AP‐1 complex and c‐fos transcription are involved in TPA provoked and trans‐synaptic inductions of the tyrosine hydroxylase gene: Insights into long‐term regulatory mechanisms

Abstract

We have previously shown that the phorbol ester, TPA, which activates protein kinase C, causes, in PC12 cells, a transcriptional activation of tyrosine hydroxylase (TH), the key enzyme in catecholamine synthesis. The study has now been extended to examine the processes that underlie this transcriptional stimulation and, in addition, to seek whether similar mechanisms are involved in long-term trans-synaptic induction of the TH gene in adrenal medullae of rats that have been given a single injection of reserpine. In both systems, it was found that the induction of c-fos gene transcription was associated with that of the TH gene but with different kinetics. The promoter of the TH gene contains (at position -207/-200) a sequence (TGATTCA) which differs from the consensus TRE or AP-1 site (TGACTCA) by one nucleotide. Experiments were carried out to investigate whether the AP-1 protein complex which is known to contain Fos and Jun binds to the putative TRE region of the TH promoter. In the gel shift assays, the nuclear protein extracts derived from TPA-treated PC12 cells and from AM of reserpine injected rats displayed a higher magnitude of binding to a 25-mer TRE-TH oligonucleotide as compared to controls. The results showed that the behaviour of TRE-TH was atypical in that two retarded complexes (A and B) were observed, which were displaced by specific competitors. Trans-activation experiments with plasmids TRE-TH/TK/CAT and -754/-19 TH/pUC18-CAT in PC12 cells showed an increase in CAT activity in response to TPA that correlates with the previously observed increase in TH transcriptional activity by TPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of tyrosine hydroxylase gene expression by a nonneuronal nonpituitary-mediated mechanism in immobilization stress.

“…To our knowledge, this is the first study examining binding of transcription factors to the TH gene in response to immobilization stress. Despite the differences in the mechanism of activation of TH, alterations in the DNA/protein complexes formed at the AP-1 site of the TH gene have been reported in adrenal medulla of rats exposed to cold stress (23) and after reserpine treatment (14). The cold stress-elicited rise in AP-1 binding was abolished in denervated adrenals (23).…”

“…[9][10][11][12][13][14]. A number of genomic regulatory elements have been found in the promoter region of the TH gene, including an AP-1 site, a cAMP regulatory element, and putative AP-2, SP1 and POU/Oct, heptamer, and E2A/ MyoD (E box) sites (15)(16)(17)(18).…”

“…The CRE region, involved in regulation by elevated cAMP (11), has been recently shown to be sufficient for the regulated expression of the TH gene by depolarization and by nicotine treatment (13,19). The AP-1 site has been shown to be involved in cell-specific expression, as well as in the induction ofTH by nerve growth factor, phorbol esters, and angiotensin (10,14,17,(20)(21)(22). On the basis of nuclear protein binding studies, the AP-1 site of the TH gene has recently been implicated in the regulation of TH by cold stress (23).…”

Unique Regulation of Immediate Early Gene and Tyrosine Hydroxylase Expression in the Odor-deprived Mouse Olfactory Bulb

“…Thus, gene specificity may occur in the composition of Fos/Jun dimers binding to the AP-1 site. Third, DNA-protein binding activities show tissue specificity as well as developmental and excitation-dependent regulation that may be attributed to IEG expression varying between brain regions and level of stimulation (5,19,21,22). Tyrosine hydroxylase (TH), the first and rate-limiting enzyme in the biosynthesis of catecholamine neurotransmitters, is present in many brain regions including the olfactory bulb.…”

“…Tyrosine hydroxylase (TH), the first and rate-limiting enzyme in the biosynthesis of catecholamine neurotransmitters, is present in many brain regions including the olfactory bulb. The rodent TH gene promoter contains putative CRE and AP-1 motifs, the latter differing from the consensus AP-1 only in the middle base (T versus C) (5,(23)(24)(25)(26). The TH CRE was found to be required not only for basal activity but also for cAMPmediated up-regulation of TH promoter activity in SK-N-BE(2)C and PC12 cells (27,28).…”