Spatiotemporal Control of ULK1 Activation by NDP52 and TBK1 during Selective Autophagy

Summary

Selective autophagy recycles damaged organelles and clears intracellular pathogens to prevent their aberrant accumulation. How ULK1 kinase is targeted and activated during selective autophagic events remains to be elucidated. In this study, we used chemically inducible dimerization (CID) assays in tandem with CRISPR KO lines to systematically analyze the molecular basis of selective autophagosome biogenesis. We demonstrate that ectopic placement of NDP52 on mitochondria or peroxisomes is sufficient to initiate selective autophagy by focally localizing and activating the ULK1 complex. The capability of NDP52 to induce mitophagy is dependent on its interaction with the FIP200/ULK1 complex, which is facilitated by TBK1. Ectopically tethering ULK1 to cargo bypasses the requirement for autophagy receptors and TBK1. Focal activation of ULK1 occurs independently of AMPK and mTOR. Our findings provide a parsimonious model of selective autophagy, which highlights the coordination of ULK1 complex localization by autophagy receptors and TBK1 as principal drivers of targeted autophagosome biogenesis.

Graphical Abstract

Highlights

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  NDP52 associates with the ULK1 complex through FIP200, facilitated by TBK1

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  NDP52/TBK1 targets ULK1 to cargo to initiate autophagy in the absence of LC3

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  ULK1 is activated on cargo independently of AMPK and mTOR activity

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  Ectopic recruitment of FIP200-binding peptide is sufficient to degrade cargo

Abstract

The targeting and activation mechanism of ULK1 complex during selective autophagy has been unclear. Here, Vargas et al. show that NDP52/TBK1 target the ULK1 complex to cargo in an LC3-independent manner and that ULK1 kinase activation is coupled to cargo localization, circumventing energy-sensing pathways.