title: Nuclear envelope-associated endosomes deliver surface proteins to the nucleus.
abstract: Endocytosis directs molecular cargo along three main routes: recycling to the cell surface, transport to the Golgi apparatus or degradation in endolysosomes. Pseudomonas exotoxin A (PE) is a bacterial protein that typically traffics to the Golgi and then the endoplasmic reticulum before translocating to the cytosol. Here we show that a substantial fraction of internalized PE is also located in nuclear envelope-associated endosomes (NAE), which display limited mobility, exhibit a propensity to undergo fusion and readily discharge their contents into the nuclear envelope. Electron microscopy and protein trapping in the nucleus indicate that NAE mediate PE transfer into the nucleoplasm. RNAi screening further revealed that NAE-mediated transfer depends on the nuclear envelope proteins SUN1 and SUN2, as well as the Sec61 translocon complex. These data reveal a novel endosomal route from the cell surface to the nucleoplasm that facilitates the accumulation of extracellular and cell surface proteins in the nucleus.
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Chaumet
authors.affiliation: Institute of Medical Biology, 8A Biomedical Grove, #06-06 Immunos, Singapore 138648, Singapore.|Joint IMB-IMCB Electron Microscopy Suite, 20 Biopolis Street, #B2-14 Matrix, Singapore 138671, Singapore.
authors.forename: Graham D
authors.identifier: http://orcid.org/0000-0003-2362-1312
authors.initials: GD
authors.lastname: Wright
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.
authors.forename: Sze Hwee
authors.initials: SH
authors.lastname: Seet
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.
authors.forename: Keit Min
authors.initials: KM
authors.lastname: Tham
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.|Institute of Medical Biology, 8A Biomedical Grove, #06-06 Immunos, Singapore 138648, Singapore.|Joint IMB-IMCB Electron Microscopy Suite, 20 Biopolis Street, #B2-14 Matrix, Singapore 138671, Singapore.
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Gounko
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore.|Department of Biochemistry, National University of Singapore, 21 Lower Kent Ridge Road, Singapore 119077, Singapore.
authors.forename: Frederic
authors.initials: F
authors.lastname: Bard
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D005098:Exotoxins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D055785:Gene Knockdown Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism*; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D021381:Protein Transport; D000069816:SEC Translocation Channels; D037521:Virulence Factors / Q000378:metabolism*; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D000069816:SEC Translocation Channels; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C506117:SUN1 protein, human; C413025:SUN2 protein, human