DEPHOSPHORYLATION OF TAU-PROTEIN FROM ALZHEIMERS-DISEASE PATIENTS

Tau protein-prepared post-mortem from brains of Alzheimer's disease patients was treated with protein phosphatase 1 catalytic subunit, 2A catalytic subunit, and 2B (calcineurin). Dephosphorylation was monitored by immunoblotting with two monoclonal antibodies, TAU-1 and SMI31, which recognize in tau the dephospho- and phospho-states, respectively, of proline-directed protein kinase phosphorylation sites. Out of the three enzymes tested, protein phosphatase 2A was only effective in dephosphorylating tau at these Alzheimer-type epitopes.