Outer Pore Domain of TRPV1 Ion Channel is Required for Temperature-Independent Step During Temperature-Activation

Abstract

TRPV1 is the founding and best-studied member of the family of temperature-activated transient receptor potential ion channels (thermoTRPs). Voltage, chemicals, and heat allosterically gate TRPV1. Molecular determinants for TRPV1 activation by capsaicin, allicin, acid, ammonia, and voltage have been identified. However, many years after the discovery of TRPV1, the structures and mechanisms mediating temperature-sensitivity remain unclear. Recent studies of the related channel TRPV3 identified residues within the pore region required for heat activation. Here we describe both random and targeted mutagenesis screens of TRPV1 to identify single point-mutations that specifically affect temperature-activation. The mutations found are all located in the outer pore region, in close proximity to but distinct from residues previously implicated in acid-activation. Electrophysiological analysis shows that mutations affect a temperature-independent step that is part of the temperature-gating pathway. These results suggest that the outer pore plays a general role in heat-sensitivity of thermoTRPs.