Cells are constantly exposed to DNA damaging insults. To protect the organism, cells developed a complex molecular response coordinated by P53, the master regulator of DNA repair, cell division and cell fate. DNA damage accumulation and abnormal cell fate decision may represent a pathomechanism shared by aging-associated disorders such as cancer and neurodegeneration. Here, we examined this hypothesis in the context of tauopathies, a neurodegenerative disorder group characterized by Tau protein deposition. For this, the response to an acute DNA damage was studied in neuroblastoma cells with depleted Tau, as a model of loss-of-function. Under these conditions, altered P53 stability and activity result in reduced cell death and increased cell senescence. This newly discovered function of Tau involves abnormal modification of P53 and its E3 ubiquitin ligase MDM2. Considering the medical need with vast social implications caused by neurodegeneration and cancer, our study may reform our approach to disease-modifying therapies.

Protein multimerization in physiological and pathological conditions constitutes an intrinsic trait of proteins related to neurodegeneration. Recent evidence shows that TDP-43, a RNA-binding protein associated with frontotemporal dementia and amyotrophic lateral sclerosis, exists in a physiological and functional nuclear oligomeric form, whose destabilization may represent a prerequisite for misfolding, toxicity and subsequent pathological deposition. Here we show the parallel implementation of two split GFP technologies, the GFP bimolecular and trimolecular fluorescence complementation (biFC and triFC) in the context of TDP-43 self-assembly. These techniques coupled to a variety of assays based on orthogonal readouts allowed us to define the structural determinants of TDP-43 oligomerization in a qualitative and quantitative manner. We highlight the versatility of the GFP biFC and triFC technologies for studying the localization and mechanisms of protein multimerization in the context of neurodegeneration.Protein mutations in Mendelian forms of neurodegenerative disorders, aberrant post-translational modifications and pathogenic conformations, all contribute to the progressive accumulation of protein inclusions. These protein assemblies initiate a chain of adverse events ultimately leading to neuronal dysfunction, synaptic loss, cell death, and brain function deterioration. A prion-like process, i.e. accumulative protein deposition, proteotoxicity and transcellular spreading of pathogenic protein forms is typical of most neurodegenerative disorders including Alzheimer's (AD), Parkinson's (PD), Huntington's disease (HD), frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) 1,2 . The molecular events protecting against proteotoxicity into adulthood or, subsequently, steering proteotoxicity during disease are only in part understood. For example, soluble oligomeric intermediates, rather than deposited amyloid fibrils, may represent the toxic protein forms 3-5 . However, the identification and classification of toxic oligomers is challenging. Some proteins associated with neurodegeneration present a physiological multimeric conformation (e.g. SOD1 6 , α-synuclein 7,8 , TDP-43 9 ), and their dissociation may cause a loss of function or may represent a prerequisite for assembly into toxic species. To understand the molecular mechanisms driving neurodegeneration, it is crucial to investigate proteins with regards to how, when and where they (self-)interact to accomplish specific functions or to build the first assemblies into toxic species.We explored the use of fluorescence reconstitution for live tracking of protein-protein interactions as a tool for elucidating the molecular mechanisms involved in the formation of protein assemblies. Fluorescent sensors are applied to determine protein interactions in cells. One prominent example is FRET from donor to acceptor fluorophores coupled to binding partners 10,11 . Another example is complementation of polypeptide fragments that restore enzymatic activity ...

Extracellular vesicles, phospholipid bilayer-membrane vesicles of cellular origin, are emerging as nanocarriers of biological information between cells. Extracellular vesicles transport virtually all biologically active macromolecules (e.g., nucleotides, lipids, and proteins), thus eliciting phenotypic changes in recipient cells. However, we only partially understand the cellular mechanisms driving the encounter of a soluble ligand transported in the lumen of extracellular vesicles with its cytosolic receptor: a step required to evoke a biologically relevant response. In this context, we review herein current evidence supporting the role of two well-described cellular transport pathways: the endocytic pathway as the main entry route for extracellular vesicles and the autophagic pathway driving lysosomal degradation of cytosolic proteins. The interplay between these pathways may result in the target engagement between an extracellular vesicle cargo protein and its cytosolic target within the acidic compartments of the cell. This mechanism of cell-to-cell communication may well own possible implications in the pathogenesis of neurodegenerative disorders.