N- and C-terminal cleavage of β-catenin by a caspaselike protease in response to anti-Fas.

(A) Tetrapeptide caspase inhibitors block β-catenin cleavage induced by anti-Fas. Jurkat cells were preincubated for 30 minutes with various inhibitors as indicated and then treated with 100 ng/mL anti-Fas for an additional 6 hours at 37°C. Untreated control cells were compared with cells treated with anti-Fas or cells treated with anti-Fas and ALLnL (100 μM), YVAD-CMK, ZVAD-FMK, ZDEVD-FMK, or BD-FMK (20 μM each). The cathepsin inhibitor ZFA-FMK (20 μM) was used as a negative control reagent for peptide-FMK compounds. (B) Differential recognition of cleaved β-catenin by 3 anti–β-catenin antibodies. Untreated log phase Jurkat cells were compared with cells treated with anti-Fas (100 ng/mL) for the time indicated. Control and apoptotic Jurkat cell lysates were analyzed for β-catenin by Western blotting with anti–β-catenin antibodies that recognize amino acids 56 to 75, 571 to 781, and 768 to 781. (C) Schematic diagram indicates location of structure-function elements in β-catenin protein and regions recognized by anti–β-catenin antibodies.