Because accumulation of PAR is a marker of PARP-1 cleavage and apoptotic cell death we chose to study the consequence of TWEAK on PARP-1 cleavage and PAR accumulation in neurons. Wt neurons were incubated with TWEAK as well as Western blot analysis with antibodies against either total PARP-1 or an 89 kDa fragment product of PARP-1 cleavage, or PAR. We learned that incubation with TWEAK raises the expression of total (un-cleaved) PARP-1, and induces its cleavage for an 89 kDa product with sub...