Search

Tau aggregation is a hallmark of a group of neurodegenerative diseases termed Tauopathies. Reduction of aggregation-prone Tau has emerged as a promising therapeutic approach. Here, we show that an anti-aggregant Tau fragment (F3ΔKPP, residues 258–360) harboring the ΔK280 mutation and two proline substitutions (I277P & I308P) in the repeat domain can inhibit aggregation of Tau constructs in vitro, in cultured cells and in vivo in a Caenorhabditis elegans model of Tau aggregation. The Tau fragment reduced Tau-dependent cytotoxicity in a N2a cell model, suppressed the Tau-mediated neuronal dysfunction and ameliorated the defective locomotion in C. elegans. In vitro the fragment competes with full-length Tau for polyanionic aggregation inducers and thus inhibits Tau aggregation. Our combined in vitro and in vivo results suggest that the anti-aggregant Tau fragment may potentially be used to address the consequences of Tau aggregation in Tauopathies. Electronic supplementary material The online version of this article (10.1007/s12035-018-1326-z) contains supplementary material, which is available to authorized users.

Following a spinal cord injury (SCI) a growth aversive environment forms, consisting of a fibroglial scar and inhibitory factors, further restricting the already low intrinsic growth potential of injured adult central nervous system (CNS) neurons. Previous studies have shown that local administration of the microtubule-stabilizing drug paclitaxel or epothilone B (Epo B) reduce fibrotic scar formation and axonal dieback as well as induce axonal growth/sprouting after SCI. Likewise, systemic administration of Epo B promoted functional recovery. In this study, we investigated the effects of epothilone D (Epo D), an analog of Epo B with a possible greater therapeutic index, on fibrotic scarring, axonal sprouting and functional recovery after SCI. Delayed systemic administration of Epo D after a moderate contusion injury (150 kDyn) in female Fischer 344 rats resulted in a reduced number of footfalls when crossing a horizontal ladder at 4 and 8 weeks post-injury. Hindlimb motor function assessed with the BBB open field locomotor rating scale and Catwalk gait analysis were not significantly altered. Moreover, formation of laminin positive fibrotic scar tissue and 5-HT positive serotonergic fiber length caudal to the lesion site were not altered after treatment with Epo D. These findings recapitulate a functional benefit after systemic administration of a microtubule-stabilizing drug in rat contusion SCI.

Summary Neuroinflammation is a hallmark of neurological disorders and is accompanied by the production of neurotoxic agents such as nitric oxide. We used stem cell-based phenotypic screening and identified small molecules that directly protected neurons from neuroinflammation-induced degeneration. We demonstrate that inhibition of CDK5 is involved in, but not sufficient for, neuroprotection. Instead, additional inhibition of GSK3β is required to enhance the neuroprotective effects of CDK5 inhibition, which was confirmed using short hairpin RNA-mediated knockdown of CDK5 and GSK3β. Quantitative phosphoproteomics and high-content imaging demonstrate that neurite degeneration is mediated by aberrant phosphorylation of multiple microtubule-associated proteins. Finally, we show that our hit compound protects neurons in vivo in zebrafish models of motor neuron degeneration and Alzheimer's disease. Thus, we demonstrate an overlap of CDK5 and GSK3β in mediating the regulation of the neuronal cytoskeleton and that our hit compound LDC8 represents a promising starting point for neuroprotective drugs., Highlights • Phenotypic screening identifies CDK inhibitors protecting neurons from inflammation • Inhibition of CDK5 is involved in neuroprotection but is not sufficient • Dual inhibition of CDK5 and GSK3β is neuroprotective in vitro and in vivo • Quantitative phosphoproteomics links neuroprotection to microtubule dynamics, Neuroinflammation is a hallmark of many neurological disorders and can be neurotoxic. Sterneckert and colleagues perform a phenotypic screening campaign identifying compounds protecting motor neurons from inflammation. Compound profiling demonstrates that dual inhibition of CDK5 and GSK3β mediates neuroprotection. Quantitative phosphoproteomics demonstrates that neuroprotection is linked to alterations in microtubule dynamics mediated by phosphorylation of microtubule-associated proteins.

The formation of paired helical filaments (PHF), which are composed of hyperphosphorylated Tau protein dissociating from microtubules, is one of the pathological hallmarks of Alzheimer’s disease (AD) and other tauopathies. The most important phosphatase that is capable of dephosphorylating Tau at AD specific phospho-sites is protein phosphatase 2 A (PP2A). Here we show that resveratrol, a polyphenol, significantly induces PP2A activity and reduces Tau phosphorylation at PP2A-dependent epitopes. The increase in PP2A activity is caused by decreased expression of the MID1 ubiquitin ligase that mediates ubiquitin-specific modification and degradation of the catalytic subunit of PP2A when bound to microtubules. Interestingly, we further show that MID1 expression is elevated in AD tissue. Our data suggest a key role of MID1 in the pathology of AD and related tauopathies. Together with previous studies showing that resveratrol reduces β-amyloid toxicity they also give evidence of a promising role for resveratrol in the prophylaxis and therapy of AD.

Aggregation of amyloid-β (Aβ) and Tau protein are hallmarks of Alzheimer's disease (AD), and according to the Aβ-cascade hypothesis, Aβ is considered toxic for neurons and Tau a downstream target of Aβ. We have investigated differentiated primary hippocampal neurons for early localized changes following exposure to Aβ oligomers. Initial events become evident by missorting of endogenous Tau into the somatodendritic compartment, in contrast to axonal sorting in normal neurons. In missorted dendritic regions there is a depletion of spines and local increase in Ca2+, and breakdown of microtubules. Tau in these regions shows elevated phosphorylation at certain sites diagnostic of AD-Tau (e.g., epitope of antibody 12E8, whose phosphorylation causes detachment of Tau from microtubules, and AT8 epitope), and local elevation of certain kinase activities (e.g., MARK/par-1, BRSK/SADK, p70S6K, cdk5, but not GSK3β, JNK, MAPK). These local effects occur without global changes in Tau, tubulin, or kinase levels. Somatodendritic missorting occurs not only with Tau, but also with other axonal proteins such as neurofilaments, and correlates with pronounced depletion of microtubules and mitochondria. The Aβ-induced effects on microtubule and mitochondria depletion, Tau missorting, and loss of spines are prevented by taxol, indicating that Aβ-induced microtubule destabilization and corresponding traffic defects are key factors in incipient degeneration. By contrast, the rise in Ca2+levels, kinase activities, and Tau phosphorylation cannot be prevented by taxol. Incipient and local changes similar to those of Aβ oligomers can be evoked by cell stressors (e.g., H2O2, glutamate, serum deprivation), suggesting some common mechanism of signaling.