title: Tau hyperphosphorylation correlates with reduced methylation of protein phosphatase 2A.
abstract: The down-regulation of protein phosphatase 2A (PP2A) activity is thought to play an important role in the formation of tau hyperphosphorylation in the Alzheimer's disease (AD) brain. Methylation of the PP2A catalytic subunit at the L309 site can potently activate PP2A for some substrates via the increasing recruitment of its regulatory subunits into the holoenzyme. Abeta is overproduced yet estrogen is deficient in the brains of the menopausal AD patients. Both Abeta and estrogen deficiency can interact with tau kinases such as protein kinase B and glycogen synthase kinase 3. In the current study, levels of demethylated (-m) PP2A (L309) were significantly increased, and methylated (+m) PP2A (L309) were significantly decreased, which corresponded with the increased tau phosphorylation at the Tau-1 and PHF-1 sites in both mouse N2a cells carrying the human APP with Swedish mutation (APPswe) and transgenic APPswe/presenilin (PS) 1 (A246E) mice. These findings were replicated in wild-type N2a cells treated with Abeta25-35, and to a relatively larger extent, in both wild-type N2a cells and APPswe treated by okadaic acid, as well as in the brains of estrogen receptor (ER) alpha-/- and ERbeta-/- mice that mimic the status of estrogen deficiency in menopausal AD patients. Together, these findings suggested that the increased demethylation of PP2A (L309) mediated by Abeta overproduction or estrogen deficiency (ERalpha-/- and ERbeta-/-) may contribute to the reduced PP2A activity observed in the AD brain, resulting in the compromised dephosphorylation of abnormally hyperphosphorylated tau.
authors.affiliation: Karolinska Institutet, KI-Alzheimer Disease Research Center (KI-ADRC), Novum, Huddinge, Sweden.
authors.forename: Xin-Wen
authors.initials: XW
authors.lastname: Zhou
authors.forename: Jan-Ake
authors.initials: JA
authors.lastname: Gustafsson
authors.forename: Heikki
authors.initials: H
authors.lastname: Tanila
authors.forename: Cecilia
authors.initials: C
authors.lastname: Bjorkdahl
authors.forename: Rong
authors.initials: R
authors.lastname: Liu
authors.forename: Bengt
authors.initials: B
authors.lastname: Winblad
authors.forename: Jin-Jing
authors.initials: JJ
authors.lastname: Pei
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D020134:Catalytic Domain / Q000502:physiology; D002460:Cell Line; D015536:Down-Regulation / Q000502:physiology; D004967:Estrogens / Q000172:deficiency*; D005260:Female; D006801:Humans; D008297:Male; D008745:Methylation; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008875:Middle Aged; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D017698:Postmenopause / Q000378:metabolism; D011496:Protein Methyltransferases / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D004967:Estrogens; D011960:Receptors, Estrogen; D016875:tau Proteins; D011496:Protein Methyltransferases; D054648:Protein Phosphatase 2