significantly by a specific ANO1 antagonist, T16Ainh-A01 (A01), in the presence of a high concentration of EGTA but not in the presence of BAPTA [1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid]. The generation of a capsaicin-evoked action potential also was inhibited by A01. Furthermore, pain-related behaviors in mice treated with capsaicin, but not with αβ-methylene ATP, were reduced significantly by the concomitant administration of A01. These results indicate that TRPV1–ANO1 interaction is a significant pain-enhancing mechanism in the peripheral nervous system. Significance The capsaicin receptor transient receptor potential cation channel vanilloid 1 (TRPV1) and anoctamin 1 (ANO1) work as receptors activated by noxious stimuli in sensory nerve endings. It is believed that activation of the two channels causes cation influx and anion efflux, respectively, both of which lead to depolarization. We show that ANO1 is activated by calcium ions entering neurons through TRPV1 activation based on their physical binding on the cell membrane. Indeed, both capsaicin-activated inward currents in sensory neurons and capsaicin-induced pain-related behaviors in mice were inhibited significantly by ANO1 blockade. To our knowledge, this is the first evidence for a mechanism by which interaction between TRPV1 and ANO1 functions as a pain-enhancing mechanism.

• Publisher: National Academy of Sciences
• Subject: Animals / Anoctamin-1 / Behavior, Animal - drug effects / Binding sites / Biological Sciences / Brain / Calcium / capsaicin / Capsaicin - pharmacology / cell membranes / Chloride Channels - metabolism / Ethane / Excitatory Postsynaptic Potentials - drug effects / Ganglia, Spinal - drug effects / Ganglia, Spinal - metabolism / HEK293 Cells / Humans / ions / mice / Mice, Inbred C57BL / Models, Biological / nerve endings / Neurons / Neuroscience / Pain / Pain - metabolism / Presynaptic Terminals - drug effects / Presynaptic Terminals - metabolism / Protein Binding - drug effects / receptors / sensory neurons / Sensory Receptor Cells - drug effects / Sensory Receptor Cells - metabolism / TRPV Cation Channels - metabolism