Abstract
Serotonin (5-HT) interacts with a wide variety of 5-HT receptors (5-HTR) of which 5-HT2AR plays an important target for antidepressant and atypical antipsychotic drugs. The carboxyl-terminal tail of 5-HT2AR encodes a motif that mediates interactions with PSD-95/disc large/zona occludens (PDZ) domain–containing proteins. In the present study, we found that 5-HT2AR interacts with synapse-associated protein 97 (SAP97; also known as DLG1) by coimmunoprecipitation in human embryonic 293 (HEK 293) cells and cortical brain lysates. We found that 5-HT2AR expression results in the recruitment of SAP97 from the cytosol to the plasma membrane and that this recruitment is dependent on an intact 5-HT2AR PDZ binding motif. We also show that 5-HT2AR interacts with SAP97 using bioluminescence energy transfer and that overexpression of SAP97 retards 5-HT2AR endocytosis, while single hairpin RNA knockdown facilitates 5-HT2AR internalization. The knockdown of SAP97 in HEK 293 cells results in a reduction in the maximum efficacy for 5-HT2AR-stimulated inositol phosphate formation and that the deletion of the 5-HT2AR PDZ motif also impairs 5-HT2AR signaling. Similarly to what has been observed for the corticotropin-releasing factor receptor 1 (CRFR1), SAP97 expression is essential for 5-HT2AR-stimulated extracellular-regulated protein kinase 1/2 (ERK1/2) phosphorylation by a PDZ interaction-independent mechanism. Moreover, we find that SAP97 is not responsible for CRFR1-mediated sensitization of 5-HT2AR signaling. Taken together, our studies show that SAP97 plays a conserved role in regulating 5-HT2AR endocytosis and ERK1/2 signaling, but plays a novel role in regulating 5-HT2AR G protein coupling.
Footnotes
- Received April 21, 2014.
- Accepted July 1, 2014.
This work was supported by a Canadian Institutes of Health Research grant [MOP-62738] to S. S. G. F. S. S. G. F. holds a Tier I Canada Research Chair in Molecular Neurobiology and is a Career Investigator of the Heart and Stroke Foundation of Ontario, Canada. H. A. D. is the recipient of a Jonathan and Joshua Memorial Scholarship in Mental Health Research, C. W. is the recipient of a Fellowship from Brain Canada.
- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
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