Bcl-2–dependent oxidation of pyruvate dehydrogenase-E2, a primary biliary cirrhosis autoantigen, during apoptosis
Joseph A. Odin, … , Nicholas F. LaRusso, Antony Rosen
Joseph A. Odin, … , Nicholas F. LaRusso, Antony Rosen
Published July 15, 2001
Citation Information: J Clin Invest. 2001;108(2):223-232. https://doi.org/10.1172/JCI10716.
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Article

Bcl-2–dependent oxidation of pyruvate dehydrogenase-E2, a primary biliary cirrhosis autoantigen, during apoptosis

Abstract

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.

Authors

Joseph A. Odin, Robert C. Huebert, Livia Casciola-Rosen, Nicholas F. LaRusso, Antony Rosen

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Figure 4

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Persistence of PDC-E2 staining by PBC patient sera in apoptotic cells is...
Persistence of PDC-E2 staining by PBC patient sera in apoptotic cells is cell-type dependent and independent of the stimulus used to induce apoptosis. Both control cells and cells treated with UV-B or staurosporine (STS) to induce apoptosis were examined by confocal, immunofluorescence microscopy. Cells were stained with DAPI (a–h) to distinguish apoptotic cells (cells labeled with stars) from nonapoptotic cells (unlabeled cells). After UV-B treatment, PBC patient sera staining of PDC-E2 was detected in apoptotic HSGs (j), but not in apoptotic Jurkat T cells (l). When inducing apoptosis with STS, PDC-E2 immunoreactivity again was undetectable in apoptotic HeLa (n), while persisting in apoptotic NRCs (p), and was undetectable in apoptotic HeLa (n). Bars, 20 μm. All cell types were stained independently with two different PDC-E2 monospecific sera at least three times with similar results each time. Representative images are shown.