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Updated: Aug 7, 2026

Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation
10:52

Radiolabeling and Quantification of Cellular Levels of Phosphoinositides by High Performance Liquid Chromatography-coupled Flow Scintillation

Published on: January 6, 2016

Phosphatidylinositol 3-kinase activity is required for early endosome fusion

A T Jones1, M J Clague

  • 1Physiological Laboratory, University of Liverpool, U.K.

The Biochemical Journal
|October 1, 1995
PubMed

Insights

The fungal metabolite wortmannin, a phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, blocks early endosome fusion in cells. This suggests PI 3-kinase plays a direct role in regulating membrane fusion processes.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Early endosome fusion is a critical process for cellular trafficking.
  • Phosphatidylinositol 3-kinases (PI 3-kinases) are enzymes involved in various cellular signaling pathways, including membrane trafficking.

Purpose of the Study:

  • To investigate the role of phosphatidylinositol 3-kinase (PI 3-kinase) in homotypic early endosome fusion.
  • To determine if PI 3-kinase activity is required for the fusion of early endosomes.

Main Methods:

  • In vitro assays were used to measure homotypic early endosome fusion.
  • The effects of wortmannin and LY294002, specific inhibitors of PI 3-kinase, on fusion were assessed.
  • Both membranous and cytosolic components were treated with wortmannin to localize the drug's effect.

Main Results:

  • Wortmannin inhibited early endosome fusion with an IC50 of approximately 15 nM.
  • LY294002, another PI 3-kinase inhibitor, also demonstrated sensitivity in the fusion assay.
  • Inhibition was observed when either the membranous or cytosolic component was treated with wortmannin, with greater inhibition when the cytosolic component was treated.

Conclusions:

  • Phosphatidylinositol 3-kinase (PI 3-kinase) activity is essential for homotypic early endosome fusion.
  • PI 3-kinase likely regulates membrane fusion directly, as no vesicular intermediates were observed.
  • These findings highlight a key regulatory role for PI 3-kinase in endosomal trafficking.

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