maitotoxin and lactacystin

We demonstrate here that both procaspase-3 (32 kDa) and PARP are calpain substrates. In calcium-channel opener maitotoxin-treated cells, a 30 kDa caspase-3 fragment is produced in a time and concentration-dependent manner. Formation of this fragment is prevented by calpain inhibitors but not by the pancaspase inhibitor, carbobenzoxy-Asp-CH(2)OC(O)-2,6-dichlorobenzene (Z-D-DCB) nor the selective proteasome inhibitor lactacystin. In maitotoxin-treated cells, PARP (113 kDa) is also cleaved into a 40 kDa immunoreactive fragment, in a calpain-inhibitor-sensitive manner. Both procaspase-3 and PARP are also cleaved in vitro by purified micro-calpain to a 30 kDa fragment and a 40 kDa fragment, respectively. Finally, we show that staurosporine-mediated caspase-3 activation is interrupted by maitotoxin pretreatment.

Topics: Acetylcysteine; Aspartic Acid; Calpain; Caspase 3; Caspase Inhibitors; Caspases; Cell Line; Cysteine Proteinase Inhibitors; Enzyme Activation; Enzyme Precursors; Humans; Marine Toxins; Oxocins; Poly(ADP-ribose) Polymerases; Protein Processing, Post-Translational; Staurosporine; Substrate Specificity