Clathrin-independent pathways do not contribute significantly to endocytic flux

  1. Vassilis Bitsikas
  2. Ivan R Corrêa
  3. Benjamin J Nichols  Is a corresponding author
  1. MRC Laboratory of Molecular Biology, United Kingdom
  2. New England Biolabs, Inc., United States

Abstract

Several different endocytic pathways have been proposed to function in mammalian cells. Clathrin-coated pits are well defined, but the identity, mechanism and function of alternative pathways have been controversial. Here we apply universal chemical labelling of plasma membrane proteins to define all primary endocytic vesicles, and labelling of specific proteins with a reducible SNAP-tag substrate. These approaches provide high temporal resolution and stringent discrimination between surface-connected and intracellular membranes. We find that at least 95% of the earliest detectable endocytic vesicles arise from clathrin-coated pits. GPI-anchored proteins, candidate cargoes for alternate pathways, are also found to enter the cell predominantly via coated pits. Experiments employing a mutated clathrin adaptor reveal distinct mechanisms for sorting into coated pits, and thereby explain differential effects on the uptake of transferrin and GPI-anchored proteins. These data call for a revision of models for the activity and diversity of endocytic pathways in mammalian cells.

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Author details

  1. Vassilis Bitsikas

    MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
    Competing interests
    No competing interests declared.
  2. Ivan R Corrêa

    New England Biolabs, Inc., Ipswich, United States
    Competing interests
    Ivan R Corrêa, An employee of New England Biolabs Inc. New England Biolabs Inc. has a commercial interest in successful application of reagents used in this study.
  3. Benjamin J Nichols

    MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
    For correspondence
    ben@mrc-lmb.cam.ac.uk
    Competing interests
    No competing interests declared.

Copyright

© 2014, Bitsikas et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Vassilis Bitsikas
  2. Ivan R Corrêa
  3. Benjamin J Nichols
(2014)
Clathrin-independent pathways do not contribute significantly to endocytic flux
eLife 3:e03970.
https://doi.org/10.7554/eLife.03970

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https://doi.org/10.7554/eLife.03970

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