title: Demonstration of a direct interaction between sigma-1 receptors and acid-sensing ion channels.
abstract: The sigma-1 receptor is a widely expressed protein that interacts with a variety of ion channels, including the acid-sensing ion channel (ASIC) 1a. Here we used atomic force microscopy to determine the architecture of the ASIC1a/sigma-1 receptor complex. When isolated His(8)-tagged ASIC1a was imaged in complex with anti-His(6) antibodies, the angle between pairs of bound antibodies was 135 degrees , consistent with the known trimeric structure of the channel. When ASIC1a was coexpressed with FLAG/His(6)-tagged sigma-1 receptor, ASIC1a became decorated with small particles, and pairs of these particles bound at an angle of 131 degrees . When these complexes were incubated with anti-FLAG antibodies, pairs of antibodies bound at an angle of 134 degrees , confirming that the small particles were sigma-1 receptors. Of interest, we found that the sigma-1 receptor ligand haloperidol caused an approximately 50% reduction in ASIC1a/sigma-receptor binding, suggesting a way in which sigma-1 ligands might modulate channel properties. For the first time, to our knowledge, we have resolved the structure of a complex between the sigma-1 receptor and a target ion channel, and demonstrated that the stoichiometry of the interaction is 1 sigma-1 receptor/1 ASIC1a subunit.
authors.affiliation: Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Stewart M
authors.initials: SM
authors.lastname: Carnally
authors.forename: Molly
authors.initials: M
authors.lastname: Johannessen
authors.forename: Robert M
authors.initials: RM
authors.lastname: Henderson
authors.forename: Meyer B
authors.initials: MB
authors.lastname: Jackson
authors.forename: J Michael
authors.initials: JM
authors.lastname: Edwardson
mesh_terms: D062565:Acid Sensing Ion Channels; D002460:Cell Line; D006220:Haloperidol / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D006801:Humans; D007477:Ions; D008024:Ligands; D018625:Microscopy, Atomic Force / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D017480:Receptors, sigma / Q000378:metabolism*; D015222:Sodium Channels / Q000737:chemistry* / Q000378:metabolism*; D014162:Transfection; D000097605:Sigma-1 Receptor
chemical_list: D062565:Acid Sensing Ion Channels; D006220:Haloperidol; D006639:Histidine; D007477:Ions; D008024:Ligands; D009419:Nerve Tissue Proteins; D017480:Receptors, sigma; D015222:Sodium Channels; D000097605:Sigma-1 Receptor; C568266:ASIC1 protein, human