DIFFERENTIAL REGULATION OF HIF-1alpha IN HUMAN TAY-SACHS NEUROGLIA

Abstract

<p>Lysosomal storage diseases (LSDs) are devastating neurological disorders caused by mutations in lysosomal hydrolases that result in accumulations of hydrolase substrates. Tay-Sachs disease (TSD) is an LSD that specifically results in the accumulation of GM2 gangliosides causing the activation of inflammatory signaling pathways, and leading to microglial activation and apoptotic cell death. The detailed mechanisms through which cell death occurs have not been completely elucidated, however, excitotoxicity is thought to play a major role. Here, we investigated the role of hypoxia-inducible factor-1α (HIF- 1α) and its effector microRNA, miR-210, and the impact they have on the expression of important molecules involved in excitotoxicity, namely neuronal pentraxin 1 (NPTX1) and potassium channel KCNK2 (KCNK2). We discovered that TSD neuroglia are inefficient at stabilizing HIF-1α in hypoxic conditions. Furthermore, miR-210 expression is significantly higher in TSD neuroglia compared to normal neuroglia at baseline and during hypoxia. In addition, TSD neuroglia expressed <em>NPTX1</em>, <em>NPTX2 </em>and <em>KCNK2 </em>at higher levels, and neuronal pentraxin receptor at lower levels than normal neuroglia, implicating excitotoxicity in disease pathogenesis. We also confirmed that miR-210 binds to the 3’ UTR of <em>NPTX1 </em>to repress its expression in TSD neuroglia. The presence of reverse hypoxia response elements in the promoter of KCNK2 and the repression of <em>KCNK2 </em>expression by HIF-1α stabilization suggest that KCNK2 is directly regulated by HIF-1α. Moreover, the glucosylceramide synthase inhibitor, NBDNJ, which is used to reduce ganglioside synthesis, caused expression of <em>NPTX1 </em>to decrease but <em>KCNK2 </em>expression to increase, indicating this drug can modify multiple parameters of disease. This study identifies major gene expression changes between normal and TSD neuroglia that affect the excitability and therefore the viability of TSD cells. This information provides new insight into the mechanisms of neurodegeneration experienced by TSD neuroglia.</p>