Coupling of serotonin 5-HT1B receptors to activation of mitogen-activated protein kinase (ERK-2) and p70 S6 kinase signaling systems.
Little is known about the coupling of serotonin 5-HT1B receptors to cellular signals other than cyclic AMP. In the present studies, the activation by 5-HT1B receptors of p70 S6 kinase and the mitogen-activated protein kinase (MAP kinase) ERK-2 was investigated. Studies were performed by using both nontransfected Chinese hamster ovary (CHO) cells, which express endogenous receptors at a very low density, and a stable transfected CHO cell line expressing 5-HT1B receptors at 230 fmol/mg of membrane protein, a density similar to that expressed in cortex. In nontransfected cells, 5-HT was found to stimulate a greater than twofold increase in MAP kinase activity with an EC50 of 20 nM. Reflecting increased density of receptors, 5-HT caused a greater than eightfold activation of ERK-2 in transfected cells with an EC50 of 2 nM. 5-HT was found to also stimulate p70 S6 kinase in both nontransfected and transfected cells. The stimulation was sixfold in both types of cells, but the EC50 for 5-HT was fourfold lower in transfected cells. The coupling of 5-HT1B receptors to ERK-2 and to p70 S6 kinase was inhibited by pertussis toxin, inhibitors of phosphatidylinositol 3-kinase, and by the inhibitor of MAP kinase kinase PD098059. Activation of p70 S6 kinase, but not ERK-2, was also inhibited by rapamycin. These findings demonstrate that 5-HT1B receptors couple to ERK-2 and p70 S6 kinase through overlapping, but nonidentical, pathways.
Pullarkat
S R
SR
Department of Psychiatry, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, Piscataway 08854, USA.
Mysels
D J
DJ
Tan
M
M
Cowen
D S
DS
D000818:Animals; D016466:CHO Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D006224:Cricetinae; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007166:Immunosuppressive Agents / Q000494:pharmacology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D037342:Pertussis Toxin; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011090:Polyenes / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000502:physiology*; D019893:Ribosomal Protein S6 Kinases / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D020123:Sirolimus; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D004791:Enzyme Inhibitors; D005419:Flavonoids; D007166:Immunosuppressive Agents; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011090:Polyenes; D011985:Receptors, Serotonin; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin; D019893:Ribosomal Protein S6 Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D020123:Sirolimus