A heterologously expressed form of the human Parkinson diseaseassociated protein α-synuclein with a 10-residue N-terminal extension is shown to form a stable tetramer in the absence of lipid bilayers or micelles. Sequential NMR assignments, intramonomer nuclear Overhauser effects, and circular dichroism spectra are consistent with transient formation of α-helices in the first 100 Nterminal residues of the 140-residue α-synuclein sequence. Total phosphorus analysis indicates that phospholipids are not associated with the tetramer as isolated, and chemical cross-linking experiments confirm that the tetramer is the highest-order oligomer present at NMR sample concentrations. Image reconstruction from electron micrographs indicates that a symmetric oligomer is present, with three-or fourfold symmetry. Thermal unfolding experiments indicate that a hydrophobic core is present in the tetramer. A dynamic model for the tetramer structure is proposed, based on expected close association of the amphipathic central helices observed in the previously described micelle-associated "hairpin" structure of α-synuclein. T he protein α-synuclein (αSyn) is associated with the two most prevalent neurodegenerative diseases, Parkinson disease (PD) and Alzheimer's disease (AD). The presence of αSyn-rich aggregates (Lewy bodies) in neurons of the substantia nigra is the defining histopathological hallmark of PD, and is used to differentiate PD from other neurological disorders (1). Monogenic point mutations (A30P, A53T, and E46K) as well as gene duplication and triplication of the αSyn locus have been identified as causal factors of early onset familial PD; E46K has also been associated with Lewy body dementia, the second most common form of dementia after AD (2-4).αSyn is small (140 residues), and though the C-terminal region (∼residues 100-140) is highly acidic and expected to be disordered, the first 100 residues are predicted to be structured and to have α-helical propensity (SI Appendix, Fig. S1). Stable helical structures have been detected by circular dichroism (CD) and NMR when αSyn is incubated with detergent micelles and lipid vesicles (5, 6). Soluble αSyn is typically referred to as an "intrinsically disordered" protein (7,8). However, we herein report the biophysical characterization of a purified soluble form of αSyn that is oligomeric and fractionally occupies helical structures in the absence of micelles or vesicles. The αSyn construct used in our work is purified by use of an N-terminal GST affinity tag under mild conditions to preserve any native structure. After removal of the GST tag, a 10-residue N-terminal extension remains on the αSyn. However, the similarity of the 1 H, 15 N heteronuclear single-quantum coherence (HSQC) fingerprint of our αSyn construct (SI Appendix, Figs. S2 and S3) to those reported by other groups for αSyn suggests that the N-terminal extension does not change structural tendencies significantly. The αSyn construct described here is not toxic to membranes or cells, does not readily aggregate or ...

The aggregation of α-synuclein (aSyn) leading to the formation of Lewy bodies is the defining pathological hallmark of Parkinson's disease (PD). Rare familial PD-associated mutations in aSyn render it aggregation-prone; however, PD patients carrying wild type (WT) aSyn also have aggregated aSyn in Lewy bodies. The mechanisms by which WT aSyn aggregates are unclear. Here, we report that inflammation can play a role in causing the aggregation of WT aSyn. We show that activation of the inflammasome with known stimuli results in the aggregation of aSyn in a neuronal cell model of PD. The insoluble aggregates are enriched with truncated aSyn as found in Lewy bodies of the PD brain. Inhibition of the inflammasome enzyme caspase-1 by chemical inhibition or genetic knockdown with shRNA abated aSyn truncation. In vitro characterization confirmed that caspase-1 directly cleaves aSyn, generating a highly aggregation-prone species. The truncation-induced aggregation of aSyn is toxic to neuronal culture, and inhibition of caspase-1 by shRNA or a specific chemical inhibitor improved the survival of a neuronal PD cell model. This study provides a molecular link for the role of inflammation in aSyn aggregation, and perhaps in the pathogenesis of sporadic PD as well.ver the past two decades, studies stimulated by the discovery of genetic mutations occurring in familial Parkinson's disease (PD) have generated a number of hypotheses concerning potential mechanisms of PD pathogenesis. Nonetheless, the causes and mechanism of sporadic PD, which constitutes the majority of cases, remain unknown.Before the genetic discoveries, epidemiologic evidence suggested environmental toxins, traumatic brain injury, and viral infection as potential causes of idiopathic PD (1-7). All of these insults could cause neural inflammation, a common feature of PD brains; however, whether neural inflammation contributes to the etiology of the disease or is part of its effect remained unclear. Suggestive evidence indicating the involvement of inflammation in the pathogenesis of PD emerged after an outbreak of encephalitis lethargica following the 1918 influenza pandemic, which killed approximately 1 million people and left many survivors with postencephalitic Parkinsonism (PEP). Affected persons presented with cardinal symptoms of typical Parkinson's disease, including stooped posture, masklike faces, muscular rigidity, and tremorous extremities. Contemporary cases of viral infection-associated Parkinsonism are rare, but both epidemiology and patient case studies indicate that infection-associated PD still occurs today (8-10).The role of viral infection in the pathogenesis of PD has been a controversial subject for more than 50 years. Proponents have pointed out the known close temporal association between infection and PEP, whereas opponents have cited studies that failed to find any viral remnants in the brains of affected patients. Moreover, there were no known routes for peripheral viral migration into the central nervous system (CNS). Recently, R. Smey...

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A series of Zr-sulfonic-based metal–organic frameworks have been synthesized by the solvothermal method, namely VNU-17 and VNU-23.