title: Neutral ceramidase secreted by endothelial cells is released in part associated with caveolin-1.
abstract: Neutral ceramidase (CDase) is a key enzyme of sphingomyelin (SM) metabolism implicated in cell signaling triggered by a variety of extracellular ligands. Previously it was shown that in murine endothelial cells a portion of neutral CDase is localized in detergent-resistant light membranes. In this study subcellular distribution of neutral CDase was further investigated. In accordance with the previous finding, the enzyme was identified in caveolae. Moreover, the same protein was detected in medium-speed supernatant of cell-conditioned medium, accounting for CDase activity measurable in the medium at neutral pH. Notably, these cells released also the caveolae-scaffolding protein caveolin-1 (cav-1). Interestingly, secreted neutral CDase and cav-1 coimmunoprecipitated. In addition, acid sphingomyelinase (SMase) activity was detectable in cav-1 immunocomplexes. These findings are consistent with the view that neutral CDase is released, in part, in association with cav-1 together with acid SMase. It remains to be established whether the here-identified secreted cav-1-enriched complex acts as platform to facilitate extracellular metabolism of SM.
authors.affiliation: Dipartimento di Scienze Biochimiche, Università degli Studi di Firenze, Viale G.B. Morgagni 50, 50134 Firenze, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Romiti
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Meacci
authors.forename: Chiara
authors.initials: C
authors.lastname: Donati
authors.forename: Lucia
authors.initials: L
authors.lastname: Formigli
authors.forename: Sandra
authors.initials: S
authors.lastname: Zecchi-Orlandini
authors.forename: Marta
authors.initials: M
authors.lastname: Farnararo
authors.forename: Makoto
authors.initials: M
authors.lastname: Ito
authors.forename: Paola
authors.initials: P
authors.lastname: Bruni
mesh_terms: D000581:Amidohydrolases / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D021941:Caveolae / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism*; D002460:Cell Line; D055572:Ceramidases; D004730:Endothelium, Vascular / Q000201:enzymology* / Q000378:metabolism* / Q000648:ultrastructure; D006863:Hydrogen-Ion Concentration; D016464:Lysosomal Storage Diseases / Q000378:metabolism; D051379:Mice; D055576:Neutral Ceramidase; D011233:Precipitin Tests; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D013108:Sphingomyelin Phosphodiesterase; D000581:Amidohydrolases; C526747:Asah2 protein, mouse; D055572:Ceramidases; D055576:Neutral Ceramidase