Evidence for regulation of tyrosine hydroxylase mRNA translation by stress in rat adrenal medulla

Lu, Xu; Chen, Xiqun; Sun, Baoyong; Sterling, C. R.; Tank, A. William

doi:10.1016/j.brainres.2007.04.080

Cited by 31 publications

(31 citation statements)

References 41 publications

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“…There are two mechanisms used to explain the efficient utilization of Cx43 mRNA. The first mechanism is by mobilization of Cx43 mRNA from translationally inactive messenger ribonucleoprotein (mRNP) particles to actively translating polysomes, whereas the second entails increased rate of ribosome initiation on mRNA in the polysome pool (35,38,(40)(41)(42). Our findings suggest an inhibition of Cx43 at or before the initiation stage of translation.…”

Section: Molecular Cancer Therapeuticsmentioning

confidence: 79%

Connexin43 pseudogene in breast cancer cells offers a novel therapeutic target

Bier

Oviedo-Landaverde

Zhao

et al. 2009

Molecular Cancer Therapeutics

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Connexin43 (Cx43) is often deregulated in breast cancer tissue compared with normal adjacent tissue. Stable reexpression of Cx43 in cancer slows growth and renders the cells more sensitive to cytotoxic chemotherapeutics. Pseudogenes are often considered nonfunctional copies of DNA. The Cx43 pseudogene (ΨCx43) possesses all the features of an expressed gene and is exclusively transcribed in breast cancer cell lines and not in normal cells. ΨCx43 can be translated in vivo, and its protein exhibits growth-suppressive behavior similar to Cx43. We showed that ΨCx43 binds to the polyribosomes in breast cancer cells and that exogenous expression of ΨCx43 induces translational inhibition of Cx43. Furthermore, ΨCx43 is translated and binds more efficiently to the translational machinery than does Cx43 in an in vitro system. Following knockdown of ΨCx43 in breast cancer cells, we observed an increase in Cx43 RNA and protein. This results in increased cellular sensitivity to cytotoxic chemotherapy. Our results show that ΨCx43 acts as a posttranscriptional regulator of Cx43 in breast cancer cells, and that this represents an example of the regulation of genes by pseudogenes with potential therapeutic implications in cancer. [Mol Cancer Ther 2009;8(4):786-93]

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Section: Molecular Cancer Therapeuticsmentioning

confidence: 79%

Connexin43 pseudogene in breast cancer cells offers a novel therapeutic target

Bier

Oviedo-Landaverde

Zhao

et al. 2009

Molecular Cancer Therapeutics

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“…Polysome profile analysis was performed as described by Xu et al (2007). In brief, MN9D cells were homogenized in ice-cold low-salt lysis buffer (20 mM Tris-HCl, pH 7.5, 10 mM NaCl, 3 mM MgCl 2 , 1 mM RNasin, 1 mM dithiothreitol, 0.3% Triton X-100, and 0.05 M sucrose).…”

mentioning

confidence: 99%

“…To control for differences in recovery of RNA from each fraction during the isolation procedure, a known amount (100 ng) of a standard control RNA was added to each fraction before RNA isolation. This standard RNA was obtained by in vitro transcription (using a kit from Ambion) of TH genomic DNA promoter sequences and detected using specific primers (for details, see Xu et al, 2007). The amount of TH mRNA in each fraction was first normalized to the recovery of this standard RNA, and then it was expressed as a percentage of the total mRNA isolated from the gradients.…”

mentioning

confidence: 99%

Activation of Tyrosine Hydroxylase mRNA Translation by cAMP in Midbrain Dopaminergic Neurons

Chen¹,

Lu²,

Radcliffe³

et al. 2008

Mol Pharmacol

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During prolonged stress or chronic treatment with neurotoxins, robust compensatory mechanisms occur that maintain sufficient levels of catecholamine neurotransmitters in terminal regions. One of these mechanisms is the up-regulation of tyrosine hydroxylase (TH), the enzyme that controls catecholamine biosynthesis. In neurons of the periphery and locus coeruleus, this up-regulation is associated with an initial induction of TH mRNA. In contrast, this induction either does not occur or it is nominal in mesencephalic dopamine neurons. The reasons for this lack of compensatory TH mRNA induction remain obscure, because so little is known about the regulation of TH expression in these neurons. In this study, we test whether activation of the cAMP signaling pathway regulates TH gene expression in two rodent models of midbrain dopamine neurons, ventral midbrain organotypic slice cultures and MN9D cells. Our results demonstrate that elevation of cAMP leads to induction of TH protein and TH activity in both model systems; however, TH mRNA levels are not up-regulated by cAMP. The induction of TH protein is the result of a novel post-transcriptional mechanism that activates TH mRNA translation. This translational activation is mediated by sequences within the 3Ј untranslated region (UTR) of TH mRNA. Our results support a model in which cAMP induces or activates trans-factors that interact with the TH mRNA 3ЈUTR to increase TH protein synthesis. An understanding of this novel regulatory mechanism may help to explain the control of TH gene expression and consequently dopamine biosynthesis in midbrain neurons under different physiological and pathological conditions.

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“…More work is required to determine the precise mechanisms by which PCBP2 binding mediates this translational response, by which cAMP induces PCBP2, what other cellular factors participate in this response, and what other neuronal mRNAs are regulated by this mechanism. A better understanding of these translational mechanisms may help to explain discrepancies between changes in TH mRNA and TH protein levels in response to different stimuli, such as stress, hypoxia, and long-term drug treatment (Kaneda et al, 1991;Nankova et al, 1994;Yoshimura et al, 2004;Gozal et al, 2005;Xu et al, 2007). It may also provide novel approaches to control TH expression in dopaminergic neurons in neurodegenerative diseases.…”

Section: Discussionmentioning

confidence: 99%

“…Many reports have measured major discrepancies between changes in TH mRNA and TH protein levels in response to stress or drug treatments in rodents (Kaneda et al, 1991;Nankova et al, 1994;Yoshimura et al, 2004;Xu et al, 2007). In a recent report, our laboratory has shown that short-term stress is associated with 2-fold or greater increases in adrenal TH mRNA and that these increases persist for at least 24 h; however, TH protein levels are not up-regulated by these short-term stressors (Xu et al, 2007). In contrast, long-term treatments with these same stressors elicit induction of both TH mRNA and TH protein.…”

mentioning

confidence: 99%

cAMP-Mediated Stimulation of Tyrosine Hydroxylase mRNA Translation Is Mediated by Polypyrimidine-Rich Sequences within Its 3′-Untranslated Region and Poly(C)-Binding Protein 2

Lu¹,

Sterling²,

Tank³

2009

Mol Pharmacol

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Tyrosine hydroxylase (TH) plays a critical role in maintaining the appropriate concentrations of catecholamine neurotransmitters in brain and periphery, particularly during long-term stress, long-term drug treatment, or neurodegenerative diseases. Its expression is controlled by both transcriptional and post-transcriptional mechanisms. In a previous report, we showed that treatment of rat midbrain slice explant cultures or mouse MN9D cells with cAMP analog or forskolin leads to induction of TH protein without concomitant induction of TH mRNA. We further showed that cAMP activates mechanisms that regulate TH mRNA translation via cis-acting sequences within its 3Ј-untranslated region (UTR). In the present report, we extend these studies to show that MN9D cytoplasmic proteins bind to the same TH mRNA 3Ј-UTR domain that is required for the cAMP response. RNase T1 mapping demonstrates binding of proteins to a 27-nucleotide polypyrimidine-rich sequence within this domain. A specific mutation within the polypyrimidine-rich sequence inhibits protein binding and cAMP-mediated translational activation. UV-cross-linking studies identify a ϳ44-kDa protein as a major TH mRNA 3Ј-UTR binding factor, and cAMP induces the 40-to 42-kDa poly(C)-binding protein-2 (PCBP2) in MN9D cells. We show that PCBP2 binds to the TH mRNA 3Ј-UTR domain that participates in the cAMP response. Overexpression of PCBP2 induces TH protein without concomitant induction of TH mRNA. These results support a model in which cAMP induces PCBP2, leading to increased interaction with its cognate polypyrimidine binding site in the TH mRNA 3Ј-UTR. This increased interaction presumably plays a role in the activation of TH mRNA translation by cAMP in dopaminergic neurons.Tyrosine hydroxylase (TH) gene expression is tightly controlled by both transcriptional and post-transcriptional mechanisms (Kumer and Vrana, 1996;Sabban and Kvetnanský , 2001;Wong and Tank, 2007). The appropriate synthesis of dopamine, norepinephrine, and epinephrine is highly dependent on TH activity; hence, these control mechanisms play an essential role in the homeostatic regulation of catecholamine levels in both brain and periphery. Transcriptional regulation of the TH gene has been highly studied. TH gene transcription is activated in adrenal medulla, locus coeruleus, and other tissues in response to many stimuli, including stress, hypoxia, and treatment with cholinergic drugs or reserpine. If this activation is sustained (1-2 h), then TH mRNA is induced. The TH gene proximal promoter comprises numerous well-studied response elements, many of which participate in this transcriptional response.Even though less well studied, post-transcriptional mechanisms also influence TH expression in adrenal medulla and brain. A number of in vivo studies have measured discrepancies between changes in TH gene transcription rate and TH mRNA levels in response to different stressors or drug treatments, suggesting that TH mRNA stability is regulated (Chang et al., 2000;Sun et al., 2004;Osterhout et a...

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Evidence for regulation of tyrosine hydroxylase mRNA translation by stress in rat adrenal medulla

Cited by 31 publications

References 41 publications

Connexin43 pseudogene in breast cancer cells offers a novel therapeutic target

Connexin43 pseudogene in breast cancer cells offers a novel therapeutic target

Activation of Tyrosine Hydroxylase mRNA Translation by cAMP in Midbrain Dopaminergic Neurons

cAMP-Mediated Stimulation of Tyrosine Hydroxylase mRNA Translation Is Mediated by Polypyrimidine-Rich Sequences within Its 3′-Untranslated Region and Poly(C)-Binding Protein 2

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