Cyanotriphenylborate: subtype-specific blocker of glycine receptor chloride channels.
The inhibitory glycine receptor is a ligand-gated ion-channel protein existing in different homo- and heterooligomeric isoforms. Here we show that the chloride channel of the recombinant alpha 1-subunit homooligomeric glycine receptor is efficiently blocked by cyanotriphenylborate (CTB) with a concentration effecting 50% inhibition (IC50) of 1.3 microM in the presence of 50 microM glycine. The antagonistic effect of CTB is noncompetitive, use dependent, and more pronounced at positive membrane potentials, suggesting open-channel block. In contrast to alpha 1-subunit receptors, alpha 2-subunit homooligomers are resistant to CTB (IC50 >> 20 microM). By exchanging the channel-lining transmembrane segment M2 of the alpha 1 polypeptide by that of the alpha 2 polypeptide, we could transfer this resistance to alpha 1 channels, indicating that a single glycine residue at position 254 of the alpha 1 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.
Rundström
N
N
Max-Planck-Institute für Hirnforschung, Frankfurt, Germany.
Schmieden
V
V
Betz
H
H
Bormann
J
J
Langosch
D
D
D000595:Amino Acid Sequence; D001483:Base Sequence; D001881:Borates / Q000494:pharmacology*; D002460:Cell Line; D018118:Chloride Channels / Q000187:drug effects*; D017931:DNA Primers / Q000737:chemistry; D006801:Humans; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D008565:Membrane Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018009:Receptors, Glycine / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics; D011994:Recombinant Proteins; D013329:Structure-Activity Relationship; D013730:Terphenyl Compounds / Q000494:pharmacology*
D001881:Borates; D018118:Chloride Channels; D017931:DNA Primers; D008565:Membrane Proteins; D018009:Receptors, Glycine; D011994:Recombinant Proteins; D013730:Terphenyl Compounds; C089415:cyanotriphenylborate