Secretogogue-induced gating of chloride channels in the secretory vesicles of parafollicular cells.
Thyroid parafollicular (PF) cells are neural crest-derived endocrine cells that secrete serotonin and calcitonin. The secretory vesicles of PF cells acidify when secretion is induced by increased extracellular Ca2+ or TSH. We tested the hypothesis that acidification is regulated by secretogogue-gated Cl- channels in vesicular membranes. Cl- channel (p64) immunoreactivity was enriched in purified PF vesicles. X-Ray microanalysis showed a change in chlorine level in PF vesicles in response to secretogogue-stimulation of isolated cells. Secretogogue stimulation also altered the degree of p64 channel phosphorylation. Protein kinase and phosphatase inhibitors antagonized secretogogue-induced vesicle acidification and secretion; however, secretion could occur even when acidification was blocked. We conclude that acidification of PF vesicles is regulated by a gatable Cl- channel in vesicle membranes and that protein phosphorylation and dephosphorylation are involved in channel activation. Acidification of vesicles is not required for exocytosis.
Tamir
H
H
Division of Neuroscience, New York State Psychiatric Institute, New York 10032.
Piscopo
I
I
Liu
K P
KP
Hsiung
S C
SC
Adlersberg
M
M
Nicolaides
M
M
al-Awqati
Q
Q
Nunez
E A
EA
Gershon
M D
MD
D000165:Acridine Orange; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D018118:Chloride Channels / Q000032:analysis / Q000187:drug effects / Q000502:physiology*; D002712:Chlorides / Q000032:analysis; D016572:Cyclosporine / Q000494:pharmacology; D004577:Electron Probe Microanalysis; D004988:Ethers, Cyclic / Q000494:pharmacology; D015151:Immunoblotting; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D019319:Okadaic Acid; D010703:Phorbol Esters / Q000494:pharmacology; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D011233:Precipitin Tests; D047428:Protein Kinase Inhibitors; D012701:Serotonin / Q000378:metabolism; D012756:Sheep; D019311:Staurosporine; D016559:Tacrolimus / Q000494:pharmacology; D013961:Thyroid Gland / Q000166:cytology* / Q000502:physiology / Q000648:ultrastructure; D013972:Thyrotropin / Q000494:pharmacology*
D000470:Alkaloids; D002147:Calmodulin; D018118:Chloride Channels; D002712:Chlorides; D004988:Ethers, Cyclic; D010703:Phorbol Esters; D047428:Protein Kinase Inhibitors; D019319:Okadaic Acid; D001464:Barium; D012701:Serotonin; D016572:Cyclosporine; D013972:Thyrotropin; D010744:Phosphoric Monoester Hydrolases; D000165:Acridine Orange; D019311:Staurosporine; D002118:Calcium; D016559:Tacrolimus