Calpain-dependent Beclin1 cleavage stimulates senescence-associated cell death in HT22 hippocampal cells under the oxidative stress conditions

Abstract

Oxidative damage in neurons including glutamate excitotoxicity has been linked to increasing numbers of neuropathological conditions. Under these conditions, cells trigger several different cellular responses such as autophagy, apoptosis, necrosis and senescence. However, the connection between these responses is not well understood. In this study, we found that the 60-kDa BECN1 was specifically degraded to a 40-kDa fragment in hippocampal HT22 cells treated with 5 mM glutamate. Increased BECN1 cleavage was specifically associated with a decrease in cell viability under oxidative stress. Interestingly, this BECN1 cleavage was specifically inhibited by a calpain inhibitor ALLN but was not affected by other protease inhibitors. Also, the BECN1 cleavage was not detected in calpain-4-deficient cell lines. Furthermore, calpain cleaved BECN1 at a specific site between the coiled-coil domain and Bcl2 homology 3 domain, which is associated with the anti-apoptotic protein Bcl-2. Moreover, some cellular senescence markers, including beta-galactosidase, p21, p27(KiPl), p53 and p16(INK4A), increased proportionally to those of BECN1 cleaved fragments. These results suggest that calpain-mediated BECN1 cleavage under oxidative conditions is specifically associated with cell death induced by cellular senescence.