The vacuolar protein sorting 35 (VPS35) is a major component of the retromer recognition core complex which regulates intracellular protein sorting and trafficking. Deficiency in VPS35 by altering APP/Aβ metabolism has been linked to late-onset Alzheimer's disease. Here we report that VPS35 is significantly reduced in Progressive Supra-nuclear Palsy and Picks' disease, two distinct primary tauopathies. In vitro studies show that overexpression of VPS35 leads to a reduction of pathological tau in neuronal cells, whereas genetic silencing of VPS35 results in its accumulation. Mechanistically the availability of active cathepsin D mediates the effect of VPS35 on pathological tau accumulation. Moreover, in a relevant transgenic mouse model of tauopathy, down-regulation of VPS35 results in an exacerbation of motor and learning impairments as well as accumulation of pathological tau and loss of synaptic integrity. Taken together, our data identify VPS35 as a novel critical player in tau metabolism and neuropathology, and a new therapeutic target for human tauopathies.

The enzyme 5-lipoxygenase (5LO) is up-regulated in Alzheimer’s disease (AD), and its pharmacological blockade with zileuton slows down the development of the AD-like phenotype in young AD mice. However, its efficacy after the AD pathology is established is unknown. To this end, starting at 12-months of age triple transgenic mice (3xTg) received zileuton, a selective 5LO inhibitor, or placebo for 3 months, and then the effect of this treatment on behavior, amyloid and tau pathology assessed. While mice on placebo showed worsening of their memory, treated mice performed even better than at baseline. Compared with placebo, treated mice had significant less Aβ deposits and tau phosphorylation secondary to reduced γ-secretase and CDK-5 activation, respectively. Our data provide novel insights into the disease-modifying action of pharmacologically inhibiting 5LO as a viable AD therapeutic approach. They represent the successful completion of preclinical studies for the development of this class of drug as clinically applicable therapy for the disease.

The retromer is a highly conserved multimeric protein complex present in all eukaryotic cells whose activity is essential for regulating the recycling and retrieval of numerous protein cargos from the endosome to trans-Golgi network or the cell surface. In recent years, molecular and genomic studies have provided evidence that aberrant regulation of endosomal protein sorting and trafficking secondary to a dysfunction of the retromer complex could be implicated in the pathogenesis of several neurodegenerative diseases. Thus, deficiency or mutations in one or more protein components of the retromer leads to increased accumulation of protein aggregates, as well as enhanced cellular neurotoxicity. In this review, we will discuss the structure and function of the retromer complex and its neurobiology, its relevance to key molecules involved in neurodegeneration and the potential role that it plays in the development of two major neurodegenerative disorders, Parkinson's disease and Alzheimer's disease. Finally, we will discuss the viability of targeting the retromer via pharmacological chaperones or genetic approaches to enhance or restore its function as a novel and unifying disease-modifying strategy against these diseases.

Neurodegenerative tauopathies are characterized by pathological accumulation of highly phosphorylated isoforms of tau protein, which leads to progressive neuronal loss. Neuroinflammation often accompanies tau-driven diseases; however, the direct role of neuroinflammation in tauopathies remains unknown. The 5-lipoxygenase (5LO) is a pro-inflammatory enzyme, which produces several bioactive metabolites and is widely expressed in the central nervous system. Previously, our group showed that 5LO influences the Alzheimer’s disease (AD) phenotype of APP transgenic mice as well as a mouse model with plaques and tangles. However, whether this protein directly modulates tau phosphorylation and subsequent neuropathology remains to be fully investigated. In the current study, we provide evidence for an age-dependent and region-specific upregulation of the 5LO pathway (protein, message and activity) in a transgenic mouse model of tauopathy, the P301S line. In addition, we demonstrate that genetic deletion of 5LO in this mouse model results in significant memory improvement, reduces tau phosphorylation at specific epitopes as well as neuroinflammation and rescues synaptic pathology. In vitro studies confirmed that 5LO directly modulates tau phosphorylation at the same epitopes as for the brain tissues. Taken together, our data reveal an active involvement of the 5LO pathway in the development of the tauopathy phenotype and provide strong support to the hypothesis that this enzymatic protein should be considered a novel and viable therapeutic target for the treatment of human tauopathy.

SummaryProgressive accumulation of highly phosphorylated tau protein isoforms is the main feature of a group of neurodegenerative diseases collectively called tauopathies. Data from human and animal models of these diseases have shown that neuroinflammation often accompanies their pathogenesis. The 5‐lipoxygenase (5LO) is an enzyme widely expressed in the brain and a source of potent pro‐inflammatory mediators, while its pharmacological inhibition modulates the phenotype of a tau transgenic mouse model, the htau mice. By employing an adeno‐associated viral vector system to over‐express 5LO in the brain, we examined its contribution to the behavioral deficits and neuropathology in a different transgenic mouse model of tauopathy, the P301S mouse line. Compared with controls, 5LO‐targeted gene brain over‐expression in these mice resulted in a worsening of behavioral and motor deficits. Over‐expression of 5LO resulted in microglia and astrocyte activation and significant synaptic pathology, which was associated with a significant elevation of tau phosphorylation at specific epitopes, tau insoluble fraction, and activation of the cdk5 kinase. In vitro studies confirmed that 5LO directly modulates tau phosphorylation at the same epitopes via the cdk5 kinase pathway. These data demonstrate that 5LO plays a direct role in tau phosphorylation and is an active player in the development of the entire tau phenotype. They provide further support to the hypothesis that 5LO is a viable therapeutic target for the treatment and/or prevention of human tauopathy.

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