Overexpression of Bcl-2 inhibits nuclear localization of annexin I during tumor necrosis factor-alpha-mediated apoptosis in porcine renal LLC-PK 1 cells

Abstract

The addition of tumor necrosis factor (TNF)-α into the cultured porcine kidney LLC-PK 1 cells caused apoptosis concomitantly with caspase-3 activation and the inductions of an endogenous Bcl-2 protein. An SDS-polyacrylamide electrophoretic analysis revealed that a 37-kDa protein in a nuclear fraction was increased during TNF-α-induced apoptosis. Partial amino acid sequence of the protein was A–L–T–G–H–L–E–E–V, perfectly matching that of annexin I. Immunocytochemistry revealed that annexin I migrated to the nucleus and/or peri-nucleus region upon exposure to TNF-α. Overexpression of Bcl-2 proteins inhibited the nuclear localization of annexin I during TNF-α-induced apoptosis. Antisense oligodeoxynucleotides complementary to annexin I-inhibited TUNEL (terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labelling) staining in TNF-α-treated cells, suggesting that annexin I expression is a possible prerequisite for the induction of apoptosis by the cytokine. Thus, it is first time to show that annexin I is regulated by an anti-apoptotic Bcl-2 protein in TNF-α-induced renal apoptotic events.