Wang Jian-zhi

The effect ofcdk-5 overexpression and overactivation on tau hyperphosphorylation in cultured N2a cells

Neurofibrillary tangles (NFTs) are one of the neuropathological hallmarks of Alzheimers disease (AD) and abnormally hyperphosphorylated tau is the major protein of NFTs. It was reported that cyclin-dependent kinase5 (Cdk-5) could phosphorylate tau at most AD-related epitopes in vivo. In this study, we investigated the effect ofcdk-5 overexpression on tau hyperphosphorylation in neuroblastoma N2a cells. We demonstrated that overexpression ofcdk-5 which resulted in a 3.5-fold Cdk-5 activation in the transfected cells induced a dramatic increase in phosphorylation of tau at several phosphorylation sites. Overexpression ofcdk-5 led to a reduced staining with antibody Tau-1 and an enhanced staining with antibody PHF-1, suggesting hyperphosphorylation of tau at Ser 199/202 and Ser396/404 sites. It implies that in vitro overexpression ofcdk-5 leads to Cdk-5 overactivation and tau hyperphosphorylation may be the underline mechanism.

Overinhibition of Mitogen.Activated Protein Kinase Inducing Tau Hyperphosphorylation

To reveal the relationship between mitogen-activated protein kinese (MAPK) and tau phosphorylation, we used different concentration of PD98059, an inhibitor of MEK (MAPK kinase), to treat mice neuroblastma (N2a) cell line for 6 h. It showed that the activity of MAPK decreased in a dose-dependent manner. But Western blot and immunofluorescence revealed that just when the cells were treated with 16 μmol/L PD98059, tau was hyperphosphorylated at Ser396/404 and Ser199/202 sites. We obtained the conclusion that overinhibited MAPK induced tau hyperphosphorylation at Ser396/404 and Ser199/202 sites.

Development of an ultrasensitive ELISA-bienzyme colorimetric substrate recycle assay for measurement of Tau

On the basis of conventional enzyme-linked immunosorbent assay (ELISA) and bienzyme substrate recycle, ELISA-bienzyme colorimetric substrate recycle was developed in the present study. The sensitivity of this method increased 15 times than that of ELISA for the measurement of Tau and increased 55 times forp-Tau. The linear detective rang of this method expanded 3 times higher than that of conventional ELISA for Tau and had the same as ELISA forp-Tau. So, ELISA-bienzyme colorimetric substrate recycle could be used to detect alnormally phosphorylated tau in cerebrospinal fluid.

Spatial Memory Deficit and Tau Hyperphosphorylation Induced by Inhibiting PP2A in Rat Brain

Hyperphosphorylation of Tau in Alzheimer’s disease (AD) brain appears to be caused by a down-regulation of protein phosphatase 2A (PP2A). In this study, we selectively inhibited PP2A by injection of okadaic acid (OA) into the Meynert nucleus basalis of rats and found that 0.4 pmol of OA injection induced approximately 60% inhibition of PP2A 24 h after injection, 13% inhibition 48 h after injection and no obvious inhibition 72 h after injection. Hyperphosphorylation of Tau at Ser-198/Ser-199/Ser-202 and Ser-396/Ser-404 and spatial memory deficit of, rats were induced 24 h after 0. 1 pmol of OA injection. This study suggests that a down-regulation of PP2A may underlie abnormal hyperphosphorylation of cytoskeletal proteins leading to neurofibrillary degeneration in AD.

A template of rat brain based on fMR ∗ 2 imaging∗

The development of functional magnetic resonance imaging (fMRI) technology has made it possible to carry out functional brain imaging experiments in small animals. Usually, group data is required to form the assessment of population, which can not only increase the sensitivity of the overall experiment, but also allow the generalization of the conclusion to the whole population. In order to average the signals of functional brain images from different subjects, it is necessary to put all the mapping images into the same standard space (template image). However, up to now, most animal brain templates remain unavailable and it must be done by ourselves. In this study, a template image based on the brains of eight male Wistar rats is obtained, and it is successfully used in our present Alzheimer disease (AD)-like rat model studies as template for spatially normalizing images to the same stereotaxical space. The fMRI results processed with statistical parametric mapping (SPM99) software are in agreement with the results from immunohistochemical experiment, which proves that this method is universally applicable to the pathologic models of other small animals and to human brain lesion studies.