Resiniferatoxin Binds to the Capsaicin Receptor (TRPV1) near the Extracellular Side of the S4 Transmembrane Domain

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• 作者：Margaret Z. Chou ; Tecla Mtui ; Ying-Duo Gao ; Martin Kohler ; and Richard E. Middleton
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：March 9, 2004
• 年：2004
• 卷：43
• 期：9
• 页码：2501 - 2511
• 全文大小：321K
• 年卷期：v.43,no.9(March 9, 2004)
• ISSN：1520-4995

文摘

The capsaicin receptor (TRPV1) is a nonselective cation channel that is activated in nociceptorsby several painful stimuli, and hence TRPV1 antagonists could represent a novel class of analgesiccompounds. Resiniferatoxin (RTX), a potent agonist of TRPV1, and iodoresiniferatoxin (I-RTX), a potentantagonist of TRPV1, both bind with higher affinity to the rat TRPV1 (rTRPV1) than the human (hTRPV1)isoform. To identify the structural features responsible for this difference in affinity, [³H]RTX binding tochimeras between hTRPV1 and rTRPV1 was characterized. The "sensor" region within the transmembranedomain (S1-S4) was found to determine [³H]RTX binding affinity. All 16 different residues in this regionwere systematically substituted in hTRPV1 with rTRPV1 residues. A single mutation in the S4 membranedomain of hTRPV1, L547M, caused a 30-fold increase in [³H]RTX affinity whereas the inverse mutationin rTRPV1, M547L, caused a 30-fold decrease in affinity for [³H]RTX, and several other agonists andantagonists were similarly affected by these mutations. TRPV1 channels with mutations at position 547were expressed in oocytes, and the relative response to RTX followed a pattern similar to that seen with[³H]RTX binding. These data suggest a model where Met-547 in the S4 domain of TRPV1 forms a bindingpocket with Tyr-511 in the S3 domain. This model places RTX near the sensor domain thought to moveduring the gating process and should help to guide further work designed to understand the gatingmechanisms of TRPV1 channels based on comparisons between the agonist RTX and the related competitiveantagonist I-RTX.