Role of cytokines in the gene expression of amyloid β-protein precursor: Identification of a 5′-UTR-Binding nuclear factor and its implications in Alzheimer's disease

One of the major neuropathological characteristics of Alzheimer's disease (AD) is the brain depositions of senile plaques that are mainly composed of toxic amyloid beta-peptide (A beta), which is generated from a family of A beta containing precursor proteins (A beta PP; 695-770 amino acids). The role of cytokines and growth factors has been implicated in the pathogenesis of AD. Our goal is to determine the mode of action of cytokines on the regulation of A beta PP gene expression. Here we studied the effect of different cytokines on the activity of 5'-untranslated region (5'-UTR) of A beta PP mRNA in human astrocytic cells (U-373). We compared A beta PP-5'-UTR activity in the presence of interleukin-1 (IL-1 alpha and IL-1 beta), transforming growth factor (TGF-beta 1) and tumor necrosis factor TNF-alpha 1. The astrocytic cells, which were treated separately with these agents, were transfected with either the vector (pSV2CAT) or pSV2UTR-CAT construct containing 90 bp of A beta PP 5'-UTR (+54 to 144 bp). This region was cloned upstream of a reporter chloramphenicol acetyl transferase gene (CAT). Our results indicate that the treatment of pSV2UTR-CAT-transfected cells with either IL-1 alpha, IL-1 beta, TGF-beta 1 or TNF-alpha 1 stimulated reporter gene activity in a factor-specific manner. This was consistent with their effects on elevating A beta PP protein levels. Transfection of the same cells with the pSV2CAT vector lacking 5'-UTR resulted in a reduced reporter gene activity with all treatments studied. DNA-gel shift experiments indicate that the 54/144 region binds to a nuclear protein(s) in a cell type specific manner. These results suggest that 5'-UTR of the A beta PP gene can respond to the stimulation of different cytokines, which likely regulate A beta PP transcription and translation via regulatory elements present in the A beta PP promoter and in 5'-UTR, respectively. The characterization of A beta PP regulatory elements, including the 5'-UTR, will accelerate the development of novel agents against new targets for AD.