Mf. Chiang et al., REVERSIBLE HEAT STRESS-RELATED LOSS OF PHOSPHORYLATED ALZHEIMER-TYPE EPITOPES IN TAU PROTEINS OF HUMAN NEUROBLASTOMA-CELLS, The Journal of neuroscience, 13(11), 1993, pp. 4854-4860
Human neuroblastoma cells, LAN, were used to study the phosphorylation
and dephosphorylation of tau proteins. These cells contained mainly a
form of tau comparable to fetal brain tau in molecular weight (55 kDa
). Neuroblastoma tau reacted with antibodies that recognize epitopes s
panning the whole tau molecule (E-1, Alz50, Tau-1, and Tau46), and ant
ibodies (PHF-1, NP8, and T3P) that recognize hyperphosphorylated tau (
PHF-tau) in Alzheimer's disease (AD) brains. Exposure of the cells to
45-degrees-C heat stress resulted in dephosphorylation of the epitopes
recognized by PHF- 1, NP8, and T3P. Transfer of the heat-stressed cel
ls to 37-degrees-C led to rephosphorylation of the dephosphorylated ep
itopes. Cells that had been treated with okadaic acid (OA), regardless
of whether they were subsequently subjected to heat stress or heat st
ress and recovery, all contained tau with a molecular weight similar t
o that of control cells. These tau proteins, similar to tau in control
cells, also reacted with antibodies to phosphorylated epitopes. Howev
er, unlike the tau from control or heat-stressed cells, the OA-treated
and heat-stressed tau had decreased reactivity with Tau-1. Alteration
of Tau-1 immunoreactivity has been reported to be an early event in A
D neurodegeneration. The reduction of Tau-1 immunoreactivity observed
in OA-treated samples could be restored by incubation of electroblots
of isolated tau with alkaline phosphatase, indicating an induction of
the Tau-1 epitope phosphorylation by OA. The results of our studies su
ggest that neuroblastoma cells may contain phosphatases/kinases that a
re comparable to that in AD, and that culture cells may be used for st
udying the mechanisms involved in AD neurofibrillary formation.