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

Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642

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 3' 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 3'UTR 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.

Received for publication December 3, 2007.

Accepted for publication March 17, 2008.

Address correspondence to: Dr. William Tank, Department of Pharmacology and Physiology, Box 711, University of Rochester Medical Center, 601 Elmwood Ave., Rochester, NY 14642. E-mail: awilliam_tank{at}urmc.rochester.edu

This article has been cited by other articles:

				L. Xu, C. R. Sterling, and A. W. Tank 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 Mol. Pharmacol., October 1, 2009; 76(4): 872 - 883. [Abstract] [Full Text] [PDF]