Phosphothreonine-212 of Alzheimer abnormally hyperphosphorylated tau is a preferred substrate of protein phosphatase-1.
We isolated and characterized several phosphoseryl/phosphothreonyl phosphatase activities (P1-P11) from frontal lobe of six autopsied human brains. Of these, PP1 (P3) was a major tau phosphatase. The enzyme required metal ions and was maximally activated by Mn2+. Western blots with antibodies to known protein phosphatases showed PP1 and PP2B immunoreactivity. However, the removal of PP2B by immunoabsorption or its inhibition with EGTA did not result in appreciable loss of P3 activity. These observations suggest that P3 was an enriched PPI. Dephosphorylation of Alzheimer disease hyperphosphorylated tau (AD P-tau) by PP1 was site-specific. PPI preferentially dephosphorylated pT212 (40%), pT217 (26%), pS262 (33%), pS396 (42%) and pS422 (31%) of AD P-tau. Dephosphorylation of tau at pT181, pS199, pS202, pT205, pS214, and pS404, was undetectable. Of the sites dephosphorylated, pT212 was only a substrate for PP1, as purified/enriched PP2A and PP2B from the same brains did not dephosphorylate this site.
Rahman
Abdur
A
Department of Neurochemistry, New York Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314, USA.
Grundke-Iqbal
Inge
I
Iqbal
Khalid
K
D000244:Adenosine Diphosphate / Q000378:metabolism; D000544:Alzheimer Disease / Q000378:metabolism*; D000814:Aniline Compounds / Q000378:metabolism; D015153:Blotting, Western; D001923:Brain Chemistry; D019703:Calcineurin / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D002847:Chromatography, Agarose; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D019319:Okadaic Acid / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism*; D011107:Polylysine / Q000378:metabolism; D054645:Protein Phosphatase 1; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D014227:Triazines; D016875:tau Proteins / Q000378:metabolism*
D000814:Aniline Compounds; D002147:Calmodulin; D004791:Enzyme Inhibitors; D009943:Organophosphorus Compounds; D011994:Recombinant Proteins; D014227:Triazines; D016875:tau Proteins; D010769:Phosphothreonine; D019319:Okadaic Acid; D011107:Polylysine; C012842:Cibacron Blue F 3GA; D000244:Adenosine Diphosphate; C068798:4-aminophenylphosphate; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1