Figure 6.

Caspase-cleavage of tau induces a conformational epitope that is recognized by the antibody MC1 and can be phosphorylated by GSK3-β. (A) MC1, a mAb that recognizes an early tau conformational change, was coupled to protein G and used to immunoprecipitate either full-length (lane 1) or caspase-3–cleaved recombinant tau (lane 2). Western blot analysis of immunoprecipitated proteins probed with an anti-tau polyclonal antibody revealed an increased affinity of the MC1 antibody for ΔTau over full-length tau. (B) In vitro phosphorylation of ΔTau: Either full-length or caspase-3–cleaved tau was phosphorylated with the kinase GSK-3β and then analyzed by Western blot with the phosphorylation-dependent antibody PHF-1. Immunoreactivity for PHF-1 demonstrates that, like full-length tau (FL), caspase-cleaved tau (ΔTau) can be hyperphosphorylated and suggests that caspase-cleavage of tau does not preclude subsequent hyperphosphorylation. Numbers over each lane indicate the number of hours that tau species were incubated with GSK-3β. MC1 and PHF-1 experiments were replicated three times, and representative immunoblots are shown.