Functional selectivity induced by mGlu₄ receptor positive allosteric modulation and concomitant activation of Gq coupled receptors.

Yin S, Zamorano R, Conn PJ, Niswender CM
Neuropharmacology. 2013 66: 122-32

PMID: 22426233 · PMCID: PMC3412075 · DOI:10.1016/j.neuropharm.2012.03.003

Metabotropic glutamate receptors (mGlus) are a group of Family C Seven Transmembrane Spanning Receptors (7TMRs) that play important roles in modulating signaling transduction, particularly within the central nervous system. mGlu(4) belongs to a subfamily of mGlus that is predominantly coupled to G(i/o) G proteins. We now report that the ubiquitous autacoid and neuromodulator, histamine, induces substantial glutamate-activated calcium mobilization in mGlu(4)-expressing cells, an effect which is observed in the absence of co-expressed chimeric G proteins. This strong induction of calcium signaling downstream of glutamate activation of mGlu(4) depends upon the presence of H(1) histamine receptors. Interestingly, the potentiating effect of histamine activation does not extend to other mGlu(4)-mediated signaling events downstream of G(i/o) G proteins, such as cAMP inhibition, suggesting that the presence of G(q) coupled receptors such as H(1) may bias normal mGlu(4)-mediated G(i/o) signaling events. When the activity induced by small molecule positive allosteric modulators of mGlu(4) is assessed, the potentiated signaling of mGlu(4) is further biased by histamine toward calcium-dependent pathways. These results suggest that G(i/o)-coupled mGlus may induce substantial, and potentially unexpected, calcium-mediated signaling events if stimulation occurs concomitantly with activation of G(q) receptors. Additionally, our results suggest that signaling induced by small molecule positive allosteric modulators may be substantially biased when G(q) receptors are co-activated. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.

Copyright © 2012 Elsevier Ltd. All rights reserved.

MeSH Terms (20)

Adenylyl Cyclase Inhibitors Adenylyl Cyclases Allosteric Regulation Animals Benzopyrans Calcium Calcium Signaling Cell Line Excitatory Amino Acid Agonists Excitatory Amino Acid Antagonists Glutamic Acid GTP-Binding Protein alpha Subunits, Gq-G11 Guinea Pigs Histamine Humans Phosphatidylinositols Rats Receptors, Histamine H1 Receptors, Metabotropic Glutamate Signal Transduction

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