title: Shining Light on an mGlu5 Photoswitchable NAM: A Theoretical Perspective.
abstract: Metabotropic glutamate receptors (mGluRs) are important drug targets because of their involvement in several neurological diseases. Among mGluRs, mGlu5 is a particularly high-profile target because its positive or negative allosteric modulation can potentially treat schizophrenia or anxiety and chronic pain, respectively. Here, we computationally and experimentally probe the functional binding of a novel photoswitchable mGlu5 NAM, termed alloswitch-1, which loses its NAM functionality under violet light. We show alloswitch-1 binds deep in the allosteric pocket in a similar fashion to mavoglurant, the co-crystallized NAM in the mGlu5 transmembrane domain crystal structure. Alloswitch-1, like NAM 2-Methyl-6-(phenylethynyl)pyridine (MPEP), is significantly affected by P655M mutation deep in the allosteric pocket, eradicating its functionality. In MD simulations, we show alloswitch-1 and MPEP stabilize the co-crystallized water molecule located at the bottom of the allosteric site that is seemingly characteristic of the inactive receptor state. Furthermore, both NAMs form H-bonds with S809 on helix 7, which may constitute an important stabilizing interaction for NAM-induced mGlu5 inactivation. Alloswitch-1, through isomerization of its amide group from trans to cis is able to form an additional interaction with N747 on helix 5. This may be an important interaction for amide-containing mGlu5 NAMs, helping to stabilize their binding in a potentially unusual cis-amide state. Simulated conformational switching of alloswitch-1 in silico suggests photoisomerization of its azo group from trans to cis may be possible within the allosteric pocket. However, photoexcited alloswitch-1 binds in an unstable fashion, breaking H-bonds with the protein and destabilizing the co-crystallized water molecule. This suggests photoswitching may have destabilizing effects on mGlu5 binding and functionality.
authors.forename: James A R
authors.initials: JA
authors.lastname: Dalton
authors.forename: Isaias
authors.initials: I
authors.lastname: Lans
authors.forename: Xavier
authors.initials: X
authors.lastname: Rovira
authors.forename: Fanny
authors.initials: F
authors.lastname: Malhaire
authors.forename: Xavier
authors.initials: X
authors.lastname: Gómez-Santacana
authors.forename: Silvia
authors.initials: S
authors.lastname: Pittolo
authors.forename: Pau
authors.initials: P
authors.lastname: Gorostiza
authors.forename: Amadeu
authors.initials: A
authors.lastname: Llebaria
authors.forename: Cyril
authors.initials: C
authors.lastname: Goudet
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pin
authors.affiliation: Laboratory of Molecular Neuropharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain. Jesus.Giraldo@uab.es.
authors.forename: Jesús
authors.initials: J
authors.lastname: Giraldo
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D006860:Hydrogen Bonding; D007536:Isomerism; D008027:Light; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D009154:Mutation; D055668:Photochemical Processes; D011485:Protein Binding; D011487:Protein Conformation; D055550:Protein Stability; D011725:Pyridines / Q000494:pharmacology; D064529:Receptor, Metabotropic Glutamate 5 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D014867:Water / Q000737:chemistry
chemical_list: D018691:Excitatory Amino Acid Antagonists; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D014867:Water; C121465:6-methyl-2-(phenylethynyl)pyridine