ScientificWorldJournal. 2001 Jan 1;1(S3):91
Altznauer F, Simon HU.
Calpain is a calcium-activated neutral cysteine-protease, which exists in two isoforms: mu-calpain (lower calcium requirement) and m-calpain (higher calcium requirement).
Both isoforms are ubiquitously expressed and exist as heterodimers of regulatory p30- and catalytic p80-subunits.
Calpain has recently been shown to be involved in the onset of several neurological diseases, such as Alzheimer disease and multiple sclerosis.
Calpain is activated in apoptotic cells via degradation of its endogenous inhibitor calpastatin, leading to degradation of the p30-subunit and autoproteolytic activation of the p80-subunit.
There are several known proteolytic targets of the calpains, including fodrin, caspase-12, I-kappaB and bax.
In this report, we show that calpain is part of the CD95-mediated apoptotic pathway and cleaves bax into its proapoptotic form, which mediates breakdown of the mitochondrial potential and the activation of caspase-3.