Autophagy requires poly(adp-ribosyl)ation-dependent AMPK nuclear export
José M Rodríguez-Vargas1, María I Rodríguez1,5,Jara Majuelos-Melguizo1,5,Ángel García-Diaz1, Ariannys González-Flores1, Abelardo López-Rivas2, László Virág3, Giuditta Illuzzi4, Valerie Schreiber4, Françoise Dantzer4 and F Javier Oliver1
Resumen: La autofagia es un proceso por el que se reciclan estructuras intracelulares cuando están defectuosas o se requiere la obtención de energía en una situación crítica para la célula, como la ausencia de nutrientes. Este proceso tiene grandes repercusiones para comprender tanto enfermedades neurodegenerativas (caracterizadas por la acumulación de proteínas mal plegadas) como para la biología del cáncer en el microambiente tumoral, caracterizado por el entorno mal vascularizado y con escasos nutrientes. En este trabajo hemos descrito una vía de señalización que conecta la ausencia de nutrientes con la activación del sensor nutricional y energético AMPK, que debe sufrir una modificación postransduccional (mediante PARylación) para salir del núcleo y activar la formación de autofagosomas. El uso de inhibidores de PARylación (que ya se están utilizando en clínica como antitumorales) puede impedir la autofagia y evitar la adaptación de las células tumorales a su microambiente
AMPK is a central energy sensor linking extracellular milieu fluctuations with the autophagic machinery. In the current study we uncover that Poly(ADP-ribosyl)ation (PARylation), a post-translational modification (PTM) of proteins, accounts for the spatial and temporal regulation of autophagy by modulating AMPK subcellular localisation and activation. More particularly, we show that the minority AMPK pool needs to be exported to the cytosol in a PARylation-dependent manner for optimal induction of autophagy, including ULK1 phosphorylation and mTORC1 inactivation. PARP-1 forms a molecular complex with AMPK in the nucleus in non-starved cells. In response to nutrient deprivation, PARP-1 catalysed PARylation, induced the dissociation of the PARP-1/AMPK complex and the export of free PARylated nuclear AMPK to the cytoplasm to activate autophagy. PARP inhibition, its silencing or the expression of PARylation-deficient AMPK mutants prevented not only the AMPK nuclear-cytosolic export but also affected the activation of the cytosolic AMPK pool and autophagosome formation. These results demonstrate that PARylation of AMPK is a key early signal to efficiently convey extracellular nutrient perturbations with downstream events needed for the cell to optimize autophagic commitment before autophagosome formation.
PARylation regulates autophagy through AMPK activation:. PARP-1 forms a complex with AMPK in nucleus (1). During the starvation-induced autophagy ROS production induces DNA damage and overactivation of PARP-1. Auto PARylated PARP-1 is able to modify by PARylation AMPK in AMPKα1 subunit (2). The complex is disrupted and PAR-AMPK is exported to cytosol (3). Presence of PAR-AMPK and continuous absence of Aminoacids and ATP depletion, favours total activation of AMPK population, inhibition of mTORC1, interaction PAR-phospho-AMPK/ULK1 and autophagosomes formation (4).
(a). Starvation-induced ROS production was abrogated during the treatment with PARP inhibitors. Following AMPKα1/PARP-1 interaction (1), AMPKα1 subunit is not PARylated and nuclear export of AMPK is inhibited (2 and 3). In spite of nutrient and energy depletion, AMPK is inhibited, mTORC1 is partially activated and interacts with ULK1 favouring it's inhibition (4). Finally the autophagosomes production will be delayed
(b)
Autophagy requires poly(adp-ribosyl)ation-dependent AMPK nuclear export
Cell Death Differ. 2016 Sep 30. doi: 10.1038/cdd.2016.80.
