Role of the over-expression of cyclin dependent kinase-5 in the phosphorylation of neurofilament

Juan CHEN; Youmei FENG; Yipeng WANG; Jie ZHOU; Jianzhi WANG

ABSTRACT

BACKGROUND:

One of the key neuropathological changes in Alzheimer disease is that neurofibrils over phosphorylated cytoskeletal protein (such as r and neurofilaments) composed of entwist together, and the phosphorylation of τ protein can be catalyzed by cyclin dependent kinase 5 (CDK5),however whether the phosphorylation of neurofilaments can be catalyzed by CDK5, as well as its role in the pathogenesis of Alzheimer diseases is less acknowledged.

OBJECTIVE:

To explore the role of over-expression of intracellular CDK5 in the phosphorylation of neurofilaments

DESIGN:

Randomized controlled study.

SETTING:

Biochemical and Molecular Biological Department of Tongji Medical College, Huazhong University of Science and Technology.MATERIALS This study was conduced at Biochemical and Molecular Biological Department of Tongji Medical College, Huazhong University of Science and Technology between February and May 2001. In vitro cultured rat neuroblastoma cell strain (N2a) was adopted as subjects.

METHODS:

In vitro cultured N2a cells were divided into 2 groups, namely transfection group and non-transfection group. In transfection group,CDK5 gene was transfected into N2a cell line by using liposome transfection technique so as to obtain N2a/CDK5 cell line stably expressing CDK5, immune-precipitation and enzyme activity assay was used to detect the CDK5 activity, meanwhile immunofluorescence technique and immuneblot assay was used to detect CDK5 expression and phosphorylation of neurofilaments.MAIN OUTCOME

MEASURES:

Phosphorylation of neurofilaments in both groups.

RESULTS:

In transfection group of N2a cell line, CDK5 expression increased presented by deep coloration of SMI31 antibody and weak coloration of SMI32 antibody, implying hyper-phosphorylation of neurofilaments. Meanwhile, the activity of CDK5 was 3.5 times higher than that in non-transfection group.

CONCLUSION:

Intracellular over-expressison of CDK5 would lead to hyperactivity of CDK5 and hyper-phosphorylation of neurofilaments, however the hyper-phosphorylation of neurofilamentsmight invlove in the pathological development of AD.