Search

Abstract Neurodegenerative disorders are characterized by the brain deposition of insoluble amyloidogenic proteins, such as α-synuclein or Tau, and the concomitant deterioration of cell functions such as the autophagy-lysosomal pathway (ALP). The ALP is involved in the degradation of intracellular macromolecules including protein aggregates. ALP dysfunction due to inherited defects in lysosomal or non-lysosomal proteins causes a group of diseases called lysosomal storage disorders (LSD) because of abnormal accumulation of lysosomal degradation substrates. Supporting the contribution of ALP defects in neurodegenerative diseases, deposition of amyloidogenic proteins occurs in LSD. Moreover, heterozygous mutations of several ALP genes represent risk factors for Parkinson’s disease. The reciprocal contribution of α-synuclein accumulation and lysosomal dysfunction have been extensively studied. However, whether this adverse crosstalk also embraces Tau pathology needs more investigation. Here, we show in human primary fibroblasts that Tau seeds isolated from the brain of Alzheimer’s disease induce Tau accumulation in acidic degradative organelles and lysosomal stress. Furthermore, inhibition of glucocerebrosidase, a lysosomal enzyme mutated in Gaucher’s disease and a main risk for Parkinson’s disease, causes lysosomal dysfunction in primary fibroblasts and contributes to the accumulation of Tau. Considering the presence of Tau lesions in Parkinson’s disease as well as in multiple neurodegenerative disorders including Alzheimer’s disease, our data call for further studies on strategies to alleviate ALP dysfunction as new therapeutic opportunity for neurodegenerative diseases and LSD.

Abstract Tau gene mutations cause a progressive dementia and neurotoxic Tau forms deposited in neurofibrillary tangles are hallmarks of neurodegenerative tauopathies. Loss of non-canonical Tau functions may contribute to disease. In fact, Tau depletion affects the cellular response to DNA damage and tauopathies exhibit the accumulation of DNA lesions. Moreover, Tau modulates P53 activity and cell fate. Considering that MDM2 is the main antagonist of P53, we investigated, using orthogonal assays, if Tau interacts with MDM2. We report the existence in cells and brain of a Tau-MDM2 complex that, in vitro, exhibits reduced P53 ubiquitination activity in a manner sensitive to a Tau mutation. The Tau-MDM2 interaction involves the microtubule-binding domain of Tau and the acidic domain of MDM2, reminiscent of the binding of Tau to negatively charged microtubules. Notably, MDM2 accumulates aberrantly in neurofibrillary tangles. Aging-associated insults may expose a novel loss-of-function of Tau in neurodegeneration and cancer.

Abstract Extracellular vesicles (EVs) are biological vehicles that are thought to mediate cell–cell communication via the transfer of biomolecules from donor to acceptor cells. Repurposing those natural vesicles into therapeutics delivery vectors is a high priority challenge for translational science. Here we engineer donor cells to produce copious amount of fusogenic EVs loaded with the catalytic domain of the Diphteria Toxin, known to trigger cell death through protein synthesis inhibition. We show that, when incubated with cancer acceptor cells, these Killer EVs block protein synthesis and lead to cell death. This proof of concept establishes the efficacy of Killer EVs in vitro, and suggests that further development may lead to tumor ablation in vivo, expanding the existing cancer therapeutics arsenal.

Abstract Mutations in the Leucine-rich repeat kinase 2 gene (LRRK2) are associated with familial Parkinson’s disease (PD). LRRK2 protein contains several functional domains, including protein-protein interaction domains at its N- and C-termini. In this study, we analyzed the functional features attributed to LRRK2 by its N- and C-terminal domains. We combined TIRF microscopy and synaptopHluorin assay to visualize synaptic vesicle trafficking. We found that N- and C-terminal domains have opposite impact on synaptic vesicle dynamics. Biochemical analysis demonstrated that different proteins are bound at the two extremities, namely β3-Cav2.1 at N-terminus part and β-Actin and Synapsin I at C-terminus domain. A sequence variant (G2385R) harboured within the C-terminal WD40 domain increases the risk for PD. Complementary biochemical and imaging approaches revealed that the G2385R variant alters strength and quality of LRRK2 interactions and increases fusion of synaptic vesicles. Our data suggest that the G2385R variant behaves like a loss-of-function mutation that mimics activity-driven events. Impaired scaffolding capabilities of mutant LRRK2 resulting in perturbed vesicular trafficking may arise as a common pathophysiological denominator through which different LRRK2 pathological mutations cause disease.