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标题：Ceramide kinase promotes Ca2+ signaling near IgG-opsonized targets and enhances phagolysosomal fusion in COS-1 cells
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作者：Vania Hinkovska-Galcheva ; Andrea Clark ; Susan VanWay 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2008
卷号：49
期号：3
页码：531-542
DOI：10.1194/jlr.M700442-JLR200
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：Ceramide-1-phosphate (C1P) is a novel bioactive sphingolipid formed by the phosphorylation of ceramide catalyzed by ceramide kinase (CERK). In this study, we evaluated the mechanism by which increased C1P during phagocytosis enhances phagocytosis and phagolysosome formation in COS-1 cells expressing hCERK. Stable transfectants of COS-1 cells expressing FcγRIIA or both FcγRIIA/hCERK expression vectors were created. Cell fractionation studies demonstrated that hCERK and the transient receptor potential channel (TRPC-1) were enriched in caveolae fractions. Our data establish that both CERK and TRPC-1 localize to the caveolar microdomains during phagocytosis and that CERK also colocalizes with EIgG in FcγRIIA/hCERK-bearing COS-1 cells. Using high-speed fluorescence microscopy, FcγRIIA/hCERK transfected cells displayed Ca²⁺ sparks around the phagosome. In contrast, cells expressing FcγRIIA under identical conditions displayed little periphagosomal Ca²⁺ signaling. The enhanced Ca²⁺ signals were accompanied by enhanced phagolysosome formation. However, the addition of pharmacological reagents that inhibit store-operated channels (SOCs) reduced the phagocytic index and phagolysosomal fusion in hCERK transfected cells. The higher Ca²⁺ signal observed in hCERK transfected cells as well as the fact that CERK colocalized with EIgG during phagocytosis support our hypothesis that Ca²⁺ signaling is an important factor for increasing phagocytosis and is regulated by CERK in a manner that involves SOCs/TRPCs.