What Do Recent Clinical Trials Teach Us About the Etiology of AD

Alzheimer's disease (AD) is the most common type of dementia caused by severe neurodegeneration in the hippocampus and neocortical regions of the brain. In addition to neurodegeneration, AD brains contain high levels of amyloid plaques (APs) and neurofibrillary tangles (NFTs) which are used as neuropathological hallmarks of the disorder. Despite intense research efforts, the mechanism(s) of the AD neurodegeneration are imperfectly understood, hampering efforts for the development of efficient therapeutics. Furthermore, failure of clinical trials to benefit AD patients suggests that AD hallmarks are poor therapeutic targets and supports the suggestion that these hallmarks are sequelae of neurodegeneration. Although genetic evidence seem to support the amyloid theory of AD, additional empirical observations and experimental data are inconsistent with the amyloid/Aβ theories of AD [Robakis and Neve (1998), TINS vol. 21 pp.15-19; Robakis (2011) NBA vol. 32, pp 372-379]. This possibility is further supported by data that amyloid plaques and neurofibrillary tangles are found in a number of distinct neurodegenerative disorders and that animal models expressing high levels of AD pathological structures show little neuronal loss. Furthermore, genetic evidence linking genetic loci to disease reveal little about the molecular mechanisms involved. Mutants of APP, PS1, and PS2 cause familial AD (FAD) suggesting these mutants can be used as models to study mechanisms of neurodegeneration. Recent reports show that the ability of efnB1 and BDNF (factors) to rescue neurons from excitotoxicity depends on PS1 but is independent of γ-secretase. Interestingly, PS1 FAD mutations block the ability of factors to protect neurons from toxicity suggesting that FAD mutants may increase neuronal death by blocking neuroprotective activities of brain neurotrophins. Other reports also suggest that proteins involved in FAD have Aβ-/γ-secretase-independent functions that can play important roles in AD. Furthermore, non-neuronal brain cells like microglia are implicated in AD pathology.

The impact of the availability of prevention studies on the desire to undergo predictive testing in persons at risk for autosomal dominant Alzheimer's disease

Persons at risk for autosomal dominant neurodegenerative diseases provide the opportunity to efficiently test preventive interventions. Only a minority of such persons, however, choose to undergo revealing genetic testing, presenting a challenge to enrollment. Thirty-four preclinical Latinos (n = 26) and non-Latinos at risk for familial Alzheimer's disease (FAD) unaware of their genetic status were administered a questionnaire exploring their interest in undergoing revealing genetic testing at baseline and in the context of eligibility for four prevention trials of increasing invasiveness. Forty-four percent of subjects expressed a baseline interest in undergoing revealing testing which increased to 85% in order to be eligible for a study of an oral drug "felt to be very safe." If there were a 50% chance of receiving placebo, this number dropped to 62% (p = 0.02). Among those not interested in a study involving a 50% chance of receiving placebo, a range of 5% to 40% chance of receiving placebo was given as acceptable. For more invasive studies, living in the United States (as opposed to Mexico) positively influenced the likelihood of participating. Our data suggest that clinical trial designs in which persons must confront their genetic status prior to enrollment are feasible. Study designs to minimize the likelihood of being placed on placebo or provide the eventual administration of the drug through open-label extensions should be considered.

Dimerization of ubiquilin is dependent upon the central region of the protein: evidence that the monomer, but not the dimer, is involved in binding presenilins

Ubiquilin proteins have been shown to interact with a wide variety of other cellular proteins, often regulating the stability and degradation of the interacting protein. Ubiquilin contains a UBL (ubiquitin-like) domain at the N-terminus and a UBA (ubiquitin-associated) domain at the C-terminus, separated by a central region containing Sti1-like repeats. Little is known about regulation of the interaction of ubiquilin with other proteins. In the present study, we show that ubiquilin is capable of forming dimers, and that dimerization requires the central region of ubiquilin, but not its UBL or the UBA domains. Furthermore, we provide evidence suggesting that monomeric ubiquilin is likely to be the active form that is involved in binding presenilin proteins. Our results provide new insight into the regulatory mechanism underlying the interaction of ubiquilin with presenilins.

Cognitive deficits in familial Alzheimer's disease associated with M239V mutation of presenilin 2

The neuropsychological assessment of non-demented subjects with gene mutation of familial Alzheimer's disease (AD) provides a model for exploring the early cognitive features of the disease. We evaluated 1 patient and 6 non-demented subjects belonging to a family with AD with M239V mutation of the presenilin 2 gene, aiming to verify the contribution of specific cognitive patterns to the characterization of familial AD. One patient, 3 non-demented subjects with M239V mutation and 3 subjects without mutation from the same family underwent neuropsychological testing. The patient's cognitive profile was characterized by anosognosia, visuospatial agnosia, apraxia and fluent aphasia. Of the 3 non-demented subjects with mutation, 1 showed no deficits, another constructive apraxia and the third spatial perception and memory deficits. The 3 subjects without mutation showed normal abilities. The cognitive deficits of the non-demented subjects with mutations indicate focal dysfunction of the posterior cortical areas, resembling the more extended parieto-occipito-temporal dysfunction of the demented patient. Such grading of visuospatial, praxis, and language impairments highlights a distinctive pattern related to the M239V mutation of the presenilin 2 gene.

Differential role of Presenilin-1 and -2 on mitochondrial membrane potential and oxygen consumption in mouse embryonic fibroblasts

Increasing evidence indicates that mitochondrial alterations contribute to the neuronal death in Alzheimer's disease (AD). Presenilin 1 (PS1) and Presenilin 2 (PS2) mutations have been shown to sensitize cells to apoptosis by mechanisms suggested to involve impaired mitochondrial function. We have previously detected active gamma-secretase complexes in mitochondria. We investigated the impact of PS/gamma-secretase on mitochondrial function using mouse embryonal fibroblasts derived from wild-type, PS1-/-, PS2-/- and PS double knock-out (PSKO) embryos. Measurements of mitochondrial membrane potential (DeltaPsim) showed a higher percentage of fully functional mitochondria in PS1-/- and PSwt as compared to PS2-/- and PSKO cells. This result was evident both in whole cell preparations and in isolated mitochondria. Interestingly, pre-treatment of isolated mitochondria with the gamma-secretase inhibitor L-685,458 resulted in a decreased population of mitochondria with high DeltaPsim in PSwt and PS1-/- cells, indicating that PS2/gamma-secretase activity can modify DeltaPsim. PS2-/- cells showed a significantly lower basal respiratory rate as compared to other cell lines. However, all cell lines demonstrated competent bioenergetic function. These data point toward a specific role of PS2/gamma-secretase activity for proper mitochondrial function and indicate interplay between PS1 and PS2 in mitochondrial functionality.

Neurodegeneration and hereditary dementias: 40 years of learning

The invitation to participate in the commemorative issue celebrating the 100 th anniversary of Dr. Alois Alzheimer's report on the disease that would later bear his name has evoked memories of my early experiences in the study of dementia, my teachers, my role-models, my aspirations and my accomplishments. Early in my career, I was fascinated with the study of hereditary neurological disorders. The observation of families in which dementia was inherited in an autosomal dominant pattern excited my scientific curiosity. Three very different phenotypes in patients from three separate families have been the basis for novel scientific discovery, which has taken place over the past 30 years. This could not have taken place without the help of many generous patients and their families as well as wonderful colleagues for whom I am deeply grateful. Some of the original observations in these families have led to the discovery of genetic mutations in three genes that are among the most commonly affected in hereditary dementia. The work on these families has enriched the scientific community and our knowledge of dementing illnesses.

Genetic complexity of Alzheimer's disease: successes and challenges

About 1% of Alzheimer's Disease (AD) cases have an early-onset autosomal dominant familial form of the disease, genetic analyses of which have found three causal genes: amyloid beta-protein precursor (AbetaPP), presenilin 1 (PS1) and presenilin 2 (PS2). The APOE gene is the only robustly replicated risk factor for the common form of AD with onset after 65 years of age. In at least half of the AD cases, there is no known cause of the disease. Here we provide an overview on known AD-linked genes and discuss the strategies of searching for novel AD genetic risk factors.

Tauroursodeoxycholic acid modulates p53-mediated apoptosis in Alzheimer's disease mutant neuroblastoma cells

Early onset familial Alzheimer's disease (FAD) is linked to autosomal dominant mutations in the amyloid precursor protein (APP) and presenilin 1 and 2 (PS1 and PS2) genes. These are critical mediators of total amyloid beta-peptide (Abeta) production, inducing cell death through uncertain mechanisms. Tauroursodeoxycholic acid (TUDCA) modulates exogenous Abeta-induced apoptosis by interfering with E2F-1/p53/Bax. Here, we used mouse neuroblastoma cells that express either wild-type APP, APP with the Swedish mutation (APPswe), or double-mutated human APP and PS1 (APPswe/DeltaE9), all exhibiting increased Abeta production and aggregation. Cell viability was decreased in APPswe and APPswe/DeltaE9 but was partially reversed by z-VAD.fmk. Nuclear fragmentation and caspase 2, 6 and 8 activation were also readily detected. TUDCA reduced nuclear fragmentation as well as caspase 2 and 6, but not caspase 8 activities. p53 activity, and Bcl-2 and Bax changes, were also modulated by TUDCA. Overexpression of p53, but not mutant p53, in wild-type and mutant neuroblastoma cells was sufficient to induce apoptosis, which, in turn, was reduced by TUDCA. In addition, inhibition of the phosphatidylinositide 3'-OH kinase pathway reduced TUDCA protection against p53-induced apoptosis. In conclusion, FAD mutations are associated with the activation of classical apoptotic pathways. TUDCA reduces p53-induced apoptosis and modulates expression of Bcl-2 family.

Altered membrane fluidity and lipid raft composition in presenilin-deficient cells

The pathology of Alzheimer's disease is closely connected with lipid metabolism. Processing of amyloid precursor protein (APP) is sensitive to membrane alterations in levels of cholesterol and gangliosides. As cholesterol and gangliosides are major components of rafts and BACE I and gamma-secretase are supposed to be localized to rafts there might be a yet unknown biological function underlying this connection. Increasing evidence shows a close connection between cholesterol homeostasis and APP processing and Abeta production respectively. We measured membrane fluidity by anisotropy determination, isolated detergent resistant membrane (DRM) fractions from membrane preparations and determined cholesterol content of these fractions by a coupled enzymatic assay. We found membrane fluidity to be changed in mouse embryonic fibroblasts (MEF) PS1/2 -/- along with altered cholesterol content in DRM fraction of these cells. In addition, total ganglioside levels were enhanced in absence of presenilin (PS).

Single cell gene expression profiling in Alzheimer's disease

Development and implementation of microarray techniques to quantify expression levels of dozens to hundreds to thousands of transcripts simultaneously within select tissue samples from normal control subjects and neurodegenerative diseased brains has enabled scientists to create molecular fingerprints of vulnerable neuronal populations in Alzheimer's disease (AD) and related disorders. A goal is to sample gene expression from homogeneous cell types within a defined region without potential contamination by expression profiles of adjacent neuronal subpopulations and nonneuronal cells. The precise resolution afforded by single cell and population cell RNA analysis in combination with microarrays and real-time quantitative polymerase chain reaction (qPCR)-based analyses allows for relative gene expression level comparisons across cell types under different experimental conditions and disease progression. The ability to analyze single cells is an important distinction from global and regional assessments of mRNA expression and can be applied to optimally prepared tissues from animal models of neurodegeneration as well as postmortem human brain tissues. Gene expression analysis in postmortem AD brain regions including the hippocampal formation and neocortex reveals selectively vulnerable cell types share putative pathogenetic alterations in common classes of transcripts, for example, markers of glutamatergic neurotransmission, synaptic-related markers, protein phosphatases and kinases, and neurotrophins/neurotrophin receptors. Expression profiles of vulnerable regions and neurons may reveal important clues toward the understanding of the molecular pathogenesis of various neurological diseases and aid in identifying rational targets toward pharmacotherapeutic interventions for progressive, late-onset neurodegenerative disorders such as mild cognitive impairment (MCI) and AD.

Estrogen receptor (ER)-beta isoforms: a key to understanding ER-beta signaling

Estrogen receptor beta (ER-beta) regulates diverse physiological functions in the human body. Current studies are confined to ER-beta1, and the functional roles of isoforms 2, 4, and 5 remain unclear. Full-length ER-beta4 and -beta5 isoforms were obtained from a prostate cell line, and they exhibit differential expression in a wide variety of human tissues/cell lines. Through molecular modeling, we established that only ER-beta1 has a full-length helix 11 and a helix 12 that assumes an agonist-directed position. In ER-beta2, the shortened C terminus results in a disoriented helix 12 and marked shrinkage in the coactivator binding cleft. ER-beta4 and -beta5 completely lack helix 12. We further demonstrated that ER-beta1 is the only fully functional isoform, whereas ER-beta2, -beta4, and -beta5 do not form homodimers and have no innate activities of their own. However, the isoforms can heterodimerize with ER-beta1 and enhance its transactivation in a ligand-dependent manner. ER-beta1 tends to form heterodimers with other isoforms under the stimulation of estrogens but not phytoestrogens. Collectively, these data support the premise that (i) ER-beta1 is the obligatory partner of an ER-beta dimer, whereas the other isoforms function as variable dimer partners with enhancer activity, and (ii) a single functional helix 12 in a dimer is sufficient for gene transactivation. Thus, ER-beta behaves like a noncanonical type-I receptor, and its action may depend on differential amounts of ER-beta1 homo- and heterodimers formed upon stimulation by a specific ligand. Our findings have provided previously unrecognized directions for studying ER-beta signaling and design of ER-beta-based therapies.

TFII-I down-regulates a subset of estrogen-responsive genes through its interaction with an initiator element and estrogen receptor alpha

TFII-I was initially identified as the general transcription factor that binds to initiator (Inr) elements in vitro. Subsequent studies have shown that TFII-I activates transcription of various genes either through Inr elements or through other upstream elements in vivo. Since, however, most studies so far on TFII-I have been limited to over-expression and reporter gene assays, we reevaluated the role of TFII-I in vivo by using stable knockdown with siRNA and by examining the expression of endogenous genes. Contrary to the widely accepted view, here we show that TFII-I is not important for cell viability in general but rather inhibits the growth of MCF-7 human breast cancer cells. MCF-7 cells are known to proliferate in an estrogen-dependent manner. Through analysis of TFII-I's cell-type specific growth inhibitory effect, we show evidence that TFII-I down-regulates a subset of estrogen-responsive genes, only those containing Inr elements, by recruiting estrogen receptor (ER) alpha and corepressors to these promoters. Thus, this study has revealed an unexpected new role of TFII-I as a negative regulator of transcription and cell proliferation.

Mean age-of-onset of familial alzheimer disease caused by presenilin mutations correlates with both increased Abeta42 and decreased Abeta40

The varied ways in which mutations in presenilins (PSEN1 and PSEN2) affect amyloid b precursor protein (APP) processing in causing early-onset familial Alzheimer disease (FAD) are complex and not yet properly understood. Nonetheless, one useful diagnostic marker is an increased ratio of Ab42 to Ab40 (Ab42/Ab40) in patients' brain and biological fluids as well as in transgenic mice and cells. We studied Ab and APP processing for a set of nine clinical PSEN mutations on a novel and highly reproducible enzyme-linked immunosorbent assay (ELISA)-based in vitro method and also sought correlation with brain Ab analyzed by image densitometry and mass spectrometry. All mutations significantly increased Ab42/Ab40 in vitro by significantly decreasing Ab40 with accumulation of APP C-terminal fragments, a sign of decreased PSEN activity. A significant increase in absolute levels of Ab42 was observed for only half of the mutations tested. We also showed that age-of-onset of PSEN1-linked FAD correlated inversely with Ab42/Ab40 (r = -0.89; P = 0.001) and absolute levels of Ab42 (r = -0.83; P = 0.006), but directly with Ab40 levels (r = 0.69; P = 0.035). These changes also partly correlated with brain Ab42 and Ab40 levels. Together, our data suggested that Ab40 might be protective by perhaps sequestering the more toxic Ab42 and facilitating its clearance. Also, the in vitro method we describe here is a valid tool for assaying the pathogenic potential of clinical PSEN mutations in a molecular diagnostic setting.

Breast Cancer–Specific mRNA Transcripts Presence in Peripheral Blood After Adjuvant Chemotherapy Predicts Poor Survival Among High-Risk Breast Cancer Patients Treated With High-Dose Chemotherapy With Peripheral Blood Stem Cell Support

Purpose

To study the prognostic significance of the presence of breast cancer–specific mRNA transcripts in peripheral blood (PB), defined by serial analysis of gene expression, in high-risk breast cancer (HRBC) patients undergoing high-dose chemotherapy after receiving adjuvant chemotherapy.

Methods

From 1994 to 2000, 84 HRBC patients (median age, 44 years; > 10 nodes; 74%) received adjuvant chemotherapy (fluorouracil, epirubicin, and cyclophosphamide for six cycles [83%] or doxorubicin and cyclophosphamide followed by paclitaxel) before undergoing one course of cyclophosphamide plus thiotepa plus carboplatin (STAMP V). Radiotherapy or hormone therapy was administered whenever indicated. Aliquots of apheresis-mononuclear blood cells were frozen from each patient. mRNA was isolated using an automatic nucleic acid extractor based on the magnetic beads technology; reverse transcription was performed using random hexamers. Cytokeratin 19, HER-2, P1B, PS2, and EGP2 transcripts were quantified to B-glucuronidase by real-time polymerase chain reaction (RT-PCR) using a linear DNA probe marked with a quencher and reporter fluorophores used in RT-PCR. Presence of PB micrometastases, estrogen receptor and progesterone receptor status, tumor size, age, tumor grade, number of nodes affected, and treatment with paclitaxel were included in the statistical analysis.

Results

Median follow-up was 68.3 months (range, 6 months to 103 months). Forty-seven relapses (56%) and 35 deaths (41.7%) were registered. Both tumor size and presence of micrometastases reached statistical significance according to the Cox multivariate model. Relapse hazard ratio (HR) for those patients with PB micrometastases was 269% (P = .006); death HR, 300% (P = .011). Time relapse was 53 months longer for patients without micrometastases: 31.3 v 84.2 months (P = .021).

Conclusion

PB micrometastases presence after adjuvant chemotherapy predicts both relapse and death more powerful than classical factors in HRBC patients undergoing high-dose chemotherapy. Micrometastases search using a gene panel appears to be a more accurate procedure than classical approaches involving only one or two genes.

A topoisomerase IIbeta-mediated dsDNA break required for regulated transcription

Multiple enzymatic activities are required for transcriptional initiation. The enzyme DNA topoisomerase II associates with gene promoter regions and can generate breaks in double-stranded DNA (dsDNA). Therefore, it is of interest to know whether this enzyme is critical for regulated gene activation. We report that the signal-dependent activation of gene transcription by nuclear receptors and other classes of DNA binding transcription factors, including activating protein 1, requires DNA topoisomerase IIbeta-dependent, transient, site-specific dsDNA break formation. Subsequent to the break, poly(adenosine diphosphate-ribose) polymerase-1 enzymatic activity is induced, which is required for a nucleosome-specific histone H1-high-mobility group B exchange event and for local changes of chromatin architecture. Our data mechanistically link DNA topoisomerase IIbeta-dependent dsDNA breaks and the components of the DNA damage and repair machinery in regulated gene transcription.

Presenilin-dependent gamma-secretase-mediated control of p53-associated cell death in Alzheimer's disease

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.

Up-regulation of inositol 1,4,5-trisphosphate receptor type 1 is responsible for a decreased endoplasmic-reticulum Ca2+ content in presenilin double knock-out cells

Presenilins (PS) are proteins involved in the pathogenesis of autosomal-dominant familial cases of Alzheimer's disease. Mutations in PS are known to induce specific alterations in cellular Ca2+ signaling which might be involved in the pathogenesis of neurodegenerative diseases. Mouse embryonic fibroblasts (MEF) deficient in PS1 and PS2 (PS DKO) as well as the latter rescued with PS1 (Rescue), were used to investigate the underlying mechanism of these alterations in Ca2+ signaling. PS DKO cells were characterized by a decrease in the [Ca2+]ER as measured by ER-targeted aequorin luminescence and an increased level of type 1 inositol 1,4,5-trisphosphate receptor (IP3R1). The lower [Ca2+]ER was associated with an increase in a Ca2+ leak from the ER. The increased IP3R1 expression and the concomitant changes in ER Ca2+ handling were reversed in the Rescue cells. Moreover using RNA-interference mediated reduction of IP3R1 we could demonstrate that the up-regulation of this isoform was responsible for the increased Ca2+ leak and the lowered [Ca2+]ER PS DKO cells. Finally, we show that the decreased [Ca2+]ER in PS DKO cells was protective against apoptosis.

The Presenilin-2 Loop Peptide Perturbs Intracellular Ca2+ Homeostasis and Accelerates Apoptosis

In cells undergoing apoptosis, a 22-amino-acid presenilin-2-loop peptide (PS2-LP, amino acids 308-329 in presenilin-2) is generated through cleavage of the carboxyl-terminal fragment of presenilin-2 by caspase-3. The impact of PS2-LP on the progression of apoptosis, however, is not known. Here we show that PS2-LP is a potent inducer of the mitochondrial-dependent cell death pathway when transduced as a fusion protein with HIV-TAT. Biochemical and functional studies demonstrate that TAT-PS2-LP can interact with the inositol 1,4,5-trisphosphate receptor and activate Ca(2+) release from the endoplasmic reticulum. These results indicate that PS2-LP-mediated alteration of intracellular Ca(2+) homeostasis may be linked to the acceleration of apoptosis. Therefore, targeting the function of PS2-LP could provide a useful therapeutic tool for the treatment of cancer and degenerative diseases.

Protease digestion indicates that endogenous presenilin 1 is present in at least two physical forms

The membrane-bound protein complex gamma-secretase is an intramembranous protease whose substrates are a number of type I transmembrane proteins including the beta-amyloid precursor protein (APP). A presenilin molecule is thought to be the catalytic unit of gamma-secretase and either of two presenilin homologues, PS1 or PS2, can play this role. Mutations in the presenilins, apparently leading to aberrant processing of APP, have been genetically linked to early-onset familial Alzheimer's disease. To look for possible molecular heterogeneity in presenilin/gamma-secretase we examined the ability of proteinase K (PK) to digest endogenously expressed presenilins in intact endoplasmic reticulum vesicles. We demonstrate the existence of two physically different forms of gamma-secretase-associated PS1, one that is relatively PK-sensitive and one that is significantly more PK-resistant. A similarly PK-resistant form of PS2 was not observed. We speculate that the structural heterogeneity we observe may underlie, at least in part, previous observations indicating the physical and functional heterogeneity of gamma-secretase. In particular, our results suggest that there are significant differences between gamma-secretase complexes incorporating PS1 and PS2. This difference may underlie the more dominant role of PS1 in the generation of beta-amyloid peptides and in familial Alzheimer's disease.

DAPT-induced intracellular accumulations of longer amyloid beta-proteins: further implications for the mechanism of intramembrane cleavage by gamma-secretase

Gamma-secretase cleaves the transmembrane domain of beta-amyloid precursor protein at multiple sites. These are referred to as gamma-, zeta-, and epsilon-cleavages. We showed previously that DAPT, a potent dipeptide gamma-secretase inhibitor, caused differential accumulations of longer amyloid beta-proteins (Abetas) (Abeta43 and Abeta46) in CHO cells that are induced to express the beta C-terminal fragment (CTF). To learn more about the cleavage mechanism by gamma-secretase, CHO cell lines coexpressing betaCTF and wild-type or mutant presenilin (PS) 1/2 were generated and treated with DAPT. In all cell lines treated with DAPT, as the levels of Abeta40 decreased, Abeta46 accumulated to varying extents. In wild-type PS1 or M146L mutant PS1 cells, substantial amounts of Abeta43 and Abeta46 accumulated. In contrast, this was not the case with wild-type PS2 cells. In M233T mutant PS1 cells, significant amounts of Abeta46 and Abeta48 accumulated differentially, whereas in N141I mutant PS2 cells, large amounts of Abeta45 accumulated concomitantly with a large decrease in Abeta42 levels. Most interestingly, in G384A mutant PS1 cells, there were no significant accumulations of longer Abetas except for Abeta46. Abeta40 was very susceptible to DAPT, but other Abetas were variably resistant. Complicated suppression and accumulation patterns by DAPT may be explained by stepwise processing of betaCTF from a zeta- or epsilon-cleavage site to a gamma-cleavage site and its preferential suppression of gamma-cleavage over zeta- or epsilon-cleavage.

TMP21 is a presenilin complex component that modulates gamma-secretase but not epsilon-secretase activity

The presenilin proteins (PS1 and PS2) and their interacting partners nicastrin, aph-1 (refs 4, 5) and pen-2 (ref. 5) form a series of high-molecular-mass, membrane-bound protein complexes that are necessary for gamma-secretase and epsilon-secretase cleavage of selected type 1 transmembrane proteins, including the amyloid precursor protein, Notch and cadherins. Modest cleavage activity can be generated by reconstituting these four proteins in yeast and Spodoptera frugiperda (sf9) cells. However, a critical but unanswered question about the biology of the presenilin complexes is how their activity is modulated in terms of substrate specificity and/or relative activities at the gamma and epsilon sites. A corollary to this question is whether additional proteins in the presenilin complexes might subsume these putative regulatory functions. The hypothesis that additional proteins might exist in the presenilin complexes is supported by the fact that enzymatically active complexes have a mass that is much greater than predicted for a 1:1:1:1 stoichiometric complex (at least 650 kDa observed, compared with about 220 kDa predicted). To address these questions we undertook a search for presenilin-interacting proteins that differentially affected gamma- and epsilon-site cleavage events. Here we report that TMP21, a member of the p24 cargo protein family, is a component of presenilin complexes and differentially regulates gamma-secretase cleavage without affecting epsilon-secretase activity.

Genetic study of Sardinian patients with Alzheimer's disease

We describe the genetic analysis of an Alzheimer's disease (AD) sample derived from a genetically isolated population. Genetic assessment included the analysis of genes involved in AD, such as the genes for amyloid precursor protein (APP), presenilin 1 (PSEN1) and presenilin 2 (PSEN2). We also assessed genes for some proteins that constitute the gamma-secretase complex: nicastrin (NCSTN), presenilin enhancer-2 (PEN2), in addition to the AD risk factor apolipoprotein E (APOE). Using polymerase chain reaction and single strand conformational polymorphism method, screens for APP, PSEN1 and PSEN2 genes revealed one mutation in PSEN1. Furthermore, we found an intronic +17G>C polymorphism in PEN2 which, in homozygous form, was greater in early onset Alzheimer's disease (EOAD) compared to controls, and one haplotype in the NCSTN gene which was linked to EOAD and familial AD (FAD). Finally, the genotyping of APOE confirmed that the varepsilon4 allele could be a risk factor for the onset of AD, in particular for FAD subjects. In conclusion, these results show the existence of Sardinian genetic peculiarities, essential in studies regarding genetically inherited and multifactorial disorders, as AD.

Lewy body pathology in familial Alzheimer disease: evidence for disease- and mutation-specific pathologic phenotype

BACKGROUND

The origin and significance of Lewy bodies and neurites (Lewy body pathology [LBP]) in Alzheimer disease (AD) are poorly understood.

OBJECTIVE

To examine LBP in the brainstem, limbic cortex, and neocortex of a large number of familial AD cases with mutations in 2 presenilin (PSEN) genes.

METHODS

Twenty-five familial AD cases with 9 known PSEN 1 mutations and 14 familial AD cases with a single PSEN 2 mutation (N141I) were examined for LBP using alpha-synuclein immunohistochemistry and sampling of multiple brainstem and cortical regions.

RESULTS

The amygdala was the most vulnerable site for LBP. In fact, virtually all (24 [96%] of 25 cases) of the PSEN 1 mutation cases had LBP in the amygdala. The PSEN 1 mutation cases also had more frequent LBP in the amygdala and neocortex than those with the PSEN 2 mutation. However, within families with a single mutation of either PSEN 1 or PSEN 2, there was frequent variability of the LBP.

CONCLUSION

These findings suggest that there are genetic influences on the presence of LBP in familial AD as demonstrated by the differences between PSEN 1 and PSEN 2 mutation cases.

Genetics, transcriptomics, and proteomics of Alzheimer's disease

OBJECTIVE

To provide an updated overview of the methods used in genetic, transcriptomic, and proteomic studies in Alzheimer's disease and to demonstrate the importance of those methods for the improvement of the current diagnostic and therapeutic possibilities.

DATA SOURCES

MEDLINE-based search of 233 peer-reviewed articles published between 1975 and 2006.

DATA SYNTHESIS

Alzheimer's disease is a genetically heterogeneous disorder. Rare mutations in the amyloid precursor protein, presenilin 1, and presenilin 2 genes have shown the importance of the amyloid metabolism for its development. In addition, converging evidence from population-based genetic studies, gene expression studies, and protein profile studies in the brain and in the cerebrospinal fluid suggest the existence of several pathogenetic pathways such as amyloid precursor protein processing, beta-amyloid degradation, tau phosphorylation, proteolysis, protein misfolding, neuroinflammation, oxidative stress, and lipid metabolism.

CONCLUSIONS

The development of high-throughput genotyping methods and of elaborated statistical analyses will contribute to the identification of genetic risk profiles related to the development and course of this devastating disease. The integration of knowledge derived from genetic, transcriptomic, and proteomic studies will greatly advance our understanding of the causes of Alzheimer's disease, improve our capability of establishing an early diagnosis, help define disease subgroups, and ultimately help to pave the road toward improved and tailored treatments.

Amyloidogenic processing of beta-amyloid precursor protein in intracellular compartments

Trafficking and proteolytic processing of amyloid precursor protein (APP) have been the focus of numerous investigations in the past two decades, since the identification of Abeta as the principal component of brain senile plaques and the cloning of APP cDNA. Tremendous progress has been made in the recent past toward the characterization of beta- and gamma-secretases. Here, we review the salient features of Alzheimer disease amyloidogenesis, and discuss the current knowledge on APP trafficking and amyloidogenic processing of APP in intracellular membrane compartments and microdomains.

Antibody-bound amyloid precursor protein upregulates ornithine decarboxylase expression

Alzheimer's disease is a neurodegenerative disorder characterised by extracellular accumulation of the Abeta peptide, derived from the amyloid precursor protein (APP). The function of APP as a cell surface receptor was examined by ligand-mimicking using an antibody against the APP extracellular domain. Alterations in gene expression evoked by antibody-bound APP were analysed using human pathway-finder gene arrays and the largest change in expression levels was found for ornithine decarboxylase (ODC). These results were confirmed by Western blotting which showed even higher upregulation on the protein level. APP knockdown by RNAi verified that upregulation of ODC was APP-mediated. This APP signalling event did not require gamma-secretase cleavage, as it was independent of the presence of presenilin-1 or -2. The induced ODC expression was rapid and biphasic, resembling growth-factor stimulated signalling events. This study shows that antibody-bound APP leads to altered gene expression that may be relevant to AD.

[Genes in Alzheimer's disease]

INTRODUCTION

Alzheimer's disease (AD) is the most frequent degenerative dementia among the elderly population. Families that have an autosomal dominant pattern for AD constitute about 13% of early cases (< or = 65 years) and less than 0.01% of the total number of patients.

DEVELOPMENT

Molecular analysis of families with early onset AD has made it possible to identify mutations in three different genes that are responsible for the disease: the gene encoding for the amyloid precursor protein peptide (APP), and the presenilin 1 (PSEN1) and presenilin 2 (PSEN2) genes. Yet, these genes are involved in less than 5% of the total number of cases of AD. The remaining AD patients are mostly cases of late or familial onset, where the disease appears as a result of a complex interaction among environmental factors and individual predisposing genetic traits. A large number of molecular genetics studies have clearly implicated the APOE epsilon4 allele as a proven risk factor for the late form of AD in almost all the populations that have been studied.

CONCLUSIONS

Although the APOE epsilon4 allele is the only proven genetic risk factor for the late form of the disease, genetic epidemiological studies suggest that other loci are also involved.

The cytosolic loop of the gamma-secretase component presenilin enhancer 2 protects zebrafish embryos from apoptosis

The gamma-secretase complex, composed of presenilin, presenilin enhancer 2 (Pen-2), nicastrin, and Aph-1, catalyzes the final cleavage of amyloid precursor protein to generate the toxic amyloid beta protein, the major component of plaques in the brains of Alzheimer disease patients. To understand the in vivo function of Pen-2, we used morphant technology available in zebrafish and transiently knocked down the expression of endogenous Pen-2 by injecting the morpholino (MO) against Pen-2. Two truncated Pen-2 proteins lacking either the cytosolic or the C-terminal domain were expressed in MO-injected embryos. This deletion analysis demonstrated that the Pen-2 cytosolic loop is essential for protecting developing embryos from caspase-dependent apoptosis caused by the reduction of Pen-2. Twelve amino acids in the C terminus of Pen-2 were dispensable and could not rescue the Pen-2 knockdown-induced apoptotic phenotype. Surprisingly, double knockdown of Pen-2 and nuclear factor kappaB component p65 abrogated the single Pen-2 MO-induced caspase activation, indicating that a previously reported pro-apoptotic role of NF-kappaB in some cell types could be manifested in a whole animal and that knockdown of Pen-2 may trigger pro-apoptotic activation of NF-kappaB.

Functional characterization of novel presenilin-2 variants identified in human breast cancers

We identified in breast cancer cases two germline alterations, R62H and R71W, in presenilin-2 (PS-2), a gene involved in familial Alzheimer's disease (FAD). The role of these alleles in FAD is unclear, but neither allele affected Abeta(42)/Abeta(40) ratio. However, both R62H and R71W alterations compromised PS-2 function in Notch signaling in Caenorhabditis elegans and cell growth inhibition in mouse embryonic fibroblasts, and these effects were dependent on gene dosage. We found that both alterations enhanced the degradation of the PS-2 full-length protein, indicating that they may have a loss-of function effect. The effect of the R71W alteration was noticeably stronger, and we observed an almost threefold higher frequency of this allele in breast cancer cases versus controls, but this difference did not reach statistical significance. Nonetheless, these results collectively suggest that the novel PS-2 alleles described here, especially R71W, affect PS-2 function and may potentially confer a moderate risk of susceptibility to breast cancer.

Zebrafish lacking Alzheimer presenilin enhancer 2 (Pen-2) demonstrate excessive p53-dependent apoptosis and neuronal loss

Gamma-secretase cleavage, mediated by a complex of presenilin, presenilin enhancer (Pen-2), nicastrin, and Aph-1, is the final proteolytic step in generating amyloid beta protein found in brains of Alzheimer's disease patients and Notch intracellular domain critical for proper neuronal development. Here, we employ the zebrafish model to study the role of Pen-2 in neuronal survival. We found that (i) knockdown of Pen-2 using antisense morpholino led to a reduction of islet-1 positive neurons, (ii) Notch signaling was reduced in embryos lacking Pen-2 or other gamma-secretase components, (iii) neuronal loss in Pen-2 knockdown embryos is not as a result of a lack of neuronal precursor cells or cell proliferation, (iv) absence of Pen-2 caused massive apoptosis in the whole animal, which could be suppressed by simultaneous knockdown of the tumor suppressor p53, (v) loss of islet-1 or acetylated tubulin positive neurons in Pen-2 knockdown embryos could be partially rescued by knockdown of p53. Our results demonstrate that knockdown of Pen-2 directly induces a p53-dependent apoptotic pathway that contributes to neuronal loss and suggest that Pen-2 plays an important role in promoting neuronal cell survival and protecting from apoptosis in vivo.

Ubiquilin regulates presenilin endoproteolysis and modulates gamma-secretase components, Pen-2 and nicastrin

Mutations in presenilin proteins (PS1 and PS2) lead to early-onset Alzheimer's disease. PS proteins are endoproteolytically cleaved into two main fragments: the NTF (PS N-terminal fragment) and the CTF (PS C-terminal fragment). The two fragments are believed to constitute the core catalytic enzyme activity called gamma-secretase, which is responsible for cleaving beta-amyloid precursor protein to release Abeta. Thus, studying factors that modulate PS fragment levels could provide important information about gamma-secretase. Previously, we demonstrated that the protein, ubiquilin-1, interacts both in vivo and in vitro with PS and that overexpression of ubiquilin-1 or -2 leads to increased accumulation of full-length PS proteins. Using wild-type HEK-293 cells (human embryonic kidney 293 cells) and PS-inducible cells, we now show that overexpression of either ubiquilin-1 or -2 decreases the PS NTF and CTF levels. Conversely, siRNA (small interfering RNA)-mediated knockdown of ubiquilin-1 and -2 proteins increased the PS NTF and CTF levels. We considered that ubiquilin might alter PS fragment accumulation by acting as a shuttle factor escorting PS fragments to the proteasome for degradation. However, through proteasome inhibition studies, we show that this does not occur. Instead, our results suggest that ubiquilin regulates PS fragment production. We also examined whether other components of the gamma-secretase complex are affected by ubiquilin expression. Interestingly, overexpression of ubiquilin resulted in a decrease in Pen-2 and nicastrin levels, two essential components of the gamma-secretase complex. In contrast, knockdown of ubiquilin-1 and -2 protein expression by RNAi (RNA interference) increased Pen-2 and nicastrin levels. Finally, we show that inhibition of the proteasome results in decreased PS fragment production and that reversal of proteasome inhibition restores PS fragment production, suggesting that the proteasome may be involved in PS endoproteolysis. These studies implicate ubiquilin as an important factor in regulating PS biogenesis and metabolism.

Inhibition of cyclooxygenase as potential novel therapeutic strategy in N141I presenilin-2 familial Alzheimer's disease

The present study was designed to further explore the potential cause/effect relationship between the expression of both the N141I presenilin (PS)2 mutant familial Alzheimer's disease (FAD) gene and cyclooxgenase (COX) in respect to the mechanism associated with programmed cell death in Alzheimer's disease (AD). We found that expression of mutant N141I PS2 resulting in apoptotic cell death in H4 neuronal cells coincided with >4-fold induction in the expression of the inducible form of COX-2, but not the constitutive COX-1. Moreover, we found that the expression of the N141I PS2 FAD gene strongly promoted (>2-fold) glycogen synthase kinase (GSK)-3beta activity coincidental with a reduction in the level of beta-catenin translocated from the cytoplasmic to the nuclear compartment. Most interestingly, we found that inhibition of COX-2-mediated generation of prostaglandin (PG)-E2 in H4 neuronal cells with the preferential COX-2 inhibitor nimesulide protects against N141I PS2-mediated apoptotic cell death coincidental with an inhibition of GSK-3beta activity and subsequent normalization of beta-catenin cellular distribution. The clinical relevance of this finding was confirmed by the evidence that COX-2 protein and PG-E2 concentrations were selectively increased >2-fold in the cerebral cortex of subjects harboring the N141I PS2 FAD mutation relative to wild-type PS2 AD cases. This study demonstrates for the first time that COX-2 may be a downstream effector of mutant N141I PS2-mediated apoptotic cell death and that inhibition of COX-2 may neuroprotect in AD through modulation of a GSK-3beta-beta-catenin-mediated response. The study provides support for the potential pharmacogenomic identification of N141I PS2 FAD cases that might preferentially benefit from inhibition of COX-2 during the progression of clinical dementia.

La expresión del receptor del factor de crecimiento epidérmico (EGFR) en carcinomas mamarios hormonoindependientes

OBJECTIVE

To determine the expression of epidermal growth factor receptor (EGFR) in ER-negative and Pg-R negative infiltrating ductal carcinomas of the breast (IDC) and to analyze the possible relationship between the EGFR positivity and some clinico-biological parameters of tumors.

MATERIAL AND METHODS

EGFR was measured by a single point radioligand assay in the cell surfaces of 115 ER-negative and Pg-R-negative (< 10 fmol/mg prot.) IDC. We measured also the cytosolic concentrations of pS2, cathepsin D, tissue-type plasminogen activator (t-PA) and hyaluronic acid (AH), as well as the levels of AH in cell surfaces. Tumor size, axillary involvement, distant metastasis, histological grading, ploidy and S-phase (SP) were taken account.

RESULTS

Using as cut-off for EGFR a value of 5 fmol/mg prot., we can observed that IDCs -EGFR + had greater global values of S-phase (p: 0.005) and were more frequently metastastatic (p: 0.004), SP > 7 % (p < 0.001) and SP > 14 % (p: 0.077); likewise, they were lower frequently pS2-positive (p < 0.01) and t-PA-positive (p < 0.01). During the follow up time (median 85 months), the number of recurrences was higher in EGFR-positive than in EGFR- negative tumors (14/41 frente a 1/29; p: 0.002), but there was not differences in the number of deaths by the tumor.

CONCLUSIONS

1) The EGFR-positivity in ER-negative and PgR-negative IDCs is associated with distant metastasis, greater cellular proliferation (SP), lower positivity for pS2 and t-PA and greater number of recurrences. 2) Using 10 fmol/mg prot. as cut-off, we observed the same findings, except the change in cellular proliferation. 3) Our findings support the possible use of EGFR as a prognostic parameter in those breast carcinomas.

Differentially expressed genes in transgenic mice carrying human mutant presenilin-2 (N141I): correlation of selenoprotein M with Alzheimer's disease

Mutations in genes for Alzheimer's disease (AD) result in a modulating of gene expressions in the brains of patients with AD. The aim of this study was to identify genes whose expression is modulated due to the over-expression of human mutant presenilin-2 (N141I) (hPS2m) in transgenic mice, which has previously been produced by us. To test this, GeneFishing DEG101 technique was performed on large-scale screen of mRNA from transgenic and non-transgenic brains. A total of 40 transcriptional products corresponding to cDNA were compared between two brains, and 17 showed a differential expression between the samples in all sets of experiments. However, all showed significant homology to known genes. Initially, a cloning corresponding to human selenoprotein M (hSelM) was chosen for investigation further because SelM induced by sodium selenite, a pro-oxidant, may have a functional role in catalyze the free radicals. We found that mouse SelM had significantly suppressed on its transcriptional products in transgenic brains. In parallel, suppression of endogenous was not observed in transgenic brains. Moreover, the levels of green fluorescence on hSelM fusion protein with EGFP were suppressed in the cells transfected with hPS2m, and its levels had actually increased by treatments of sodium selenite. Thus, the results indicate that SelM might play a suppressive or protective role in the pathology of patients with AD and it will be necessary to investigate further on functional roles of other up- and down-regulated gene in future.

Presenilin immunoreactivity in Alzheimer's disease

The role of presenilin (PS) mutations in familial Alzheimer's disease (AD) may be as a toxic gain of function, but in sporadic disease their contribution is more difficult to understand. In this study, we investigated PS proteins in sporadic AD by comparing the immunocytochemical profiles in sporadic AD with control brains using a quantitative immunocytochemical approach to both the N- and C-terminals of PS1 and PS2. Ten patients with pathologically proven AD (using modified Consortium to Establish a Registry for Alzheimer's Disease [CERAD] criteria) and 10 controls were age- and sex-matched. The immunocytochemical primary antibodies were affinity-purified goat polyclonal antibodies and the secondary antibodies were biotinylated donkey anti-goat to the N- and C-terminal of both PS1 and PS2. The number of PS-containing neurones was quantified manually and without the knowledge of the diagnosis. We found no significant differences in the number of PS1- and PS2-containing neurones in three anatomical regions for both N- and C-terminals between AD and controls. Our findings argue in favour of functional changes in PS molecules contributing to the pathogenesis of AD and are consistent with the hypothesis of dysfunction of the entire gamma-secretase complex, of which PS proteins are a constituent.

Regulation of CRE-dependent transcription by presenilins: prospects for therapy of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder and is characterized by memory loss and other cognitive disabilities. Mutations in the presenilin genes are the major cause of familial AD. Analysis of conditional knockout mice has shown that inactivation of presenilins results in progressive memory impairment and age-dependent neurodegeneration, suggesting that reduced presenilin activity might represent an important pathogenic mechanism. Presenilins positively regulate the transcription of cAMP response element (CRE)-containing genes, some of which are known to be important for memory formation and neuronal survival. Phosphodiesterase 4 and histone deacetylase inhibitors, which can enhance CRE-dependent gene expression, have been shown to ameliorate memory deficits and neurodegeneration in animal models. Thus, modulation of CRE-dependent transcription might be beneficial for the treatment of dementia in AD.

Regulation of tyrosinase trafficking and processing by presenilins: partial loss of function by familial Alzheimer's disease mutation

Presenilins (PS) are required for gamma-secretase cleavage of multiple type I membrane proteins including the amyloid precursor protein and Notch and also have been implicated in regulating intracellular protein trafficking and turnover. Using genetic and pharmacological approaches, we reveal here a unique function of PS in the pigmentation of retinal pigment epithelium and epidermal melanocytes. PS deficiency leads to aberrant accumulation of tyrosinase (Tyr)-containing 50-nm post-Golgi vesicles that are normally destined to melanosomes. This trafficking is gamma-secretase-dependent, and abnormal localization of Tyr in the absence of PS is accompanied by the simultaneous accumulation of its C-terminal fragment. Furthermore, we show that the PS1M146V familial Alzheimer's disease mutation exhibits a partial loss-of-function in pigment synthesis. Our results identify Tyr and related proteins as physiological substrates of PS and link gamma-secretase activity with intracellular protein transport.

Diminished taxol/GTP-stimulated tubulin polymerization in diseased region of brain from patients with late-onset or inherited Alzheimer's disease or frontotemporal dementia with parkinsonism linked to chromosome-17 but not individuals with mild cognitive impairment

Neuronal microtubules are morphologically abnormal in diseased regions of brain from patients with late-onset Alzheimer's disease (LOAD). Here we tested the hypothesis that tubulin derived from gray matter of patients with multiple forms of dementia was functionally impaired. Following taxol/GTP stimulation of tubulin polymerization of gray matter extracts we observed reduced capacity of tubulin to polymerize in LOAD, but not individuals with mild cognitive impairment (MCI), compared to controls. Moreover, we observed similarly reduced taxol/GTP-stimulated tubulin polymerization from gray matter obtained from patients with AD caused by PSEN2 N141I mutation or frontotemporal dementia with parkinsonism linked to chromosome-17 caused (FTDP-17) by TAU V337M or P301L mutation. Our results show that modification of tubulin function may contribute to intermediate or late stages in the pathogenesis of sporadic and inherited AD as well as FTDP-17.

Presenilins in the developing, adult, and aging cerebral cortex

Mutations in presenilins are the major cause of familial Alzheimer disease. The involvement of presenilins in the pathogenesis of Alzheimer disease, therefore, has been the subject of intense investigation during the past decade. Genetic analysis of phenotypes associated with presenilin mutations in invertebrate and vertebrate systems has greatly advanced our understanding of the in vivo functions of presenilins. In this review, the authors will summarize the current understanding of presenilin function, with an emphasis on the mammalian cerebral cortex. During development, presenilins play crucial roles in the maintenance of neural progenitor cell proliferation, the temporal control of neuronal differentiation, the survival of Cajal-Retzius neurons, and proper neuronal migration in the developing cerebral cortex. Analysis of presenilin function in the adult cerebral cortex has revealed essential roles for presenilins in synaptic plasticity, long-term memory, and neuronal survival. The authors will also discuss the molecular mechanisms through which presenilins may mediate these functions, including the Notch, CREB, and NMDA receptor-mediated signaling pathways. These diverse functions of presenilins in cortical development and function and neuronal survival have important implications for the pathogenesis of neurodegenerative dementia.

Identification of differentially expressed genes in psoriasis using expression profiling approaches

To identify differentially expressed genes which play causal roles in pathogenesis and maintenance for psoriasis, we used BodyMapping and introduced amplified fragment length polymorphism approaches. From the BodyMap database, we selected 2007 genes which specifically expressed in epithelial tissues. Among 2007 genes, we surveyed genes which differentially expressed in involved or uninvolved psoriatic lesional skin samples compared with atopic dermatitis, mycosis fungoides, and normal skin samples. As a result of surveying 2007 genes, 241 genes were differentially expressed only in involved psoriatic skin but not in the other samples. Hierarchical cluster analysis of gene expression profiles showed that 13 independent psoriatic-involved skin samples clustered tightly together, reflecting highly similar expression profiles. Using the same 2007 gene set, we examined gene expression levels in five serial lesions from distal uninvolved psoriatic skin to involved psoriatic plaque. We identified seven genes such as alpha-1-microglobulin/bikunin precursor, calnexin, claudin 1, leucine zipper down-regulated in cancer 1, tyrosinase-related protein 1, Yes-associated protein 1, and unc-13-like protein (Coleonyx elegans) which show high-expression levels only in uninvolved psoriatic lesions. These seven genes, which were reported to be related to apoptosis or antiproliferation, might have causal roles in pathophysiology in psoriasis.

Stigmatization in Alzheimer's disease research on African American elders

Stigmatization in research sustains the spread of the silent epidemic of Alzheimer's disease (AD) in African American populations. Researchers use stereotypes and inappropriate assumptions to select a paradigm to examine the symptoms of AD. This paradigm fails to encompass the symptoms as manifested by African American elders. Yet, stigmatization can be minimized by recognizing the genetic heterogeneity of the symptoms within the general population, especially those manifested by African American elders. Thus, researchers can utilize pioneering genetic analyses to identify other paradigms critical in the assessment and proactive treatment of the symptoms of AD needed for this vulnerable population.

Recent Insights on the Pro-Apoptotic Phenotype Elicited by Presenilin 2 and its Caspase and Presenilinase-Derived Fragments

Programmed cell death (PCD) also called apoptosis, is a normal and genetically controlled event that could play, when mis-regulated, a pivotal role in the development of several neurodegenerative disorders such as Parkinson's disease. Sporadic Alzheimer's disease is one of the most prominent age-related syndromes whose etiology, although still unknown, could be related to biochemical or environmental causes. A few cases of Alzheimer's disease are likely of genetic origin and linked to mutations on the genes coding for the amyloid precursor protein (betaAPP) and presenilins 1 and 2. Although still discussed, the hypothesis of an implication of apoptotic cell death in Alzheimer's disease neuropathology has been recently supported by a growing body of biochemical evidences. Thus, the implication of presenilins in apoptotic processes in vitro has been well documented but the mechanisms underlying this function are still a matter of intense research. The aim of this review is to focus on the mechanisms by which presenilin 2 affects the programmed cell death with special emphasis on the role of the proteolytically derived presenilin fragments generated by both presenilinase- and caspases. The distinct apoptotic phenotypes elicited by the two parent proteins presenilins 1 and 2 and their functional cross talk will be briefly discussed.

Trastuzumab therapy for tamoxifen-stimulated endometrial cancer

A novel in vivo model of tamoxifen-stimulated endometrial cancer was developed and the role of HER-2/neu investigated by using trastuzumab. Tamoxifen-stimulated tumors (ECC-1TAM) were growth stimulated by 17beta-estradiol (E2), tamoxifen, or raloxifene. Trastuzumab inhibited growth of E2-stimulated ECC-1E2 tumors by 50% and tamoxifen-stimulated ECC-1TAM tumors by 100%. ECC-1 tumors expressed functional estrogen receptor alpha (ER alpha) as measured by induction of pS2 and c-myc mRNAs. E2 induced pS2 and c-myc mRNAs up to 40-fold in ECC-1E2 and ECC-1TAM. Tamoxifen induced pS2 and c-myc mRNAs up to 5-fold in ECC-1E2 tumors and up to 10-fold in ECC-TAM tumors. Trastuzumab blocked E2-induced pS2 mRNA (P < 0.01) in ECC-1E2 by 50% and tamoxifen-induced c-myc mRNA (P < 0.1) in ECC-1TAM tumors by 70%. Trastuzumab decreased phosphorylated and total HER-2/neu protein in ECC-1E2 and ECC-1TAM tumors. However, only phospho-ERK-1/2 and not phospho-Akt protein was decreased by trastuzumab in tamoxifen-treated ECC-1TAM tumors. The insulin-like growth factor (IGF-I) signaling pathway also activates extracellular signal-related kinase (ERK)-1/2 and could block the efficacy of trastuzumab in ECC-1E2 tumors. The results showed that IGF-I, IGF-IR mRNAs, and phospho-insulin receptor substrate-1 (IRS-1) protein were decreased in ECC-1TAM compared with ECC-1E2 tumors. The results show that trastuzumab is an effective therapy for both E2-stimulated and tamoxifen-stimulated endometrial cancer. The data suggest estrogenic activities of E2 and tamoxifen at ER alpha-regulated pS2 and c-myc genes are in part mediated by HER-2/neu. However, trastuzumab is a better growth inhibitor of ECC-1TAM tumors where there is diminished IGF-I signaling allowing for complete blockade of the downstream phospho-ERK-1/2 signal.

A presenilin-independent aspartyl protease prefers the gamma-42 site cleavage

beta-Amyloid peptides (Abeta40 and Abeta42) are the major constituents of amyloid plaques, which are one of the hallmarks of Alzheimer's disease (AD). The Abeta is derived from sequential cleavages of amyloid precursor protein (APP) by beta- and gamma-secretases. gamma-Secretase consists of at least four proteins where presenilins (PS1 and PS2 or PS) are the catalytic subunit involved in the gamma-site cleavage of APP. Secretion of both Abeta40 and Abeta42 is significantly reduced in PS1 knock-out cells and completely abolished in cells deficient for both PS1 and PS2. Consequently, both the PS proteins play essential roles in the production of the secretory of Abeta from cells. Recent studies in primary neurons, however, suggest that PSs are not required for intracellular Abeta42 accumulation; thus the intracellular Abeta42 appears to be generated in a PS-independent manner. Here we present the first biochemical evidence indicating that Abeta, especially Abeta42, can be generated in the absence of PS based on an in vitrogamma-secretase assay employing membranes prepared from PS-deficient Blastocyst-derived (BD) cells. This PS-independent gamma-secretase (PSIG) activity is sensitive to the changes in pH and displays an optimal activity at pH 6.0. Pepstatin A is a potent inhibitor for this proteolytic activity with IC50 of 1.2 nm and 0.4 nm for Abeta40 and Abeta42 generation, respectively. These results indicate that these PS-independent gamma-site cleavages are mediated by an aspartyl protease. More importantly, the PSIG activity displays a distinct preference in mediating the 42-site cleavage over the 40-site cleavage, thereby generating Abeta42 as the predominant product.

Regulation of cholesterol and sphingomyelin metabolism by amyloid-beta and presenilin

Amyloid beta peptide (Abeta) has a key role in the pathological process of Alzheimer's disease (AD), but the physiological function of Abeta and of the amyloid precursor protein (APP) is unknown. Recently, it was shown that APP processing is sensitive to cholesterol and other lipids. Hydroxymethylglutaryl-CoA reductase (HMGR) and sphingomyelinases (SMases) are the main enzymes that regulate cholesterol biosynthesis and sphingomyelin (SM) levels, respectively. We show that control of cholesterol and SM metabolism involves APP processing. Abeta42 directly activates neutral SMase and downregulates SM levels, whereas Abeta40 reduces cholesterol de novo synthesis by inhibition of HMGR activity. This process strictly depends on gamma-secretase activity. In line with altered Abeta40/42 generation, pathological presenilin mutations result in increased cholesterol and decreased SM levels. Our results demonstrate a biological function for APP processing and also a functional basis for the link that has been observed between lipids and Alzheimer's disease (AD).