Localization of neutral ceramidase in caveolin-enriched light membranes ofmurine endothelial cells

Sphingomyelinase (SMase) and ceramidase (CDase) activities participate in s phingomyelin (SM) metabolism and have a role in the signal transduction of a variety of ligands. In this study evidence is presented that caveolin-enr iched light membranes (CELMs) of murine endothelial cells, characterized by high SM, ceramide (Cer) and cholesterol content, bear acid and neutral SMa se as well as neutral CDase activities. Localization of neutral CDase in CE LMs was confirmed by Western analysis. Notably, cell treatment with cyclode xtrin, which depleted cell cholesterol, did not affect acid or neutral SMas e activities but significantly enhanced neutral CDase activity in CELMs, in dicating a negative role for cholesterol in CDase regulation. These finding s suggest that neutral CD se is implicated, together with SMase activities, in the control of caveolar Cer content that may be critical for caveola dy namics. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.