Acid-sensing ion channel (ASIC) 1a/2a heteromers have a flexible 2:1/1:2 stoichiometry.
Acid-sensing ion channels (ASICs) are widely expressed proton-gated Na(+) channels playing a role in tissue acidosis and pain. A trimeric composition of ASICs has been suggested by crystallization. Upon coexpression of ASIC1a and ASIC2a in Xenopus oocytes, we observed the formation of heteromers and their coexistence with homomers by electrophysiology, but could not determine whether heteromeric complexes have a fixed subunit stoichiometry or whether certain stoichiometries are preferred over others. We therefore imaged ASICs labeled with green and red fluorescent proteins on a single-molecule level, counted bleaching steps from GFP and colocalized them with red tandem tetrameric mCherry for many individual complexes. Combinatorial analysis suggests a model of random mixing of ASIC1a and ASIC2a subunits to yield both 2:1 and 1:2 ASIC1a:ASIC2a heteromers together with ASIC1a and ASIC2a homomers.
Institute of Physiology II andBIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; and.
Tudor
T
Bartoi
Institute of Physiology, Rheinisch-Westfälische Technische Hochschule Aachen University, 52074 Aachen, Germany.
Katrin
K
Augustinowski
Institute of Physiology, Rheinisch-Westfälische Technische Hochschule Aachen University, 52074 Aachen, Germany.
Georg
G
Polleichtner
Institute of Physiology, Rheinisch-Westfälische Technische Hochschule Aachen University, 52074 Aachen, Germany max.ulbrich@physiologie.uni-freiburg.de sgruender@ukaachen.de.
Stefan
http://orcid.org/0000-0002-7635-9883
S
Gründer
Institute of Physiology II andBIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany; and max.ulbrich@physiologie.uni-freiburg.de sgruender@ukaachen.de.
Maximilian H
MH
Ulbrich
D062565:Acid Sensing Ion Channels / Q000737:chemistry* / Q000502:physiology*; D000138:Acidosis / Q000503:physiopathology; D000700:Analgesics / Q000737:chemistry; D000818:Animals; D015195:Drug Design; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008164:Luminescent Proteins / Q000737:chemistry; D008956:Models, Chemical; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011522:Protons; D014981:Xenopus; D000097573:Red Fluorescent Protein
D062565:Acid Sensing Ion Channels; D000700:Analgesics; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D011522:Protons; D000097573:Red Fluorescent Protein; C568266:ASIC1 protein, human; C568424:ASIC2 protein, human
BLINaC; ENaC; single-molecule imaging; subunit counting