mTOR activates the VPS34-UVRAG complex to regulate autolysosomal tubulation and cell survival

EMBO J. 2015 Sep 2;34(17):2272-90. doi: 10.15252/embj.201590992. Epub 2015 Jul 2.

Abstract

Lysosomes are essential organelles that function to degrade and recycle unwanted, damaged and toxic biological components. Lysosomes also act as signalling platforms in activating the nutrient-sensing kinase mTOR. mTOR regulates cellular growth, but it also helps to maintain lysosome identity by initiating lysosomal tubulation through a process termed autophagosome-lysosome reformation (ALR). Here we identify a lysosomal pool of phosphatidylinositol 3-phosphate that, when depleted by specific inhibition of the class III phosphoinositide 3-kinase VPS34, results in prolonged lysosomal tubulation. This tubulation requires mTOR activity, and we identified two direct mTOR phosphorylation sites on UVRAG (S550 and S571) that activate VPS34. Loss of these phosphorylation sites reduced VPS34 lipid kinase activity and resulted in an increase in number and length of lysosomal tubules. In cells in which phosphorylation at these UVRAG sites is disrupted, the result of impaired lysosomal tubulation alongside ALR activation is massive cell death. Our data imply that ALR is critical for cell survival under nutrient stress and that VPS34 is an essential regulatory element in this process.

Keywords: UVRAG; VPS34; lysosome; mTOR; tubule.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Class III Phosphatidylinositol 3-Kinases / genetics
  • Class III Phosphatidylinositol 3-Kinases / metabolism*
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Lysosomes / genetics
  • Lysosomes / metabolism*
  • Mice
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism
  • Phosphorylation / physiology
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*

Substances

  • Multiprotein Complexes
  • Tumor Suppressor Proteins
  • UVRAG protein, human
  • UVRAG protein, mouse
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Class III Phosphatidylinositol 3-Kinases