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Regulation and expression of the Alzheimer's beta/A4 amyloid protein precursor in health, disease, and Down's syndrome.

Abstract：

:A four- to fivefold overexpression of the gene for the Alzheimer beta/A4 amyloid precursor protein (APP) in individuals with Down's Syndrome (DS) appears to be responsible for the fifty year earlier onset of Alzheimer's disease (AD) pathology in DS compared to the normal population. It is therefore likely that a deregulated overexpression of the APP gene is a risk factor for the beta/A4 amyloid formation. To test this hypothesis and to get a better understanding of how APP expression is regulated, we studied the 5' control region of the human APP gene, alternative splicing of the 19 APP exons, and APP biogenesis, metabolism and function. The analysis of the APP promoter revealed its similarity with those of housekeeping genes by the presence of a GC-rich region around the transcription start site and the lack of a TATA box. Gene transfer experiments showed this GC-rich region to contain overlapping binding sites for different transcription factors whose binding is mutually excluded. An imbalance between these factors may cause APP overexpression and predispose to AD pathology. Another putative risk factor for AD is regulation of splicing of exon 7 in APP mRNA's which changes in brain during aging. This is relevant for APP processing since exon 7 codes for a Kunitz protease inhibitory domain. Investigation of further splicing adjacent to the beta/A4 exons 16 and 17 which might also interfere with APP processing led to the identification of the leukocyte-derived (L-APP) splice forms which lack exon 15. In brain this splicing occurs in activated astrocytes and microglia. The localization of APP at synaptic sites in brain suggests that APP regulation and expression are critical determinants of a potential and early impairment of central synapses. This may be the case during pathological evolution of AD and DS when beta/A4 derived from synaptic APP is converted to beta/A4 amyloid by radical generation.

journal_name

Ann N Y Acad Sci

journal_title

Annals of the New York Academy of Sciences

authors

Beyreuther K,Pollwein P,Multhaup G,Mönning U,König G,Dyrks T,Schubert W,Masters CL

doi

10.1111/j.1749-6632.1993.tb23035.x

subject

Has Abstract

pub_date

1993-09-24 00:00:00

pages

91-102

eissn

0077-8923

issn

1749-6632

journal_volume

695

pub_type

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Regulation and expression of the Alzheimer's beta/A4 amyloid protein precursor in health, disease, and Down's syndrome.