In this work, we explored the existence of genetic variants within the apolipoprotein E gene transcriptional regulatory region, using a denaturing gradient gel electrophoresis screening of a region comprising nucleotides 31017 to +406. Upon a population study, three new polymorphic sites (3491, 3427 and 3219) and two mutations were found. Functional effects of the polymorphisms, assayed by transient transfection and electrophoretic mobility shift assays in a human hepatoma cell line, showed that polymorphisms at sites 3491 and 3219 of the APOE promoter produce variations in the transcriptional activity of the gene, most probably through differential binding of nuclear proteins.z 1998 Federation of European Biochemical Societies.

The epsilon4 allele of the apolipoprotein E gene (APOE) has been associated with an increased risk of developing Alzheimer's disease (AD; refs 1,2). However, it is apparent that the APOEepsilon4 allele alone is neither necessary nor sufficient to cause the disease. We have recently found three new polymorphisms within the APOE transcriptional regulatory region (M.J.A. et al., manuscript submitted) and now establish an association between one of these polymorphisms (-491A/T) and dementia as observed in Alzheimer's disease, in two independent clinical populations. The results suggest that homozygosity of a common variant (-491A) is associated with increased risk for AD, and that this association is independent of APOEepsilon4 status. In vitro studies suggest that the -491A/T polymorphism may increase risk for AD by altering the level of ApoE protein expression.

While the straightepsilon4 allele of apolipoprotein E ( APOE, gene; ApoE, protein) is widely accepted as a major genetic risk factor for the late onset form of Alzheimer's disease (AD), recent evidence points to variations in ApoE levels as another important factor. We have previously reported that a common variant in the regulatory region of APOE (-491A) is associated with risk for late onset AD. In this report we analyze the association of another APOE promoter polymorphism (-427T/C) with AD in two case-control clinical samples and demonstrate a correlation between APOE promoter transcriptional activity and risk for AD. The association studies show that the allelic variant (-427C) and the haplotype [-491A-427C] of the APOE promoter are associated with increased risk for AD. Study of the transcriptional activity of the common haplotypes defined by combination of the -491 and -427 alleles indicated that the risk for late onset AD positively correlates with transcriptional activity of the APOE gene, suggesting that increases in the local expression of ApoE could be responsible for the association of APOE promoter polymorphism with AD.

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Mounting evidence suggests that Herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of Alzheimer’s disease (AD). Previous work from our laboratory has shown HSV-1 infection to induce the most important pathological hallmarks of AD brains. Oxidative damage is one of the earliest events of AD and is thought to play a crucial role in the onset and development of the disease. Indeed, many studies show the biomarkers of oxidative stress to be elevated in AD brains. In the present work the combined effects of HSV-1 infection and oxidative stress on Aβ levels and autophagy (neurodegeneration markers characteristic of AD) were investigated. Oxidative stress significantly potentiated the accumulation of intracellular Aβ mediated by HSV-1 infection, and further inhibited its secretion to the extracellular medium. It also triggered the accumulation of autophagic compartments without increasing the degradation of long-lived proteins, and enhanced the inhibition of the autophagic flux induced by HSV-1. These effects of oxidative stress were not due to enhanced virus replication. Together, these results suggest that HSV-1 infection and oxidative damage interact to promote the neurodegeneration events seen in AD.

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Autophagy is a homeostatic process involved in the turnover or elimination of cytoplasmic components, damaged organelles, and protein aggregates via a lysosomal degradation mechanism. Autophagy also provides a mechanism of innate immunity, known as xenophagy, designed to protect cells from intracellular pathogens, but it may unfortunately be subverted to act as a pro-viral pathway facilitating the replication of certain viruses. Herpes simplex virus type I (HSV-1) is a neurotropic virus that remains latent in host neurons; it is the most common cause of sporadic viral encephalitis. Moreover, HSV-1 has been related to the pathogenesis of Alzheimer's disease. HSV-1 can modulate the autophagic process through a mechanism mediated by the viral protein ICP34.5. Here we report that HSV-1 induces a strong increase in GFP-LC3 and endogenous LC3 lipidation, and triggers the accumulation of intracellular autophagic compartments (mainly autophagosomes) without enhancing autophagic long-lived protein degradation in the late stages of infection. Autophagy inhibition mediated by ATG5 gene silencing had no effect on viral growth. The present results suggest that HSV-1 infection activates the host autophagic machinery and strongly controls the autophagic process, blocking the fusion of autophagosomes with lysosomes. These events might be important in the neurodegenerative process associated with HSV-1 infection.