Defining functional domains of temperature- and capsaicin-activated TRPV1 channels

Authors

• KE Huffer
• A Jara-Oseguera
• KJ Swartz

Abstract

The transient receptor potential vanilloid 1 channel (TRPV1) is a nonselective cation channel that responds to painful stimuli, including noxious heat (above 42°C), capsaicin, protons, resiniferatoxin, and double-knot toxin from tarantula venom. Recent work by our lab has shown that TRPV1 channel activity is inhibited by extracellular sodium, which appears to exert allosteric control over TRPV1 temperature sensitivity. Although previous work has shown that several TRP channels, including TRPML2, TRPML3, and a splice variant of TRPM3, are activated by the removal of external sodium, we have determined that other thermo-sensitive TRP channels, including the closely-related TRPV2 channel, are not sensitive to external sodium at room temperature. In an attempt to localize the TRPV1 sodium binding site, we have transferred extracellular portions of TRPV1 into TRPV2. Transferring the TRPV1 pore domain or transmembrane region into TRPV2 produces functional chimeras that respond to 2-aminoethoxydiphenyl borate, an agonist for both wild type TRPV1 and TRPV2. The transmembrane chimera also demonstrates successful transfer of sensitivity to some TRPV1-selective agonists, including capsaicin and protons. However, both the pore domain and transmembrane chimeras remain insensitive to external sodium at room temperature. Ongoing work is focused on the creation and characterization of additional chimeras as well as further characterization of existing chimeras in the presence of other agonists, including toxins and temperature.

Scientific Focus Area: Neuroscience

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