title: Ceramide-rich membrane rafts mediate CD40 clustering.
abstract: Many receptor systems use receptor clustering for transmembrane signaling. In this study, we show that acid sphingomyelinase (ASM) is essential for the clustering of CD40. Stimulation of lymphocytes via CD40 ligation results in ASM translocation from intracellular stores, most likely vesicles, into distinct membrane domains on the extracellular surface of the plasma membrane. Surface ASM initiates a release of extracellularly oriented ceramide, which in turn mediates CD40 clustering in sphingolipid-rich membrane domains. ASM, ceramide, and CD40 colocalize in the cap-like structure of stimulated cells. Deficiency of ASM, destruction of sphingolipid-rich rafts, or neutralization of surface ceramide prevents CD40 clustering and CD40-initiated cell signaling. These findings indicate that the ASM-mediated release of ceramide and/or metabolites of ceramide regulate clustering of CD40, which seems to be a prerequisite for cellular activation via CD40.
authors.affiliation: Department of Immunology, St. Jude Children's Research Hospital, 332 North Lauderdale Street, Memphis, TN 38105, USA.
authors.forename: Heike
authors.initials: H
authors.lastname: Grassmé
authors.forename: Verena
authors.initials: V
authors.lastname: Jendrossek
authors.forename: Jürgen
authors.initials: J
authors.lastname: Bock
authors.forename: Andrea
authors.initials: A
authors.lastname: Riehle
authors.forename: Erich
authors.initials: E
authors.lastname: Gulbins
mesh_terms: D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D019013:CD40 Antigens / Q000378:metabolism*; D002478:Cells, Cultured; D002518:Ceramides / Q000032:analysis / Q000502:physiology*; D005434:Flow Cytometry; D006801:Humans; D018664:Interleukin-12 / Q000096:biosynthesis; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D008213:Lymphocyte Activation; D020935:MAP Kinase Signaling System; D021962:Membrane Microdomains / Q000737:chemistry* / Q000502:physiology*; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D021381:Protein Transport; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism / Q000494:pharmacology
chemical_list: D019013:CD40 Antigens; D002518:Ceramides; D018664:Interleukin-12; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D013108:Sphingomyelin Phosphodiesterase