Guanylin stimulates regulated secretion from human neuroendocrine pancreatic cells.
OBJECTIVE
Gastroenteropancreatic neuroendocrine cells secrete chemical messengers in a calcium-dependent fashion. So far, other second messenger systems involved in regulated secretion have gained little attention. The aim of this study was to characterize guanosine 3',5'-cyclic monophosphate (cGMP)-mediated vesicular secretion in pancreatic neuroendocrine cells.


METHODS
In a human pancreatic cell line, BON, cyclic nucleotide levels and chromogranin A release were monitored with specific immunoassays. Uptake and release of gamma-aminobutyric acid were measured. Intracellular Ca2+ concentration was monitored with fura-2. Guanylyl cyclase C was analyzed by reverse-transcription polymerase chain reaction.


RESULTS
Guanylin increased cGMP concentrations in BON cells via guanylyl cyclase C. Stimulation of the cGMP pathway by guanylin or Escherichia coli heat-stable enterotoxin increased the release of chromogranin A and gamma-aminobutyric acid from BON cells. This effect was mimicked by the cGMP analogue 8-bromo-cGMP.


CONCLUSIONS
Guanylin and STa stimulate the regulated secretion from BON cells via guanylyl cyclase C and cGMP. Our study yields novel information about secretory properties of guanylin, mediated via a signal transduction pathway, increasing cGMP and leading to regulated secretion of neuroendocrine cells.
John
M
M
Department of Gastroenterology, Klinikum Benjamin Franklin, Freie Universität Berlin, Berlin, Germany.
Wiedenmann
B
B
Kruhøffer
M
M
Adermann
K
K
Ankorina-Stark
I
I
Schlatter
E
E
Ahnert-Hilger
G
G
Forssmann
W G
WG
Kuhn
M
M
D001427:Bacterial Toxins / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D053379:Chromogranin A; D002864:Chromogranins / Q000378:metabolism; D006152:Cyclic GMP / Q000032:analysis; D004768:Enterotoxins / Q000494:pharmacology; D029968:Escherichia coli Proteins; D005768:Gastrointestinal Hormones; D006801:Humans; D045265:Natriuretic Peptides; D009490:Neurosecretory Systems / Q000187:drug effects*; D010190:Pancreatic Neoplasms / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D001427:Bacterial Toxins; D053379:Chromogranin A; D002864:Chromogranins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D005768:Gastrointestinal Hormones; D045265:Natriuretic Peptides; D010455:Peptides; D012333:RNA, Messenger; C034151:heat stable toxin (E coli); C072685:guanylin; D005680:gamma-Aminobutyric Acid; D006152:Cyclic GMP; D002118:Calcium