Activation and possible involvement of calpain, a calcium-activated cysteine protease, in down-regulation of apoptosis of human monoblast U937 cells.
An active form of calpain mu, a low-Ca(2+)-requiring intracellular cysteine protease, was detected using a cleavage site-directed antibody in apoptotic human monoblast U937 cells treated with tumor necrosis factor-alpha and interferon-gamma. Membrane-permeable calpain inhibitors accelerated apoptosis of U937 cells thus induced and suppressed the activation of procalpain. These findings suggest that calpain down-regulates apoptosis by shutting off the intracellular signals for cell death.
Kikuchi
H
H
Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108, Japan.
Imajoh-Ohmi
S
S