TRP Channels and Thermosensation

Recent years have seen great advances in the molecular description of sensory neurobiology. Of the five popularly characterized senses (sight, hearing, taste, smell and touch), touch is perhaps the most varied and least understood. Within this modality is the ability to sense mechanical forces, chemical stimuli, and temperature, and the molecules that mediate this ability have been a long-standing mystery. Temperature sensation in particular has received relatively little attention from physiologists and yet is critical for interaction with the environment (Hensel, 1981). My group and others have recently discovered the proteins that enable sensory neurons to convey temperature information. These proteins are ion channels activated by specific changes in temperature, thus acting as the molecular thermometers of our body. Channels play a central role in neurobiology as membrane-spanning proteins that regulate the flux of ions. Categorized according to their mechanism of gating, ion channels can be activated by signals such as specific ligands, voltage, or mechanical force. Another type of signal, temperatures above 43°C, was shown to activate the ion channel TRPV1 (VR1), a member of transient receptor potential (TRP) family of cation channels (Caterina et al., 1997). These high temperatures are perceived as painful or noxious by many organisms. Interestingly, TRPV1 is also activated by capsaicin, the active ingredient of chili peppers. A second TRP, TRPV2 (VRL1) was soon found to respond to yet higher temperatures (53°C) (Caterina et al., 1999). Building on these initial findings, my lab focused on identifying additional temperature-activated ion channels.