Liquid-liquid phase separation of tau and α-synuclein: A new pathway of overlapping neuropathologies.

Liquid-liquid phase separation (LLPS) is a critical phenomenon that leads to the formation of liquid-like membrane-less organelles within cells. Advances in our understanding of condensates reveal their significant roles in biology and highlight how their dysregulation may contribute to disease. Recent evidence indicates that the high protein concentration in coacervates may lead to abnormal protein aggregation associated with several neurodegenerative diseases.

Heterotypic liquid-liquid phase separation of tau and α-synuclein: Implications for overlapping neuropathologies.

Tauopathies and synucleinopathies are characterized by the aggregation of Tau and α-synuclein (AS) into amyloid structures, respectively. Individuals with these neuropathies have an elevated risk of developing subsequent neurodegenerative or comorbid disorders. Intriguingly, post-mortem brain examinations have revealed co-localization of Tau and AS aggregates, suggesting a synergistic pathological relationship with an adverse prognosis.

Modulation of α-synuclein phase separation by biomolecules.

Liquid-liquid phase separation (LLPS) is currently recognized as a common mechanism involved in the regulation of a number of cellular functions. On the other hand, aberrant phase separation has been linked to the biogenesis of several neurodegenerative disorders since many proteins that undergo LLPS are also found in pathological aggregates. The formation of mixed protein coacervates may constitute a risk factor in overlapping neuropathologies, such as Parkinson's (PD) and Alzheimer's (AD) diseases.

Influence of the macromolecular crowder alginate in the fibrillar organization of the functional amyloid FapC from Pseudomonas aeruginosa.

Bacterial biofilms are an alternative lifestyle in which communities of bacteria are embedded in an extracellular matrix manly composed by polysaccharides, nucleic acids and proteins, being the hallmark of bacterial survival in a variety of ecological niches. Amyloid fibrils are one of the proteinaceous components of such extracellular crowded environments. FapC is the main component of the functional amyloid recently discovered in Pseudomonas species, including the opportunistic pathogen P.

Replicated, urban-driven exposure to metallic trace elements in two passerines.

While there are increasing examples of phenotypic and genotypic differences between urban and non-urban populations of plants and animals, few studies identified the mechanisms explaining those dissimilarities. The characterization of the urban landscape, which can only be achieved by measuring variability in relevant environmental factors within and between cities, is a keystone prerequisite to understand the effects of urbanization on wildlife. Here, we measured variation in bird exposure to metal pollution within 8 replicated urbanization gradients and within 2 flagship bird species in urban evolutionary ecology: the blue tit (Cyanistes caeruleus) and the great tit (Parus major).

Alpha-synuclein fibrils recruit TBK1 and OPTN to lysosomal damage sites and induce autophagy in microglial cells.

Autophagic dysfunction and protein aggregation have been linked to several neurodegenerative disorders, but the exact mechanisms and causal connections are not clear and most previous work was done in neurons and not in microglial cells. Here, we report that exogenous fibrillary, but not monomeric, alpha-synuclein (AS, also known as SNCA) induces autophagy in microglial cells. We extensively studied the dynamics of this response using both live-cell imaging and correlative light-electron microscopy (CLEM), and found that it correlates with lysosomal damage and is characterised by the recruitment of the selective autophagy-associated proteins TANK-binding kinase 1 (TBK1) and optineurin (OPTN) to ubiquitylated lysosomes.

Amyloid oligomerization of the Parkinson's disease related protein α-synuclein impacts on its curvature-membrane sensitivity.

The amyloid aggregation of the presynaptic protein α-synuclein (AS) is pathognomonic of Parkinson's disease and other neurodegenerative disorders. Physiologically, AS contributes to synaptic homeostasis by participating in vesicle maintenance, trafficking, and release. Its avidity for highly curved acidic membranes has been related to the distinct chemistry of the N-terminal amphipathic helix adopted upon binding to appropriated lipid interfaces.

α-Synuclein interacts directly but reversibly with psychosine: implications for α-synucleinopathies.

Aggregation of α-synuclein, the hallmark of α-synucleinopathies such as Parkinson's disease, occurs in various glycosphingolipidoses. Although α-synuclein aggregation correlates with deficiencies in the lysosomal degradation of glycosphingolipids (GSL), the mechanism(s) involved in this aggregation remains unclear. We previously described the aggregation of α-synuclein in Krabbe's disease (KD), a neurodegenerative glycosphingolipidosis caused by lysosomal deficiency of galactosyl-ceramidase (GALC) and the accumulation of the GSL psychosine.

Autophagy down regulates pro-inflammatory mediators in BV2 microglial cells and rescues both LPS and alpha-synuclein induced neuronal cell death.

Autophagy is a fundamental cellular homeostatic mechanism, whereby cells autodigest parts of their cytoplasm for removal or turnover. Neurodegenerative disorders are associated with autophagy dysregulation, and drugs modulating autophagy have been successful in several animal models. Microglial cells are phagocytes in the central nervous system (CNS) that become activated in pathological conditions and determine the fate of other neural cells.

Structural remodeling during amyloidogenesis of physiological Nα-acetylated α-synuclein.

The misfolding and aggregation of the presynaptic protein α-synuclein (AS) into amyloid fibrils is pathognomonic of Parkinson's disease, though the mechanism by which this structural conversion occurs is largely unknown. Soluble oligomeric species that accumulate as intermediates in the process of fibril formation are thought to be highly cytotoxic. Recent studies indicate that oligomer-to-fibril AS transition plays a key role in cell toxicity and progression of neurodegeneration.

Amyloid fibrils are the molecular trigger of inflammation in Parkinson's disease.

Parkinson's disease (PD) is an age-related movement disorder characterized by a progressive degeneration of dopaminergic neurons in the midbrain. Although the presence of amyloid deposits of α-synuclein (α-syn) is the main pathological feature, PD brains also present a severe permanent inflammation, which largely contributes to neuropathology. Although α-syn has recently been implicated in this process, the molecular mechanisms underlying neuroinflammation remain unknown.

Alpha-synuclein levels in blood plasma decline with healthy aging.

There is unequivocal evidence that alpha-synuclein plays a pivotal pathophysiological role in neurodegenerative diseases, and in particular in synucleinopathies. These disorders present with a variable extent of cognitive impairment and alpha-synuclein is being explored as a biomarker in CSF, blood serum and plasma. Considering key events of aging that include proteostasis, alpha-synuclein may not only be useful as a marker for differential diagnosis but also for aging per se.

Structural insights into amyloid oligomers of the Parkinson disease-related protein α-synuclein.

The presence of intraneuronal deposits mainly formed by amyloid fibrils of the presynaptic protein α-synuclein (AS) is a hallmark of Parkinson disease. Currently, neurotoxicity is attributed to prefibrillar oligomeric species rather than the insoluble aggregates, although their mechanisms of toxicity remain elusive. Structural details of the supramolecular organization of AS oligomers are critically needed to decipher the structure-toxicity relationship underlying their pathogenicity.

Structural characterization of heparin-induced glyceraldehyde-3-phosphate dehydrogenase protofibrils preventing α-synuclein oligomeric species toxicity.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional enzyme that has been associated with neurodegenerative diseases. GAPDH colocalizes with α-synuclein in amyloid aggregates in post-mortem tissue of patients with sporadic Parkinson disease and promotes the formation of Lewy body-like inclusions in cell culture. In a previous work, we showed that glycosaminoglycan-induced GAPDH prefibrillar species accelerate the conversion of α-synuclein to fibrils.

Neuronal inclusions of α-synuclein contribute to the pathogenesis of Krabbe disease.

Demyelination is a major contributor to the general decay of neural functions in children with Krabbe disease. However, recent reports have indicated a significant involvement of neurons and axons in the neuropathology of the disease. In this study, we have investigated the nature of cellular inclusions in the Krabbe brain.

Altered serum IgG levels to α-synuclein in dementia with Lewy bodies and Alzheimer's disease.

Natural self-reactive antibodies in the peripheral blood may play a considerable role in the control of potentially toxic proteins that may otherwise accumulate in the aging brain. The significance of serum antibodies reactive against α-synuclein is not well known. We explored serum IgG levels to monomeric α-synuclein in dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) with a novel and validated highly sensitive ELISA assay.

Imaging nanometer-sized α-synuclein aggregates by superresolution fluorescence localization microscopy.

The morphological features of α-synuclein (AS) amyloid aggregation in vitro and in cells were elucidated at the nanoscale by far-field subdiffraction fluorescence localization microscopy. Labeling AS with rhodamine spiroamide probes allowed us to image AS fibrillar structures by fluorescence stochastic nanoscopy with an enhanced resolution at least 10-fold higher than that achieved with conventional, diffraction-limited techniques. The implementation of dual-color detection, combined with atomic force microscopy, revealed the propagation of individual fibrils in vitro.

Toxic prefibrillar α-synuclein amyloid oligomers adopt a distinctive antiparallel β-sheet structure.

Parkinson's disease is an age-related movement disorder characterized by the presence in the mid-brain of amyloid deposits of the 140-amino-acid protein AS (α-synuclein). AS fibrillation follows a nucleation polymerization pathway involving diverse transient prefibrillar species varying in size and morphology. Similar to other neurodegenerative diseases, cytotoxicity is currently attributed to these prefibrillar species rather than to the insoluble aggregates.

Binding of the highly toxic tetracycline derivative, anhydrotetracycline, to bovine serum albumin.

Tetracycline (TC) derivatives are extensively used as antibiotics in human and animal medicine and, very recently, they have been screened as anti-amyloidogenic drugs. Anhydrotetracycline (AHTC) is one of the major degradation products of TC that has been linked to several side effects of the drug. We evaluated the interaction of AHTC with bovine serum albumin (BSA), one of the main carriers of amphiphilic molecules in blood, using three complementary analytical methods: fluorescence spectroscopy, isothermal titration calorimetry and differential scanning calorimetry.

Small molecule fluorescent probes for the detection of amyloid self-assembly in vitro and in vivo.

The misfolding and aggregation of amyloidogenic polypeptides are characteristics of many neurodegenerative syndromes including Alzheimer's and Parkinson's disease. There is a major interest in the availability of amyloid-specific probes that exhibit fluorescence properties, for its use as reporters of protein aggregation in spectroscopy and microscopy methodologies. In this review, we intend to provide an overview of novel fluorescence-based probes and procedures applied for addressing fundamental aspects of amyloid self-assembly in vitro and in vivo.

A triple-emission fluorescent probe reveals distinctive amyloid fibrillar polymorphism of wild-type alpha-synuclein and its familial Parkinson's disease mutants.

Intracytoplasmic neuronal deposits containing amyloid fibrils of the 140-amino acid presynaptic protein alpha-synuclein (AS) are the hallmark of Parkinson's (PD) disease and related neurodegenerative disorders. Three point mutations (A53T, A30P, and E46K) are linked to early onset PD. Compared to the wild-type (WT) protein, the mutants aggregate faster in vitro, but their fibrillar products are quite similar.

Solid-state NMR reveals structural differences between fibrils of wild-type and disease-related A53T mutant alpha-synuclein.

Fibrils from the Parkinson's-disease-related A53T mutant of alpha-synuclein were investigated by solid-state NMR spectroscopy, electron microscopy, and atomic force microscopy. Sequential solid-state NMR resonance assignments were obtained for a large fraction of the fibril core. Experiments conducted above and below the freezing point suggest that the fibrils contain regions with increased mobility and structural elements different from beta-strand character, in addition to the rigid beta-sheet-rich core region.

Fluorescent N-arylaminonaphthalene sulfonate probes for amyloid aggregation of alpha-synuclein.

The deposition of fibrillar structures (amyloids) is characteristic of pathological conditions including Alzheimer's and Parkinson's diseases. The detection of protein deposits and the evaluation of their kinetics of aggregation are generally based on fluorescent probes such as thioflavin T and Congo red. In a search for improved fluorescence tools for studying amyloid formation, we explored the ability of N-arylaminonaphthalene sulfonate (NAS) derivatives to act as noncovalent probes of alpha-synuclein (AS) fibrillation, a process linked to Parkinson's disease and other neurodegenerative disorders.

Differential scanning calorimetry as a tool to estimate binding parameters in multiligand binding proteins.

The stability of proteins and their interactions with other molecules is a topic of special interest in biochemistry because many cellular processes depend on that. New methods and approaches are constantly developed to elucidate the energetics of biomolecular recognition. In this sense, the application of the theory of macromolecular unfolding linked to ligand binding to differential scanning calorimetry (DSC) has proved to be a useful tool to simultaneously characterize the energetics of unfolding and binding.