Hypoxia affects Slc7a5 expression through HIF-2α in differentiated neuronal cells

An imbalance of branched-chain amino acids (BCAAs) in the brain may result in neuropathological conditions, such as autism spectrum disorders. The L-type amino acid transporter 1 (LAT1), encoded by the solute carrier transporter 7a5 (Slc7a5) gene, is critical for maintaining normal levels of BCAAs in the brain. However, our understanding of the mechanisms that regulate the expression of LAT1/Slc7a5 in neurons is currently limited. Here, we demonstrate that hypoxic conditions result in upregulated expression of Slc7a5 in differentiated neuronal cells (Neuro2A cells induced to differentiate using all-trans retinoic acid). Mechanistically, hypoxia-induced expression of Slc7a5 is markedly reduced by short hairpin RNA (shRNA)-mediated knockdown of hypoxia-inducible factor 2α (HIF-2α), but not by shRNA targeting HIF-1α, in differentiated neuronal cells. Moreover, hypoxia increased the binding of HIF-2α to the proximal promoter of Slc7a5 in differentiated neuronal cells. These results indicate that hypoxia directly enhances the recruitment of HIF-2α to the proximal promoter of Slc7a5, resulting in its upregulated expression in differentiated neuronal cells. These findings indicate that Slc7a5 may be a novel gene responsive to hypoxia in a HIF-2α-dependent manner in differentiated neuronal cells.