TY - JOUR
T1 - Contribution to antimitochondrial antibody production
T2 - Cleavage of pyruvate dehydrogenase complex-E2 by apoptosis-related proteases
AU - Matsumura, Shuji
AU - Van De Water, Judy
AU - Kita, Hiroto
AU - Coppel, Ross L.
AU - Tsuji, Takao
AU - Yamamoto, Kazuhide
AU - Ansari, Aftab A.
AU - Gershwin, M. Eric
PY - 2002
Y1 - 2002
N2 - Patients with PBC produce a directed, specific response to a single immunodominant autoepitope of PDC-E2 within the inner lipoyl domain. In contrast, immunized animals react to multiple epitopes and rarely recognize the inner lipoyl domain. In other autoimmune diseases, apoptosis plays a critical role in antigen presentation; the caspases and granzyme B are the key proteases in the generation of autoepitopes. To determine the specific cleavage pattern of full-length recombinant PDC-E2, we performed in vitro digestion with caspases-3, -6, -8 and granzyme B. The resulting fragments were immunoblotted and probed with an extensive panel of monoclonal anti-PDC-E2 antibodies and sera from patients with PBC. Interestingly, on granzyme B digestion, PDC-E2 lost reactivity, suggesting the destruction of the immunodominant epitope. Because this site contains the major epitope for both B cells and T cells, it suggests that granzyme B is unlikely to be involved in generation of autoepitopes in primary biliar cirrhosis (PBC). In contrast, following treatment with the caspase enzymes, immunoreactive fragments were generated. Indeed, by confocal microscopy, activated caspase-3 is found in the marginal hepatocytes and bile ducts. Moreover, caspase-3 staining was strongest in the small intrahepatic bile ducts, the major site of tissue destruction in PBC. In conclusion, these data suggest that following apoptosis, the caspase family of proteolytic enzymes have the potential to generate immunogenic fragments that contribute to the autoantigen reservoir and the production of antimitochondrial antibodies. These findings are also consistent with the generation of an autoimmune response against an intracellular antigen that evades catabolism during apoptosis.
AB - Patients with PBC produce a directed, specific response to a single immunodominant autoepitope of PDC-E2 within the inner lipoyl domain. In contrast, immunized animals react to multiple epitopes and rarely recognize the inner lipoyl domain. In other autoimmune diseases, apoptosis plays a critical role in antigen presentation; the caspases and granzyme B are the key proteases in the generation of autoepitopes. To determine the specific cleavage pattern of full-length recombinant PDC-E2, we performed in vitro digestion with caspases-3, -6, -8 and granzyme B. The resulting fragments were immunoblotted and probed with an extensive panel of monoclonal anti-PDC-E2 antibodies and sera from patients with PBC. Interestingly, on granzyme B digestion, PDC-E2 lost reactivity, suggesting the destruction of the immunodominant epitope. Because this site contains the major epitope for both B cells and T cells, it suggests that granzyme B is unlikely to be involved in generation of autoepitopes in primary biliar cirrhosis (PBC). In contrast, following treatment with the caspase enzymes, immunoreactive fragments were generated. Indeed, by confocal microscopy, activated caspase-3 is found in the marginal hepatocytes and bile ducts. Moreover, caspase-3 staining was strongest in the small intrahepatic bile ducts, the major site of tissue destruction in PBC. In conclusion, these data suggest that following apoptosis, the caspase family of proteolytic enzymes have the potential to generate immunogenic fragments that contribute to the autoantigen reservoir and the production of antimitochondrial antibodies. These findings are also consistent with the generation of an autoimmune response against an intracellular antigen that evades catabolism during apoptosis.
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U2 - 10.1053/jhep.2002.30280
DO - 10.1053/jhep.2002.30280
M3 - Article
C2 - 11786955
AN - SCOPUS:0036139024
VL - 35
SP - 14
EP - 22
JO - Hepatology
JF - Hepatology
SN - 0270-9139
IS - 1
ER -