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      Endoplasmic reticulum–endosome contact increases as endosomes traffic and mature

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          Abstract

          Endosomes do not traffic autonomously but instead associate with the ER membrane. ER tubules wrap around and maintain contact with both early and late endosomes by ER ring rearrangements. As endosomes mature, they increase the degree of their ER association, which suggests that the ER might play a role in endosomal maturation.

          Abstract

          The endosomal pathway is responsible for plasma membrane cargo uptake, sorting, and, in many cases, lysosome targeting. Endosome maturation is complex, requiring proper spatiotemporal recruitment of factors that regulate the size, maturity, and positioning of endosomal compartments. In animal cells, it also requires trafficking of endosomes on microtubules. Recent work has revealed the presence of contact sites between some endosomes and the endoplasmic reticulum (ER). Although these contact sites are believed to have multiple functions, the frequency, dynamics, and physical attributes of these contacts are poorly understood. Here we use high-resolution three-dimensional electron microscopy to reveal that ER tubules wrap around endosomes and find that both organelles contact microtubules at or near membrane contact sites. As endosomes traffic, they remain bound to the ER, which causes the tubular ER to rearrange its structure around dynamic endosomes at contact sites. Finally, as endosomes transition through steps of maturation, they become more tightly associated with the ER. The major implication of these results is that endosomes mature and traffic while coupled to the ER membrane rather than in isolation.

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          Author and article information

          Contributors
          Role: Monitoring Editor
          Journal
          Mol Biol Cell
          Mol. Biol. Cell
          molbiolcell
          mbc
          Mol. Bio. Cell
          Molecular Biology of the Cell
          The American Society for Cell Biology
          1059-1524
          1939-4586
          01 April 2013
          : 24
          : 7
          : 1030-1040
          Affiliations
          Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309
          National Institutes of Health
          Author notes
          1Address correspondence to: Gia K. Voeltz ( gia.voeltz@ 123456colorado.edu ).
          Article
          E12-10-0733
          10.1091/mbc.E12-10-0733
          3608491
          23389631
          8f191a65-fd83-4171-96c9-8c397efcc5de
          © 2013 Friedman et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License ( http://creativecommons.org/licenses/by-nc-sa/3.0).

          “ASCB®,” “The American Society for Cell Biology®,” and “Molecular Biology of the Cell®” are registered trademarks of The American Society of Cell BD; are registered trademarks of The American Society of Cell Biology.

          History
          : 11 October 2012
          : 07 January 2013
          : 24 January 2013
          Categories
          Articles
          Membrane Trafficking

          Molecular biology
          Molecular biology

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