Mechanisms of membrane estrogen receptor-alpha-mediated rapid stimulation of Ca2+ levels and prolactin release in a pituitary cell line.
The role of membrane estrogen receptor-alpha (mERalpha) in rapid nongenomic responses to 17beta-estradiol (E(2)) was tested in sublines of GH3/B6 rat prolactinoma cells selected for high (GH3/B6/F10) and low (GH3/B6/D9) mERalpha expression. E(2) elicited rapid, concentration-dependent intracellular Ca(2+) concentration ([Ca(2+)](i)) increases in the F10 subline. Lack of inhibition by thapsigargin depletion of intracellular Ca(2+) pools, together with abrogation of the response in Ca(2+)-free medium, suggested an extracellular source of Ca(2+) for this response. The participation of voltage-dependent channels in the E(2)-induced [Ca(2+)](i) increase was confirmed by the specific L-type Ca(2+) channel inhibitor nifedipine. For comparison, the D9 mERalpha-depleted subline was insensitive to steroid action via this signaling mechanism. [Ca(2+)](i) elevation was correlated with prolactin (PRL) release in the F10 cell line in as little as 3 min. E(2) caused a much higher PRL release than KCl treatment (which caused maximal Ca(2+) elevation), suggesting that secretion was also controlled by additional mechanisms. Participation of mERalpha in these effects was confirmed by the ability of E(2)-peroxidase (a cell-impermeable analog of E(2)) to cause these responses, blockage of the responses with the ER antagonist ICI 182 780, and the inability of the E(2) stereoisomer 17alpha-E(2) to elicit a response. Thus rapid exocytosis of PRL is regulated in these cells by mERalpha signaling to specific Ca(2+) channels utilizing extracellular Ca(2+) sources and additional signaling mechanisms.
Bulayeva
Nataliya N
NN
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0645, USA.
Wozniak
Ann L
AL
Lash
L Leanne
LL
Watson
Cheryl S
CS
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011388:Prolactin / Q000493:pharmacokinetics*; D015175:Prolactinoma / Q000378:metabolism*; D051381:Rats
D047628:Estrogen Receptor alpha; D004958:Estradiol; D011388:Prolactin; D009543:Nifedipine; D002118:Calcium