Directionality of Temperature Activation in Mouse TRPA1 Ion Channel Can Be Inverted by Single-Point Mutations in Ankyrin Repeat Six

Abstract

Summary Several transient receptor potential (TRP) ion channels are activated with high sensitivity by either cold or hot temperatures. However, structures and mechanism that determine temperature-directionality (cold vs. heat) are not established. Here we screened 12,000 random mutant clones of the cold-activated mouse TRPA1 ion channel with a heat stimulus. We identified three single-point mutations that are individually sufficient to make mouse TRPA1 warm-activated, while leaving sensitivity to chemicals unaffected. Mutant channels have high temperature-sensitivity of voltage-activation, specifically of channel opening, but not channel closing, which is reminiscent of other heat-activated TRP channels. All mutations are located in ankyrin repeat six, which identifies this domain as a sensitive modulator of thermal activation. We propose that a change in the coupling of temperature-sensing to channel-gating generates this sensitivity to warm temperatures. Our results demonstrate that minimal changes in protein sequence are sufficient to generate a wide diversity of thermal sensitivities in TRPA1.

Low-cost functional plasticity of TRPV1 supports heat tolerance in squirrels and camels

“…Our results are in line with the observations that a point mutation in the ankyrin repeat domain can shift temperature responses in TRPV1 of different Xenopus species (38) and confer thermal activation to mouse transient receptor potential channel A1 (TRPA1) (39), suggesting a common mechanism of activation. We hypothesize that the mutations affect coupling between the gate and a heat-sensing module(s) located elsewhere in the molecule.…”

Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine

“…In mice, the temperature sensitivity of the TRPA1 channel protein (cold vs. warm) is apparently determined by only three amino acid residues (Jabba et al, 2014); however, the native channel is not involved in autonomic thermoregulation (de Oliveira et al, 2014). It is noteworthy that TRPA1 blockade exerted an anxiolytic-like action in mice (de Moura et al, 2014).…”

The N-terminal Ankyrin Repeat Domain Is Not Required for Electrophile and Heat Activation of the Purified Mosquito TRPA1 Receptor

“…However, these and similar conclusions have to be regarded with some caution because the use of mutagenic and chimeric strategies results in artificial constructs, which makes it difficult to exclude indirect effects on a temperature sensor located elsewhere in the protein (5,10). Furthermore, each of three single point mutations of amino acids in the N-terminal ARD, not previously regarded critical, like certain cysteine and lysine residues (28,29), changed the mouse TRPA1 from being cold-sensitive to being heat-sensitive (30). Importantly, the authors concluded that this could best be explained by an effect on the coupling of temperature to channel gating rather than altering the nature of the thermosensitive domain itself (30).…”

“…Furthermore, each of three single point mutations of amino acids in the N-terminal ARD, not previously regarded critical, like certain cysteine and lysine residues (28,29), changed the mouse TRPA1 from being cold-sensitive to being heat-sensitive (30). Importantly, the authors concluded that this could best be explained by an effect on the coupling of temperature to channel gating rather than altering the nature of the thermosensitive domain itself (30). This reasoning is in line with our view that conformational changes of the N-terminal ARD indirectly affect thermo-and chemosensitive structures outside the N-terminal ARD of TRPA1 (10,14).…”