title: Transglutaminase type 2-dependent selective recruitment of proteins into exosomes under stressful cellular conditions.
abstract: Numerous studies are revealing a role of exosomes in intercellular communication, and growing evidence indicates an important function for these vesicles in the progression and pathogenesis of cancer and neurodegenerative diseases. However, the biogenesis process of exosomes is still unclear. Tissue transglutaminase (TG2) is a multifunctional enzyme with different subcellular localizations. Particularly, under stressful conditions, the enzyme has been also detected in the extracellular matrix, but the mechanism(s) by which TG2 is released outside the cells requires further investigation. Therefore, the goal of the present study was to determine whether exosomes might be a vehicle for TG2 to reach the extracellular space, and whether TG2 could be involved in exosomes biogenesis. To address this issue, we isolated and characterized exosomes derived from cells either expressing or not TG2, under stressful conditions (i.e. proteasome impairment or expressing a mutated form of huntingtin (mHtt) containing 84 polyglutamine repeats). Our results show that TG2 is present in the exosomes only upon proteasome blockade, a condition in which TG2 interacts with TSG101 and ALIX, two key proteins involved in exosome biogenesis. Interestingly, we found that TG2 favours the assembly of a protein complex including mHtt, ALIX, TSG101 and BAG3, a co-chaperone involved in the clearance of mHtt. The formation of this complex is paralleled by the selective recruitment of mHtt and BAG3 in the exosomes derived from TG2 proficient cells only. Overall, our data indicate that TG2 is an important player in the biogenesis of exosomes controlling the selectivity of their cargo under stressful cellular conditions. In addition, these vesicles represent the way by which cells can release TG2 into the extracellular space under proteostasis impairment.
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Diaz-Hidalgo
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Altuntas
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Rossin
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: D'Eletto
authors.affiliation: National Institute for Infectious Diseases, IRCCS "Lazzaro Spallanzani", Rome, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Marsella
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Farrace
authors.affiliation: National Institute for Infectious Diseases, IRCCS "Lazzaro Spallanzani", Rome, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Falasca
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy.
authors.forename: Manuela
authors.initials: M
authors.lastname: Antonioli
authors.affiliation: National Institute for Infectious Diseases, IRCCS "Lazzaro Spallanzani", Rome, Italy; Department of Biological and Environmental Science and Technology (Di.S.Te.B.A.), University of Salento, 73100 Lecce, Italy.
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Fimia
authors.affiliation: Department of Biology, University of Rome "Tor Vergata", Rome, Italy; National Institute for Infectious Diseases, IRCCS "Lazzaro Spallanzani", Rome, Italy. Electronic address: mauro.piacentini@uniroma2.it.
authors.forename: Mauro
authors.initials: M
authors.lastname: Piacentini
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism / Q000502:physiology*; D055354:Exosomes / Q000378:metabolism*; D005347:Fibroblasts; D019204:GTP-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D055786:Gene Knockout Techniques; D057809:HEK293 Cells; D006801:Humans; D000071058:Huntingtin Protein / Q000235:genetics / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology*; D051379:Mice; D009154:Mutation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D066263:Protein Aggregation, Pathological / Q000378:metabolism; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D025941:Protein Interaction Mapping; D021381:Protein Transport / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D011503:Transglutaminases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D018911:Trinucleotide Repeats; D000099177:Tsg101 Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D019204:GTP-Binding Proteins; D000071058:Huntingtin Protein; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D014157:Transcription Factors; D011503:Transglutaminases; D000099177:Tsg101 Protein; C498806:Bag3 protein, mouse; C086055:HTT protein, human; C117020:PDCD6IP protein, human; C492144:Pdcd6ip protein, mouse; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: ALIX; BAG3; Exosomes; Huntington's disease; MG132; TSG101; Transglutaminase type 2