Neurotensin induces tyrosine hydroxylase gene activation through nitric oxide and protein kinase C signaling pathways.
The regulation of tyrosine hydroxylase (TH) represents an effective means to control the level of catecholamines, because TH is the major limiting enzyme of monoamine biosynthesis. The neuropeptide neurotensin (NT) is a neuromodulator of dopaminergic systems, and a direct interaction between NT and TH expression has been demonstrated in vivo and in vitro. In the present work, the molecular mechanisms and signaling pathways responsible for TH gene activation have been explored. In N1E-115 cells, NT agonist induced a TH protein level increase, correlating with a significant increase in TH mRNA abundance. This cellular response was the result of TH promoter activation, via c-fos and Jun D binding at the AP-1 responsive element. Using selective protein kinase C and nitric oxide synthase inhibitors, we demonstrate, by quantitative reverse transcription-polymerase chain reaction, gel shift, and protein assays, that TH gene activation by NT agonist requires both protein kinase C stimulation and nitric oxide production. The two pathways exert distinct roles; whereas nitric oxide synthase inhibitors blocked c-fos expression, protein kinase C inhibitors blocked that of Jun D. The requirement for two distinct and concomitant pathways by NT demonstrates a very fine level of control of specificity on TH gene activation.
Najimi
Mustapha
M
Centre National de la Recherche Scientifique Unité Mixte Recherche 9223, Hôpital de la Pitié-Salpétrière, Paris, France.
Robert
Jean-Jacques
JJ
Mallet
Jacques
J
Rostène
William
W
Forgez
Patricia
P
D000818:Animals; D005786:Gene Expression Regulation / Q000187:drug effects*; D051379:Mice; D009496:Neurotensin / Q000819:agonists / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000502:physiology; D011493:Protein Kinase C / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000502:physiology; D016755:Proto-Oncogene Proteins c-jun / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000502:physiology; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics* / Q000378:metabolism
D009842:Oligopeptides; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; C077827:JMV 449; D009569:Nitric Oxide; D009496:Neurotensin; D014446:Tyrosine 3-Monooxygenase; D011493:Protein Kinase C