title: Up-regulation of mitogen-activated protein kinases ERK1/2 and MEK1/2 is associated with the progression of neurofibrillary degeneration in Alzheimer's disease.
abstract: The abnormal hyperphosphorylation of tau in Alzheimer's disease (AD) has been proposed to involve the extracellular-signal-regulated protein kinase (ERK) of the mitogen-activated protein (MAP) kinase family. ERK is phosphorylated and thereby activated by MAP kinase kinase (MEK). In the present study, we determined the intracellular and regional distribution of the active forms of both MEK1/2 and ERK1/2, i.e. p-MEK1/2 and p-ERK1/2 in the entorhinal, hippocampal, and temporal cortices of 49 brains staged for neurofibrillary changes according to Braak and Braak's protocol. We found that p-MEK1/2 and p-ERK1/2 were present in the initial stages of neurofibrillary degeneration in the projecting neurons in the transentorhinal region, and extended into other brain regions co-incident with the progressive sequence of neurofibrillary changes up to and including Braak stage VI. It appeared that the accumulation of p-MEK1/2 and p-ERK1/2 was initiated in the cytoplasm of pretangle neurons in varying size granules, which grew into large aggregates co-existing with the progressive development of neurofibrillary tangles. Accumulation of p-MEK1/2 and p-ERK1/2 was found in cases with stages I-III neurofibrillary degeneration, which were devoid of amyloid deposition. These data provide direct in situ evidence consistent with the possible involvement of MAP kinase pathway in the hyperphosphorylation of tau and the presence of this lesion before deposition of beta-amyloid in AD.
authors.affiliation: Karolinska Institutet, NEUROTEC, Division of Experimental Geriatrics, Novum, KFC Plan 4, Novum, S-141 86, Huddinge, Sweden. jin-jing.pei@neurotec.ki.se
authors.forename: Jin-Jing
authors.initials: JJ
authors.lastname: Pei
authors.forename: Heiko
authors.initials: H
authors.lastname: Braak
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: An
authors.forename: Bengt
authors.initials: B
authors.lastname: Winblad
authors.forename: Richard F
authors.initials: RF
authors.lastname: Cowburn
authors.forename: Khalid
authors.initials: K
authors.lastname: Iqbal
authors.forename: Inge
authors.initials: I
authors.lastname: Grundke-Iqbal
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism; D005260:Female; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008297:Male; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009454:Neurofibrils / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology*; D016875:tau Proteins / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D016875:tau Proteins; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases