title: ISGylation controls exosome secretion by promoting lysosomal degradation of MVB proteins.
abstract: Exosomes are vesicles secreted to the extracellular environment through fusion with the plasma membrane of specific endosomes called multivesicular bodies (MVB) and mediate cell-to-cell communication in many biological processes. Posttranslational modifications are involved in the sorting of specific proteins into exosomes. Here we identify ISGylation as a ubiquitin-like modification that controls exosome release. ISGylation induction decreases MVB numbers and impairs exosome secretion. Using ISG15-knockout mice and mice expressing the enzymatically inactive form of the de-ISGylase USP18, we demonstrate in vitro and in vivo that ISG15 conjugation regulates exosome secretion. ISG15 conjugation triggers MVB co-localization with lysosomes and promotes the aggregation and degradation of MVB proteins. Accordingly, inhibition of lysosomal function or autophagy restores exosome secretion. Specifically, ISGylation of the MVB protein TSG101 induces its aggregation and degradation, being sufficient to impair exosome secretion. These results identify ISGylation as a novel ubiquitin-like modifier in the control of exosome production.
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.|Immunology Service, Hospital de la Princesa, Instituto Investigación Sanitaria Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.
authors.forename: Carolina
authors.initials: C
authors.lastname: Villarroya-Beltri
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.|Immunology Service, Hospital de la Princesa, Instituto Investigación Sanitaria Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.
authors.forename: Francesc
authors.initials: F
authors.lastname: Baixauli
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Mittelbrunn
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.|Immunology Service, Hospital de la Princesa, Instituto Investigación Sanitaria Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: Fernández-Delgado
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.|Immunology Service, Hospital de la Princesa, Instituto Investigación Sanitaria Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.
authors.forename: Daniel
authors.identifier: 0000-0002-7970-1277
authors.initials: D
authors.lastname: Torralba
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.|Immunology Service, Hospital de la Princesa, Instituto Investigación Sanitaria Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.
authors.forename: Olga
authors.initials: O
authors.lastname: Moreno-Gonzalo
authors.affiliation: Department of Preventive Medicine, Public Health and Microbiology, Universidad Autónoma de Madrid, 28029 Madrid, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Baldanta
authors.affiliation: Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, 08036 Barcelona, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Enrich
authors.affiliation: Department of Preventive Medicine, Public Health and Microbiology, Universidad Autónoma de Madrid, 28029 Madrid, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Guerra
authors.affiliation: Centro Nacional de Investigaciones Cardiovasculares (CNIC), 28029 Madrid, Spain.|Immunology Service, Hospital de la Princesa, Instituto Investigación Sanitaria Princesa, Universidad Autónoma de Madrid, 28006 Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Sánchez-Madrid
mesh_terms: D000818:Animals; D001343:Autophagy; D016207:Cytokines / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D055354:Exosomes / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D019169:Jurkat Cells; D008247:Lysosomes / Q000378:metabolism*; D008264:Macrophages; D051379:Mice; D018345:Mice, Knockout; D057146:Multivesicular Bodies / Q000378:metabolism*; D013601:T-Lymphocytes; D014157:Transcription Factors / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics; D000099177:Tsg101 Protein
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D014157:Transcription Factors; D043222:Ubiquitin Thiolesterase; D014452:Ubiquitins; D000099177:Tsg101 Protein; C489550:G1p2 protein, mouse; C074034:ISG15 protein, human; C118306:Usp18 protein, mouse