2 research outputs found
Structural Determinants of the γ‑8 TARP Dependent AMPA Receptor Antagonist
The forebrain specific
AMPA receptor antagonist, LY3130481/CERC-611,
which selectively antagonizes the AMPA receptors associated with TARP
γ-8, an auxiliary subunit enriched in the forebrain, has potent
antiepileptic activities without motor side effects. We designated
the compounds with such activities as γ-8 TARP dependent AMPA
receptor antagonists (γ-8 TDAAs). In this work, we further investigated
the mechanisms of action using a radiolabeled γ-8 TDAA and ternary
structural modeling with mutational validations to characterize the
LY3130481 binding to γ-8. The radioligand binding to the cells
heterologously expressing GluA1 and/or γ-8 revealed that γ-8
TDAAs binds to γ-8 alone without AMPA receptors. Homology modeling
of γ-8, based on the crystal structures of a distant TARP homologue,
murine claudin 19, in conjunction with knowledge of two γ-8
residues previously identified as critical for the LY3130481 TARP-dependent
selectivity provided the basis for a binding mode prediction. This
allowed further rational mutational studies for characterization of
the structural determinants in TARP γ-8 for LY3130481 activities,
both thermodynamically as well as kinetically
Discovery of the First α‑Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Antagonist Dependent upon Transmembrane AMPA Receptor Regulatory Protein (TARP) γ‑8
Transmembrane
AMPA receptor regulatory proteins (TARPs) are a family
of scaffolding proteins that regulate AMPA receptor trafficking and
function. TARP γ-8 is one member of this family and is highly
expressed within the hippocampus relative to the cerebellum. A selective
TARP γ-8-dependent AMPA receptor antagonist (TDAA) is an innovative
approach to modulate AMPA receptors in specific brain regions to potentially
increase the therapeutic index relative to known non-TARP-dependent
AMPA antagonists. We describe here, for the first time, the discovery
of a noncompetitive AMPA receptor antagonist that is dependent on
the presence of TARP γ-8. Three major iteration cycles were
employed to improve upon potency, CYP1A2-dependent challenges, and
in vivo clearance. An optimized molecule, compound (−)-<b>25</b> (LY3130481), was fully protective against pentylenetetrazole-induced
convulsions in rats without the motor impairment associated with non-TARP-dependent
AMPA receptor antagonists. Compound (−)-<b>25</b> could
be utilized to provide proof of concept for antiepileptic efficacy
with reduced motor side effects in patients