Saposin C is required for lipid presentation by human CD1b

Florian Winau, Vera Schwierzeck, Robert Hurwitz, Natascha Remmel, Peter A. Sieling, Robert L. Modlin, Steven A. Porcelli, Volker Brinkmann, Masahiko Sugita, Konrad Sandhoff, Stefan H.E. Kaufmann, Ulrich E. Schaible

Research output: Contribution to journalArticlepeer-review

144 Scopus citations

Abstract

Lipids from Mycobacterium tuberculosis are presented through CD1 proteins to T lymphocytes in humans, but the accessory molecules required for antigen loading and presentation remain unidentified. Here we show that fibroblasts deficient in sphingolipid activator proteins (SAPs) transfected with CD1b failed to activate lipid-specific T cells. However, the T cell response was restored when fibroblasts were reconstituted with SAP-C but not other SAPs. Lipid antigen and SAP-C colocalized in lysosomal compartments, and liposome assays showed that SAP-C efficiently extracts antigen from membranes. Coprecipitation demonstrated direct molecular interaction between SAP-C and CD1b. We propose a model in which SAP-C exposes lipid antigens from intralysosomal membranes for loading onto CD1b. Thus, SAP-C represents a missing link in antigen presentation of lipids through CD1b to human T cells.

Original languageEnglish (US)
Pages (from-to)169-174
Number of pages6
JournalNature Immunology
Volume5
Issue number2
DOIs
StatePublished - Feb 1 2004

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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