5-Hydroxytryptamine2A receptors expressed in rat renal mesangial cells inhibit cyclic AMP accumulation.
Second messenger coupling of the 5-hydroxytryptamine (5-HT)2A receptor endogenous to cultured rat glomerular mesangial cells was studied. 5-HT induced an increase in total inositol phosphate levels (EC50 = 265 +/- 55 nM, maximum stimulation = 150 +/- 23%). That effect was sensitive to antagonists of the 5-HT2A receptor and was insensitive to pertussis toxin at doses that eliminated detectable pertussis toxin substrate, as determined by membrane ADP-ribosylation. Surprisingly, 5-HT also induced an inhibition of forskolin-stimulated cAMP accumulation (55 +/- 6%, IC50 = 5 +/- 3 nM). This effect was competitively antagonized by the 5-HT2A receptor antagonists ketanserin, ritanserin, and spiperone and could be produced by the 5-HT2 receptor agonists alpha-methyl-5-HT (66 +/- 13%, IC50 = 23 +/- 14 nM) and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (65 +/- 4%, IC50 = 14 +/- 7 nM). The inhibition of cAMP accumulation occurred in the presence of a number of agents that either stimulate or inhibit protein kinase C activity, arachidonic acid metabolism, or Ca2+ mobilization. In isolated membranes, 5-HT induced a 36 +/- 5% inhibition of adenylyl cyclase activity (IC50 = 8 +/- 4 nM). Inhibition of cAMP accumulation in intact cells and of adenylyl cyclase activity in washed membranes was (> 50%) sensitive to pertussis toxin, implicating Gi alpha or Go alpha subunits in the inhibitory signal. These data suggest that the 5-HT2A receptor can be permissive in its coupling to G proteins and second messengers.
Garnovskaya
M N
MN
Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
Nebigil
C G
CG
Arthur
J M
JM
Spurney
R F
RF
Raymond
J R
JR
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism; D005920:Glomerular Mesangium / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D011985:Receptors, Serotonin / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D015398:Signal Transduction
D011985:Receptors, Serotonin; D012701:Serotonin; D000242:Cyclic AMP; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases