Psalmotoxin-1 Docking to Human Acid-sensing Ion Channel-1

Yawar J Qadri,Bakhrom K Berdiev,Yuhua Song,Howard L Lippton,Catherine M Fuller,Dale J Benos

doi:10.1074/jbc.m109.003913

Yawar J Qadri, Bakhrom K Berdiev + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m109.003913

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Abstract

Acid-sensing ion channel-1 (ASIC-1) is a proton-gated ion channel implicated in nociception and neuronal death during ischemia. Recently the first crystal structure of a chicken ASIC was obtained. Expanding upon this work, homology models of the human ASICs were constructed and evaluated. Energy-minimized structures were tested for validity by in silico docking of the models to psalmotoxin-1, which potently inhibits ASIC-1 and not other members of the family. The data are consistent with prior radioligand binding and functional assays while also explaining the selectivity of PcTX-1 for homomeric hASIC-1a. Binding energy calculations suggest that the toxin and channel create a complex that is more stable than the channel alone. The binding is dominated by the coulombic contributions, which account for why the toxin-channel interaction is not observed at low pH. The computational data were experimentally verified with single channel and whole-cell electrophysiological studies. These validated models should allow for the rational design of specific and potent peptidomimetic compounds that may be useful for the treatment of pain or ischemic stroke.

Highlights

This work used homology modeling to deduce structures of the human ASICs
␣␤␥-epithelial sodium channel channels expressed in the kidney are important in blood pressure homeostasis, whereas homomeric Acid-sensing ion channel-1 (ASIC-1) channels found in neurons are implicated in nociception and neuronal death during ischemia [1, 3]
Studies of homology modeling of membrane proteins have shown that MODELLER is able to produce valid results with as little as 25% identity; it is expected that valid models can be obtained for the ASIC proteins [23]

Summary

Introduction

This work used homology modeling to deduce structures of the human ASICs. These models were evaluated using structural verification suites and validated using in silico inhibitor docking to recapitulate functional results. Previously suggested that the docking site was self-contained When synthetic toxin was applied to these cells at 25 nM in within one subunit and our computational findings disagreed both pH 7.4 and the acid pulse, there was a significant decrease with this, we tested the finding using a chimeric hASIC-2b sub- in acid-induced currents after 2 pulses or ϳ60 s of exposure to unit.

Results

Conclusion