Caspase-12 mediates endoplasmic-reticulum-specific apoptosis and cytotoxicity by amyloid-β

Abstract

Apoptosis, or cellular suicide, is important for normal development and tissue homeostasis, but too much or too little apoptosis can also cause disease^1,2. The family of cysteine proteases, the so-called caspases, are critical mediators of programmed cell death³, and thus far 14 family members have been identified. Some of these, such as caspase-8 (refs 4, 5), mediate signal transduction downstream of death receptors located on the plasma membrane. Others, such as caspase-9 (ref. 6), mediate apoptotic signals after mitochondrial damage. Stress in the endoplasmic reticulum (ER) can also result in apoptosis⁷. Here we show that caspase-12 is localized to the ER and activated by ER stress, including disruption of ER calcium homeostasis and accumulation of excess proteins in ER, but not by membrane- or mitochondrial-targeted apoptotic signals. Mice that are deficient in caspase-12 are resistant to ER stress-induced apoptosis, but their cells undergo apoptosis in response to other death stimuli. Furthermore, we show that caspase-12-deficient cortical neurons are defective in apoptosis induced by amyloid-β protein but not by staurosporine or trophic factor deprivation. Thus, caspase-12 mediates an ER-specific apoptosis pathway and may contribute to amyloid-β neurotoxicity.