Ivermectin Interaction with transmembrane helices reveals widespread rearrangements during opening of P2X receptor channels.
P2X receptors are trimeric cation channels that open in response to binding of extracellular ATP. Each subunit contains a large extracellular ligand binding domain and two flanking transmembrane (TM) helices that form the pore, but the extent of gating motions of the TM helices is unclear. We probed these motions using ivermectin (IVM), a macrocyclic lactone that stabilizes the open state of P2X(4) receptor channels. We find that IVM partitions into lipid membranes and that transfer of the TM regions of P2X(4) receptors is sufficient to convey sensitivity to the lactone, suggesting that IVM interacts most favorably with the open conformation of the two TM helices at the protein-lipid interface. Scanning mutagenesis of the two TMs identifies residues that change environment between closed and open states, and substitutions at a subset of these positions weaken IVM binding. The emerging patterns point to widespread rearrangements of the TM helices during opening of P2X receptor channels.
Silberberg
Shai D
SD
Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA. silberbs@ninds.nih.gov
Li
Mufeng
M
Swartz
Kenton J
KJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D004247:DNA / Q000235:genetics; D004594:Electrophysiology; D015640:Ion Channel Gating / Q000187:drug effects; D007559:Ivermectin / Q000494:pharmacology*; D007783:Lactones / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009865:Oocytes / Q000502:physiology; D016062:Porosity; D011487:Protein Conformation; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000187:drug effects*; D058476:Receptors, Purinergic P2X2; D014981:Xenopus
D007783:Lactones; D008565:Membrane Proteins; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D007559:Ivermectin; D000255:Adenosine Triphosphate; D004247:DNA