Expression of neurotensin messenger RNA in a human carcinoid tumor.
Neurotensin (NT), a distal gut peptide, has important regulatory and trophic effects throughout the gut; however the intracellular mechanisms that regulate the gene expression and release of human NT are not known. The purpose of this endeavor was to study a functioning human pancreatic carcinoid cell line (called BON) in vitro that expresses the NT gene, and to study the effect of the cyclic adenosine monophosphate (cAMP) signal-transduction pathway on the expression and release of human NT. RNA was prepared from BON cell line (which has been established in this laboratory); the RNA was analyzed for NT mRNA expression by Northern hybridization with a complementary DNA probe. RNA blot analysis demonstrated that the NT gene is expressed in BON and is transcribed to two mRNAs of 1.0- and 1.5-kb sizes. In the second part of this study, BON cells were treated with either forskolin (FSK), which increases intracellular levels of cAMP, or with serotonin (5-HT), which reduces cAMP in BON cells. Forskolin produced a dose-dependent increase in NT peptide release and, furthermore, FSK (10(-6) mol/L) rapidly increased NT mRNA abundance 1 hour after addition; conversely, 5-HT (10(-5) mol/L) decreased NT mRNA at 1 hour. Neurotensin mRNA levels returned to control values by 3 hours after either FSK or 5-HT, which suggests that the transcript half-life for NT is relatively short. These findings show that the expression and peptide release of human NT is mediated, in part, by the cAMP signal-transduction pathway. Our human carcinoid cell line will provide a useful model to study the in vitro regulation of NT gene expression and peptide release.
Evers
B M
BM
Department of Surgery, University of Texas Medical Branch, Galveston 77550.
Ishizuka
J
J
Townsend
C M
CM
Rajaraman
S
S
Thompson
J C
JC
D000818:Animals; D002276:Carcinoid Tumor / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D005770:Gastrointestinal Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D008854:Microscopy, Electron; D009496:Neurotensin / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis*; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology
D012333:RNA, Messenger; D005576:Colforsin; D009496:Neurotensin; D000242:Cyclic AMP