on Defeating Alzheimer's Disease and other dementias: a priority for European science and society Dementia includes a range of neurological disorders characterized by memory loss and cognitive impairment. The most common early symptom is difficulties remembering recent events. With the development of the disease, symptoms occur such as disorientation, mood swings, confusion, more serious memory loss, behavioural changes, difficulties in speaking and swallowing, as well as walking. Alzheimer Disease (AD) is the most common form of dementia (50-70% of dementia cases). Increasing age is the most important risk factor for AD.In 2012 and 2015, the World Health Organization (WHO) presented reports suggesting that Alzheimer Disease and other dementias (ADOD) should be regarded as a global public health priority 1,2 . Similar policy declarations have been presented by the European Union 3 , as well as by some individual countries. These policy declarations acknowledge trends that sometimes are described in terms of an epidemic or a "time-bomb". In 2015, the number of people affected by dementia worldwide is estimated to be almost 47 million and the numbers are expected to reach 75 million by 2030 and 131 million by 2050, with the greatest increase in low and middle income countries. The main reason for the increase is the global aging trend, since dementias are associated with a high age-specific prevalence, i.e., increasing prevalence with higher age. The global economic costs of dementia were estimated to be more than 600 billion USD in 2010 6 and 818 billion USD in 2015 5 . The direct costs in the medical and social care sectors, 487 billion USD, represent 0.65% of the aggregated global gross domestic products (GDP), which is an enormous economic impact of a single group of disorders, especially considering that 87% of the costs occur in high income countries. Care of people with dementia impacts several sectors in the society with the social care (long term care and home services) and informal care sectors constituting the greatest proportions -even greater than direct medical care 6 . In cost of illness studies, European cost estimates in 2010 ranged between 238,6 billion USD 6 and 105,6 billion € 7 .However, the economic and societal burden of ADOD corresponds to the aggregate burden of people with dementia and their next of kin. The progressive nature of dementia can influence the whole life situation for families over many years. So far, no cure or substantial symptom relieving treatment is available for ADOD. Thus, the impact of this terminal disease is already today enormous, and given the predictions for the future, ADOD represents an enormous challenge for any society, and particularly to the ageing European society.Further knowledge is needed regarding the causes of ADOD. A more complete understanding of the disease mechanisms is required for new diagnostic and therapeutic strategies. There is also a need to establish new cell-based and animal models representing, as far as possible, major clinical component...

Polymerization of amyloid ␤-peptide (A␤) into amyloid fibrils is a critical step in the pathogenesis of Alzheimer's disease. Here, we show that peptides incorporating a short A␤ fragment (KLVFF; A␤ 16 -20 ) can bind full-length A␤ and prevent its assembly into amyloid fibrils. Through alanine substitution, it was demonstrated that amino acids Lys 16 , Leu 17 , and Phe 20 are critical for binding to A␤ and inhibition of A␤ fibril formation. A mutant A␤ molecule, in which these residues had been substituted, had a markedly reduced capability of forming amyloid fibrils. The present data suggest that residues A␤ 16 -20 serve as a binding sequence during A␤ polymerization and fibril formation. Moreover, the present KLVFF peptide may serve as a lead compound for the development of peptide and nonpeptide agents aimed at inhibiting A␤ amyloidogenesis in vivo.The preeminent neuropathological feature of Alzheimer's disease is the deposition of amyloid in the brain parenchyma and cerebrovasculature (1, 2). The basic components of the amyloid are thin fibrils of a peptide termed A␤ (3, 4). This peptide is a 40-to 42-amino acid-long proteolytic fragment of the Alzheimer amyloid precursor protein (APP), 1 a protein expressed in most tissues (5). Genetic and neuropathological studies provide strong evidence for a central role of A␤ amyloid in the pathogenesis of Alzheimer's disease (6), but the pathophysiological consequences of the amyloid deposition are unclear. However, it has been suggested that A␤ polymers and amyloid are toxic to neurons, either directly or via induction of radicals, and hence cause neurodegeneration (7-9). Previous studies indicate that A␤ polymerization in vivo and in vitro is a specific process that probably involves interactions between binding sequences in the A␤ peptide (10 -12). A rational pharmacological approach for prevention of amyloid formation would therefore be to use drugs that specifically interfere with A␤-A␤ interaction and polymerization. We hypothesized that ligands capable of binding to and blocking such sequences might inhibit amyloid fibril formation as outlined schematically in Fig. 1. Our strategy in searching for an A␤ ligand was to identify binding sequences in A␤ and then, based on their primary structures, synthesize a peptide ligand. Binding sequences were identified by systematically synthesizing short peptides corresponding to sequences of the A␤ molecule. The minimum length of an identified binding sequence was determined by truncating the peptide. Residues critical for binding were identified by alanine scanning. These critical residues were then substituted in an A␤ fragment (A␤ ) that normally is capable of forming amyloid fibrils (13,14) in order to determine if they indeed are important for A␤ amyloid fibril formation. Finally, it was determined if the identified ligand, in addition to binding to the A␤ molecule, was capable of inhibiting fibril formation of A␤ . EXPERIMENTAL PROCEDURES Materials-Synthetic A␤1-40 and all other soluble peptides were synthesized b...

Macroautophagy, which is a lysosomal pathway for the turnover of organelles and long-lived proteins, is a key determinant of cell survival and longevity. In this study, we show that neuronal macroautophagy is induced early in Alzheimer's disease (AD) and before β-amyloid (Aβ) deposits extracellularly in the presenilin (PS) 1/Aβ precursor protein (APP) mouse model of β-amyloidosis. Subsequently, autophagosomes and late autophagic vacuoles (AVs) accumulate markedly in dystrophic dendrites, implying an impaired maturation of AVs to lysosomes. Immunolabeling identifies AVs in the brain as a major reservoir of intracellular Aβ. Purified AVs contain APP and β-cleaved APP and are highly enriched in PS1, nicastrin, and PS-dependent γ-secretase activity. Inducing or inhibiting macroautophagy in neuronal and nonneuronal cells by modulating mammalian target of rapamycin kinase elicits parallel changes in AV proliferation and Aβ production. Our results, therefore, link β-amyloidogenic and cell survival pathways through macroautophagy, which is activated and is abnormal in AD.

The Alzhlmer Af3 amyloid peptide (A3) is the principal protelnaceous component of amylold associated with Alzheimer disease (AD Since slight differences in structure may affect amyloidogenesis, a thorough knowledge of the actual AP composition of amyloid is therefore important. Moreover, knowledge of the exact structure is important for characterization of the proteolytic enzymes involved in AB formation. In addition, amyloid associated with normal aging has, to our knowledge, not been characterized biochemically and its peptide composition is unknown.In the present work, AP was purified from the cerebral cortex of a number of sporadic AD cases and nondemented elderly controls, as well as two familial AD (FAD) cases. One of the two FAD cases had the APP K670N/M671L mutation (13), and the other had the APP V717I mutation (14). Primary structures and relative abundances of the purified AB variants were determined by N-terminal microsequencing and electrospray-ionization mass spectrometry (ESI-MS).Alzheimer disease (AD) is associated with deposition of amyloid in the brain parenchyma and within the cerebromeningeal vasculature (for review, see ref. 1). Amyloid displaying properties similar to those of AD amyloid can also be detected in normal aging (2). Whether this amyloid accompanies normal aging or is an early histopathological sign of presymptomatic AD is not known. The AD-associated amyloid deposits are mainly composed of the 4-kDa Alzheimer A, amyloid peptide (AB) (3, 4). AB is a proteolytic fragment of a transmembrane glycoprotein, the Alzheimer AP amyloid precursor protein (APP) (5).Since the initial isolation of AP from amyloid deposits (3), a variety of methods for purification and analysis of the peptide have been used (4, 6-8). Various forms of the native peptide have been reported. For instance, it has been stated that the N terminus of AP is blocked (6), that AB is deposited as a mixture of N-terminally truncated ("ragged") variants (4), and that the C terminus is different in vascular and parenchymal AP (7). More recently, it was proposed that A/-(1-40) is the major variant in brain (9) and that cerebrovascular amyloid is composed primarily of A(-(1-40) and Af-(1-42) (10) (Fig. 1)

Polymerization of the amyloid beta (A␤) peptide into protease-resistant fibrils is a significant step in the pathogenesis of Alzheimer's disease. It has not been possible to obtain detailed structural information about this process with conventional techniques because the peptide has limited solubility and does not form crystals. In this work, we present experimental results leading to a molecular level model for fibril formation. Systematically selected A␤-fragments containing the A␤ 16 -20 sequence, previously shown essential for A␤-A␤ binding, were incubated in a physiological buffer. Electron microscopy revealed that the shortest fibril-forming sequence was A␤ 14 -23 . Substitutions in this decapeptide impaired fibril formation and deletion of the decapeptide from A␤ 1-42 inhibited fibril formation completely. All studied peptides that formed fibrils also formed stable dimers and/or tetramers. Molecular modeling of A␤ 14 -23 oligomers in an antiparallel ␤-sheet conformation displayed favorable hydrophobic interactions stabilized by salt bridges between all charged residues. We propose that this decapeptide sequence forms the core of A␤-fibrils, with the hydrophobic C terminus folding over this core. The identification of this fundamental sequence and the implied molecular model could facilitate the design of potential inhibitors of amyloidogenesis.

Amyloid fibrils in which specific proteins have polymerized into a cross-␤-sheet structure are found in about 20 diseases. In contrast to the close structural similarity of fibrils formed in different amyloid diseases, the structures of the corresponding native proteins differ widely. We show here that peptides as short as 4 residues with the sequences KFFE or KVVE can form amyloid fibrils that are practically identical to fibrils formed in association with disease, as judged by electron microscopy and Congo red staining. In contrast, KLLE or KAAE do not form fibrils. The fibril-forming KFFE and KVVE show partial ␤-strand conformation in solution, whereas the non-fibril-forming KLLE and KAAE show random structure only, suggesting that inherent propensity for ␤-strand conformation promotes fibril formation. The peptides KFFK or EFFE do not form fibrils on their own but do so in an equimolar mixture. Thus, intermolecular electrostatic interactions, either between charged dipolar peptides or between complementary charges of co-fibrillating peptides favor fibril formation.Protein aggregates in the form of amyloid fibrils are found in about 20 diseases, including Alzheimer's disease, transmissible spongiform encephalopathies, Parkinson's disease, and type II diabetes mellitus (1). X-ray diffraction data suggest that the proteins have polymerized into a cross-␤-sheet structure with the ␤-strands perpendicular to the fibril axis (2). The structure of amyloid fibrils is typically very similar, although the polypeptides they are formed from can be highly dissimilar in their native states. Initially, only a few peptides and proteins were considered capable of forming fibrils, although also short fragments of amyloidogenic proteins form fibrils. More recently, it has been established that even globular all-helical proteins like myoglobin, which normally do not give rise to amyloid, can be converted to fibrils if incubated under partly denaturing conditions (3). This suggests that most proteins have the potential to form amyloid fibrils.It is not known which features cause a few specific proteins to form amyloid fibrils in vivo. Some amyloidogenic peptides and proteins harbor specific ␣-helices that are predicted to generate ␤-strands (4), and evidence that aggregation is initiated from particular regions of a polypeptide chain is accumulating (5). For example, the peptides NFGAIL from islet amyloid polypeptide, HQKLVFFAED from the amyloid ␤-peptide (A␤), 1 and VQIVYK from tau form fibrils and are crucial for fibril formation of the full-length peptides (6 -8). Common to these sequences is the presence of hydrophobic amino acids of which at least one is aromatic. In this work, we aimed to explore the minimum requirements for fibril formation in short model peptides. The results show that peptides as short as 4 residues can form amyloid fibrils. Hydrophobic residues with high propensities for ␤-strand conformation and residues with complementary charges promote fibril formation, and positively and negatively charged peptides...

Glycosylation is one of the most common, and the most complex, forms of post-translational modification of proteins. This review serves to highlight the role of protein glycosylation in Alzheimer disease (AD), a topic that has not been thoroughly investigated, although glycosylation defects have been observed in AD patients. The major pathological hallmarks in AD are neurofibrillary tangles and amyloid plaques. Neurofibrillary tangles are composed of phosphorylated tau, and the plaques are composed of amyloid b-peptide (Ab), which is generated from amyloid precursor protein (APP). Defects in glycosylation of APP, tau and other proteins have been reported in AD. Another interesting observation is that the two proteases required for the generation of amyloid b-peptide (Ab), i.e. c-secretase and b-secretase, also have roles in protein glycosylation. For instance, c-secretase and b-secretase affect the extent of complex N-glycosylation and sialylation of APP, respectively. These processes may be important in AD pathogenesis, as proper intracellular sorting, processing and export of APP are affected by how it is glycosylated. Furthermore, lack of one of the key components of c-secretase, presenilin, leads to defective glycosylation of many additional proteins that are related to AD pathogenesis and/or neuronal function, including nicastrin, reelin, butyrylcholinesterase, cholinesterase, neural cell adhesion molecule, v-ATPase, and tyrosine-related kinase B. Improved understanding of the effects of AD on protein glycosylation, and vice versa, may therefore be important for improving the diagnosis and treatment of AD patients.

We have previously shown that short peptides incorporating the sequence KLVFF can bind to the ϳ40-amino acid residue Alzheimer amyloid ␤-peptide (