Stimulation of the A(2A) adenosine receptor increases expression of the tyrosine hydroxylase gene

PC12 cells are known to express A(2A) adenosine receptors that are linked to adenylyl cyclase. We investigated the role played by A(2A) adenosine receptors in the expression of the rat tyrosine hydroxylase (TH) gene in PC12 cells. The A,, selective adenosine receptor agonist 2-(p-2-carboxyethyl)phenylethylamino)-5'-N-ethylcarboxyamidoadenosine (CGS21680) caused TH mRNA levels to increase to more than twice the level of the untreated control. Transient transfection analysis demonstrated that the transcription of the TH gene was markedly enhanced upon treatment with CGS21680. The adenosine receptor-mediated TH gene expression was confirmed by the inhibitory effects that adenosine receptor antagonists had on the CGS21680 response. Mutational analysis of the 5' upstream region of the TH gene revealed that the cAMP response element (CRE) at -45 to -38 bp was responsible for the CGS21680 effect. Gel mobility shift assays revealed that six CRE-specific DNA-protein complexes were formed, and the amounts of three of them were significantly increased by treatment with CGS21680. Co-transfection with an expression vector containing protein kinase A (PKA) inhibitor markedly decreased the CGS21680 effect. The results suggest that stimulation of the A,, adenosine receptor leads to an elevated expression of the TH gene by changing the binding pattern of DNA binding proteins that interact with CRE through activation of protein kinase A.