Role of hypoxia and P1 receptor activation on the high affinity concentrative adenosine transporter CNT2 in PC12 cells

Under several adverse conditions, such as hypoxia or ischemia, extracellular levels of adenosine (Ado) upraise due to increased energy demands and ATP metabolism. Because extracellular Ado affects metabolism through G protein-coupled receptors, its regulation is of high adaptive importance. Concentrative nucleoside transporter 2 (CNT2) may play physiological roles beyond nucleoside salvage in brain as it does in other tissues. Even though nucleoside transport in brain has mostly been seen as of equilibrative-type, in this work we prove that the rat pheocromocytoma cell line PC12 shows a concentrative Ado transport of CNT2 type when cells are differentiated to a neuronal phenotype by treatment with nerve growth factor (NGF). Differentiation of PC12 cells was also associated with the up-regulation of Ado A1 receptors (A1R). Addition of Ado receptor agonists to cell cultures increased CNT2 related activity by a mechanism consistent with A1R and A2AR activation. The addition of Ado to the culture medium also induced the phosphorylation of the intracellular regulatory kinase AMP-activated kinase (AMPK) being this effect dependent upon Ado transport. CNT2-related activity of differentiated PC12 cells was also dramatically down-regulated under hypoxic conditions. Interestingly, the analysis of nucleoside transporter expression after experimental focal ischemia in rat brain showed that CNT2 expression was down-regulated in the infarcted tissue, being this effect somehow restricted to...
Source: BJ Cell - Category: Biochemistry Authors: Tags: BJ Metabolism Source Type: research