Detection of caspase-6 activity in the absence of endogenous lamin cleavage Caspase-6 activity can be localized to the nucleus, which is commonly associated with cell death and the cleavage of nuclear substrates such as lamin A, whereas a cytoplasmic localization of active caspase-6 as it is the case in neurodegeneration does not result in immediate apoptosis [5, 21, 32] . We therefore decided to test whether spiking of cell extracts with pure lamin A protein can detect active caspase-6 at early timepoints, before its translocation to the nucleus and cleavage of endogenous lamin A. To this end we transiently transfected COS7 cells with full-length human caspase-6, a system in which the enzyme auto-activates in the cytosol before translocating to the nucleus [32] . After transfection, the active form of caspase-6 becomes detectable by Western blotting at the 9 h timepoint (Fig. 5A) . After 24 h of incubation, low levels of endogenous lamin A cleavage were observed with the ELISA method, indicating that at this time point active caspase-6 is present in the nucleus (Fig. 5B) . However, when cell lysates were supplemented with purified lamin A protein and endogenous, active caspase-6 was allowed to cleave the spiked protein, activity could already be detected after 9 h and increased dramatically at later time points (Fig. 5B ), in agreement with the Western blot data (Fig. 5A ). This indicates that the spiking method can detect caspase-6 activity before endogenous lamin is cleaved and is thus suitable to detect non-nuclear caspase-6 activity.