Endothelin-induced, long lasting, and Ca2+ influx-independent blockade of intrinsic secretion in pituitary cells by Gz subunits.
The G protein-coupled receptors in excitable cells have prominent roles in controlling Ca2+-triggered secretion by modulating voltage-gated Ca2+ influx. In pituitary lactotrophs, spontaneous voltage-gated Ca2+ influx is sufficient to maintain prolactin release high. Here we show that endothelin in picomolar concentrations can interrupt such release for several hours downstream of spontaneous and high K+-stimulated voltage-gated Ca2+ influx. This action occurred through the Gz signaling pathway; the adenylyl cyclase-signaling cascade could mediate sustained inhibition of secretion, whereas rapid inhibition also occurred at elevated cAMP levels regardless of the status of phospholipase C, tyrosine kinases, and protein kinase C. In a nanomolar concentration range, endothelin also inhibited voltage-gated Ca2+ influx through the G i/o signaling pathway. Thus, the coupling of seven-transmembrane domain endothelin receptors to Gz proteins provided a pathway that effectively blocked hormone secretion distal to Ca2+ entry, whereas the cross-coupling to G i/o proteins reinforced such inhibition by simultaneously reducing the pacemaking activity.
Andric
Silvana A
SA
Section on Cellular Signaling, Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.
Zivadinovic
Dragoslava
D
Gonzalez-Iglesias
Arturo E
AE
Lachowicz
Agnieszka
A
Tomic
Melanija
M
Stojilkovic
Stanko S
SS
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects; D019332:Endothelin-1 / Q000494:pharmacology*; D005260:Female; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D015398:Signal Transduction
D015220:Calcium Channels; D019332:Endothelin-1; C099387:GNAZ protein, human; D044385:GTP-Binding Protein alpha Subunits; D021122:Protein Subunits; D017466:Receptors, Endothelin; D043562:Receptors, G-Protein-Coupled; D011388:Prolactin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; D002118:Calcium