COMPLEMENTARY DISTRIBUTION OF TAU PROTEINS IN DIFFERENT PHOSPHORYLATION STATES WITHIN GROWING AXONS

MICROTUBULE-associated tau proteins are hyperphosphorylated in brains from patients with Alzheimer's disease compared with normal adult huma n brain. At least some of the phosphorylated residues are also transie ntly phosphorylated in juvenile brain, but not in more mature stages. Using the monoclonal anti-tau antibodies TAU-1 and AT8, we found in cu ltured embryonic chicken and rat neurones a clear differential distrib ution of immunostaining within growing axons. Tau proteins that are ph osphorylated at Ser202 (recognized by AT8) appear to be concentrated i n the axonal portion that is close to the cell body and they decrease in proximal-distal direction. In contrast, tau proteins carrying an ep itope that contains dephospho-Ser202 (recognized by TAU-1) are enriche d in the distal axon and the growth cone. In colchicine-treated, growt h-inhibited neurones there was an intense TAU-1 staining of the perika rya, but no longer any staining by AT8.