title: Involvement of I2PP2A in the abnormal hyperphosphorylation of tau and its reversal by Memantine.
abstract: The activity of protein phosphatase (PP)-2A, which regulates tau phosphorylation, is compromised in Alzheimer disease brain. Here we show that the transient transfection of PC12 cells with inhibitor-2 (I2PP2A) of PP2A causes abnormal hyperphosphorylation of tau at Ser396/Ser404 and Ser262/Ser356. This hyperphosphorylation of tau is observed only when a sub-cellular shift of I2PP2A takes place from the nucleus to the cytoplasm and is accompanied by cleavage of I2PP2A into a 20 kDa fragment. Memantine, an un-competitive inhibitor of N-methyl-D-aspartate receptors, inhibits this abnormal phosphorylation of tau and cell death and prevents the I2PP2A-induced inhibition of PP2A activity in vitro. These findings demonstrate novel mechanisms by which I2PP2A regulates the intracellular activity of PP2A and phosphorylation of tau, and by which Memantine modulates PP2A signaling and inhibits neurofibrillary degeneration.
authors.affiliation: Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314-6399, USA.
authors.forename: Muhammad Omar
authors.initials: MO
authors.lastname: Chohan
authors.forename: Sabiha
authors.initials: S
authors.lastname: Khatoon
authors.forename: Inge-Grundke
authors.initials: IG
authors.lastname: Iqbal
authors.forename: Khalid
authors.initials: K
authors.lastname: Iqbal
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D006801:Humans; D008559:Memantine / Q000494:pharmacology*; D016716:PC12 Cells; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport; D051381:Rats; D014157:Transcription Factors / Q000378:metabolism*; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; C513473:SET protein, human; D014157:Transcription Factors; D016875:tau Proteins; D010749:Phosphoprotein Phosphatases; D008559:Memantine