Functional analysis of a novel positive allosteric modulator of AMPA receptors derived from a structure-based drug design strategy

Abstract

Positive allosteric modulators of α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid (AMPA) receptors facilitate synaptic plasticity and can improve various forms of learning and memory. These modulators show promise as therapeutic agents for the treatment of neurological disorders such as schizophrenia, ADHD, and mental depression. Three classes of positive modulator, the benzamides, the thiadiazides, and the biarylsulfonamides differentially occupy a solvent accessible binding pocket at the interface between the two subunits that form the AMPA receptor ligand-binding pocket. Here, we describe the electrophysiological properties of a new chemotype derived from a structure-based drug design strategy (SBDD), which makes similar receptor interactions compared to previously reported classes of modulator. This pyrazole amide derivative, JAMI1001A, with a promising developability profile, efficaciously modulates AMPA receptor deactivation and desensitization of both flip and flop receptor isoforms.

Positive Allosteric Modulation of AMPA Receptors from Efficacy to Toxicity: The Interspecies Exposure-Response Continuum of the Novel Potentiator PF-4778574

“…Because it is unknown which AMPAR subtype(s) should (and/or can) be selectively potentiated for an optimal TI, PF-4778574 binding affinity was determined in primary rat cortical tissue while functional potency was assessed in both mouse embryonic stem (ES) cell-derived neurons (McNeish et al, 2010) and primary cultures of rat cortical neurons, as these matrices are expected to express a native mixture of AMPAR subunits and their associated proteins to afford composite pharmacological values. Functional activity was also quantified in recombinant cell lines stably expressing human GluA2i and GluA2o, given that other AMPAR potentiators interact with residues within these flip/flop domains (Fleming and England, 2010;Harms et al, 2013). For efficacy, PF-4778574 was evaluated in two contemporary animal models of pharmacologically induced NMDAR hypofunction (Olney et al, 1999): MK-801 ([5R,10S]-5-methyl-10,11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine (dizocilpine))-induced subiculummedial prefrontal cortex (PFC) dysfunction in rats (Kiss et al, 2011a) and ketamine-mediated spatial working memory impairment in nonhuman primates (nhp) (Roberts et al, 2010).…”

A Charge-inverting Mutation in the “Linker” Region of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors Alters Agonist Binding and Gating Kinetics Independently of Allosteric Modulators

“…Simulations of AMPA Receptor Activity-Simulations were conducted with IGOR Pro 6.22 software (Wavemetrics, Lake Oswego, OR) using a custom written plug-in file with code originally written by John Clements and modified extensively by Benveniste et al (15) as described previously (16). Briefly, receptor state occupancies were calculated from predefined transition rates into and out of each receptor state (see Fig.…”

“…Allosteric Modulation of R628E Is Preserved-The ability of the R628E mutation to perturb both receptor deactivation and desensitization is reminiscent of the actions of positive allosteric modulators that bind at the dimer interface of the ligandbinding core (11,16,(25)(26)(27)(28) and is also similar to the allosteric modulation of receptor gating conferred by transmembrane accessory receptor proteins such as stargazin (29,30). Therefore, we hypothesized that assessing the efficacy of positive allosteric modulators on gating of the R628E mutation might provide insight into the molecular mechanism through which the mutation perturbs channel gating compared with wild type receptors.…”

“…These drugs were chosen because of their contrasting isoform and deactivation/desensitization efficacies. CTZ has been shown to be a flip-selective modulator of GluA2 desensitization with little effect on deactivation kinetics (27,(31)(32)(33), whereas CX614 is more selective for GluA2 flop, modulating both deactivation and desensitization of that isoform (16,32).…”

“…To simulate our electrophysiological data, we used our previously published kinetic model (Ref. 16 and Fig. 7A), which manipulates the proportion of modulator-bound and modulator-unbound populations.…”