Inhibition of phospholipase C-epsilon by Gi-coupled receptors.
We recently reported that several Gs-coupled receptors stimulate phospholipase C (PLC)-epsilon via increased formation of cyclic AMP and subsequent activation of the small GTPase Rap2B by the cyclic AMP-activated exchange factor Epac1. Here we show by studies in HEK-293 and N1E-115 neuroblastoma cells that this stimulation induced by Gs-coupled receptors or the direct adenylyl cyclase activator, forskolin, is potently inhibited by Gi-coupled receptors, known to inhibit cyclic AMP formation. PLC inhibition by the overexpressed M2 muscarinic receptor and the endogenously expressed sphingosine-1-phosphate and delta-opioid receptors was fully pertussis toxin-sensitive and accompanied by a reduction in Rap2B activation induced by Gs-coupled receptors. In contrast, Rap2B activation and PLC stimulation induced by membrane-permeable cyclic AMP analogues, including an Epac-specific activator, or PLC stimulation caused by constitutively active Rap2B were not affected by the Gi-coupled receptors. In summary, our data indicate that Gi-coupled receptors can inhibit PLC-epsilon, most likely by suppressing formation of cyclic AMP required for Epac-mediated Rap2B activation.
vom Dorp
Frank
F
Institut für Pharmakologie, Universitätsklinikum Essen, Hufelandstrasse 55, D-45122 Essen, Germany.
Sari
Aysegül Y
AY
Sanders
Harald
H
Keiper
Melanie
M
Oude Weernink
Paschal A
PA
Jakobs
Karl H
KH
Schmidt
Martina
M
D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D008246:Lysophospholipids / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D054801:Phosphoinositide Phospholipase C; D011976:Receptors, Muscarinic / Q000378:metabolism; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*; D020668:rap GTP-Binding Proteins / Q000378:metabolism
D004791:Enzyme Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D008246:Lysophospholipids; C116122:RAPGEF3 protein, human; D011976:Receptors, Muscarinic; D017465:Receptors, Opioid, delta; D005576:Colforsin; C060506:sphingosine 1-phosphate; D000242:Cyclic AMP; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; C423320:phospholipase C epsilon; C065562:RAP2B protein, human; D020668:rap GTP-Binding Proteins; D013110:Sphingosine