Bcl-2-dependent oxidation of pyruvate dehydrogenase-E2, a primary biliary cirrhosis autoantigen, during apoptosis.
The close association between autoantibodies against pyruvate dehydrogenase-E2 (PDC-E2), a ubiquitous mitochondrial protein, and primary biliary cirrhosis (PBC) is unexplained. Many autoantigens are selectively modified during apoptosis, which has focused attention on apoptotic cells as a potential source of "neo-antigens" responsible for activating autoreactive lymphocytes. Since increased apoptosis of bile duct epithelial cells (cholangiocytes) is evident in patients with PBC, we evaluated the effect of apoptosis on PDC-E2. Autoantibody recognition of PDC-E2 by immunofluorescence persisted in apoptotic cholangiocytes and appeared unchanged by immunoblot analysis. PDC-E2 was neither cleaved by caspases nor concentrated into surface blebs in apoptotic cells. In other cell types, autoantibody recognition of PDC-E2, as assessed by immunofluorescence, was abrogated after apoptosis, although expression levels of PDC-E2 appeared unchanged when examined by immunoblot analysis. Both overexpression of Bcl-2 and depletion of glutathione before inducing apoptosis prevented this loss of autoantibody recognition, suggesting that glutathiolation, rather than degradation or loss, of PDC-E2 was responsible for the loss of immunofluorescence signal. We postulate that apoptotic cholangiocytes, unlike other apoptotic cell types, are a potential source of immunogenic PDC-E2 in patients with PBC.
Odin
J A
JA
Department of Medicine, The Mount Sinai School of Medicine, New York, New York 10029, USA. odinj01@doc.mssm.edu
Huebert
R C
RC
Casciola-Rosen
L
L
LaRusso
N F
NF
Rosen
A
A
D017209:Apoptosis / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology; D001324:Autoantigens / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D001652:Bile Ducts / Q000378:metabolism* / Q000473:pathology; D002460:Cell Line / Q000528:radiation effects; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D004229:Dithiothreitol / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic; D019254:Genes, bcl-2; D005978:Glutathione / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D007106:Immune Sera; D015151:Immunoblotting; D008105:Liver Cirrhosis, Biliary / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D008213:Lymphocyte Activation / Q000276:immunology; D008928:Mitochondria / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000032:analysis / Q000276:immunology / Q000378:metabolism*; D014162:Transfection
D001323:Autoantibodies; D001324:Autoantigens; D007106:Immune Sera; D011768:Pyruvate Dehydrogenase Complex; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D005978:Glutathione; D004229:Dithiothreitol