RT Journal Article
SR Electronic
T1 Probing the Metabotropic Glutamate Receptor 5 (mGlu5) Positive Allosteric Modulator (PAM) Binding Pocket: Discovery of Point Mutations that Engender a "Molecular Switch" in PAM Pharmacology
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.112.083949
DO 10.1124/mol.112.083949
A1 Karen J Gregory
A1 Elizabeth Dong Nguyen
A1 Sean D Reiff
A1 Emma F Squire
A1 Shaun R Stauffer
A1 Craig W Lindsley
A1 Jens Meiler
A1 P. Jeffrey Conn
YR 2013
UL http://molpharm.aspetjournals.org/content/early/2013/02/26/mol.112.083949.1.abstract
AB Positive allosteric modulation of metabotropic glutamate receptor subtype 5 (mGlu5) is a promising novel approach for the treatment of schizophrenia and cognitive disorders. Allosteric binding sites are topographically distinct from the endogenous ligand-(orthosteric) binding site, allowing for co-occupation of a single receptor with the endogenous ligand and an allosteric modulator. Negative allosteric modulators (NAMs) inhibit, while positive allosteric modulators (PAMs) enhance, the affinity and/or efficacy of the orthosteric agonist. The molecular determinants that govern mGlu5 modulator affinity versus cooperativity are not well understood. Focusing on the modulators based on the acetylene scaffold, we sought to determine the molecular interactions that contribute to PAM versus NAM pharmacology. Generation of a comparative model of the transmembrane-spanning region of mGlu5 served as a tool to predict and interpret the impact of mutations in this region. Application of an operational model of allosterism allowed for determination of PAM and NAM affinity estimates at receptor constructs that possessed no detectable radioligand binding as well as delineation of effects on affinity versus cooperativity. Novel mutations within the transmembrane domain regions were identified that had differential effects on acetylene PAMs versus 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a prototypical NAM. Three conserved amino acids (Y658, T780, S808) and two non-conserved residues (P654, A809) were identified as key determinants of PAM activity. Interestingly, we identified two point mutations in TM6 and 7 that, when mutated, engender a mode switch in the pharmacology of certain PAMs.