Phosphorylation of Syntaxin 17 by TBK1 Controls Autophagy Initiation

Dev Cell. 2019 Apr 8;49(1):130-144.e6. doi: 10.1016/j.devcel.2019.01.027. Epub 2019 Feb 28.

Abstract

Syntaxin 17 (Stx17) has been implicated in autophagosome-lysosome fusion. Here, we report that Stx17 functions in assembly of protein complexes during autophagy initiation. Stx17 is phosphorylated by TBK1 whereby phospho-Stx17 controls the formation of the ATG13+FIP200+ mammalian pre-autophagosomal structure (mPAS) in response to induction of autophagy. TBK1 phosphorylates Stx17 at S202. During autophagy induction, Stx17pS202 transfers from the Golgi, where its steady-state pools localize, to the ATG13+FIP200+ mPAS. Stx17pS202 was in complexes with ATG13 and FIP200, whereas its non-phosphorylatable mutant Stx17S202A was not. Stx17 or TBK1 knockouts blocked ATG13 and FIP200 puncta formation. Stx17 or TBK1 knockouts reduced the formation of ATG13 protein complexes with FIP200 and ULK1. Endogenous Stx17pS202 colocalized with LC3B following induction of autophagy. Stx17 knockout diminished LC3 response and reduced sequestration of the prototypical bulk autophagy cargo lactate dehydrogenase. We conclude that Stx17 is a TBK1 substrate and that together they orchestrate assembly of mPAS.

Keywords: TBK1; ULK1; autophagy; pre-autophagosomal structure.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Autophagosomes / metabolism
  • Autophagy / genetics*
  • Autophagy-Related Proteins / genetics
  • Gene Knockout Techniques
  • Golgi Apparatus / genetics
  • Golgi Apparatus / metabolism
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Lysosomes / metabolism
  • Membrane Fusion / genetics
  • Multiprotein Complexes / genetics*
  • Multiprotein Complexes / metabolism
  • Mutation / genetics
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Tyrosine Kinases / genetics
  • Qa-SNARE Proteins / genetics*
  • Signal Transduction / genetics

Substances

  • ATG13 protein, human
  • Adaptor Proteins, Signal Transducing
  • Autophagy-Related Proteins
  • Multiprotein Complexes
  • Qa-SNARE Proteins
  • RB1CC1 protein, human
  • STX17 protein, human
  • Protein-Tyrosine Kinases
  • Protein-Serine-Threonine Kinases
  • TBK1 protein, human