title: Immobilized alpha2,6-linked sialic acid suppresses caspase-3 activation during anti-IgM antibody-induced apoptosis in Ramos cells.
abstract: In Ramos cells, a human Burkitt's lymphoma cell line, stimulation of the B cell antigen receptor with anti-IgM antibody (Ab) induces apoptosis as indicated by a decrease in cell viability and an increase in DNA fragmentation and cell surface exposure of phosphatidylserine. Furthermore, these changes are suppressed by incubating the cells in alpha(1)-acid glycoprotein (AGP)-coated tissue culture plates. Here, we found that, during Anti-IgM Ab-induced apoptosis in Ramos cells, caspase-3 is activated downstream of caspase-8 and the mitochondrial pathway is activated, as indicated by a loss of mitochondrial membrane potential, an increase in the release of cytochrome c to the cytoplasm, and enhanced Bax expression. Anti-IgM Ab-induced apoptosis of neuraminidase-treated Ramos cells was suppressed by incubating the cells on plates coated with AGP, which contains a high concentration of alpha2,6-linked sialic acid. The incubation on plates coated with AGP also suppressed anti-IgM Ab-stimulated caspase-3 activity and increased the level of X-linked inhibitor of apoptosis protein (XIAP), but it did not affect caspase-8 activity, the mitochondrial membrane potential, cytochrome c release, or Bax expression. The results indicate that the interaction of Ramos cells with immobilized alpha2,6-linked sialic acid enhances XIAP expression, directly or indirectly suppressing caspase-3 activity and inhibiting anti-IgM Ab-induced apoptosis.
authors.affiliation: Department of Clinical Chemistry, School of Pharmaceutical Sciences, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan. yutaro@phar.toho-u.ac.jp
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Azuma
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Higurashi
authors.forename: Kojiro
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D002051:Burkitt Lymphoma; D053148:Caspase 3 / Q000378:metabolism*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007075:Immunoglobulin M / Q000494:pharmacology*; D008563:Membrane Lipids / Q000032:analysis; D008564:Membrane Potentials / Q000187:drug effects; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000502:physiology; D019158:N-Acetylneuraminic Acid / Q000494:pharmacology*; D010718:Phosphatidylserines / Q000032:analysis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D061945:Caspase Inhibitors; D007075:Immunoglobulin M; D008563:Membrane Lipids; D010718:Phosphatidylserines; D019253:Proto-Oncogene Proteins c-bcl-2; D051636:X-Linked Inhibitor of Apoptosis Protein; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c; D053148:Caspase 3; D020169:Caspases; D019158:N-Acetylneuraminic Acid