Small heat shock proteins Hsp27 or alphaB-crystallin and the protein components of neurofibrillary tangles: tau and neurofilaments.
The heat-shock proteins (HSPs) Hsp27 and alphaB-crystallin are up-regulated in Alzheimer's disease (AD), but the extent of this and the consequences are still largely unknown. The HSPs are involved in protein degradation and protection against protein aggregation, and they interact with several cytoskeletal components such as microtubules (MT) and neurofilaments (NF). AD pathology includes aggregated proteins (tau, NF), decreased protein degradation, and cytoskeletal disruption. It is thus of interest to investigate more closely the possible roles of the HSPs in AD pathology. The expressions of Hsp27 and alphaB-crystallin in AD brain samples were significantly increased (by approximately 20% and approximately 30%, respectively) and correlated significantly with phosphorylated tau and NF proteins. To investigate the consequences of increased HSP levels on tau and NF regulation, N2a cells were transfected with Hsp27 or alphaB-crystallin constructs, and overexpression of the HSPs was confirmed in the cells. Increased tau phosphorylation at the Ser262 site in the N2a cells was regulated by Hsp27 overexpression (possibly through p70S6k), whereas the overexpression of alphaB-crystallin resulted in decreased levels of phosphorylated tau, NF, and GSK-3beta. It was also shown that overexpression of HSPs causes an increase in the percentage of cells present in the G(1) phase. The results presented suggest that a cellular defense against dysregulated proteins, in the form of Hsp27 and alphaB-crystallin, might contribute to the cell cycle reentry seen in AD cells. Furthermore, Hsp27 might also be involved in AD pathology by aggravating MT disruption by tau phosphorylation.
Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, KI-Alzheimer's Disease Research Center, Novum, Huddinge, Sweden.
Cecilia
C
Björkdahl
Magnus J
MJ
Sjögren
Xinwen
X
Zhou
Hernan
H
Concha
Jesus
J
Avila
Bengt
B
Winblad
Jin-Jing
JJ
Pei
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D005260:Female; D005434:Flow Cytometry; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D006801:Humans; D015151:Immunoblotting; D008297:Male; D051379:Mice; D008875:Middle Aged; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D016874:Neurofibrillary Tangles / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D016900:Neurofilament Proteins / Q000096:biosynthesis* / Q000378:metabolism; D010766:Phosphorylation; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D014162:Transfection; D038203:alpha-Crystallin B Chain / Q000096:biosynthesis*; D016875:tau Proteins / Q000096:biosynthesis* / Q000378:metabolism
D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D016900:Neurofilament Proteins; D038203:alpha-Crystallin B Chain; D016875:tau Proteins; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D038362:Glycogen Synthase Kinase 3