The endocytic recycling compartment maintains cargo segregation acquired upon exit from the sorting endosome

The endocytic recycling compartment (ERC) is a series of perinuclear tubular and vesicular membranes that regulates recycling to the plasma membrane. Despite evidence that cargo is sorted at the early/sorting endosome (SE), whether cargo mixes downstream at the ERC or remains segregated is an unansw...

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Bibliographic Details
Published in:Molecular biology of the cell 2016-01, Vol.27 (1), p.108-126
Main Authors: Xie, Shuwei, Bahl, Kriti, Reinecke, James B, Hammond, Gerald R V, Naslavsky, Naava, Caplan, Steve
Format: Article
Language:English
Subjects:
Adaptor Proteins, Vesicular Transport - metabolism
Cell Membrane - metabolism
Clathrin - metabolism
Endocytosis - physiology
Endosomes - metabolism
HeLa Cells
Humans
Microscopy - methods
Protein Transport - physiology
Transferrin - metabolism
Transport Vesicles - metabolism
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Summary:The endocytic recycling compartment (ERC) is a series of perinuclear tubular and vesicular membranes that regulates recycling to the plasma membrane. Despite evidence that cargo is sorted at the early/sorting endosome (SE), whether cargo mixes downstream at the ERC or remains segregated is an unanswered question. Here we use three-dimensional (3D) structured illumination microscopy and dual-channel and 3D direct stochastic optical reconstruction microscopy (dSTORM) to obtain new information about ERC morphology and cargo segregation. We show that cargo internalized either via clathrin-mediated endocytosis (CME) or independently of clathrin (CIE) remains segregated in the ERC, likely on distinct carriers. This suggests that no further sorting occurs upon cargo exit from SE. Moreover, 3D dSTORM data support a model in which some but not all ERC vesicles are tethered by contiguous "membrane bridges." Furthermore, tubular recycling endosomes preferentially traffic CIE cargo and may originate from SE membranes. These findings support a significantly altered model for endocytic recycling in mammalian cells in which sorting occurs in peripheral endosomes and segregation is maintained at the ERC.
ISSN:1059-1524
1939-4586
DOI:10.1091/mbc.e15-07-0514