pH of endophagosomes controls association of their membranes with Vps34 and PtdIns(3)P levels

J Cell Biol. 2018 Jan 2;217(1):329-346. doi: 10.1083/jcb.201702179. Epub 2017 Oct 31.

Abstract

Phagocytosis of filamentous bacteria occurs through tubular phagocytic cups (tPCs) and takes many minutes to engulf these filaments into phagosomes. Contravening the canonical phagocytic pathway, tPCs mature by fusing with endosomes. Using this model, we observed the sequential recruitment of early and late endolysosomal markers to the elongating tPCs. Surprisingly, the regulatory early endosomal lipid phosphatidylinositol-3-phosphate (PtdIns(3)P) persists on tPCs as long as their luminal pH remains neutral. Interestingly, by manipulating cellular pH, we determined that PtdIns(3)P behaves similarly in canonical phagosomes as well as endosomes. We found that this is the product of a pH-based mechanism that induces the dissociation of the Vps34 class III phosphatidylinositol-3-kinase from these organelles as they acidify. The detachment of Vps34 stops the production of PtdIns(3)P, allowing for the turnover of this lipid by PIKfyve. Given that PtdIns(3)P-dependent signaling is important for multiple cellular pathways, this mechanism for pH-dependent regulation of Vps34 could be at the center of many PtdIns(3)P-dependent cellular processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Membrane / metabolism*
  • Class III Phosphatidylinositol 3-Kinases / metabolism*
  • Endosomes / metabolism
  • Hydrogen-Ion Concentration
  • Legionella pneumophila / immunology*
  • Macrophages / immunology
  • Mice
  • Phagocytosis / immunology*
  • Phagosomes / immunology*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • RAW 264.7 Cells
  • Signal Transduction
  • rab GTP-Binding Proteins / metabolism
  • rab5 GTP-Binding Proteins / metabolism

Substances

  • rab7 protein
  • Phosphatidylinositol 3-Kinases
  • Class III Phosphatidylinositol 3-Kinases
  • PIK3C3 protein, mouse
  • rab GTP-Binding Proteins
  • rab5 GTP-Binding Proteins

Grant support