Neutral ceramidase secreted by endothelial cells is released in part associated with caveolin-1.
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.
Romiti
Elena
E
Dipartimento di Scienze Biochimiche, Università degli Studi di Firenze, Viale G.B. Morgagni 50, 50134 Firenze, Italy.
Meacci
Elisabetta
E
Donati
Chiara
C
Formigli
Lucia
L
Zecchi-Orlandini
Sandra
S
Farnararo
Marta
M
Ito
Makoto
M
Bruni
Paola
P
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
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