ERK-CREB Signaling Dysregulation with Increasing Levels of The β-amyloid Protein

Abstract

Introduction: alzheimer’s Disease is characterized by cognitive impairment and neurodegeneration, for which the pathogenic cause is considered to be the accumulation of the β-amyloid peptide (aβ42). The swedish and Indiana mutations of the amyloid precursor protein gene (appswe,Ind), found in the genetic familial form of aD, increase aβ42 levels due to augmented enzymatic cleavage. previous experiments demonstrate that high levels of soluble aβ42 upregulate extracellular regulated kinase 1/2 (eRK1/2) and downregulate cyclic amp-response element (CRe) binding protein (CReB) phosphorylation. Increasing levels of soluble aβ42 protein are hypothesized to dysregulate the eRK-CReB signalling pathway. Methods: Three plasmid constructs containing wild type amyloid precursor protein (appWt), appswe or appswe,Ind, each producing increasing levels of aβ42, were stably transfected into eukaryotic cell lines. Immunocytochemistry was performed using the mcsa1 antibody to measure the amount of aβ protein in the appswe,Ind and appWt cell lines. Cells were stimulated with forskolin and KCl. eRK and CReB phosphorylation were analyzed by western blot. results: mcsa1 staining demonstrated increased aβ protein in the appswe,Ind cell line compared to the appWt cell line. upon cell stimulation at 30 minutes, the appWt cell line demonstrated the highest levels of CReB phosphorylation and appswe,Ind demonstrated the lowest levels. eRK phosphorylation increased upon stimulation and was sustained across all four time points, but there was no significant difference in levels between the clones. discussion: These results suggest that the aβ protein has beneficial effects on CRe-regulated gene expression at physiological levels and negative consequences that mimic alzheimer’s disease at pathogenic levels.