Temperature sensing by thermal TRP channels: thermodynamic basis and molecular insights

All organisms need to sense temperature in order to survive and adapt. But how they detect and perceive temperature remains poorly understood. Recent discoveries of thermal Transient Receptor Potential (TRP) ion channels have shed light on the problem and unravel molecular entities for temperature detection and transduction in mammals. Thermal TRP channels belong to the large family of transient receptor potential channels. They are directly activated by heat or cold in physiologically relevant temperature ranges, and the activation is exquisitely sensitive to temperature changes. Thermodynamically, this strong temperature dependence of thermal channels occurs due to large enthalpy and entropy changes associated with channel opening. Thus understanding how the channel proteins obtain their exceptionally large energetics is central toward determining functional mechanisms of thermal TRP channels. The purpose of this chapter is to provide a comprehensive review on critical issues and challenges facing the problem, with emphases on underlying biophysical and molecular mechanisms.