TNF-induced necroptosis initiates early autophagy events via RIPK3-dependent AMPK activation, but inhibits late autophagy

Macroautophagy/autophagy and necroptosis represent two opposing cellular s tress responses. Whereas autophagy primarily fulfills a cyto-protective function, necroptosis is a form of regulated cell death induced via death receptors. Here, we aimed at investigating the molecular crosstalk between these two pathways. We observed that RIPK3 directly associates with AMPK and phosphorylates its catalytic subunit PRKAA1/2 at T183/T172. Activated AMPK then phosphorylates the autophagy-regulating proteins ULK1 and BECN1. However, the lysosomal degradation of autophagosomes is blocked by TNF-induced necroptosis. Specifically, we observed dysregulated SNARE complexes upon TNF treatment; e.g., reduced levels of full-length STX17. In summary, we identified RIPK3 as an AMPK-activating kinase and thus a direct link between autophagy- and necroptosis-regulating kinases.

Automated summary

This study identified RIPK3 as an AMPK-activating kinase, establishing a direct link between the kinases regulating autophagy and necroptosis.Activation of AMPK by RIPK3 leads to phosphorylation of autophagy-regulating proteins ULK1 and BECN1, while TNF-induced necroptosis blocks lysosomal degradation of autophagosomes. Dysregulation of SNARE complexes, including reduced levels of full-length STX17, was observed upon TNF treatment.