Alzheimer's presenilin-1 mutation potentiates inositol 1,4,5-trisphosphate-mediated calcium signaling in Xenopus oocytes.

Perturbations in intracellular Ca2+ signaling may represent one mechanism underlying Alzheimer's disease (AD). The presenilin-1 gene (PS1), associated with the majority of early onset familial AD cases, has been implicated in this signaling pathway. Here we used the Xenopus oocyte expression system to investigate in greater detail the role of PS1 in intracellular Ca2+ signaling pathways.

Herpes simplex virus infections and Alzheimer's disease. Implications for drug treatment and immunotherapy.

Interest in the possible role of herpes simplex virus type 1 (HSV1) as a cofactor in the pathogenesis of Alzheimer's disease (AD) has re-emerged following the detection of viral DNA sequences in the central nervous system (CNS). Evidence from 2 independent laboratories indicates that HSV1 may interact with a host-specific factor, the apolipoprotein E epsilon 4 allele, to further augment the risk for AD. In this review, we consider the arguments implicating HSV1 in the pathogenesis of AD.

Neuronal cell death in Alzheimer's disease correlates with apoE uptake and intracellular Abeta stabilization.

The brains of individuals with Alzheimer's disease (AD) are characterized by extracellular deposition of beta-amyloid protein (Abeta), intracellular neurofibrillary tangles, and loss of neurons. To study molecular markers associated with dying cells in the AD brain, in situ DNA labeling techniques were used to visualize cells with DNA fragmentation. We observed that intracellular accumulation of apolipoprotein E (apoE) is correlated with the detection of intracellular Abeta-like immunoreactivity within the same cytoplasmic granules, suggesting that uptake of lipids may have stabilized the hydrophobic Abeta protein within the cell.

Presenilin-1 immunoreactivity is localized intracellularly in Alzheimer's disease brain, but not detected in amyloid plaques.

The identification of the cellular and subcellular regions of the Alzheimer's disease brain to which the presenilin-1 (PS-1) protein localizes is expected to contribute to an understanding of its pathophysiological role. Toward this end, we have derived an affinity-purified antibody to a synthetic PS-1 peptide. In this report, we demonstrate that this antibody, called SW2, specifically recognizes full-length, 47-kDa PS-1 protein from rat primary cortical neurons, from a human neuronal cell line, and from human brain extracts on Western immunoblots.

Extracellular deposition of beta-amyloid upon p53-dependent neuronal cell death in transgenic mice.

The finding that intracellular expression of the beta-amyloid protein (Abeta) under a neuron-specific promoter led progressively to degeneration and death of neurons in the brains of transgenic mice provides a unique opportunity to utilize this animal model to both understand the mechanism that underlies neuronal cell death and define the complexity of events which may ensue. We observed a correlation between Abeta accumulation in selective neurons and activation of p53, a protein that has been implicated in the induction of apoptosis. Histological and immunohistochemical evaluations of adjacent brain sections suggest that expression of p53 is accompanied by nuclear DNA fragmentation.

Injury induces presenilin-1 gene expression in mouse brain.

Information regarding the genetic factors and environmental conditions that influence presenilin-1 (PS-1) gene expression is essential for the elucidation of its pathophysiological role in Alzheimer's disease (AD). Previous in situ hybridization studies have demonstrated that neurons are the predominant cell type expressing PS-1 in the mammalian central nervous system (CNS) under physiological conditions. In this study, we examined the consequences of an experimentally induced focal injury on PS-1 gene expression in the mouse CNS.

Widespread neuronal expression of the presenilin-1 early-onset Alzheimer's disease gene in the murine brain.

Mutations in the presenilin-1 (S182) gene have been genetically linked to early-onset Alzheimer's disease. To clarify the underlying molecular mechanism through which presenilin-1 is involved in the pathogenesis of this neurodegenerative disorder, the regional and cellular transcription profile of this gene was characterized in primary cells isolated from the murine brain by Northern blot hybridization using digoxigenin-labeled riboprobes. Our results indicate that presenilin-1 mRNA transcripts are widely distributed throughout the adult mouse brain.

The Alzheimer's A beta peptide induces neurodegeneration and apoptotic cell death in transgenic mice.

To test whether the hypothesis that the Alzheimer's A beta peptide is neurotoxic, we introduced a transgene into mice to direct expression of this peptide to neurons. We show that the transgene is expressed in brain regions which are severely affected in Alzheimer's disease resulting in extensive neuronal degeneration. Morphological and biochemical evidence indicates that the eventual death of these cells occurs by apoptosis.