title: Atomic level characterization of the nonproton ligand-sensing domain of ASIC3 channels.
abstract: Acid-sensing ion channels (ASICs) are known to be primarily activated by extracellular protons. Recently, we characterized a novel nonproton ligand (2-guanidine-4-methylquinazoline, GMQ), which activates the ASIC3 channel subtype at neutral pH. Using an interactive computational-experimental approach, here we extend our investigation to delineate the architecture of the GMQ-sensing domain in the ASIC3 channels. We first established a GMQ binding mode and revealed that residues Glu-423, Glu-79, Leu-77, Arg-376, Gln-271, and Gln-269 play key roles in forming the GMQ-sensing domain. We then verified the GMQ binding mode using ab initio calculation and mutagenesis and demonstrated the critical role of the above GMQ-binding residues in the interplay among GMQ, proton, and Ca(2+) in regulating the function of ASIC3. Additionally, we showed that the same residues involved in coordinating GMQ responses are also critical for activation of the ASIC3(E79C) mutant by thiol-reactive compound DTNB. Thus, a range of complementary techniques provide independent evidence for the structural details of the GMQ-sensing domain at atomic level, laying the foundation for further investigations of endogenous nonproton ligands and gating mechanisms of the ASIC3 channels.
authors.affiliation: Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Yu
authors.forename: Wei-Guang
authors.initials: WG
authors.lastname: Li
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Cao
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Yang
authors.forename: Hualiang
authors.initials: H
authors.lastname: Jiang
authors.forename: Tian-Le
authors.initials: TL
authors.lastname: Xu
mesh_terms: D062565:Acid Sensing Ion Channels; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D003198:Computer Simulation; D006224:Cricetinae; D003412:Cricetulus; D006146:Guanidines / Q000737:chemistry*; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011799:Quinazolines / Q000737:chemistry*; D015222:Sodium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C106067:2-guanidine-4-methylquinazoline; C112231:ASIC3 protein, human; D062565:Acid Sensing Ion Channels; D006146:Guanidines; D011799:Quinazolines; D015222:Sodium Channels; D002118:Calcium