Heterocomplex formation of 5-HT2A-mGlu2 and its relevance for cellular signaling cascades.
Dopamine, serotonin and glutamate play a role in the pathophysiology of schizophrenia. In the brain a functional crosstalk between the serotonin receptor 5-HT(2A) and the metabotropic glutamate receptor mGlu(2) has been demonstrated. Such a crosstalk may be mediated indirectly through neuronal networks or directly by receptor oligomerization. A direct link of the 5-HT(2A)-mGlu(2) heterocomplex formation to receptor function, i.e. to intracellular signaling, has not been fully demonstrated yet. Here we confirm the formation of 5-HT(2A)-mGlu(2) heterocomplexes using quantitative Snap/Clip-tag based HTRF methods. Additionally, mGlu(2) formed complexes with 5-HT(2B) and mGlu(5) but not 5-HT(2C) indicating that complex formation is not specific to the 5-HT(2A)-mGlu(2) pair. We studied the functional consequences of the 5-HT(2A)-mGlu(2) heterocomplex addressing cellular signaling pathways. Co-expression of receptors in HEK-293 cells had no relevant effects on signaling mediated by the individual receptors when mGlu(2) agonists, antagonists and PAMs, or 5-HT(2A) hallucinogenic and non-hallucinogenic agonists and antagonists were used. Hallucinogenic 5-HT(2A) agonists induced signaling through G(q/11), but not G(i) and thus did not lead to modulation of intracellular cAMP levels. In membranes of the medial prefrontal cortex [(3)H]-LY341495 binding competition of mGlu(2/3) agonist LY354740 was not influenced by 2,5-dimethoxy-4-iodoamphetamine (DOI). Taken together, the formation of GPCR heterocomplexes does not necessarily translate into second messenger effects. These results do not put into question the well-documented functional cross-talk of the two receptors in the brain, but do challenge the biological relevance of the 5-HT(2A)-mGlu(2) heterocomplex.
Abbott GmbH & Co KG, Neuroscience Research, Global Pharmaceutical Research & Development, Knollstrasse 50, 67061 Ludwigshafen, Germany.
Hannah K
HK
Delille
Judith M
JM
Becker
Sabrina
S
Burkhardt
Barbara
B
Bleher
Georg C
GC
Terstappen
Martin
M
Schmidt
Axel H
AH
Meyer
Liliane
L
Unger
Gerard J
GJ
Marek
Mario
M
Mezler
D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D055503:Protein Multimerization / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D020239:Receptor Cross-Talk / Q000502:physiology; D044402:Receptor, Serotonin, 5-HT2A / Q000378:metabolism* / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D044402:Receptor, Serotonin, 5-HT2A; D018094:Receptors, Metabotropic Glutamate; C108822:metabotropic glutamate receptor 2