Different tau epitopes define Abeta42-mediated tau insolubility.
ABSTRACT Alzheimer's disease (AD) is characterized by extracellular beta-amyloid (Abeta(42))-containing plaques and intracellular neurofibrillary tangles. The latter are composed of hyperphosphorylated filamentous aggregates of the microtubule-associated protein tau. Previously we demonstrated pathological interactions between these two histopathological hallmarks using human SH-SY5Y neuroblastoma cells overexpressing wild-type and mutant forms of human tau. Exposure to pre-aggregated forms of Abeta(42) caused both the formation of AD-like tau-containing filaments and a decreased solubility of tau, both of which were prevented by mutating the S422 phospho-epitope of tau. Here, we expressed additional tau mutants in SH-SY5Y cells to assess the role of phosphorylation and cleavage sites of tau in tau aggregation. We found that the Abeta(42)-mediated decrease in tau solubility depends on the interplay of distinct phospho-epitopes of tau and not only on phosphorylation of the S422 epitope.
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ABSTRACT: Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) are complex human brain disorders that affect an increasing number of people worldwide. With the identification first of the proteins that aggregate in AD and FTLD brains and subsequently of pathogenic gene mutations that cause their formation in the familial cases, the foundation was laid for the generation of animal models. These recapitulate essential aspects of the human conditions; expression of mutant forms of the amyloid-β protein-encoding APP gene in mice reproduces amyloid-β (Aβ) plaque formation in AD, while that of mutant forms of the tau-encoding microtubule-associated protein tau (MAPT) gene reproduces tau-containing neurofibrillary tangle formation, a lesion that is also prevalent in FTLD-Tau. The mouse models have been complemented by those in lower species such as C. elegans or Drosophila, highlighting the crucial role for Aβ and tau in human neurodegenerative disease. In this review, we will introduce selected AD/FTLD models and discuss how they were instrumental, by identifying deregulated mRNAs, miRNAs and proteins, in dissecting pathogenic mechanisms in neurodegenerative disease. We will discuss some recent examples, which includes miRNA species that are specifically deregulated by Aβ, mitochondrial proteins that are targets of both Aβ and tau, and the nuclear splicing factor SFPQ that accumulates in the cytoplasm in a tau-dependent manner. These examples illustrate how a functional genomics approach followed by a careful validation in experimental models and human tissue leads to a deeper understanding of the pathogenesis of AD and FTLD and ultimately, may help in finding a cure.Frontiers in Physiology 08/2012; 3:320. DOI:10.3389/fphys.2012.00320
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ABSTRACT: The severity of tau pathology in Alzheimer's disease brain correlates closely with disease progression. Tau immunotherapy has therefore been proposed as a new therapeutic approach to Alzheimer's disease and encouraging results have been obtained by active or passive immunization of tau transgenic mice. This work investigates the mechanism by which immunotherapy can impact tau pathology. We demonstrate the development of Alzheimer's disease-like tau pathology in a triple transgenic mouse model of Alzheimer's disease and show that tau/pS422 is present in membrane microdomains on the neuronal cell surface. Chronic, peripheral administration of anti-tau/pS422 antibody reduces the accumulation of tau pathology. The unequivocal presence of anti-tau/pS422 antibody inside neurons and in lysosomes is demonstrated. We propose that anti-tau/pS422 antibody binds to membrane-associated tau/pS422 and that the antigen-antibody complexes are cleared intracellularly, thereby offering one explanation for how tau immunotherapy can ameliorate neuronal tau pathology.Brain 07/2014; 137. DOI:10.1093/brain/awu213 · 10.23 Impact Factor
Article: Dedicated to Inge Grundke-Iqbal.[Show abstract] [Hide abstract]
ABSTRACT: This review is dedicated to Inge Grundke-Iqbal who laid the foundations of the tau field, by isolating tau from the Alzheimer's disease (AD) brain, discovering that tau is hyperphosphorylated, and proving a critical role of protein phosphatase 2A (PP2A) and its endogenous inhibitor I2PP2A in this process. This memorial starts with a few personal notes, and then covers how subcellular fractionation helped in isolating tau. We review in detail the role of PP2A and its endogenous inhibitor in tau phosphorylation. We discuss the role that methylation and phosphorylation have in regulating PP2A activity. We add what we have contributed to understanding the role of tau and PP2A in AD using PP2A transgenic and knockout models, and conclude by addressing two underexplored areas in tau research: tau's non-canonical functions and the role distinct tau isoforms have in a physiological context.Journal of Alzheimer's disease: JAD 07/2013; DOI:10.3233/JAD-130503 · 3.61 Impact Factor