title: Nedd4 family-interacting protein 1 (Ndfip1) is required for the exosomal secretion of Nedd4 family proteins.
abstract: The ability to remove unwanted proteins is an important cellular feature. Classically, this involves the enzymatic addition of ubiquitin moieties followed by degradation in the proteasome. Nedd4 proteins are ubiquitin ligases important not only for protein degradation, but also for protein trafficking. Nedd4 proteins can bind to target proteins either by themselves or through adaptor protein Ndfip1 (Nedd4 family-interacting protein 1). An alternative mechanism for protein removal and trafficking is provided by exosomes, which are small vesicles (50-90-nm diameter) originating from late endosomes and multivesicular bodies (MVBs). Exosomes provide a rapid means of shedding obsolete proteins and also for cell to cell communication. In the present work, we show that Ndfip1 is detectable in exosomes secreted from transfected cells and also from primary neurons. Compared with control, Ndfip1 increases exosome secretion from transfected cells. Furthermore, while Nedd4, Nedd4-2, and Itch are normally absent from exosomes, expression of Ndfip1 results in recruitment of all three Nedd4 proteins into exosomes. Together, these results suggest that Ndfip1 is important for protein trafficking via exosomes, and provides a mechanism for cargoing passenger proteins such as Nedd4 family proteins. Given the positive roles of Ndfip1/Nedd4 in improving neuronal survival during brain injury, it is possible that exosome secretion provides a novel route for rapid sequestration and removal of proteins during stress.
authors.affiliation: Brain Development Laboratory, Howard Florey Institute and Centre for Neuroscience, The University of Melbourne, Parkville 3010, Victoria, Australia.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Putz
authors.forename: Jason
authors.initials: J
authors.lastname: Howitt
authors.forename: Jenny
authors.initials: J
authors.lastname: Lackovic
authors.forename: Natalie
authors.initials: N
authors.lastname: Foot
authors.forename: Sharad
authors.initials: S
authors.lastname: Kumar
authors.forename: John
authors.initials: J
authors.lastname: Silke
authors.forename: Seong-Seng
authors.initials: SS
authors.lastname: Tan
mesh_terms: D001921:Brain / Q000473:pathology; D020126:Brefeldin A / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology*; D002450:Cell Communication; D002460:Cell Line; D002470:Cell Survival; D056827:Endosomal Sorting Complexes Required for Transport; D055354:Exosomes; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D000075702:Nedd4 Ubiquitin Protein Ligases; D009474:Neurons / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D008565:Membrane Proteins; C451223:NDFIP1 protein, human; D012097:Repressor Proteins; D020126:Brefeldin A; C432966:ITCH protein, human; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618485:Nedd4L protein, human; D044767:Ubiquitin-Protein Ligases