Coilin is a substrate for calpain-1. (A) Calpain digests bacterial expressed His-T7-tagged coilin. His-coilin was incubated alone, with 1mM CaCl2 or with both 1mM CaCl2 and calpain-1 (0.5 U) at 30°C for 15 minutes. Following incubation, reactions were subjected to SDS-PAGE, Western transfer, and blots probed with polyclonal H300 anti-coilin antibodies. An arrow marks an additional coilin fragment of around 50 kDa. (B) Calpain digests endogenous coilin. U2OS cell lysates were incubated alone, or with a combination of 1mM CaCl2, calpain (1U), and the calpain inhibitor ALLN (0.5 mM) at 30°C for 15 minutes. Following incubation, reactions were subjected to SDS-PAGE, Western transfer, and blots probed with polyclonal anti-coilin H300 antibodies.