Functional cycle of EEA1-positive early endosome: Direct evidence for pre-existing compartment of degradative pathway

PLoS One. 2020 May 1;15(5):e0232532. doi: 10.1371/journal.pone.0232532. eCollection 2020.

Abstract

Early endosomes, regarded as the main sorting station on endocytic pathway, are characterized by high frequency of homotypic fusions mediated by tethering protein EEA1. Despite intensive investigations, biogenesis of endosomes, boundaries between early and late endosomes, and process of cargo transition though them remain obscure. Here, using EGF/EGFR endocytosis as a model and confocal microscopy of fixed and live cells, we provide evidence favoring EEA1-vesicles being pre-existed vesicular compartment, that maintains its resident proteins' level and is sensitive to biosynthetic, but not endocytic pathway disturbance. EEA1-vesicles directly fuse with incoming EGF/EGFR-vesicles into hybrid endosomes with separated EEA1- and EGFR-domains, thus providing a platform for rapid achievement of an excess of surface-derived membrane that is used to form intraluminal vesicles (ILVs). Thus, multivesicular structures colocalized with EEA1 are still early endosomes. "EEA1-cycle" ends by exclusion of EGFR-containing domains with ILVs inside that turns into MVE and restoration of initial EEA1-vesicles population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biosynthetic Pathways
  • Culture Media, Serum-Free
  • Cytoplasmic Vesicles / metabolism
  • Endocytosis
  • Endosomes / metabolism*
  • ErbB Receptors / metabolism
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Microscopy, Confocal
  • Models, Biological
  • Protein Transport
  • Recombinant Fusion Proteins / metabolism
  • Vesicular Transport Proteins / metabolism*

Substances

  • Culture Media, Serum-Free
  • Recombinant Fusion Proteins
  • Vesicular Transport Proteins
  • early endosome antigen 1
  • Green Fluorescent Proteins
  • EGFR protein, human
  • ErbB Receptors

Grants and funding

This work was supported by Russian Science Foundation grant № 19-14-00108.