Autophagy captures the retromer-TBC1D5 complex to inhibit receptor recycling

Autophagy. 2024 Apr;20(4):863-882. doi: 10.1080/15548627.2023.2281126. Epub 2023 Nov 17.

Abstract

Retromer prevents the destruction of numerous receptors by recycling them from endosomes to the trans-Golgi network or plasma membrane. This enables retromer to fine-tune the activity of many signaling pathways in parallel. However, the mechanism(s) by which retromer function adapts to environmental fluctuations such as nutrient withdrawal and how this affects the fate of its cargoes remains incompletely understood. Here, we reveal that macroautophagy/autophagy inhibition by MTORC1 controls the abundance of retromer+ endosomes under nutrient-replete conditions. Autophagy activation by chemical inhibition of MTOR or nutrient withdrawal does not affect retromer assembly or its interaction with the RAB7 GAP protein TBC1D5, but rather targets these endosomes for bulk destruction following their capture by phagophores. This process appears to be distinct from amphisome formation. TBC1D5 and its ability to bind to retromer, but not its C-terminal LC3-interacting region (LIR) or nutrient-regulated dephosphorylation, is critical for retromer to be captured by autophagosomes following MTOR inhibition. Consequently, endosomal recycling of its cargoes to the plasma membrane and trans-Golgi network is impaired, leading to their lysosomal turnover. These findings demonstrate a mechanistic link connecting nutrient abundance to receptor homeostasis.Abbreviations: AMPK, 5'-AMP-activated protein kinase; APP, amyloid beta precursor protein; ATG, autophagy related; BafA, bafilomycin A1; CQ, chloroquine; DMEM, Dulbecco's minimum essential medium; DPBS, Dulbecco's phosphate-buffered saline; EBSS, Earle's balanced salt solution; FBS, fetal bovine serum; GAP, GTPase-activating protein; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; LIR, LC3-interacting region; LANDO, LC3-associated endocytosis; LP, leupeptin and pepstatin; MTOR, mechanistic target of rapamycin kinase; MTORC1, MTOR complex 1; nutrient stress, withdrawal of amino acids and serum; PDZ, DLG4/PSD95, DLG1, and TJP1/zo-1; RPS6, ribosomal protein S6; RPS6KB1/S6K1, ribosomal protein S6 kinase B1; SLC2A1/GLUT1, solute carrier family 2 member 1; SORL1, sortillin related receptor 1; SORT1, sortillin 1; SNX, sorting nexin; TBC1D5, TBC1 domain family member 5; ULK1, unc-51 like autophagy activating kinase 1; WASH, WASH complex subunit.

Keywords: Autophagy; MTOR; MTORC1; TBC1D5; VPS35; retromer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Autophagosomes / metabolism
  • Autophagy* / physiology
  • Endosomes* / metabolism
  • GTPase-Activating Proteins*
  • HeLa Cells
  • Humans
  • Mechanistic Target of Rapamycin Complex 1 / metabolism
  • TOR Serine-Threonine Kinases / metabolism
  • Vesicular Transport Proteins / metabolism
  • rab GTP-Binding Proteins / metabolism
  • rab7 GTP-Binding Proteins
  • trans-Golgi Network / metabolism

Substances

  • TBC1D5 protein, human
  • Mechanistic Target of Rapamycin Complex 1
  • rab GTP-Binding Proteins
  • rab7 GTP-Binding Proteins
  • Vesicular Transport Proteins
  • rab7 GTP-binding proteins, human
  • TOR Serine-Threonine Kinases
  • GTPase-Activating Proteins

Grants and funding

The work was supported by the Australian Government Australian Research Council [DP10100665]; National Health and Medical Research Council [GNT1103006]; National Health and Medical Research Council [2007739]; National Health and Medical Research Council [1124490]; University of South Australia; The Hospital Research Foundation Group [2022-CF-EMCR-007].