Amyloid beta protein gene: cDNA, mRNA distribution, and genetic linkage near the Alzheimer locus.
ABSTRACT The amyloid beta protein has been identified as an important component of both cerebrovascular amyloid and amyloid plaques of Alzheimer's disease and Down syndrome. A complementary DNA for the beta protein suggests that it derives from a larger protein expressed in a variety of tissues. Overexpression of the gene in brain tissue from fetuses with Down syndrome (trisomy 21) can be explained by dosage since the locus encoding the beta protein maps to chromosome 21. Regional localization of this gene by both physical and genetic mapping places it in the vicinity of the genetic defect causing the inherited form of Alzheimer's disease.
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ABSTRACT: The amyloid-β protein precursor (APP) plays a crucial role in the pathogenesis of Alzheimer's disease (AD). Knock-out and transgenic mouse studies of the adaptor protein Mint2 have revealed that it is a major player in regulating APP metabolism physiologically through the binding of its phosphotyrosine-binding (PTB) domain to the intracellular domain of APP. However, the molecular mechanism of APP dynamically binding to Mint2 remains elusive. Here, we report the structures of APP peptide-free and APP peptide-bound C-terminal Mint2 mutants at resolutions of 2.7 and 3.3 Å, respectively. Our structures reveal that APP peptide-free Mint2 exists in a closed state in which the ARM domain blocks the peptide-binding groove of the PTB domain. In sharp contrast, APP peptide-bound Mint2 exists in an open state in which the ARM domain drastically swings away from the bound peptide. Mutants that control the open-closed motion of Mint2 dynamically regulated APP metabolism both in vitro and in vivo. Our results uncover a novel open-closed mechanism of the PTB domain dynamically binding to its peptide substrate. Moreover, such a conformational switch may represent a general regulation mode of APP family members by Mint proteins, providing useful information for the treatment of AD.Journal of Molecular Cell Biology 06/2013; 5(1). DOI:10.1093/jmcb/mjs033
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ABSTRACT: A role of amyloid β (Aβ) peptide aggregation and deposition in Alzheimer's disease (AD) pathogenesis is widely accepted. Significantly, abnormalities induced by aggregated Aβ have been linked to synaptic and neuritic degeneration, consistent with the "dying-back" pattern of degeneration that characterizes neurons affected in AD. However, molecular mechanisms underlying the toxic effect of aggregated Aβ remain elusive. In the last 2 decades, a variety of aggregated Aβ species have been identified and their toxic properties demonstrated in diverse experimental systems. Concurrently, specific Aβ assemblies have been shown to interact and misregulate a growing number of molecular effectors with diverse physiological functions. Such pleiotropic effects of aggregated Aβ posit a mayor challenge for the identification of the most cardinal Aβ effectors relevant to AD pathology. In this review, we discuss recent experimental evidence implicating amyloid β precursor protein (APP) as a molecular target for toxic Aβ assemblies. Based on a significant body of pathologic observations and experimental evidence, we propose a novel pathologic feed-forward mechanism linking Aβ aggregation to abnormalities in APP processing and function, which in turn would trigger the progressive loss of neuronal connectivity observed early in AD.Neurobiology of aging 05/2013; 34(11). DOI:10.1016/j.neurobiolaging.2013.04.021
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ABSTRACT: Down's syndrome (DS) is the most frequent genetic cause of intellectual disability and patients with DS show significant psychopathology (18-23%). Moreover, individuals with DS often show a cognitive decline associated with ageing characterized by a deterioration in memory, language and cognitive functioning. According to these relevant findings, an overview is presented of state-of-the-art knowledge of the neurocognitive, neurobiological and psychopathological profile, assessment and treatment of patients with DS. The linguistic characteristics of DS develop differently along distinct developmental trajectories. Thus, for example, morphosyntax deficit, especially in production, is more evident in adolescence than in early childhood and lexicon is usually better preserved in all ages (at least in comprehension). So far, rehabilitation is the only effective approach for improving cognitive and linguistic abilities. However, ongoing preliminary reports on other approaches such as transmagnetic stimulation or drugs suggest alternative or integrative treatment for the future. Individuals with DS show typical organization of brain structures related to some cognitive abilities, such as reduced volume in frontal and prefrontal areas, which is related to poor executive and linguistic abilities. They also frequently show psychiatric disorders such as externalizing disorders as well as depression, anxiety and obsessive-compulsive disorder. Nevertheless, as for other genetic syndrome with intellectual disability, there is a significant lack of research specifically focused on treatments of psychiatric and behavioural problems in DS. This is true both for psychosocial and for pharmacological interventions.Psychiatric genetics 03/2013; 23(3). DOI:10.1097/YPG.0b013e32835fe426