Autoantibodies to BCOADC-E2 in patients with primary biliary cirrhosis recognize a conformational epitope

Patrick S Leung, David T. Chuang, R. Max Wynn, Sanghoon Cha, Dean J. Danner, Aftab Ansari, Ross L. Coppel, M. Eric Gershwin

Research output: Contribution to journalArticle

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Abstract

Primary biliary cirrhosis (PBC) is an autoimmune disease of liver associated with a unique serologic response to mitochondrial autoantigens. Many of the autoantigens recognized by autoantibodies in PBC are members of the 2-oxo-acid dehydrogenase complex. The two major autoantigens are the E2 component of the pyruvate dehydrogenase complex (PDC-E2) and the E2 component of the branched chain 2-oxo-acid dehydrogenase complex (BCOADC-E2). The autoantibody response to PDCE2 has been mapped to one immunodominant epitope, which consists of both linear and conformational components. The presence of a single immunodominant epitope in PDC-E2 is unusual when contrasted to the immune response to autoantigens in other human autoimmune diseases. We have mapped the epitope recognized by antimitochondrial autoantibodies (AMA) specific to BCOADC-E2 in patients with PBC by taking advantage of the full-length bovine BCOADC-E2 complementary DNA (cDNA) and a series of expression clones spanning the entire molecule. Reactivity to the various expression clones was studied by immunoblotting, enzyme-linked immunosorbent assay (ELISA), as well as selective absorption of patient sera by expressed protein fragments. Autoantibodies to BCOADC-E2 map within peptides spanning amino acid residues 1 to 227 of the mature protein; our data demonstrate that the epitope is dependent on conformation and includes the lipoic acid binding region. However, only the full-length clone (amino acid residue 1 to 421) is sufficient to remove all detectable BCOADC-E2 reactivity. Moreover, the absence of lipoic acid on the recombinant polypeptides used in this study indicates that antibody binding to BCOADC-E2 is not dependent on the presence of lipoic acid.

Original languageEnglish (US)
Pages (from-to)505-513
Number of pages9
JournalHepatology
Volume22
Issue number2
DOIs
StatePublished - 1995

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Biliary Liver Cirrhosis
Autoantibodies
Epitopes
Thioctic Acid
Immunodominant Epitopes
Clone Cells
Autoantigens
Autoimmune Diseases
Dihydrolipoyllysine-Residue Acetyltransferase
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
Keto Acids
Amino Acids
Peptides
Immunoblotting
dihydrolipoamide acyltransferase
Blood Proteins
Oxidoreductases
Complementary DNA
Enzyme-Linked Immunosorbent Assay
Antibodies

ASJC Scopus subject areas

  • Hepatology

Cite this

Autoantibodies to BCOADC-E2 in patients with primary biliary cirrhosis recognize a conformational epitope. / Leung, Patrick S; Chuang, David T.; Wynn, R. Max; Cha, Sanghoon; Danner, Dean J.; Ansari, Aftab; Coppel, Ross L.; Gershwin, M. Eric.

In: Hepatology, Vol. 22, No. 2, 1995, p. 505-513.

Research output: Contribution to journalArticle

Leung, Patrick S ; Chuang, David T. ; Wynn, R. Max ; Cha, Sanghoon ; Danner, Dean J. ; Ansari, Aftab ; Coppel, Ross L. ; Gershwin, M. Eric. / Autoantibodies to BCOADC-E2 in patients with primary biliary cirrhosis recognize a conformational epitope. In: Hepatology. 1995 ; Vol. 22, No. 2. pp. 505-513.
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abstract = "Primary biliary cirrhosis (PBC) is an autoimmune disease of liver associated with a unique serologic response to mitochondrial autoantigens. Many of the autoantigens recognized by autoantibodies in PBC are members of the 2-oxo-acid dehydrogenase complex. The two major autoantigens are the E2 component of the pyruvate dehydrogenase complex (PDC-E2) and the E2 component of the branched chain 2-oxo-acid dehydrogenase complex (BCOADC-E2). The autoantibody response to PDCE2 has been mapped to one immunodominant epitope, which consists of both linear and conformational components. The presence of a single immunodominant epitope in PDC-E2 is unusual when contrasted to the immune response to autoantigens in other human autoimmune diseases. We have mapped the epitope recognized by antimitochondrial autoantibodies (AMA) specific to BCOADC-E2 in patients with PBC by taking advantage of the full-length bovine BCOADC-E2 complementary DNA (cDNA) and a series of expression clones spanning the entire molecule. Reactivity to the various expression clones was studied by immunoblotting, enzyme-linked immunosorbent assay (ELISA), as well as selective absorption of patient sera by expressed protein fragments. Autoantibodies to BCOADC-E2 map within peptides spanning amino acid residues 1 to 227 of the mature protein; our data demonstrate that the epitope is dependent on conformation and includes the lipoic acid binding region. However, only the full-length clone (amino acid residue 1 to 421) is sufficient to remove all detectable BCOADC-E2 reactivity. Moreover, the absence of lipoic acid on the recombinant polypeptides used in this study indicates that antibody binding to BCOADC-E2 is not dependent on the presence of lipoic acid.",
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