Temperature-Driven Activation of Thermotrps: A Distinct Pathway Involved

Abstract

A group of thermosensitive transient receptor potential (ThermoTRP) channels, with high temperature sensitivity of channel gating, are the cellular temperature sensors. ThermoTRPs are polymodal receptors. Besides temperature they are gated by voltage, ligand, extracellular pH and other stimuli. How temperature changes drive activation conformational rearrangement remains unknown. Here we combine functional, mutational, and site-directed fluorescence studies to demonstrate that temperature-dependent activation uses a pathway distinct from those for ligand- and voltage-dependent activation.We observed that neither strong depolarization nor application of capsaicin could significantly alter thermodynamics of temperature-driven TRPV1 activation. In addition, voltage and ligand exhibited additive gating effects over temperature gating. Indeed, a TRPV1 mutant in which part of the outer pore region was replaced by an artificial sequence showed virtually no temperature sensitivity but maintained near normal capsaicin sensitivity. Furthermore, site-directed FRET measurements showed that conformational changes in outer pore can only be induced by heating, but not by voltage or ligand. Together these observations suggest that a distinct pathway for temperature to gate TRPV1 involves the outer pore region.View Large Image | View Hi-Res Image | Download PowerPoint Slide