Evaluation of PhTX-74 as Subtype-Selective Inhibitor of GluA2-Containing AMPA Receptors

TY - JOUR

T1 - Evaluation of PhTX-74 as Subtype-Selective Inhibitor of GluA2-Containing AMPA Receptors

AU - Poulsen, Mette Homann

AU - Lucas, Simon

AU - Strømgaard, Kristian

AU - Kristensen, Anders Skov

PY - 2014/2

Y1 - 2014/2

N2 - ABSTRACT The a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are glutamate-gated cation channels that mediate fast excitatory synaptic transmission in the central nervous system. AMPARs are tetramers formed by homo- or heteromeric assembly of GluA1-4 subunits to produce multiple subtypes with varying biophysical properties. Polyamine toxins such as joro spider toxins, philanthotoxins (PhTXs), and argiotoxins are use-dependent ion channel blockers of AMPARs widely employed as highly potent antagonists of GluA2-lacking receptor subtypes. In addition to this use, recent findings have indicated that a philanthotoxin analog, PhTX-74, can distinguish among GluA2- containing AMPAR subtypes in the presence of the prototypical transmembrane AMPAR regulatory protein g-2 (or stargazin). Thus, PhTX-74 may be of potential use in studies of the neurobiological role of GluA2-containing subtypes. We have evaluated the pharmacological profile of PhTX-74 and related polyamine toxins at homo- and heteromeric AMPARs in the presence and absence of g-2. Determination of IC50 values for inhibition of glutamate-evoked currents from Xenopus oocytes expressing recombinant homo- or heteromeric combinations of GluA1, GluA2, and GluA3 in the presence of g-2 shows that PhTX-74 inhibits homomeric GluA1 and GluA3 receptors nonselectively, with IC50 values in the nanomolar range (252-356 nM), and heteromeric GluA1/A2 and GluA2/A3 receptors nonselectively, with IC50 values in the micromolar range (22 mM). Thus, in contrast to earlier findings, we find that PhTX-74 cannot pharmacologically discriminate between GluA2-containing AMPAR subtypes.

AB - ABSTRACT The a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs) are glutamate-gated cation channels that mediate fast excitatory synaptic transmission in the central nervous system. AMPARs are tetramers formed by homo- or heteromeric assembly of GluA1-4 subunits to produce multiple subtypes with varying biophysical properties. Polyamine toxins such as joro spider toxins, philanthotoxins (PhTXs), and argiotoxins are use-dependent ion channel blockers of AMPARs widely employed as highly potent antagonists of GluA2-lacking receptor subtypes. In addition to this use, recent findings have indicated that a philanthotoxin analog, PhTX-74, can distinguish among GluA2- containing AMPAR subtypes in the presence of the prototypical transmembrane AMPAR regulatory protein g-2 (or stargazin). Thus, PhTX-74 may be of potential use in studies of the neurobiological role of GluA2-containing subtypes. We have evaluated the pharmacological profile of PhTX-74 and related polyamine toxins at homo- and heteromeric AMPARs in the presence and absence of g-2. Determination of IC50 values for inhibition of glutamate-evoked currents from Xenopus oocytes expressing recombinant homo- or heteromeric combinations of GluA1, GluA2, and GluA3 in the presence of g-2 shows that PhTX-74 inhibits homomeric GluA1 and GluA3 receptors nonselectively, with IC50 values in the nanomolar range (252-356 nM), and heteromeric GluA1/A2 and GluA2/A3 receptors nonselectively, with IC50 values in the micromolar range (22 mM). Thus, in contrast to earlier findings, we find that PhTX-74 cannot pharmacologically discriminate between GluA2-containing AMPAR subtypes.

KW - Faculty of Health and Medical Sciences

U2 - 10.1124/mol.113.089961

DO - 10.1124/mol.113.089961

M3 - Journal article

C2 - 24220009

SN - 0026-895X

VL - 85

SP - 261

EP - 268

JO - Molecular Pharmacology

JF - Molecular Pharmacology

IS - 2

ER -