Caspase-6 (Csp-6) is activated in the early stages in Alzheimer’s disease and is sequestered to the neurites of neuropil threads, neuritic plaques and neurofibrillary tangles (Guo et al., A.J.P., 2004), suggesting a role for Csp-6 in neurodegeneration. Many Csp-6 substrates in non-neuronal cells types are intermediate filament proteins like vimentin, cytokeratin 18 and desmin or microtubule-associated protein, tau. Proteomic analysis allowed us to identify Csp-6 substrates (Petzke et al., SfN, 2005). Two of these, beta-actin and alpha-tubulin, are cytoskeleton proteins. The objective of this work is to determine the effect of Csp-6-cleaved beta-actin and alpha-tubulin on the cytoskeleton structure. In vitro, beta-actin is cleaved by Csp-6 at 3 different sites: after aspartate 14, aspartate 179 and aspartate 244. Beta-actin cleavage by Csp-6 at aspartate 244 is the same site previously described to be cleaved by Csp-3 and this cleavage site is recognized by the neoepitope Fractin antibody (kind gift from Gr...