Annexin V binds to viable B cells and colocalizes with a marker of lipid rafts upon B cell receptor activation.
Recombinant annexin V (rAnV) has been used to identify apoptotic cells based on its ability to bind phosphatidylserine (PS), a lipid normally restricted to the cytoplasmic face of the plasma membrane, but externalized early during apoptosis. However, this association of rAnV binding and apoptosis is not an obligatory one. We demonstrate that rAnV binds to a large fraction of murine B cells bearing selectable Ag receptors despite the fact that these cells are not apoptotic. Phosphatidylserine, which is uniformly distributed on resting B cells, is mobilized to co-cap with IgM on anti-IgM-treated B cells and to colocalize with GM1, a marker of lipid rafts. Cross-linking PS before anti-IgM treatment sequesters this lipid and alters signaling through IgM. Thus, PS exposed on the majority of B cells in vivo does not reflect early apoptosis, but, instead, plays a role in receptor-mediated signaling events.
Dillon
S R
SR
Department of Medicine, Division of Rheumatology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Mancini
M
M
Rosen
A
A
Schlissel
M S
MS
D000818:Animals; D017304:Annexin A5 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology; D017209:Apoptosis / Q000276:immunology; D001402:B-Lymphocytes / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D015415:Biomarkers / Q000032:analysis; D001710:Biotin / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D017635:Clonal Anergy; D002999:Clone Cells; D005677:G(M1) Ganglioside / Q000378:metabolism; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism; D050356:Lipid Metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010718:Phosphatidylserines / Q000378:metabolism; D011485:Protein Binding / Q000276:immunology; D011940:Receptor Aggregation / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism* / Q000502:physiology; D011994:Recombinant Proteins / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013194:Staining and Labeling; D019809:Streptavidin / Q000494:pharmacology
D017304:Annexin A5; D000888:Antibodies, Anti-Idiotypic; D015415:Biomarkers; D007075:Immunoglobulin M; D010718:Phosphatidylserines; D011947:Receptors, Antigen, B-Cell; D011994:Recombinant Proteins; C044203:anti-IgM; D005677:G(M1) Ganglioside; D001710:Biotin; D019809:Streptavidin