Alzheimer Disease: St George-Hyslop P

Mayeux R, St George-Hyslop P. · No affiliation provided · Arch Neurol. · Pubmed #19364927 No free full text.

This publication has no abstract.

Checler F, Sunyach C, Pardossi-Piquard R, Sévalle J, Vincent B, Kawarai T, Girardot N, St George-Hyslop P, da Costa CA. · Institut de Pharmacologie Moléculaire et Cellulaire, UMR6097CNRS/UNSA, Valbonne 06560, France. · Curr Alzheimer Res. · Pubmed #17908046 No free full text.

Abstract: Amyloid beta-peptide (Abeta), which plays a central role in Alzheimer Disease, is generated by presenilin-dependent and presenilin-independent gamma-secretase cleavages of beta-amyloid precursor protein (betaAPP). We report that the presenilins (PS1 and PS2) also regulate p53-associated cell death. Thus, we established that PS deficiency, catalytically inactive PS mutants, gamma-secretase inhibitors and betaAPP or APLP2 depletion reduced the expression and activity of p53, and lowered the transactivation of its promoter and mRNA levels. p53 expression was also reduced in the brains or betaAPP-deficient mice or in brains where both PS had been invalidated by double conditional knock out. AICDC59 and AICDC50, the gamma- and epsilon-secretase-derived C-terminal fragments of betaAPP, respectively, trigger the activation of caspase-3, p53-dependent cell death, and increase p53 activity and mRNA. Finally, HEK293 cells expressing PS1 harboring familial AD (FAD) mutations or FAD-affected brains, all display enhanced p53 activity and p53 expression. Our studies demonstrate that AICDs control p53 at a transcriptional level, in vitro and in vivo and unravel a still unknown function for presenilins.

Gelinas DS, DaSilva K, Fenili D, St George-Hyslop P, McLaurin J. · Centre for Research in Neurodegenerative Diseases, University of Toronto, 6 Queen's Park Crescent West, Toronto, ON M5S 3H2, Canada. · Proc Natl Acad Sci U S A. · Pubmed #15297619 links to  free full text

Abstract: The utility of vaccine strategies to treat neurodegenerative diseases such as Alzheimer's disease (AD) may still hold promise. Both active and passive immunization strategies reduced AD-like pathology and restored cognitive deficits in transgenic mice. These results were initially met with considerable optimism; however, phase IIa clinical trials were halted because of a small but significant occurrence of meningoencephalitis. Knowledge gained from studies on amyloid-beta peptide (A beta) immunotherapy will allow optimization of new-generation vaccines, targeting highly specific epitopes while reducing undesired side effects. In harnessing and steering the immune system, an effective response can be generated against A beta. If this proves successful, A beta vaccination could provide the first definitive treatment for AD.

Kennedy JL, Farrer LA, Andreasen NC, Mayeux R, St George-Hyslop P. · Departments of Psychiatry and Medicine, Centre for Addiction and Mental Health, Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario M5S 3H9, Canada. · Science. · Pubmed #14593167 No free full text.

Abstract: Genetic factors play a major role in the etiology of adult-onset neurodegenerative and neuropsychiatric disorders. Several highly penetrant genes have been cloned for rare, autosomal-dominant, early-onset forms of neurodegenerative diseases. These genes have provided important insights into the mechanisms of these diseases (often altering neuronal protein processing). However, the genes associated with inherited susceptibility to late-onset neurodegenerative diseases, schizophrenia, and bipolar disorder appear to have smaller effects and are likely to interact with each other (and with nongenetic factors) to modulate susceptibility and/or disease phenotype. Several strategies have recently been applied to address this complexity, leading to the identification of a number of candidate susceptibility loci/genes.

Fraser PE, Yang DS, Yu G, Lévesque L, Nishimura M, Arawaka S, Serpell LC, Rogaeva E, St George-Hyslop P. · Centre for Research in Neurodegenerative Diseases, University of Toronto, Ont, Canada. · Biochim Biophys Acta. · Pubmed #10899427 No free full text.

Abstract: Numerous missense mutations in the presenilins are associated with the autosomal dominant form of familial Alzheimer disease. Presenilin genes encode polytopic transmembrane proteins, which are processed by proteolytic cleavage and form high-molecular-weight complexes under physiological conditions. The presenilins have been suggested to be functionally involved in developmental morphogenesis, unfolded protein responses and processing of selected proteins including the beta-amyloid precursor protein. Although the underlying mechanism by which presenilin mutations lead to development of Alzheimer disease remains elusive, one consistent mutational effect is an overproduction of long-tailed amyloid beta-peptides. Furthermore, presenilins interact with beta-catenin to form presenilin complexes, and the physiological and mutational effects are also observed in the catenin signal transduction pathway.

Swartz RH, Black SE, St George-Hyslop P. · Cognitive Neurology Unit, Sunnybrook Health Science Centre, University of Toronto, Ontario, Canada. · Can J Neurol Sci. · Pubmed #10352866 No free full text.

Abstract: Alzheimer's disease (AD) is the most common cause of dementia in the elderly and an increasingly significant health concern in our aging population. In the past 10 years, our understanding of this disease has increased dramatically. While the discovery of three rare genetic mutations that can cause AD has provided much information about the causes and progression of the disease, a great deal of attention has been focused on apolipoprotein (ApoE) because of its involvement in the more common, later onset form of AD. Due to the rapid pace of recent advances, it has not been easy for health care professionals, researchers and the general public to keep abreast of these developments. This paper reviews recent research in ApoE and late-onset AD, emphasizing molecular neuropathological, genetic and neuroimaging findings and highlighting current controversies that remain to be addressed.

Hinerfeld DA, Moonis M, Swearer JM, Baker SP, Caselli RJ, Rogaeva E, St George-Hyslop P, Pollen DA. · No affiliation provided · Arch Neurol. · Pubmed #17998454 No free full text.

This publication has no abstract.

Lindquist SG, Hasholt L, Bahl JM, Heegaard NH, Andersen BB, Nørremølle A, Stokholm J, Schwartz M, Batbayli M, Laursen H, Pardossi-Piquard R, Chen F, St George-Hyslop P, Waldemar G, Nielsen JE. · Memory Disorders Research Group, Department of Neurology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. · Eur J Neurol. · Pubmed #18727676 No free full text.

Abstract: BACKGROUND: Mutations in the Presenilin 2 gene (PSEN2) are rare causes of Alzheimer's disease (AD). Pathogenic mutations in the genes associated with autosomal dominant inherited AD have been shown to alter processing of the amyloid precursor protein (APP) resulting in a relative increase of the amount of Abeta42 peptide. METHODS AND RESULTS: We present a patient with neuropathologically confirmed early-onset AD characterized by profound language impairment. The patient was heterozygous for a novel missense mutation in exon 11 of the PSEN2 gene leading to a predicted amino acid substitution from valine to methionine in position 393, a conserved residue. However, in vitro expression of PSEN2 V393M cDNA did not result in detectable increase of the secreted Abeta42/40 peptide ratio. The mutation was not found in 384 control individuals tested. CONCLUSIONS: The possible pathogenic nature of the mutation is not clarified. We discuss the limitations of functional PSEN2 studies and the challenges associated with genetic counselling of family members at risk.

Pettersen JA, Sathiyamoorthy G, Gao FQ, Szilagyi G, Nadkarni NK, St George-Hyslop P, Rogaeva E, Black SE. · Division of Neurology, Department of Medicine, Sunnybrook Health Sciences Centre, A421-2075 Bayview Ave, Toronto, ON M4N 3M5, Canada. · Arch Neurol. · Pubmed #18541799 links to  free full text

Abstract: BACKGROUND: Microbleeds are hemosiderin deposits around small vessels and are well visualized with T2*-weighted gradient-recalled echo (GRE) imaging. OBJECTIVES: To determine frequency and topography of microbleeds in Alzheimer disease (AD) and to assess their association with leukoaraiosis and cognition. DESIGN: Case-control cross-sectional analysis. Microbleeds were counted using GRE imaging. Leukoaraiosis was rated on T2-weighted and proton density-weighted scans using the Age-Related White Matter Changes Rating Scale (ARWMC). Neuropsychological tests indexed cognition. SETTING: The Cognitive Neurology Clinic, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. PATIENTS: Individuals with probable AD (n = 80) and healthy controls (n = 25) from a longitudinal cohort with GRE sequences as part of standard imaging protocol (2002-2006). RESULTS: Microbleeds occurred in 29% of patients with AD and 12% of controls and were multiple (> 1) in 48% of patients with AD and 33% of controls. There was lobar (vs centrencephalic) predominance in 92% of AD patients, with occipital lobes accounting for 57% of these microbleeds. The ARWMC scores (P < .005) were significantly higher in AD patients with microbleeds than in those without, and microbleeds correlated with total (r = 0.39, P = .01) and parietooccipital (r = 0.28, P < .01) ARWMC scores. We were unable to demonstrate an association between microbleeds (or leukoaraiosis) and cognitive performance. CONCLUSIONS: Occipital predominance of microbleeds with corresponding parietooccipital leukoaraiosis has not been well described in prior imaging studies of AD. Microbleeds were frequent, often multiple, and predicted greater leukoaraiosis. These findings illustrate the complexity of AD vasculopathy and the need for additional studies in dementia and stroke populations.

Lee JH, Cheng R, Rogaeva E, Meng Y, Stern Y, Santana V, Lantigua R, Medrano M, Jimenez-Velazquez IZ, Farrer LA, St George-Hyslop P, Mayeux R. · Taub Institute for Research of Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY 10032, USA. · Neurogenetics. · Pubmed #18340469 links to  free full text

Abstract: A broad region on chromosome 12p13 has been intensely investigated for novel genetic variants associated with Alzheimer disease (AD). We examined this region with 23 microsatellite markers using 124 North European (NE) families and 209 Caribbean Hispanic families with late-onset AD (FAD). Significant evidence for linkage was present in a 5-cM interval near 20 cM in both the NE FAD (LOD = 3.5) and the Caribbean Hispanic FAD (LOD = 2.2) datasets. We further investigated these families and an independent NE case-control dataset using 14 single nucleotide polymorphisms (SNPs). The initial screening of the region at approximately 20 cM in the NE case-control dataset revealed significant association between AD and seven SNPs in several genes, with the strongest result for rs2532500 in TAPBPL (p = 0.006). For rs3741916 in GAPDH, the C allele, rather than the G allele as was observed by Li et al. (Proc Natl Acad Sci U S A 101(44):15688-15693, 2004), was the risk allele. When the two family datasets were examined, none of the SNPs were significant in NE families, but two SNPs were associated with AD in Caribbean Hispanics: rs740850 in NCAPD2 (p = 0.0097) and rs1060620 in GAPDH (p = 0.042). In a separate analysis combining the Caribbean Hispanic families and NE cases and controls, rs740850 was significant after correcting for multiple testing (empirical p = 0.0048). Subsequent haplotype analyses revealed that two haplotype sets-haplotype C-A at SNPs 6-7 within NCAPD2 in Caribbean Hispanics, and haplotypes containing C-A-T at SNPs 8-10 within GAPDH in Caribbean Hispanic family and NE case-control datasets-were associated with AD. Taken together, these SNPs may be in linkage disequilibrium with a pathogenic variant(s) on or near NCAPD2 and GAPDH.

Meng Y, Lee JH, Cheng R, St George-Hyslop P, Mayeux R, Farrer LA. · Department of Medicine (Genetics Program), Boston University School of Medicine, Boston, Massachusetts 02118, USA. · Neuroreport. · Pubmed #18090307 links to  free full text

Abstract: Several studies have reported an association of Alzheimer's disease (AD) with polymorphic markers in SORL1. Data from a recently published genome-wide association study in AD have been made publicly available. We tested the association of AD with SORL1 in this dataset (Translational Genomics Research Institute; TGEN), which included 31 SORL1 single nucleotide polymorphisms (SNPs), eight of which overlapped the original study. Six SNPs, near the 3' region of SORL1 containing SNPs which were strongly associated with AD in previous studies, showed significant association in the TGEN dataset. These results provide an independent replication of the association between AD and SORL1.

Lee JH, Barral S, Cheng R, Chacon I, Santana V, Williamson J, Lantigua R, Medrano M, Jimenez-Velazquez IZ, Stern Y, Tycko B, Rogaeva E, Wakutani Y, Kawarai T, St George-Hyslop P, Mayeux R. · The Taub Institute on Alzheimer's Disease and the Aging Brain, Columbia University, New York, NY 10032, USA. · Neurogenetics. · Pubmed #17940814 links to  free full text

Abstract: The aim of the study was to identify chromosomal regions that may harbor putative genetic variants influencing age at onset in familial late-onset Alzheimer's disease (LOAD). Data from a genome-wide scan that included genotyping of APOE were analyzed in 1,161 individuals from 209 families of Caribbean Hispanic ancestry with a mean age at onset of 73.3 years multiply affected by LOAD. Two-point and multipoint analyses were conducted using variance component methods using 376 microsatellite markers with an average intermarker distance of 9.3 cM. Family-based test of association was also conducted for the same set of markers. Age at onset of symptoms among affected individuals was used as the quantitative trait. Our results showed that the presence of APOE-epsilon4 lowered the age at onset by 3 years. Several candidate loci were identified. Using linkage analysis strategy, the highest logarithm of odds (LOD) scores were obtained using a conservative definition of LOAD at 5q15 (LOD = 3.1), 17q25.1 (LOD = 2.94), 14q32.12 (LOD = 2.36), and 7q36.3 (LOD = 2.29) in a model that adjusted for APOE-epsilon4 and other covariates. Both linkage and family-based association identified 17p13 as a candidate region. Family-based association analysis showed markers at 12q13 (p = 0.00002), 13q33 (p = 0.00043), and 14q23 (p = 0.00046) to be significantly associated with age at onset. The current study supports the hypothesis that there are additional genetic loci that could influence age at onset of late onset Alzheimer's disease. The novel loci at 5q15, 17q25.1, 13q33, and 17p13 and the previously reported loci at 7q36.3, 12q13, 14q23, and 14q32 need further investigation.

Lee JH, Cheng R, Schupf N, Manly J, Lantigua R, Stern Y, Rogaeva E, Wakutani Y, Farrer L, St George-Hyslop P, Mayeux R. · Taub Institute on Alzheimer's Disease and the Aging Brain, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA. · Arch Neurol. · Pubmed #17420311 links to  free full text

Abstract: OBJECTIVE: To investigate the association between Alzheimer disease (AD) and variant alleles in SORL1 using a series of single nucleotide polymorphisms (SNPs) in an urban, multiethnic, community-based population. DESIGN: We used a nested case-control analysis in a population-based, prospective study of aging and dementia in Medicare recipients, 65 years and older. SETTING: Northern Manhattan, NY. PARTICIPANTS: There were 296 patients with probable AD and 428 healthy, elderly controls. The participants were African American (34%), Caribbean Hispanic (51%), or non-Hispanic white (15%). MAIN OUTCOME MEASURES: We genotyped all 29 SNPs in SORL1 that were examined in the earlier report. We assessed allelic association with AD using standard case-control methods, which included apolipoprotein E genotype as a covariate. RESULTS: Several individual SNPs and SNP haplotypes were significantly associated with AD in this prospectively collected community-based cohort, confirming the previously reported positive association of SORL1 with AD. Single nucleotide polymorphism 12, near the 5' region, was associated with AD in African American and Hispanic individuals. Two SNPs in the 3' region were also associated with AD in African American (SNP 26) and non-Hispanic white (SNP 20) individuals. A single haplotype in the 3' region was associated with AD in Hispanic individuals. However, several different haplotypes were associated with AD in African American and white individuals, including the TTC haplotypes at SNPs 23 through 25 (P = .035), which was significantly associated with AD in the North European white individuals in our previous report. CONCLUSIONS: This study confirms the association between genetic variants in SORL1 and AD. While the associations observed in these data sets overlap with those previously reported, the finding of novel SNP and haplotype associations suggests that there may be extensive allelic heterogeneity in SORL1. Broad regions of the SORL1 gene will therefore need to be scrutinized for functional pathogenic variants.

Rogaeva E, Meng Y, Lee JH, Gu Y, Kawarai T, Zou F, Katayama T, Baldwin CT, Cheng R, Hasegawa H, Chen F, Shibata N, Lunetta KL, Pardossi-Piquard R, Bohm C, Wakutani Y, Cupples LA, Cuenco KT, Green RC, Pinessi L, Rainero I, Sorbi S, Bruni A, Duara R, Friedland RP, Inzelberg R, Hampe W, Bujo H, Song YQ, Andersen OM, Willnow TE, Graff-Radford N, Petersen RC, Dickson D, Der SD, Fraser PE, Schmitt-Ulms G, Younkin S, Mayeux R, Farrer LA, St George-Hyslop P. · Centre for Research in Neurodegenerative Diseases, Department of Medicine, Department, University of Toronto, Toronto, Ontario, Canada. · Nat Genet. · Pubmed #17220890 links to  free full text

Abstract: The recycling of the amyloid precursor protein (APP) from the cell surface via the endocytic pathways plays a key role in the generation of amyloid beta peptide (Abeta) in Alzheimer disease. We report here that inherited variants in the SORL1 neuronal sorting receptor are associated with late-onset Alzheimer disease. These variants, which occur in at least two different clusters of intronic sequences within the SORL1 gene (also known as LR11 or SORLA) may regulate tissue-specific expression of SORL1. We also show that SORL1 directs trafficking of APP into recycling pathways and that when SORL1 is underexpressed, APP is sorted into Abeta-generating compartments. These data suggest that inherited or acquired changes in SORL1 expression or function are mechanistically involved in causing Alzheimer disease.

Lee JH, Cheng R, Santana V, Williamson J, Lantigua R, Medrano M, Arriaga A, Stern Y, Tycko B, Rogaeva E, Wakutani Y, Kawarai T, St George-Hyslop P, Mayeux R. · Gertrude H. Sergievsky Center, Columbia University, 630 W 168th St, New York, NY 10032, USA. · Arch Neurol. · Pubmed #17101828 links to  free full text

Abstract: OBJECTIVES: To identify novel candidate regions for late-onset Alzheimer disease (LOAD) and to confirm linkage in previously identified chromosomal regions. DESIGN: Family-based linkage analysis. SETTING: Probands with familial LOAD identified in clinics in the Dominican Republic, Puerto Rico, and the United States. Patients We conducted a genome scan in 1161 members primarily clinically diagnosed as having LOAD; these members were from 209 families of Caribbean Hispanic ancestry. MAIN OUTCOME MEASURES: We analyzed 376 microsatellite markers with an average intermarker distance of 9.3 centimorgan. We conducted linkage analysis using possible and probable LOAD, and we performed affecteds-only 2-point linkage analyses assuming either an autosomal dominant or a recessive model. Subsequently, we conducted a multipoint affected sibling pair linkage analysis. RESULTS: Two-point parametric linkage analysis identified a locus at 3q28 with a genomewide empirical P value of .03 (logarithm of odds [LOD], 3.09) in a dominant model for probable and possible LOAD. Other regions suggestive of linkage included 2p25.3 (LOD, 1.77), 7p21.1 (LOD, 1.82), and 9q32 (LOD, 1.94). Under a recessive model, we also identified loci at 5p15.33 (LOD, 1.86), 12q24.21 (LOD, 2.43), 14q22.3 (LOD, 2.53), and 14q23.1 (LOD, 2.16) as suggestive for linkage. Restricted to probable LOAD, many of these loci continued to meet criteria suggestive for linkage, as did loci at 2p25.3 (LOD, 2.72), 3q28 (LOD, 2.28), 6p21.31 (LOD, 2.19), and 7p21.1 (LOD, 2.05). APOE conditional analysis indicated that the observed linkage at 3q28 was independent of the APOE epsilon4 allele. Multipoint nonparametric affected sibling pair linkage analysis provided confirmation of suggestive linkage for most, but not all, loci. CONCLUSIONS: Seven loci with LOD scores greater than 2.0 were identified among multiple affected Caribbean Hispanic families with LOAD. The highest LOD score was found at chromosome 3q28. At least 2 other independent studies have observed support for significant linkage at chromosome 3q28, highlighting this region as a locus for further genetic exploration.

Brijbassi S, Amtul Z, Newbigging S, Westaway D, St George-Hyslop P, Rozmahel RF. · Department of Biochemistry, University of Western Ontario, London, Ontario, Canada. · Neurobiol Dis. · Pubmed #17071095 No free full text.

Abstract: Nicastrin is an integral member of PS-complexes that perform gamma-secretase cleavage of numerous type I membrane proteins including amyloid precursor protein that underlies Alzheimer's disease; thus, diminishing gamma-secretase activity by reducing levels of functional PS-complexes is suggested as a possible preventative/therapeutic avenue for the disease. One means of reducing PS-complex activity entails decreasing the levels of one or more of its components, such as nicastrin, which is fundamental to its assembly. Two previous studies detailing the effects of decreased nicastrin on gamma-secretase cleavage of APP in nicastrin heterozygous mouse fibroblast, which express relatively low levels of endogenous nicastrin compared to neurons, were contradictory. One report documented a 50% reduction in gamma-secretase cleavage of APP while the second showed markedly higher levels of this activity. Here we report that brains of heterozygous nicastrin mice show no difference in levels of APP gamma-secretase cleavage, APP C-terminal fragments or beta-amyloid peptides, compared to wild-type. This result is explained by the levels of nicastrin protein and functional presenilin complexes being similar between the heterozygous and wild-type brains, though nicastrin mRNA levels were diminished appropriately in the former. These in vivo results indicate that nicastrin mRNA and its immature protein are likely in overabundance in neurons and not limiting for assembly of PS-complexes, and that a 50% reduction of its mRNA or protein production would not affect APP processing, in contrast to fibroblast. Thus, partial reduction (maintaining a level above 50% of normal) of brain nicastrin would likely not be efficacious in reducing functional PS-complexes and gamma-secretase activity as a therapeutic strategy for Alzheimer's disease.

Li Y, Chu LW, Chen YQ, Cheung BM, Leung RY, Yik PY, Ng KM, Mak W, Jin DY, St George-Hyslop P, Song YQ. · Department of Biochemistry, University of Hong Kong, Hong Kong, SAR, China. · Dement Geriatr Cogn Disord. · Pubmed #16960449 No free full text.

Abstract: BACKGROUND: Cholesterol metabolism has been implicated in the pathophysiology of Alzheimer's disease (AD), and cholesterol-related genes are plausible candidate genes for AD. Genetic association of CYP46A1 polymorphisms with AD had been under extensive investigations; however, observations on intron 2 T-->C (rs754203) generated inconclusive results. OBJECTIVE: To analyse an independent data set in a Chinese population to see whether the polymorphic site rs754203 of the CYP46A1 gene is associated with AD. METHODS: We analysed 130 sporadic AD patients and 110 healthy controls of the Southern Chinese origin. RESULTS: An association between the genotype frequency and AD was suggested in the general population (p = 0.047, odds ratio, OR = 1. 61, 95% confidence interval, CI = 0.96-2.70), while the association was most significant in the apolipoprotein E (ApoE) epsilon4-negative group (p = 0.004, OR = 2.54, 95% CI =1.31-4.95). Linkage disequilibrium block prediction results also favoured this association. Consistent with previous reports, intron 3 C-->T (rs4900442) polymorphism did not show any evidence of association; in our data set ApoEepsilon4 was confirmed to be a genetic risk factor for AD (p = 0.0016, OR = 2.76, 95% CI = 1.50-5.11).

Burgess BL, McIsaac SA, Naus KE, Chan JY, Tansley GH, Yang J, Miao F, Ross CJ, van Eck M, Hayden MR, van Nostrand W, St George-Hyslop P, Westaway D, Wellington CL. · Department of Pathology and Laboratory Medicine, University of British Columbia, 980 West 28th Avenue, Vancouver, BC, Canada V5Z 4H4. · Neurobiol Dis. · Pubmed #16899370 No free full text.

Abstract: Dietary or pharmacological manipulation of plasma lipids markedly influences amyloid deposition in animal models of Alzheimer's Disease (AD). However, it is not known whether baseline plasma lipids in AD models differ from wild-type littermates throughout the natural history of disease. To address this question, we measured plasma total cholesterol and triglyceride levels over time in three transgenic AD mouse models in the absence of dietary or pharmacological treatments. Total cholesterol levels were not significantly different between transgenic and wild-type mice during the development of AD neuropathology in all models tested. In contrast, elevated very-low-density lipoprotein (VLDL) triglyceride levels preceded amyloid deposition in two AD models with abundant plasma A beta. Elevated triglycerides were not accompanied by increased inflammatory markers nor decreased lipase activity, but were associated with a significant 30% increase in VLDL-triglyceride secretion rate. Our results suggest that the presence of A beta in plasma may affect peripheral lipid metabolism early in AD pathogenesis.

McLaurin J, Kierstead ME, Brown ME, Hawkes CA, Lambermon MH, Phinney AL, Darabie AA, Cousins JE, French JE, Lan MF, Chen F, Wong SS, Mount HT, Fraser PE, Westaway D, St George-Hyslop P. · Centre for Research in Neurodegenerative Diseases, 6 Queen's Park Crescent West, Toronto, Ontario M5S 3H2 Canada. · Nat Med. · Pubmed #16767098 No free full text.

Abstract: When given orally to a transgenic mouse model of Alzheimer disease, cyclohexanehexol stereoisomers inhibit aggregation of amyloid beta peptide (Abeta) into high-molecular-weight oligomers in the brain and ameliorate several Alzheimer disease-like phenotypes in these mice, including impaired cognition, altered synaptic physiology, cerebral Abeta pathology and accelerated mortality. These therapeutic effects, which occur regardless of whether the compounds are given before or well after the onset of the Alzheimer disease-like phenotype, support the idea that the accumulation of Abeta oligomers has a central role in the pathogenesis of Alzheimer disease.

Alves da Costa C, Sunyach C, Pardossi-Piquard R, Sévalle J, Vincent B, Boyer N, Kawarai T, Girardot N, St George-Hyslop P, Checler F. · Institute of Molecular and Cellular Pharmacology, Coeducational Unit of Research 6097, National Center of Scientific Research/Nice-Sophia-Antipolis University, 06560 Valbonne, France. · J Neurosci. · Pubmed #16763046 links to  free full text

Abstract: Presenilins (PSs) are part of the gamma-secretase complex that produces the amyloid beta-peptide (Abeta) from its precursor [beta-amyloid precursor protein (betaAPP)]. Mutations in PS that cause familial Alzheimer's disease (FAD) increase Abeta production and trigger p53-dependent cell death. We demonstrate that PS deficiency, catalytically inactive PS mutants, gamma-secretase inhibitors, and betaAPP or amyloid precursor protein-like protein 2 (APLP2) depletion all reduce the expression and activity of p53 and lower the transactivation of its promoter and mRNA expression. p53 expression also is diminished in the brains of PS- or betaAPP-deficient mice. The gamma- and epsilon-secretase-derived amyloid intracellular C-terminal domain (AICD) fragments (AICDC59 and AICDC50, respectively) of betaAPP trigger p53-dependent cell death and increase p53 activity and mRNA. Finally, PS1 mutations enhance p53 activity in human embryonic kidney 293 cells and p53 expression in FAD-affected brains. Thus our study shows that AICDs control p53 at a transcriptional level, in vitro and in vivo, and that FAD mutations increase p53 expression and activity in cells and human brains.

Pardossi-Piquard R, Dunys J, Yu G, St George-Hyslop P, Alves da Costa C, Checler F. · Institut de Pharmacologie Moléculaire et Cellulaire du Centre National de la Recherche Scientifique, Equipe labellisée Fondation pour la Recherche Médicale, Valbonne, France. · J Neurochem. · Pubmed #16606360 No free full text.

Abstract: We recently demonstrated that the presenilin-dependent gamma-secretase complex regulates the expression and activity of neprilysin, one of the main enzymes that degrade the amyloid beta-peptide (Abeta) which accumulates in Alzheimer's disease. Here, we examined the influence of endogenous nicastrin (NCT), a member of the gamma-secretase complex, on neprilysin physiology. We show that nicastrin deficiency drastically lowers neprilysin expression, membrane-bound activity and mRNA levels, but it did not modulate the expression of two other putative Abeta-cleaving enzymes, endothelin-converting enzyme and insulin-degrading enzyme. Furthermore, we show that nicastrin restores neprilysin activity and expression in nicastrin-deficient, but not presenilin-deficient fibroblasts, indicating that the control of neprilysin necessitates the complete gamma-secretase complex harbouring its four reported components. Finally, we show that NCT expression peaked 24 h after NCT cDNA transfection of wild-type and NCT-/- fibroblasts, while neprilysin expression drastically increased only after 36 h and was maximal at 48 h. This delayed effect on neprilysin expression correlates well with our demonstration of an indirect gamma-secretase-dependent modulation of neprilysin at its transcriptional level.

Tian X, Cecal R, McLaurin J, Manea M, Stefanescu R, Grau S, Harnasch M, Amir S, Ehrmann M, St George-Hyslop P, Kohlmann M, Przybylski M. · Department of Chemistry, Analytical Chemistry, University of Konstanz, 78457 Konstanz, Germany. · Eur J Mass Spectrom (Chichester, Eng). · Pubmed #16322661 No free full text.

Abstract: Alzheimer's disease (AD) is the most common cause for human age-related dementia, characterised by formation of diffuse plaques in brain that are directly involved in AD pathogenesis. The major component of AD plaques is beta-amyloid, a 40 to 42 amino acid polypeptide derived from the amyloid precursor protein (APP) by proteolytic degradation involving the specific proteases, beta-and gamma-secretase acting at the N- and C- terminal cleavage site, respectively. In this study we have prepared polypeptides comprising the carboxy-terminal and transmembrane sequences of APP, by bacterial expression and chemical synthesis, as substrates for studying the C-terminal processing of APP and its interaction with the gamma-secretase complex. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used as a major tool for structure analysis. Immunisation of transgenic mouse models of AD with Abeta42 has been recently shown to be effective to inhibit and disaggregate Abeta-fibrils, and to reduce AD-related neuropathology and memory impairments. However, the mechanism underlying these therapeutic effects has been as yet unclear. Using proteolytic epitope excision from immune complexes in combination with FT-ICR-MS, we identified the epitope recognised by the therapeutically active antibody as the N-terminal Abeta(4-10) sequence; this soluble, nontoxic epitope opens new lead structures for AD vaccine development. A monoclonal antibody (Jonas; JmAb) directed against the cytosolic APP domain was used in studies of APP biochemistry and metabolism. Here we report the identification of the epitope recognised by the JmAb, using the combination of epitope excision and peptide mapping by FT-ICR-MS. The epitope was determined to be located at the C-terminal APP(740-747) sequence; it was confirmed by ELISA binding assays and authentic synthetic peptides and will be an efficient tool in the development of new specific vaccines. These results demonstrate high-resolution FT-ICR-MS as a powerful method for characterising biochemical pathways and molecular recognition structures of APP.

Moonis M, Swearer JM, Dayaw MP, St George-Hyslop P, Rogaeva E, Kawarai T, Pollen DA. · Department of Neurology, University of Massachusetts Medical School, 55 Lake Ave. N., Worcester, MA 01655, USA. · Neurology. · Pubmed #16043812 No free full text.

Abstract: CSF amyloid beta-peptide 42 (Abeta42) levels in presymptomatic subjects with pathogenic mutations in the PS1 gene are significantly lower than in an age-matched control group. Consequently, in these subjects, there is a window of opportunity estimated as at least 4 to 12 years to evaluate the ability of any putative prophylactic therapy to decrease, arrest, or reverse abnormalities in Abeta42 metabolism many years before clinical symptoms of Alzheimer disease are otherwise likely to occur.

Mastrangelo P, Mathews PM, Chishti MA, Schmidt SD, Gu Y, Yang J, Mazzella MJ, Coomaraswamy J, Horne P, Strome B, Pelly H, Levesque G, Ebeling C, Jiang Y, Nixon RA, Rozmahel R, Fraser PE, St George-Hyslop P, Carlson GA, Westaway D. · Centre for Research in Neurodegenerative Diseases, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada M5S 3H2. · Proc Natl Acad Sci U S A. · Pubmed #15951428 links to  free full text

Abstract: Gamma-secretase depends on presence of presenilins (PS), Nct, Aph-1, and PEN-2 within a core complex. This endoproteolytic activity cleaves within transmembrane domains of amyloid-beta precursor protein (APP) and Notch, and familial Alzheimer's disease (FAD) mutations in PS1 or PS2 genes shift APP cleavage from production of amyloid-beta (Abeta) 40 peptide to greater production of Abeta42. Although studies in PS1/PS2-deficient embryonic cells define overlapping activities for these proteins, in vivo complementation of PS1-deficient animals described here reveals an unexpected spectrum of activities dictated by PS1 and PS2 alleles. Unlike PS1 transgenes, wild-type PS2 transgenes expressed in the mouse CNS support little Abeta40 or Abeta42 production, and FAD PS2 alleles support robust production of only Abeta42. Although wild-type PS2 transgenes failed to rescue Notch-associated skeletal defects in PS1 hypomorphs, a "gained" competence in this regard was apparent for FAD alleles of PS2. The range of discrete and divergent processing activities in mice reconstituted with different PS genes and alleles argues against gamma-secretase being a single enzyme with intrinsically relaxed substrate and cleavage site specificities. Instead, our studies define functionally distinct gamma-secretase variants. We speculate that extrinsic components, in combination with core complexes, may tailor functional variants of this enzyme to their preferred substrates.

Nakaya Y, Yamane T, Shiraishi H, Wang HQ, Matsubara E, Sato T, Dolios G, Wang R, De Strooper B, Shoji M, Komano H, Yanagisawa K, Ihara Y, Fraser P, St George-Hyslop P, Nishimura M. · Molecular Neuroscience Research Center, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan. · J Biol Chem. · Pubmed #15764596 links to  free full text

Abstract: Familial Alzheimer disease-causing mutations in the presenilins increase production of longer pathogenic amyloid beta-peptides (A beta(42/43)) by altering gamma-secretase activity. The mechanism underlying this effect remains unknown, although it has been proposed that heteromeric macromolecular complexes containing presenilins mediate gamma-secretase cleavage of the amyloid beta-precursor protein. Using a random mutagenesis screen of presenilin-1 (PS1) for PS1 endoproteolysis-impairing mutations, we identified five unique mutants, including R278I-PS1 and L435H-PS1, that exclusively generated a high level of A beta43, but did not support physiological PS1 endoproteolysis or A beta40 generation. These mutants did not measurably alter the molecular size or subcellular localization of PS1 complexes. Pharmacological studies indicated that the up-regulation of activity for A beta43 generation by these mutations was not further enhanced by the difluoroketone inhibitor DFK167 and was refractory to inhibition by sulindac sulfide. These results suggest that PS1 mutations can lead to a wide spectrum of changes in the activity and specificity of gamma-secretase and that the effects of PS1 mutations and gamma-secretase inhibitors on the specificity are mediated through a common mechanism.