LEVELS OF TAU-PHOSPHORYLATION AT DIFFERENT SITES IN ALZHEIMER-DISEASEBRAIN

THE microtubule-associated protein tau is abnormally hyperphosphorylat ed in Alzheimer's disease (AD) brain. To date, 21 phosphorylated sites of tau have been identified. In the present study the levels of phosp horylation at Ser(199)/Ser(202), Thr(231)/Ser(235), Ser(262)/Ser(356) and Ser(196)/Ser(404) of tau in AD brain homogenate and its 100 000 x g supernatant were determined using radioimmuno-dot-blot assay. In hom ogenate, Ser(199)/Ser(202) and Ser(262)/Ser(356) were phosphorylated t o similar level and were more phosphorylated than Thr(231) Or Ser(396) /Ser(404). In supernatant, there was no significant difference in phos phorylated tau level among the investigated sites except for Thr(231)/ Ser(235) which was least phosphorylated. These results suggest that Se r(199)/Ser(202) and Ser(262)/Ser(356) are major sites of phosphorylati on of tan in AD brain. NeuroReport 9: 2375-2379 (C) 1998 Rapid Science Ltd.