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Amyloid precursor protein (APP) is a type one transmembrane protein and has two mammalian homologues, amyloid precursor-like protein 1 (APLP1) and amyloid precursor-like protein 2 (APLP2). APP is the parent molecule to amyloid-[beta] (A[beta]), the amyloidogenic species found in the plaques of people with Alzheimer's disease (AD). Several lines of evidence suggest A[beta] to lie at the center of AD pathology, with converging evidence to indicate that synapses are the site of the initial damage. Recent studies have shown that APP may be necessary for the toxicity induced by A[beta], in part by cleavage of a caspase site on the intracellular domain of the APP protein and the subsequent release of the toxic molecule, C31. This caspase cleavage is shown to induce APP-mediated A[beta] toxicity in cell culture models, however assays were based on contribution to cell death. Thus, the physiologic relevance of the cleavage event has never been tested and in particular, whether this pathway contributes to synaptic damage is unclear. Here, we seek to test the role of caspase cleavage of APP in A[beta]-induced synaptic damage and to test the specificity of this event by testing whether caspase cleavage of APLP2, the protein most homologous to APP, also contributes to these A[beta]-driven synaptic changes. Additionally, because APP dimerization was shown to be necessary for the A & beta;-induced caspase cleavage of APP and subsequent release of C31, we wanted to test the effects of dimerization on APP proteolysis and A[beta] production.
The amyloid precursor protein APP plays a key role in the pathogenesis of Alzheimer’s disease (AD), as proteolytical cleavage of APP gives rise to the Aβ peptide which is deposited in the brains of Alzheimer patients. Despite this, our knowledge of the normal cell biological and physiological functions of APP and the closely related APLPs is limited. This may have hampered our understanding of AD, since evidence has accumulated that not only the production of the Aβ peptide but also the loss of APP-mediated functions may contribute to AD pathogenesis. Thus, it appears timely and highly relevant to elucidate the functions of the APP gene family from the molecular level to their role in the intact organism, i.e. in the context of nervous system development, synapse formation and adult synapse function, as well as neural homeostasis and aging. Why is our understanding of the APP functions so limited? APP and the APLPs are multifunctional proteins that undergo complex proteolytical processing. They give rise to an almost bewildering array of different fragments that may each subserve specific functions. While Aβ is aggregation prone and neurotoxic, the large secreted ectodomain APPsα - produced in the non-amyloidogenic α-secretase pathway - has been shown to be neurotrophic, neuroprotective and relevant for synaptic plasticity, learning and memory. Recently, novel APP cleavage pathways and enzymes have been discovered that have gained much attention not only with respect to AD but also regarding their role in normal brain physiology. In addition to the various cleavage products, there is also solid evidence that APP family proteins mediate important functions as transmembrane cell surface molecules, most notably in synaptic adhesion and cell surface signaling. Elucidating in more detail the molecular mechanisms underlying these divers functions thus calls for an interdisciplinary approach ranging from the structural level to the analysis in model organisms. Thus, in this research topic of Frontiers we compile reviews and original studies, covering our current knowledge of the physiological functions of this intriguing and medically important protein family.
There is now considerable genetic evidence that the type 4 allele of the apolipoprotein E gene is a major susceptibility factor associated with late-onset Alzheimer's disease, the common form of the disease defined as starting after sixty years of age. The role of apolipoprotein E in normal brain metabolism and in the pathogenesis of Alzheimer's disease are new and exciting avenues of research. This book, written by the most outstanding scientists in this new filed, is the first presentation of results concerning the implications of apolipoprotein E on the genetics, cell biology, neuropathology, biochemistry, and therapeutic management of Alzheimer's disease.
Neurofibrillary tangles (NFTs) composed of intracellular aggregates of tau protein are a key neuropathological feature of Alzheimer’s Disease (AD) and other neurodegenerative diseases, collectively termed tauopathies. The abundance of NFTs has been reported to correlate positively with the severity of cognitive impairment in AD. However, accumulating evidences derived from studies of experimental models have identified that NFTs themselves may not be neurotoxic. Now, many of tau researchers are seeking a “toxic” form of tau protein. Moreover, it was suggested that a “toxic” tau was capable to seed aggregation of native tau protein and to propagate in a prion-like manner. However, the exact neurotoxic tau species remain unclear. Because mature tangles seem to be non-toxic component, “tau oligomers” as the candidate of “toxic” tau have been investigated for more than one decade. In this topic, we will discuss our consensus of “tau oligomers” because the term of “tau oligomers” [e.g. dimer (disulfide bond-dependent or independent), multimer (more than dimer), granular (definition by EM or AFM) and maybe small filamentous aggregates] has been used by each researchers definition. From a biochemical point of view, tau protein has several unique characteristics such as natively unfolded conformation, thermo-stability, acid-stability, and capability of post-translational modifications. Although tau protein research has been continued for a long time, we are still missing the mechanisms of NFT formation. It is unclear how the conversion is occurred from natively unfolded protein to abnormally mis-folded protein. It remains unknown how tau protein can be formed filaments [e.g. paired helical filament (PHF), straight filament and twisted filament] in cells albeit in vitro studies confirmed tau self-assembly by several inducing factors. Researchers are still debating whether tau oligomerization is primary event rather than tau phosphorylation in the tau pathogenesis. Inhibition of either tau phosphorylation or aggregation has been investigated for the prevention of tauopathies, however, it will make an irrelevant result if we don’t know an exact target of neurotoxicity. It is a time to have a consensus of definition, terminology and methodology for the identification of “tau oligomers”.
This book discusses the primary functions of microtubule-associated proteins (MAPs) such as MAP2 and tau in neuronal morphogenesis, as well as relationships between neuronal differentiation and the expression of neuronal intermediate filaments (nestin, alpha internexin, and neurofilament triplet proteins). It emphasizes the importance of several cytoskeletal proteins for neuronal differentiation and morphogenesis, organelle transport, and synaptic functions. The book considers the involvement of tau MAPs in the formation of paired helical filaments in Alzheimer's disease, and it examines the mechanisms of organelle transports and molecular motors such as kinesin, braindynein, and kinesin superfamily proteins. Cytoskeletal proteins involved in synaptic formation and transmitter release and new synaptic junctional-associated proteins are explored as well.
The costs associated with a drug's clinical trials are so significant that it has become necessary to validate both its safety and efficacy in animal models prior to the continued study of the drug in humans. Featuring contributions from distinguished researchers in the field of cognitive therapy research, Animal Models of Cognitive Impairmen
A biochemical hypothesis - that Alzheimer’s disease (AD) is a progressive cerebral amyloidosis caused by the aggregation of the amyloid b-protein (Ab) - preceded and enabled the discovery of etiologies. This volume serves as a record focused on bringing together investigators at the forefront of elucidating the structure and function of hippocampal synapses with investigators focused on understanding how early assemblies of Ab may compromise some of these synapses.
The brain is the most complex organ in our body. Indeed, it is perhaps the most complex structure we have ever encountered in nature. Both structurally and functionally, there are many peculiarities that differentiate the brain from all other organs. The brain is our connection to the world around us and by governing nervous system and higher function, any disturbance induces severe neurological and psychiatric disorders that can have a devastating effect on quality of life. Our understanding of the physiology and biochemistry of the brain has improved dramatically in the last two decades. In particular, the critical role of cations, including magnesium, has become evident, even if incompletely understood at a mechanistic level. The exact role and regulation of magnesium, in particular, remains elusive, largely because intracellular levels are so difficult to routinely quantify. Nonetheless, the importance of magnesium to normal central nervous system activity is self-evident given the complicated homeostatic mechanisms that maintain the concentration of this cation within strict limits essential for normal physiology and metabolism. There is also considerable accumulating evidence to suggest alterations to some brain functions in both normal and pathological conditions may be linked to alterations in local magnesium concentration. This book, containing chapters written by some of the foremost experts in the field of magnesium research, brings together the latest in experimental and clinical magnesium research as it relates to the central nervous system. It offers a complete and updated view of magnesiums involvement in central nervous system function and in so doing, brings together two main pillars of contemporary neuroscience research, namely providing an explanation for the molecular mechanisms involved in brain function, and emphasizing the connections between the molecular changes and behavior. It is the untiring efforts of those magnesium researchers who have dedicated their lives to unraveling the mysteries of magnesiums role in biological systems that has inspired the collation of this volume of work.
Neuroscience Perspectives provides multidisciplinary reviews of topics in one of the most diverse and rapidly advancing fields in the life sciences.Whether you are a new recruit to neuroscience, or an established expert, look to this series for 'one-stop' sources of the historical, physiological, pharmacological, biochemical, molecular biological and therapeutic aspects of chosen research areas.The last decade has seen tremendous advances in our understanding of the pathobiology of Alzheimer's disease. These will lead to the first generation of drugs aimed at prevention rather than cure. This book covers some of the most important and exciting of these advances, with chapters written by many of the leading researchers in the field.With genetic studies as a backbone to this volume many chapters are devoted to the function and regulation of amyloid b-protein precursor (APP) and apolipoprotein E (ApoE). Other chapters describe cell biological approaches helping to piece together the link between the genetic alterations and the phenotype we call Alzheimer's disease.Although APP and its proteolytic cleavage product, amyloid b-protein, do not answer all the questions, detailed research into this system has undoubtedly increased our knowledge of the pathobiology of AD and has lead to the identification of other risk factors. Understanding the role of ApoE in the pathology of Alzheimer's disease promises to open a whole new field in AD research. * * Reviews the current knowledge of the pathogenesis of Alzheimer's Disease from a clinical perspective to a genetic and cell biological perspective* A comprehensive description of the role of amyloid B-protein precursor in Alzheimer's disease.* Up-to-date research data* Clear illustrations complement the text
This foundational work comprehensively examines the current state of the genetics, genomics and brain circuitry of psychiatric and neurological disorders. It consolidates discoveries of specific genes and genomic regions associated with these conditions, the genetic and anatomic architecture of these syndromes, and addresses how recent advances in genomics are leading to a reappraisal of the biology underlying clinical neuroscience. In doing so, it critically examines the promise and limitations of these discoveries toward treatment, and to the interdisciplinary nature of understanding brain and behavior. Coverage includes new discoveries regarding autism, epilepsy, intellectual disability, dementias, movement disorders, language impairment, disorders of attention, schizophrenia, and bipolar disorder. Genomics, Circuits, and Pathways in Clinical Neuropsychiatry focuses on key concepts, challenges, findings, and methods in genetics, genomics, molecular pathways, brain circuitry, and related neurobiology of neurologic and psychiatric disorders. Provides interdisciplinary appeal in psychiatry, neurology, neuroscience, and genetics Identifies key concepts, methods, and findings Includes coverage of multiple disorders from autism to schizophrenia Reviews specific genes associated with disorders Discusses the genetic architecture of these syndromes Explains how recent findings are influencing the understanding of biology Clarifies the promise of these findings for future treatment