Aspartyl-(asparaginyl) β-hydroxylase, hypoxia-inducible factor-1α and Notch cross-talk in regulating neuronal motility

Aspartyl-(Asparaginyl)-beta-Hydroxylase (AAH) promotes cell motility by hydroxylating Notch. Insulin and insulin-like growth factor, type 1 (IGF-I) stimulate AAH through Erk MAPK and phosphoinositol-3-kinase-Akt (PI3K-Akt). However, hypoxia/oxidative stress may also regulate AAH. Hypoxia-inducible factor-1alpha (HIF-1 alpha) regulates cell migration, signals through Notch, and is regulated by hypoxia/oxidative stress, insulin/IGF signaling and factor inhibiting HIF-1 alpha (FIN) hydroxylation. To examine cross-talk between HIF-1 alpha and AAH, we measured AAH, Notch-1, Jagged-1, FIH, HIF-1 alpha, HIF-1 beta and the hairy and enhancer of split 1 (HES-1) transcription factor expression and directional motility in primitive neuroectodermal tumor 2 (PNET2) human neuronal cells that were exposed to H2O2 or transfected with short interfering RNA duplexes (siRNA) targeting AAH, Notch-1 or HIF-1 alpha. We found that: (1) AAH, HIF-1 alpha and neuronal migration were stimulated by H2O2; (2) si-HIF-1 alpha reduced AAH expression and cell motility; (3) si-AAH inhibited Notch and cell migration, but not HIF-1 alpha; and (4) si-Notch-1 increased FIH and inhibited HIF-1 alpha. These findings suggest that AAH and HIF-1 alpha cross-talk within a hydroxylation-regulated signaling pathway that may be transiently driven by oxidative stress and chronically regulated by insulin/IGF signaling.