Cyanotriphenylborate: Subtype-Specific Blocker of Glycine Receptor Chloride Channels

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 91; no. 19; pp. 8950 - 8954
• Main Authors: Rundstrom, Nils, Schmieden, Volker, Betz, Heinrich, Bormann, Joachim, Langosch, Dieter
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 13.09.1994; National Acad Sciences; National Academy of Sciences
• Subjects: Amino Acid Sequence; Base Sequence; Borates - pharmacology; Cell Line; Chloride Channels - drug effects; Complementary RNA; DNA Primers - chemistry; Glycine receptors; Humans; In Vitro Techniques; Inhibitory concentration 50; Ion Channel Gating - drug effects; Kidney cells; Membrane potential; Membrane Proteins - chemistry; Molecular Sequence Data; Molecules; Mutagenesis, Site-Directed; Neurons; Oocytes; Protein isoforms; Proteins; Receptors; Receptors, Glycine - chemistry; Receptors, Glycine - drug effects; Receptors, Glycine - genetics; Recombinant Proteins; Structure-Activity Relationship; Terphenyl Compounds - pharmacology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.19.8950

The inhibitory glycine receptor is a ligandgated ion-channel protein existing in different homo- and heterooligomeric isoforms. Here we show that the chloride channel of the recombinant α1-subunit homooligomeric glycine receptor is efficiently blocked by cyanotriphenylborate (CTB) with a concentration effecting 50% inhibition (IC50) of 1.3 μM in the presence of 50 μM glycine. The antagonistic effect of CTB is noncompetitive, use dependent, and more pronounced at positive membrane potentials, suggesting open-channel block. In contrast to α1-subunit receptors, α2-subunit homooligomers are resistant to CTB (IC50>> 20 μM). By exchanging the channel-lining transmembrane segment M2 of the α1 polypeptide by that of the α2 polypeptide, we could transfer this resistance to α1 channels, indicating that a single glycine residue at position 254 of the α1 subunit is critical for CTB sensitivity. The blocker did not affect the cation-selective channel of the nicotinic acetylcholine receptor. Thus, CTB may prove useful as a tool to probe the subunit structure of native glycine receptors in mammalian neurons.