Abstract
Background Prenatal alcohol exposure is a leading cause of permanent neurodevelopmental disability. Diagnosis is often initiated by a distinctive craniofacial appearance that originates, in part, from the apoptotic deletion of craniofacial progenitors, a stem cell lineage called the neural crest (NC). We recently demonstrated that alcohol causes nucleolar stress in NC through its suppression of Ribosome Biogenesis (RBG) and this suppression is causative in their p53/MDM2-mediated apoptosis. Here, we show that this nucleolar stress originates from alcohol’s activation of AMPK, which suppresses TORC1 and the p70/S6K-mediated stimulation of RBG.
Methods Alcohol-exposed cells of the pluripotent, primary cranial NC line O9-1 were evaluated with respect to their p70/S6K, TORC1, and AMPK activity. The functional impact of these signals with respect to RBG, p53, and apoptosis were assessed using gain-of-function constructs and small molecule mediators.
Results Alcohol rapidly (<2hr) increased pAMPK, p-Raptor, p-mTOR(S2446), and reduced both total and p-p70/S6K in NC cells. These changes persisted for at least 12hr to 18hr following alcohol exposure. Attenuation of these signals via gain- or loss-of-function approaches prevented alcohol’s suppression of rRNA synthesis and the induction of p53-stimulated apoptosis.
Conclusions We conclude that alcohol induces ribosome dysbiogenesis and activates their p53/MDM2-mediated apoptosis via its activation of pAMPK, which in turn activates Raptor to suppress the TORC1/S6K-mediated promotion of ribosome biogenesis. This represents a novel mechanism underlying alcohol’s neurotoxicity and is consistent with findings that TORC1/S6K networks are critical for cranial NC survival.
Competing Interest Statement
The authors have declared no competing interest.