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The Journal of Neuroscience, May 7, 2008, 28(19):5063-5071; doi:10.1523/JNEUROSCI.0047-08.2008

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Cellular/Molecular
Molecular Determinants of Species-Specific Activation or Blockade of TRPA1 Channels

Jun Chen,¹ Xu-Feng Zhang,¹ Michael E. Kort,¹ Jeffrey R. Huth,² Chaohong Sun,² Laura J. Miesbauer,² Steven C. Cassar,¹ Torben Neelands,¹ Victoria E. Scott,¹ Robert B. Moreland,¹ Regina M. Reilly,¹ Philip J. Hajduk,² Philip R. Kym,¹ Charles W. Hutchins,² and Connie R. Faltynek¹

¹Neuroscience and ²Advanced Technology, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064-6125

Correspondence should be addressed to Dr. Jun Chen, Building AP9A, 100 Abbott Park Road, Abbott Park, IL 60064-6125. Email: jun.x.chen{at}abbott.com

TRPA1 is an excitatory, nonselective cation channel implicated in somatosensory function, pain, and neurogenic inflammation. Through covalent modification of cysteine and lysine residues, TRPA1 can be activated by electrophilic compounds, including active ingredients of pungent natural products (e.g., allyl isothiocyanate), environmental irritants (e.g., acrolein), and endogenous ligands (4-hydroxynonenal). However, how covalent modification leads to channel opening is not understood. Here, we report that electrophilic, thioaminal-containing compounds [e.g., CMP1 (4-methyl-N-[2,2,2-trichloro-1-(4-nitro-phenylsulfanyl)-ethyl]-benzamide)] covalently modify cysteine residues but produce striking species-specific effects [i.e., activation of rat TRPA1 (rTRPA1) and blockade of human TRPA1 (hTRPA1) activation by reactive and nonreactive agonists]. Through characterizing rTRPA1 and hTRPA1 chimeric channels and point mutations, we identified several residues in the upper portion of the S6 transmembrane domains as critical determinants of the opposite channel gating: Ala-946 and Met-949 of rTRPA1 determine channel activation, whereas equivalent residues of hTRPA1 (Ser-943 and Ile-946) determine channel block. Furthermore, side-chain replacements at these critical residues profoundly affect channel function. Therefore, our findings reveal a molecular basis of species-specific channel gating and provide novel insights into how TRPA1 respond to stimuli.

Key words: TRPA1; species specific; covalent modification; channel gating; activation; block

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Received Jan. 5, 2008; revised March 31, 2008; accepted April 2, 2008.

Correspondence should be addressed to Dr. Jun Chen, Building AP9A, 100 Abbott Park Road, Abbott Park, IL 60064-6125. Email: jun.x.chen{at}abbott.com

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