Characterization of serotonin 5-HT2C receptor signaling to extracellular signal-regulated kinases 1 and 2.
Serotonin 5-HT2C receptors (5-HT(2C)Rs) are almost exclusively expressed in the CNS, and implicated in disorders such as obesity, depression, and schizophrenia. The present study investigated the mechanisms governing the coupling of the 5-HT(2C)R to the extracellular signal-regulated kinases (ERKs) 1/2, using a Chinese hamster ovary (CHO) cell line stably expressing the receptor at levels comparable to those found in the brain. Using the non-RNA-edited isoform of the 5-HT(2C)R, constitutive ERK1/2 phosphorylation was observed and found to be modulated by full, partial and inverse agonists. Interestingly, agonist-directed trafficking of receptor stimulus was also observed when comparing effects on phosphoinositide accumulation and intracellular Ca2+ elevation to ERK1/2 phosphorylation, whereby the agonists, [+/-]-2,5-dimethoxy-4-iodoamphetamine (DOI) and quipazine, showed reversal of efficacy between the phosphoinositide/Ca2+ pathways, on the one hand, and the ERK1/2 pathway on the other. Subsequent molecular characterization found that 5-HT-stimulated ERK1/2 phosphorylation in this cellular background requires phospholipase D, protein kinase C, and activation of the Raf/MEK/ERK module, but is independent of both receptor- and non-receptor tyrosine kinases, phospholipase C, phosphoinositide 3-kinase, and endocytosis. Our findings underscore the potential for exploiting pathway-selective receptor states in the differential modulation of signaling pathways that play prominent roles in normal and abnormal neuronal signaling.
Werry
Tim D
TD
Department of Pharmacology and Howard Florey Institute, University of Melbourne, Parkville, Victoria, Australia.
Gregory
Karen J
KJ
Sexton
Patrick M
PM
Christopoulos
Arthur
A
D000818:Animals; D016466:CHO Cells; D020013:Calcium Signaling / Q000502:physiology; D006224:Cricetinae; D004075:Diglycerides / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D006801:Humans; D008024:Ligands; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D044302:Receptor, Serotonin, 5-HT1B / Q000235:genetics / Q000378:metabolism; D044405:Receptor, Serotonin, 5-HT2C / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism
D004075:Diglycerides; D008024:Ligands; D010716:Phosphatidylinositols; D044302:Receptor, Serotonin, 5-HT1B; D044405:Receptor, Serotonin, 5-HT2C; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010741:Phospholipases A; D010738:Type C Phospholipases; D010739:Phospholipase D