title: Ubiquitination as a Mechanism To Transport Soluble Mycobacterial and Eukaryotic Proteins to Exosomes.
abstract: Exosomes are extracellular vesicles of endocytic origin that function in intercellular communication. Our previous studies indicate that exosomes released from Mycobacterium tuberculosis-infected macrophages contain soluble mycobacterial proteins. However, it was unclear how these secreted proteins were targeted to exosomes. In this study, we determined that exosome production by the murine macrophage cell line RAW264.7 requires the endosomal sorting complexes required for transport and that trafficking of mycobacterial proteins from phagocytosed bacilli to exosomes was dependent on protein ubiquitination. Moreover, soluble mycobacterial proteins, when added exogenously to RAW264.7 or human HEK293 cells, were endocytosed, ubiquitinated, and released via exosomes. This suggested that endocytosed proteins could be recycled from cells through exosomes. This hypothesis was supported using the tumor-associated protein He4, which, when endocytosed by RAW264.7 or HEK293 cells, was transported to exosomes in a ubiquitin-dependent manner. Our data suggest that ubiquitination is a modification sufficient for trafficking soluble proteins within the phagocytic/endocytic network to exosomes.
authors.affiliation: Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Smith
authors.affiliation: Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556.
authors.forename: Liam
authors.initials: L
authors.lastname: Jackson
authors.affiliation: Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556 schorey.1@nd.edu.
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Schorey
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D002450:Cell Communication / Q000276:immunology* / Q000502:physiology; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004705:Endocytosis / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism*; D057809:HEK293 Cells; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D008264:Macrophages / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D051379:Mice; D020102:Mycobacterium smegmatis / Q000276:immunology / Q000378:metabolism; D009169:Mycobacterium tuberculosis / Q000276:immunology / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics; D021381:Protein Transport / Q000502:physiology; D011506:Proteins / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering; D014157:Transcription Factors / Q000235:genetics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics; D054875:Ubiquitination; D000081102:WAP Four-Disulfide Core Domain Protein 2; D000099177:Tsg101 Protein
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D002966:Clathrin; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D006360:Heat-Shock Proteins; D010750:Phosphoproteins; D011506:Proteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases; D000081102:WAP Four-Disulfide Core Domain Protein 2; D000099177:Tsg101 Protein; C118127:HspX protein, Mycobacterium tuberculosis; C576287:Wfdc2 protein, mouse; C058749:groES protein, Mycobacterium tuberculosis; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; C111567:parkin protein