Overexpression of the familial Alzheimer's disease gene Presenilin 2 (PS2) in nerve growth factor-differentiated PC12 cells increased apoptosis induced by trophic factor withdrawal or beta-amyloid. Transfection of antisense PS2 conferred protection against apoptosis induced by trophic withdrawal in nerve growth factor-differentiated or amyloid precursor protein-expressing PC12 cells. The apoptotic cell death induced by PS2 protein was sensitive to pertussis toxin, suggesting that heterotrimeric GTP-binding proteins are involved. A PS2 mutation associated with familial Alzheimer's disease was found to generate a molecule with enhanced basal apoptotic activity. This gain of function might accelerate the process of neurodegeneration that occurs in Alzheimer's disease, leading to the earlier age of onset characteristic of familial Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. Although the pathogenesis of AD is unknown, it is widely accepted that AD is caused by extracellular accumulation of a neurotoxic peptide, known as A␤. Mutations in the ␤-amyloid precursor protein (APP), from which A␤ arises by proteolysis, are associated with some forms of familial AD (FAD) and result in increased A␤ production. Two other FAD genes, presenilin-1 and -2, have also been shown to regulate A␤ production; however, studies examining the biological role of these FAD genes suggest an alternative theory for the pathogenesis of AD. In fact, all three genes have been shown to regulate programmed cell death, hinting at the possibility that dysregulation of apoptosis plays a primary role in causing neuronal loss in AD. In an attempt to reconcile these two hypotheses, we investigated APP processing during apoptosis and found that APP is processed by the cell death proteases caspase-6 and -8. APP is cleaved by caspases in the intracellular portion of the protein, in a site distinct from those processed by secretases. Moreover, it represents a general effect of apoptosis, because it occurs during cell death induced by several stimuli both in T cells and in neuronal cells.Alzheimer's disease (AD), 1 a progressive neurodegenerative disorder of later life, is characterized by deposition of ␤-amyloid plaques, accumulation of intracellular neurofibrillary tangles, and neuronal cell loss (1). It is widely believed that this disease is caused by the extracellular accumulation of the aggregated amyloidogenic form of A␤ peptide (A␤1-42). This peptide arises from the processing of ␤-amyloid precursor protein (APP) by still unknown proteases (secretases) (2). The recent discovery of three genes linked to familial, early-onset forms of AD (FAD) has brought further support to this theory. The first to be discovered was, in fact, APP, the protein from which A␤ derives (3). Moreover, mutations in APP associated with FAD are more efficiently processed by secretases and generate increased amounts of long A␤ (4). Two other FAD genes, the highly homologous multipass membrane proteins presenilin-1 (5) and presenilin-2 (6, 7) (PS-1 and PS-2), also regulate APP processing (8). Of more importance, mutations in presenilins linked to FAD all increased processing of APP and the formation of A␤1-42 (9 -11).Recent studies focusing on the physiologic role of APP, PS-1, and PS-2 have shown that these FAD genes regulate apoptosis and also that AD-associated mutations result in enhanced proapoptotic activity of these molecules (12-18). Finally, PS-1 and PS-2 have been found to be cleaved during apoptosis by caspase-3 (19 -21), a protease whose activity is essential for neuronal apoptosis (22). Together, these data suggest an alternative model for the pathogenesis of AD according to which AD is caused by dysregulation of programmed cell death (PCD) and enhanced susceptibility of neurons to apoptotic stimuli.These two apparently contrasting theories need not be mutually excl...

Serotonergic and opioidergic neurotransmitter system alterations have been observed in people with eating disorders; the genes for the serotonin 1D receptor (HTR1D) and the opioid delta receptor (OPRD1) are found on chr1p36.3-34.3, a region identified by our group in a linkage analysis of anorexia nervosa (AN). These candidate genes were evaluated for sequence variation and for linkage and association of this sequence variation to AN in family and case : control data sets. Resequencing of the HTR1D locus and a portion of the OPRD1 locus identified novel SNPs and confirmed existing SNPs. Genotype assay development and genotyping of nine SNPs (four at HTR1D and five at OPRD1) was performed on 191 unrelated individuals fulfilling DSM-IV criteria (w/o amenorrhea criterion) for AN, 442 relatives of AN probands and 98 psychiatrically screened controls. Linkage analysis of these candidate gene SNPs with 33 microsatellite markers in families including relative pairs concordantly affected with restricting AN (N=37) substantially increased the evidence for linkage of this region to restricting AN to an NPL score of 3.91. Statistically significant genotypic, allelic, and haplotypic association to AN in the case : control design was observed at HTR1D and OPRD1 with effect sizes for individual SNPs of 2.63 (95% CI=1.21-5.75) for HTR1D and 1.61 (95% CI=1.11-2.44) for OPRD1. Using genotype data on parents and AN probands, three SNPs at HTR1D were found to exhibit significant transmission disequilibrium (Po0.05). The combined statistical genetic evidence suggests that HTR1D and OPRD1 or linked genes may be involved in the etiology of AN.

To investigate whether the dopaminergic system plays a role in the etiology of anorexia nervosa (AN) via the dopamine D2 receptor, we investigated association and transmission disequilibrium at seven single-nucleotide polymorphisms (SNPs) spanning about 75 kbp of the gene DRD2. We studied 191 probands with a DSM-IV diagnosis of AN, 457 parents and affected relatives with a DSM-IV eating disorder diagnosis, and 98 unrelated, female, normal weight controls. The À141 C/À insertion/deletion (À141 Indel), previously shown to affect DRD2 transcription efficiency, and multiple exon seven polymorphisms, one of which has previously been shown to affect DRD2 transcript stability, exhibited statistically significant association with diagnosis in haplotype transmission disequilibrium and in haplotype case : control analyses. Significant linkage disequilibrium between the À141 Indel and two exon seven SNPs (939Y and 957Y) was observed over a distance of 450 kbp in the AN probands but not in the controls. Genetically transmitted variation in D2 dopamine receptor expression mediated by functional polymorphisms affecting transcription and translation efficiency may play a role in vulnerability to AN.

ALG-3, a truncated mouse homologue of the chromosome 1 familial Alzheimer's disease gene PS2, rescues T hybridoma 3DO cells from T-cell receptor-induced apoptosis by inhibiting Fas ligand induction and Fas signaling. Here we show that ALG-3 transfected 3DO cells express a COOH-terminal PS2 polypeptide. Overexpression of PS2 in ALG-3 transfected 3DO cells reconstitutes sensitivity to receptor-induced cell death, suggesting that the artificial PS2 polypeptide functions as a dominant negative mutant of PS2. ALG-3 and antisense PS2 protect PC12 cells from glutamate-induced apoptosis but not from death induced by hydrogen peroxide or the free radical MPP ؉ . Thus, the PS2 gene is required for some forms of cell death in diverse cell types, and its function is opposed by ALG-3.