title: The unconventional secretion of stress-inducible protein 1 by a heterogeneous population of extracellular vesicles.
abstract: The co-chaperone stress-inducible protein 1 (STI1) is released by astrocytes, and has important neurotrophic properties upon binding to prion protein (PrP(C)). However, STI1 lacks a signal peptide and pharmacological approaches pointed that it does not follow a classical secretion mechanism. Ultracentrifugation, size exclusion chromatography, electron microscopy, vesicle labeling, and particle tracking analysis were used to identify three major types of extracellular vesicles (EVs) released from astrocytes with sizes ranging from 20-50, 100-200, and 300-400 nm. These EVs carry STI1 and present many exosomal markers, even though only a subpopulation had the typical exosomal morphology. The only protein, from those evaluated here, present exclusively in vesicles that have exosomal morphology was PrP(C). STI1 partially co-localized with Rab5 and Rab7 in endosomal compartments, and a dominant-negative for vacuolar protein sorting 4A (VPS4A), required for formation of multivesicular bodies (MVBs), impaired EV and STI1 release. Flow cytometry and PK digestion demonstrated that STI1 localized to the outer leaflet of EVs, and its association with EVs greatly increased STI1 activity upon PrP(C)-dependent neuronal signaling. These results indicate that astrocytes secrete a diverse population of EVs derived from MVBs that contain STI1 and suggest that the interaction between EVs and neuronal surface components enhances STI1-PrP(C) signaling.
authors.affiliation: International Research Center, A.C. Camargo Hospital, Rua Taguá 540, São Paulo, 01508-010, Brazil.
authors.forename: Glaucia N M
authors.initials: GN
authors.lastname: Hajj
authors.forename: Camila P
authors.initials: CP
authors.lastname: Arantes
authors.forename: Marcos Vinicios Salles
authors.initials: MV
authors.lastname: Dias
authors.forename: Martín
authors.initials: M
authors.lastname: Roffé
authors.forename: Bruno
authors.initials: B
authors.lastname: Costa-Silva
authors.forename: Marilene H
authors.initials: MH
authors.lastname: Lopes
authors.forename: Isabel
authors.initials: I
authors.lastname: Porto-Carreiro
authors.forename: Tatiana
authors.initials: T
authors.lastname: Rabachini
authors.forename: Flávia R
authors.initials: FR
authors.lastname: Lima
authors.forename: Flávio H
authors.initials: FH
authors.lastname: Beraldo
authors.forename: Marco A M
authors.initials: MA
authors.lastname: Prado
authors.forename: Marco M A
authors.initials: MM
authors.lastname: Prado
authors.forename: Rafael
authors.initials: R
authors.lastname: Linden
authors.forename: Vilma R
authors.initials: VR
authors.lastname: Martins
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D015151:Immunoblotting; D051379:Mice; D018621:PrPC Proteins / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002352:Carrier Proteins; D006360:Heat-Shock Proteins; D018621:PrPC Proteins; C429767:TP53INP1 protein, human
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