Cul3-KLHL20 Ubiquitin Ligase Governs the Turnover of ULK1 and VPS34 Complexes to Control Autophagy Termination

Mol Cell. 2016 Jan 7;61(1):84-97. doi: 10.1016/j.molcel.2015.11.001. Epub 2015 Dec 10.

Abstract

Autophagy, a cellular self-eating mechanism, is important for maintaining cell survival and tissue homeostasis in various stressed conditions. Although the molecular mechanism of autophagy induction has been well studied, how cells terminate autophagy process remains elusive. Here, we show that ULK1, a serine/threonine kinase critical for autophagy initiation, is a substrate of the Cul3-KLHL20 ubiquitin ligase. Upon autophagy induction, ULK1 autophosphorylation facilitates its recruitment to KLHL20 for ubiquitination and proteolysis. This autophagy-stimulated, KLHL20-dependent ULK1 degradation restrains the amplitude and duration of autophagy. Additionally, KLHL20 governs the degradation of ATG13, VPS34, Beclin-1, and ATG14 in prolonged starvation through a direct or indirect mechanism. Impairment of KLHL20-mediated regulation of autophagy dynamics potentiates starvation-induced cell death and aggravates diabetes-associated muscle atrophy. Our study identifies a key role of KLHL20 in autophagy termination by controlling autophagy-dependent turnover of ULK1 and VPS34 complex subunits and reveals the pathophysiological functions of this autophagy termination mechanism.

Keywords: ULK1; VPS34 complex; autophagy; ubiquitination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Adaptor Proteins, Vesicular Transport / metabolism
  • Animals
  • Apoptosis Regulatory Proteins / metabolism
  • Autophagy*
  • Autophagy-Related Protein-1 Homolog
  • Autophagy-Related Proteins
  • Beclin-1
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Class III Phosphatidylinositol 3-Kinases / genetics
  • Class III Phosphatidylinositol 3-Kinases / metabolism*
  • Cullin Proteins / genetics
  • Cullin Proteins / metabolism*
  • Diabetes Complications / enzymology
  • Diabetes Complications / genetics
  • Diabetes Complications / pathology
  • Feedback, Physiological
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Male
  • Membrane Proteins / metabolism
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / pathology
  • Muscular Atrophy / enzymology
  • Muscular Atrophy / genetics
  • Muscular Atrophy / pathology
  • Phosphorylation
  • Protein Transport
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proteolysis
  • RNA Interference
  • Signal Transduction
  • Time Factors
  • Transfection
  • Ubiquitin-Protein Ligases / deficiency
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination
  • Vesicular Transport Proteins / metabolism

Substances

  • ATG14 protein, human
  • Adaptor Proteins, Signal Transducing
  • Adaptor Proteins, Vesicular Transport
  • Apoptosis Regulatory Proteins
  • Atg14 protein, mouse
  • Autophagy-Related Proteins
  • BECN1 protein, human
  • Beclin-1
  • Becn1 protein, mouse
  • CUL3 protein, human
  • Carrier Proteins
  • Cul3 protein, mouse
  • Cullin Proteins
  • Intracellular Signaling Peptides and Proteins
  • KLHL20 protein, human
  • KLHL20 protein, mouse
  • Membrane Proteins
  • Vesicular Transport Proteins
  • Ubiquitin-Protein Ligases
  • Class III Phosphatidylinositol 3-Kinases
  • Autophagy-Related Protein-1 Homolog
  • Protein-Serine-Threonine Kinases
  • ULK1 protein, human
  • Ulk1 protein, mouse