Cognitive decline in Alzheimer's disease (AD) involves pathological accumulation of synaptotoxic amyloid-␤ (A␤) oligomers and hyperphosphorylated tau. Because recent evidence indicates that glycogen synthase kinase 3␤ (GSK3␤) activity regulates these neurotoxic pathways, we developed an AD therapeutic strategy to target GSK3␤. The strategy involves the use of copper-bis(thiosemicarbazonoto) complexes to increase intracellular copper bioavailability and inhibit GSK3␤ through activation of an Akt signaling pathway. Our lead compound Cu II (gtsm) significantly inhibited GSK3␤ in the brains of APP/PS1 transgenic AD model mice. Cu II (gtsm) also decreased the abundance of A␤ trimers and phosphorylated tau, and restored performance of AD mice in the Y-maze test to levels expected for cognitively normal animals. Improvement in the Y-maze correlated directly with decreased A␤ trimer levels. This study demonstrates that increasing intracellular copper bioavailability can restore cognitive function by inhibiting the accumulation of neurotoxic A␤ trimers and phosphorylated tau.Alzheimer's disease ͉ bioinorganic chemistry ͉ glycogen synthase kinase ͉ therapeutic ͉ animal model A lzheimer's disease (AD) is a neurodegenerative disorder characterized clinically by impaired cognitive performance and pathologically by cerebral deposition of extracellular amyloid plaques and intracellular neurofibrillary tangles. Amyloid plaques in AD contain aggregated forms of the 39-to 43-aa amyloid-␤ peptide (A␤) and A␤ is strongly implicated as a causative agent responsible for cognitive failure in AD. A diverse range of mechanisms for A␤ toxicity has been reported (1). A␤ is produced from the amyloid precursor protein (APP) (2-5) and readily aggregates to form insoluble, high-molecular-mass amyloid structures. Intermediates on the A␤ aggregation pathway, primarily low-molecular-mass oligomers such as dimers and trimers, exhibit the greatest neurotoxicity (6-8). In addition to A␤ oligomers, aberrantly phosphor ylated microtubuleassociated protein tau is also associated with cognitive decline in AD (9). Intracellular neurofibrillary tangles in the AD brain contain hyperphosphorylated tau, and A␤ induced cognitive deficits characteristic of AD transgenic mice are attenuated by decreasing levels of endogenous tau (10).It is now widely recognized that a truly effective therapeutic compound for treating AD needs to attenuate both the A␤-and tau-mediated pathologies. Recent positive outcomes for PBT2 in clinical and preclinical trials are therefore pertinent. Lannfelt et al.(11) demonstrated in phase IIa clinical trials that PBT2 lowers plasma A␤ levels and attenuates cognitive decline, and Adlard et al. (12) have shown that PBT2 decreases interstitial A␤ and phosphorylated tau in the brains of AD model mice. PBT2 is a secondgeneration 8-OH quinoline, which, unlike its predecessor clioquinol, lacks iodine and was selected for clinical development because of its easier chemical synthesis, higher solubility, and increased blood-brain barrier perme...

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BackgroundTDP-43 proteinopathies are characterized by loss of nuclear TDP-43 expression and formation of C-terminal TDP-43 fragmentation and accumulation in the cytoplasm. Recent studies have shown that TDP-43 can accumulate in RNA stress granules (SGs) in response to cell stresses and this could be associated with subsequent formation of TDP-43 ubiquinated protein aggregates. However, the initial mechanisms controlling endogenous TDP-43 accumulation in SGs during chronic disease are not understood. In this study we investigated the mechanism of TDP-43 processing and accumulation in SGs in SH-SY5Y neuronal-like cells exposed to chronic oxidative stress. Cell cultures were treated overnight with the mitochondrial inhibitor paraquat and examined for TDP-43 and SG processing.ResultsWe found that mild stress induced by paraquat led to formation of TDP-43 and HuR-positive SGs, a proportion of which were ubiquitinated. The co-localization of TDP-43 with SGs could be fully prevented by inhibition of c-Jun N-terminal kinase (JNK). JNK inhibition did not prevent formation of HuR-positive SGs and did not prevent diffuse TDP-43 accumulation in the cytosol. In contrast, ERK or p38 inhibition prevented formation of both TDP-43 and HuR-positive SGs. JNK inhibition also inhibited TDP-43 SG localization in cells acutely treated with sodium arsenite and reduced the number of aggregates per cell in cultures transfected with C-terminal TDP-43 162-414 and 219-414 constructs.ConclusionsOur studies are the first to demonstrate a critical role for kinase control of TDP-43 accumulation in SGs and may have important implications for development of treatments for FTD and ALS, targeting cell signal pathway control of TDP-43 aggregation.

Accumulation of neurotoxic amyloid‐β (Aβ) is central to the pathology of Alzheimer’s disease (AD). Elucidating the mechanisms of Aβ accumulation will therefore expedite the development of Aβ‐targeting AD therapeutics. We examined activity of an Aβ‐degrading protease (matrix metalloprotease 2) to investigate whether biochemical factors consistent with conditions in the AD brain contribute to Aβ accumulation by altering Aβ sensitivity to proteolytic degradation. An Aβ amino acid mutation found in familial AD, Aβ interactions with zinc (Zn), and increased Aβ hydrophobicity all strongly prevented Aβ degradation. Consistent to all of these factors is the promotion of specific Aβ aggregates where the protease cleavage site, confirmed by mass spectrometry, is inaccessible within an amyloid structure. These data indicate decreased degradation due to amyloid formation initiates Aβ accumulation by preventing normal protease activity. Zn also prevented Aβ degradation by the proteases neprilysin and insulin degrading enzyme. Treating Zn‐induced Aβ amyloid with the metal‐protein attenuating compound clioquinol reversed amyloid formation and restored the peptide’s sensitivity to degradation by matrix metalloprotease 2. This provides new data indicating that therapeutic compounds designed to modulate Aβ‐metal interactions can inhibit Aβ accumulation by restoring the catalytic potential of Aβ‐degrading proteases.