Emerging Concepts in Ion Channel Biophysics

91 / 119

Emerging Concepts in Ion Channel Biophysics Poster Abstracts
86
62-POS Board 62
Structural Insight into the Molecular Mechanism of TRPA1 Activation and Inhibition
Amrita Samanta1,2, Janna Kiselar3, Seungil Han4, Vera Moiseenkova Bell1,2.
1Case Western Reserve University, Cleveland, OH, USA, 2Case Western Reserve University,
Cleveland, OH, USA, 3 Case Western Reserve University, Cleveland, OH, USA, 4Pfizer Inc.,
Groton, CT, USA.
Pain, while serving the beneficial function of provoking our attention to dangerous situations, is
an unpleasant sensory and emotional experience. Transient Receptor Potential Ankyrin 1
(TRPA1) is a member of the transient receptor potential (TRP) cation channel family and is
localized in nerve fibers called “nociceptors” where it plays a key role in the transduction of
chemical, inflammatory and neuropathic pain signals from the periphery to the brain.
TRPA1 is a Ca2+ permeable, nonselective cation channel that is activated by a large variety of
structurally unrelated chemical compounds. This diverse group of ligands can be subdivided into
two classes: electrophilic and non-electrophilic. Covalent modification of critical cysteine
residues on the N-terminus of the channel and/or disulfide bond formation between them is the
accepted molecular mechanism of TRPA1 channel opening upon electrophilic activation.
Activation is clearly dependent on a thiol-reactive moiety, thus explaining the structural diversity
of this group. Non-electrophilic ligands do not require interaction with critical cysteines of the
channel. Although near-atomic resolution structures of TRPA1 were resolved recently by cryo-
EM, both in the presence of agonist and antagonists, detailed mechanisms of channel activation
and inhibition by these modulators could not be determined.
To determine the structural details of TRPA1 conformation upon agonist and antagonist binding,
we used limited proteolysis and mass spectrometry. Our study indicates that conformational
rearrangements of the N-terminus ankyrin repeats and the linker region between the cytosolic
doamin and the transmembrane domain contribute to channel modulation.