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Identification of positive allosteric modulators VU0155094 (ML397) and VU0422288 (ML396) reveals new insights into the biology of metabotropic glutamate receptor 7.

Jalan-Sakrikar N, Field JR, Klar R, Mattmann ME, Gregory KJ, Zamorano R, Engers DW, Bollinger SR, Weaver CD, Days EL, Lewis LM, Utley TJ, Hurtado M, Rigault D, Acher F, Walker AG, Melancon BJ, Wood MR, Lindsley CW, Conn PJ, Xiang Z, Hopkins CR, Niswender CM - ACS Chem Neurosci (2014)

Bottom Line: Here we report two new pan-group III mGlu positive allosteric modulators, VU0155094 and VU0422288, which show differential activity at the various group III mGlus.By pairing studies of these nonselective compounds with a synapse in the hippocampus that expresses only mGlu7, we have validated activity of these compounds in a native tissue setting.These studies provide proof-of-concept evidence that mGlu7 activity can be modulated by positive allosteric modulation, paving the way for future therapeutics development.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology and Vanderbilt Center for Neuroscience Drug Discovery, ‡Department of Pharmacology and Vanderbilt Institute of Chemical Biology, and §Department of Chemistry, Vanderbilt University , Nashville, Tennessee 37212, United States.

ABSTRACT
Metabotropic glutamate receptor 7 (mGlu7) is a member of the group III mGlu receptors (mGlus), encompassed by mGlu4, mGlu6, mGlu7, and mGlu8. mGlu7 is highly expressed in the presynaptic active zones of both excitatory and inhibitory synapses, and activation of the receptor regulates the release of both glutamate and GABA. mGlu7 is thought to be a relevant therapeutic target for a number of neurological and psychiatric disorders, and polymorphisms in the GRM7 gene have been linked to autism, depression, ADHD, and schizophrenia. Here we report two new pan-group III mGlu positive allosteric modulators, VU0155094 and VU0422288, which show differential activity at the various group III mGlus. Additionally, both compounds show probe dependence when assessed in the presence of distinct orthosteric agonists. By pairing studies of these nonselective compounds with a synapse in the hippocampus that expresses only mGlu7, we have validated activity of these compounds in a native tissue setting. These studies provide proof-of-concept evidence that mGlu7 activity can be modulated by positive allosteric modulation, paving the way for future therapeutics development.

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Schematicdiagram of operational modeling parameters. (A) Schematicof an mGlu dimeric receptor. Glutamate or orthosteric agonists (redcircle) bind in the large extracellular binding domain of the mGlus,and modulators (blue stars) bind in the transmembrane domains. KA represents orthosteric agonist affinity, while KB is allosteric modulator affinity. The resultsshown here demonstrate interactions between the allosteric and orthostericsites in terms of affinity modulation. Affinity modulation is governedby the cooperativity factor α, and efficacy modulation is governedby β. The parameters τA and τB represent the ability of orthosteric agonist and allosteric ligands,respectively, to directly activate the receptor. (B) Interaction ofallosteric parameters and effects on response shown using the allostericternary complex model. Adapted from ref (42).
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fig5: Schematicdiagram of operational modeling parameters. (A) Schematicof an mGlu dimeric receptor. Glutamate or orthosteric agonists (redcircle) bind in the large extracellular binding domain of the mGlus,and modulators (blue stars) bind in the transmembrane domains. KA represents orthosteric agonist affinity, while KB is allosteric modulator affinity. The resultsshown here demonstrate interactions between the allosteric and orthostericsites in terms of affinity modulation. Affinity modulation is governedby the cooperativity factor α, and efficacy modulation is governedby β. The parameters τA and τB represent the ability of orthosteric agonist and allosteric ligands,respectively, to directly activate the receptor. (B) Interaction ofallosteric parameters and effects on response shown using the allostericternary complex model. Adapted from ref (42).

Mentions: To understand changes in the activity ofagonists in the presence of these PAMs, as well as to compare activitiesof these agonists themselves across receptors, we applied an operationalmodel of agonism to orthosteric agonist concentration-response curvesin the presence and absence of increasing concentration of VU0155094or VU0422288 (shown conceptually in Figure 5 and data are shown in Supporting Information Figures S3–S5). As the orthosteric binding site of the mGlusis physically removed from the transmembrane domains, we initiallyfit the curves using eq 2 (Methods) and assumed no effect on orthosteric agonist affinity(i.e., α = 1) induced by the PAMs. As shown in Supporting Information Table 1, we observed significant differencesin several of the agonist KA values inthe presence of VU0155094 or VU0422288; additionally, probe dependencefor this effect was noted. For example, the KA values for LSP4-2022 were right-shifted at each receptorwhen at least one modulator was present. At mGlu7, theaffinity of glutamate was increased in the presence of VU0155094 butnot significantly changed by VU0422288. At mGlu7 and mGlu8, we observed a decrease in affinity of L-AP4 induced by VU0422288;this was true for the mGlu8/L-AP4 combination with VU0155094as well. These results clearly show distinct interactions betweenthe orthosteric and allosteric sites on the different receptors.


Identification of positive allosteric modulators VU0155094 (ML397) and VU0422288 (ML396) reveals new insights into the biology of metabotropic glutamate receptor 7.

Jalan-Sakrikar N, Field JR, Klar R, Mattmann ME, Gregory KJ, Zamorano R, Engers DW, Bollinger SR, Weaver CD, Days EL, Lewis LM, Utley TJ, Hurtado M, Rigault D, Acher F, Walker AG, Melancon BJ, Wood MR, Lindsley CW, Conn PJ, Xiang Z, Hopkins CR, Niswender CM - ACS Chem Neurosci (2014)

Schematicdiagram of operational modeling parameters. (A) Schematicof an mGlu dimeric receptor. Glutamate or orthosteric agonists (redcircle) bind in the large extracellular binding domain of the mGlus,and modulators (blue stars) bind in the transmembrane domains. KA represents orthosteric agonist affinity, while KB is allosteric modulator affinity. The resultsshown here demonstrate interactions between the allosteric and orthostericsites in terms of affinity modulation. Affinity modulation is governedby the cooperativity factor α, and efficacy modulation is governedby β. The parameters τA and τB represent the ability of orthosteric agonist and allosteric ligands,respectively, to directly activate the receptor. (B) Interaction ofallosteric parameters and effects on response shown using the allostericternary complex model. Adapted from ref (42).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306484&req=5

fig5: Schematicdiagram of operational modeling parameters. (A) Schematicof an mGlu dimeric receptor. Glutamate or orthosteric agonists (redcircle) bind in the large extracellular binding domain of the mGlus,and modulators (blue stars) bind in the transmembrane domains. KA represents orthosteric agonist affinity, while KB is allosteric modulator affinity. The resultsshown here demonstrate interactions between the allosteric and orthostericsites in terms of affinity modulation. Affinity modulation is governedby the cooperativity factor α, and efficacy modulation is governedby β. The parameters τA and τB represent the ability of orthosteric agonist and allosteric ligands,respectively, to directly activate the receptor. (B) Interaction ofallosteric parameters and effects on response shown using the allostericternary complex model. Adapted from ref (42).
Mentions: To understand changes in the activity ofagonists in the presence of these PAMs, as well as to compare activitiesof these agonists themselves across receptors, we applied an operationalmodel of agonism to orthosteric agonist concentration-response curvesin the presence and absence of increasing concentration of VU0155094or VU0422288 (shown conceptually in Figure 5 and data are shown in Supporting Information Figures S3–S5). As the orthosteric binding site of the mGlusis physically removed from the transmembrane domains, we initiallyfit the curves using eq 2 (Methods) and assumed no effect on orthosteric agonist affinity(i.e., α = 1) induced by the PAMs. As shown in Supporting Information Table 1, we observed significant differencesin several of the agonist KA values inthe presence of VU0155094 or VU0422288; additionally, probe dependencefor this effect was noted. For example, the KA values for LSP4-2022 were right-shifted at each receptorwhen at least one modulator was present. At mGlu7, theaffinity of glutamate was increased in the presence of VU0155094 butnot significantly changed by VU0422288. At mGlu7 and mGlu8, we observed a decrease in affinity of L-AP4 induced by VU0422288;this was true for the mGlu8/L-AP4 combination with VU0155094as well. These results clearly show distinct interactions betweenthe orthosteric and allosteric sites on the different receptors.

Bottom Line: Here we report two new pan-group III mGlu positive allosteric modulators, VU0155094 and VU0422288, which show differential activity at the various group III mGlus.By pairing studies of these nonselective compounds with a synapse in the hippocampus that expresses only mGlu7, we have validated activity of these compounds in a native tissue setting.These studies provide proof-of-concept evidence that mGlu7 activity can be modulated by positive allosteric modulation, paving the way for future therapeutics development.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology and Vanderbilt Center for Neuroscience Drug Discovery, ‡Department of Pharmacology and Vanderbilt Institute of Chemical Biology, and §Department of Chemistry, Vanderbilt University , Nashville, Tennessee 37212, United States.

ABSTRACT
Metabotropic glutamate receptor 7 (mGlu7) is a member of the group III mGlu receptors (mGlus), encompassed by mGlu4, mGlu6, mGlu7, and mGlu8. mGlu7 is highly expressed in the presynaptic active zones of both excitatory and inhibitory synapses, and activation of the receptor regulates the release of both glutamate and GABA. mGlu7 is thought to be a relevant therapeutic target for a number of neurological and psychiatric disorders, and polymorphisms in the GRM7 gene have been linked to autism, depression, ADHD, and schizophrenia. Here we report two new pan-group III mGlu positive allosteric modulators, VU0155094 and VU0422288, which show differential activity at the various group III mGlus. Additionally, both compounds show probe dependence when assessed in the presence of distinct orthosteric agonists. By pairing studies of these nonselective compounds with a synapse in the hippocampus that expresses only mGlu7, we have validated activity of these compounds in a native tissue setting. These studies provide proof-of-concept evidence that mGlu7 activity can be modulated by positive allosteric modulation, paving the way for future therapeutics development.

Show MeSH
Related in: MedlinePlus