Binding of calpain fragments to calpastatin

Engineering Calpastatin to Develop a Sensor to Detect Active Calpain

Caspase-mediated fragmentation of calpain inhibitor protein calpastatin during apoptosis.

Two cysteine protease families (caspase and calpain) participate in apoptosis. Here we report that the endogenous calpain inhibitor calpastatin is fragmented by caspase(s) to various extents during early apoptosis in two cell types. In anti-fas or staurosporine-treated Jurkat T-cells, the high-molecular-weight form (HMW) of calpastatin (apparent Mr 110 K) was extensively degraded to immunoreact...

Changes in intracellular localization of calpastatin during calpain activation.

Localization of the two main components of the Ca(2+)-dependent proteolytic system has been investigated in human neuroblastoma LAN-5 cells. Using a monoclonal antibody which recognizes the N-terminal calpastatin domain, it has been shown that this inhibitory protein is almost completely confined in two granule-like structures not surrounded by membranes. Similar calpastatin distribution has be...

Inhibition of human mu-calpain by conformationally constrained calpastatin peptides.

The 27-mer peptide CP1B-[1-27] derived from exon 1B of calpastatin stands out among the known inhibitors for mu- and m-calpain due to its high potency and selectivity. By systematical truncation, a 20-mer peptide, CP1B-[4-23], was identified as the core sequence required to maintain the affinity/selectivity profile of CP1B-[1-27]. Starting with this peptide, the turn-like region Glu(10)(i)-Leu(...

Calpastatin subdomains A and C are activators of calpain.

The inhibitory domains of calpastatin contain three highly conserved regions, A, B, and C, of which A and C bind calpain in a strictly Ca(2+)-dependent manner but have no inhibitory activity whereas region B inhibits calpain on its own. We synthesized the 19-mer oligopeptides corresponding to regions A and C of human calpastatin domain I and tested their effect on human erythrocyte mu-calpain a...