ULK1-mediated phosphorylation regulates the conserved role of YKT6 in autophagy

J Cell Sci. 2023 Feb 1;136(3):jcs260546. doi: 10.1242/jcs.260546. Epub 2023 Feb 9.


Autophagy is a catabolic process during which cytosolic material is enwrapped in a newly formed double-membrane structure called the autophagosome, and subsequently targeted for degradation in the lytic compartment of the cell. The fusion of autophagosomes with the lytic compartment is a tightly regulated step and involves membrane-bound SNARE proteins. These play a crucial role as they promote lipid mixing and fusion of the opposing membranes. Among the SNARE proteins implicated in autophagy, the essential SNARE protein YKT6 is the only SNARE protein that is evolutionarily conserved from yeast to humans. Here, we show that alterations in YKT6 function, in both mammalian cells and nematodes, produce early and late autophagy defects that result in reduced survival. Moreover, mammalian autophagosomal YKT6 is phospho-regulated by the ULK1 kinase, preventing premature bundling with the lysosomal SNARE proteins and thereby inhibiting autophagosome-lysosome fusion. Together, our findings reveal that timely regulation of the YKT6 phosphorylation status is crucial throughout autophagy progression and cell survival.

Keywords: Autophagosome; Autophagy; SNARE; ULK1; YKT6.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagosomes / metabolism
  • Autophagy* / genetics
  • Autophagy-Related Protein-1 Homolog / genetics
  • Autophagy-Related Protein-1 Homolog / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lysosomes / metabolism
  • Mammals / metabolism
  • Membrane Fusion / physiology
  • Phosphorylation
  • R-SNARE Proteins / metabolism
  • SNARE Proteins / genetics
  • SNARE Proteins / metabolism
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins* / metabolism


  • R-SNARE Proteins
  • SNARE Proteins
  • ULK1 protein, human
  • Autophagy-Related Protein-1 Homolog
  • Intracellular Signaling Peptides and Proteins
  • YKT6 protein, human
  • YKT6 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins