Cover image for Vol. 17 Issue 2

Early View (Online Version of Record published before inclusion in an issue)

Edited By: Michael S. Marks, Trina A. Schroer, Tom H. Stevens and Sharon A. Tooze

Online ISSN: 1600-0854


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  1. Original Articles

    1. Spatiotemporal Resolution of Rab9 and CI-MPR Dynamics in the Endocytic Pathway

      Ana Kucera, Marita Borg Distefano, Axel Berg-Larsen, Frode Skjeldal, Urska Repnik, Oddmund Bakke and Cinzia Progida

      Article first published online: 10 JAN 2016 | DOI: 10.1111/tra.12357

      Thumbnail image of graphical abstract

      Rab9 regulates the transport from late endosomes to the trans-Golgi network, and mediates the recycling of mannose-6-phosphate receptors (MPRs). Using live confocal imaging, we characterized the spatiotemporal dynamics of Rab9 and its active mutant, Rab9Q66L. We show that Rab9 and CI-MPR are recruited to endosomes at the early-to-late transition point. As endosomes mature, Rab5 detaches, and Rab7a is recruited. CI-MPR leaves the endosome swiftly after, while Rab9 persists. We propose a novel Rab9-mediated pathway directed toward the maturing endosomes.

  2. Reviews

    1. N-Glycan-based ER Molecular Chaperone and Protein Quality Control System: The Calnexin Binding Cycle

      Lydia Lamriben, Jill B. Graham, Benjamin M. Adams and Daniel N. Hebert

      Article first published online: 10 JAN 2016 | DOI: 10.1111/tra.12358

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      Over two-decades ago, Ari Helenius proposed a model that described a novel molecular chaperone binding cycle that was controlled by the composition of the N-linked glycans on the substrates. This review highlights the recent advances in our understanding of the molecular mechanism, role in protein homeostasis and links to disease states for the endoplasmic reticulum carbohydrate-binding chaperones, calnexin and calreticulin.

  3. Original Articles

    1. Analysis of COPII Vesicles Indicates a Role for the Emp47–Ssp120 Complex in Transport of Cell Surface Glycoproteins

      Neil G. Margulis, Joshua D. Wilson, Christine M. Bentivoglio, Nripesh Dhungel, Aaron D. Gitler and Charles Barlowe

      Article first published online: 10 JAN 2016 | DOI: 10.1111/tra.12356

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      A comprehensive proteomic analysis of COPII vesicles identified the putative calcium-binding Ssp120 protein as an efficiently packaged component of these endoplasmic reticulum (ER)-derived transport vesicles. Purification of Ssp120 revealed a tight association with Emp47, a transmembrane protein that contains a luminal carbohydrate recognition domain. Cell biological and genetic analyses indicated functional relationships between Ssp120 and Emp47 in trafficking. The collective findings support a model in which the Emp47–Ssp120 complex together functions as an anterograde cargo receptor for specific glycosylated secretory cargo.

    2. The Na+-Taurocholate Cotransporting Polypeptide Traffics with the Epidermal Growth Factor Receptor

      Xintao Wang, Pijun Wang, Wenjun Wang, John W. Murray and Allan W. Wolkoff

      Article first published online: 10 JAN 2016 | DOI: 10.1111/tra.12354

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      Na+-taurocholate cotransporting polypeptide (ntcp) mediates bile acid transport, also serving as the hepatitis B virus receptor. It traffics in vesicles along microtubules, requiring activity of protein kinase C (PKC)ζ for motility. We have now found that the epidermal growth factor receptor (EGFR) is the target of PKCζ activity and that EGFR and ntcp colocalize in vesicles. ntcp-containing vesicles that are not associated with EGFR have reduced microtubule-based motility, consistent with intracellular accumulation and reduced surface expression of ntcp in cells following EGFR knockdown.

    3. RNF121 Inhibits Angiogenic Growth Factor Signaling by Restricting Cell Surface Expression of VEGFR-2

      Armin Maghsoudlou, Rosana D. Meyer, Kobra Rezazadeh, Emad Arafa, Jeffrey Pudney, Edward Hartsough and Nader Rahimi

      Article first published online: 21 DEC 2015 | DOI: 10.1111/tra.12353

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      RING finger protein 121 (RNF121) is an endoplasmic reticulum (ER) ubiquitin E3 ligase that binds to and ubiquitinates the newly synthesized immature vascular endothelial growth factor receptor-2 (VEGFR-2). RNF-121 ubiquitination of VEGFR-2 inhibits the trafficking of immature VEGFR-2 from the ER complex to the Golgi apparatus. This restricts the expression of VEGFR-2 at the cell surface and minimizes the VEGF angiogenic signaling in endothelial cells.


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