Lipid Rafts Associate with Intracellular B Cell Receptors and Exhibit a B Cell Stage-Specific Protein Composition

Lipid rafts serve as platforms for BCR signal transduction. To better define the molecular basis of these membrane microdomains, we used two-dimensional gel electrophoresis and mass spectrometry to characterize lipid raft proteins from mature as well as immature B cell lines. Of 51 specific raft pro...

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Bibliographic Details
Published in:The Journal of immunology (1950) 2005-03, Vol.174 (6), p.3508-3517
Main Authors: Mielenz, Dirk, Vettermann, Christian, Hampel, Martin, Lang, Christiane, Avramidou, Athanasia, Karas, Michael, Jack, Hans-Martin
Format: Article
Language:English
Subjects:
Animals
Apoptosis
B-Lymphocytes - cytology
B-Lymphocytes - immunology
B-Lymphocytes - metabolism
Cell Differentiation
Cell Line
Detergents
Electrophoresis, Gel, Two-Dimensional
Glycosylation
Histocompatibility Antigens Class II - metabolism
Membrane Microdomains - chemistry
Membrane Microdomains - immunology
Membrane Microdomains - metabolism
Membrane Proteins - chemistry
Membrane Proteins - immunology
Membrane Proteins - metabolism
Mice
Peptide Mapping
Receptors, Antigen, B-Cell - metabolism
Signal Transduction
Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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Summary:Lipid rafts serve as platforms for BCR signal transduction. To better define the molecular basis of these membrane microdomains, we used two-dimensional gel electrophoresis and mass spectrometry to characterize lipid raft proteins from mature as well as immature B cell lines. Of 51 specific raft proteins, we identified a total of 18 proteins by peptide mass fingerprinting. Among them, we found vacuolar ATPase subunits alpha-1 and beta-2, vimentin, gamma-actin, mitofilin, and prohibitin. None of these has previously been reported in lipid rafts of B cells. The differential raft association of three proteins, including a novel potential signaling molecule designated swiprosin-1, correlated with the stage-specific sensitivity of B cells to BCR-induced apoptosis. In addition, MHC class II molecules were detected in lipid rafts of mature, but not immature B cells. This intriguing finding points to a role for lipid rafts in regulating Ag presentation during B cell maturation. Finally, a fraction of the BCR in the B cell line CH27 was constitutively present in lipid rafts. Surprisingly, this fraction was neither expressed at the cell surface nor fully O-glycosylated. Thus, we conclude that partitioning the BCR into lipid rafts occurs in the endoplasmic reticulum/cis-Golgi compartment and may represent a control mechanism for surface transport.
ISSN:0022-1767
1550-6606
DOI:10.4049/jimmunol.174.6.3508