ACS Chemical Neuroscience最新文献

The corona virus (SARS-CoV-2) pandemic and the resulting long-term neurological complications in patients, known as long COVID, have renewed interest in the correlation between viral infections and neurodegenerative brain disorders. While many viruses can reach the central nervous system (CNS) causing acute or chronic infections (such as herpes simplex virus 1, HSV-1), the lack of a clear mechanistic link between viruses and protein aggregation into amyloids, a characteristic of several neurodegenerative diseases, has rendered such a connection elusive. Recently, we showed that viruses can induce aggregation of purified amyloidogenic proteins via the direct physicochemical mechanism of heterogeneous nucleation (HEN). In the current study, we show that the incubation of HSV-1 and SARS-CoV-2 with human cerebrospinal fluid (CSF) leads to the amyloid aggregation of several proteins known to be involved in neurodegenerative diseases, such as APLP1 (amyloid β precursor like protein 1), ApoE, clusterin, α2-macroglobulin, PGK-1 (phosphoglycerate kinase 1), ceruloplasmin, nucleolin, 14-3-3, transthyretin, and vitronectin. Importantly, UV-inactivation of SARS-CoV-2 does not affect its ability to induce amyloid aggregation, as amyloid formation is dependent on viral surface catalysis via HEN and not its ability to replicate. Additionally, viral amyloid induction led to a dramatic drop in the soluble protein concentration in the CSF. Our results show that viruses can physically induce amyloid aggregation of proteins in human CSF and result in soluble protein depletion, thus providing a potential mechanism that may account for the association between persistent and latent/reactivating brain infections and neurodegenerative diseases.

Parkinson's disease (PD) is one of the most prevalent neurodegenerative disorders, with current treatments offering only temporary symptomatic relief. There is an urgent need for the development of novel therapeutic approaches. Abnormal increases in LRRK2 kinase activity have been identified in both sporadic and familial PD patients, suggesting that inhibiting LRRK2 kinase activity presents a promising avenue for the pursuit of effective PD treatment strategies. In this Viewpoint, we discuss the exciting new insights regarding the development of LRRK2 kinase inhibitors as a treatment for Parkinson's disease.

The aromatic amino acid hydroxylases (AAAHs) phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylases 1 and 2 are structurally related enzymes that contain an active site iron atom and depend on tetrahydrobiopterin (BH₄) as cosubstrate. Due to their important roles in synthesis of serotonin, dopamine, noradrenaline, and adrenaline and their involvement in cardiovascular, neurological, and endocrine disorders, AAAHs have been targeted by substrate analogs, iron chelators, and allosteric ligands. Phenylalanine hydroxylase is also off-target of the histone deacetylase (HDAC) inhibitor panobinostat. To systematically explore the binding of HDAC inhibitors to AAAHs, we screened a library of 307 HDAC inhibitors and structural analogs against tryptophan hydroxylase 1 using a fluorescence-based thermal stability assay, followed by activity assays. Selected hits were enzymatically tested against all four purified human AAAHs. Cellular thermal shift assay was performed for phenylalanine hydroxylase. We show that panobinostat and structurally related compounds such as TB57, which similarly to panobinostat also contains a cinnamoyl hydroxamate, bind to human AAAHs and inhibit these enzymes with high selectivity within the class (panobinostat inhibition (IC₅₀): phenylalanine hydroxylase (18 nM) > tyrosine hydroxylase (450 nM) > tryptophan hydroxylase 1 (1960 nM). This study shows that panobinostat and related hydroxamic acid type HDAC inhibitors inhibit all AAAHs at therapeutically relevant concentrations. Our results warrant further investigations of the off-target relevance of HDAC inhibitors intended for clinical use and provide directions for new dual HDAC/AAAH and selective AAAH inhibitors. These findings may also provide a new mechanistic link between regulation of histone modification, AAAH function, and monoaminergic neurotransmission.

Sepsis-associated encephalopathy (SAE), one of the common complications of sepsis, is associated with higher ICU mortality, prolonged hospitalization, and long-term cognitive decline. Sepsis can induce neuroinflammation, which negatively affects hippocampal neurogenesis. Dexmedetomidine has been shown to protect against SAE. However, the potential mechanism remains unclear. In this study, we added lipopolysaccharide (LPS)-stimulated astrocytes-conditioned media (LPS-CM) to neural stem cells (NSCs) culture, which were pretreated with dexmedetomidine in the presence or absence of the α2-adrenoceptor antagonist yohimbine or the α2A-adrenoceptor antagonist BRL-44408. LPS-CM impaired the neurogenesis of NSCs, characterized by decreased proliferation, enhanced gliogenesis, and declined viability. Dexmedetomidine alleviated LPS-CM-induced impairment of neurogenesis in a dose-dependent manner. Yohimbine, as well as BRL-44408, reversed the effects of dexmedetomidine. We established a mouse model of SAE via cecal ligation and perforation (CLP). CLP-induced astrocyte-related neuroinflammation and hippocampal neurogenesis deficits, accompanied by learning and memory decline, which were reversed by dexmedetomidine. The effect of dexmedetomidine was blocked by BRL-44408. Collectively, our findings support the conclusion that dexmedetomidine can protect against SAE, likely mediated by the combination of inhibiting neuroinflammation via the astrocytic α2A-adrenoceptor with attenuating neuroinflammation-induced hippocampal neurogenesis deficits via NSCs α2A-adrenoceptor.

This study explores the intricacies of dopamine receptor-ligand interactions, focusing on the D1R and D5R subtypes. Using molecular modeling techniques, we investigated the binding of the pan-agonist rotigotine, revealing a universal binding mode at the orthosteric binding pocket. Additionally, we analyze the stability of antagonist-receptor complexes with SKF83566 and SCH23390. By examining the impact of specific mutations on ligand-receptor interactions through computational simulations and thermostability assays, we gain insights into binding stability. Our research also delves into the structural and energetic aspects of antagonist binding to D1R and D5R in their inactive states. These findings enhance our understanding of dopamine receptor pharmacology and hold promise for drug development in central nervous system disorders, opening doors to future research and innovation in this field.

The accumulation of aggregated α-synuclein (α-syn) is a pathological hallmark of Parkinson's disease (PD) and other synucleinopathies. Here within, we report the in vitro characterization targeting site 2 of α-syn fibrils and in vivo evaluation of NHPs of KAC-50.1 as a potential α-syn positron emission tomography (PET) radioligand. Preclinical studies were performed using a multidimensional approach of post-mortem brain imaging techniques, radioligand binding, and biochemical studies. These experiments were followed by PET imaging in cynomolgus monkeys using [¹¹C]KAC-50.1. [3H]KAC-50.1 displayed a KD of 35 nM toward site 2 in recombinant α-syn fibrils. Specific binding of [3H]KAC-50.1 was observed in brain tissues with abundant α-syn pathology but also in AD, PSP, and CBD cases, indicating binding to amyloid β (Aβ) and tau pathology. PET studies showed a rapid entrance of [¹¹C]KAC-50.1 into the brain and relatively rapid washout from cortical brain regions, with slower washout in subcortical regions. [3H]KAC-50.1 is a ligand that binds to fibrillar α-syn but shows limited selectivity for α-syn versus Aβ and tau fibrils. PET studies in NHPs indicate that [¹¹C]KAC-50.1, despite reversible kinetic properties, displays retention in white matter. Altogether, the in vitro and in vivo properties do not support further development of [¹¹C]KAC-50.1 as a PET imaging agent.

A defining hallmark of Alzheimer’s disease (AD) is the synaptic aggregation of the amyloid β (Aβ) peptide. In vivo, Aβ production results in a diverse mixture of variants, of which Aβ40, Aβ42, and Aβ43 are profusely present in the AD brain, and their relative abundance is recognized to play a role in disease onset and progression. Nonetheless, the occurrence of Aβ40, Aβ42, and Aβ43 hetero-oligomerization and the subsequent effects on Aβ aggregation remain elusive and were investigated here. Using thioflavin-T (ThT)-monitored aggregation assays and native mass spectrometry coupled to ion mobility analysis (IM-MS), we first show that all Aβ peptides are aggregation-competent and self-assemble into homo-oligomers with distinct conformational populations, which are more pronounced between Aβ40 than the longer variants. ThT assays were then conducted on binary mixtures of Aβ variants, revealing that Aβ42 and Aβ43 aggregate independently from Aβ40 but significantly speed up Aβ40 fibrillation. Aβ42 and Aβ43 were observed to aggregate concurrently and mutually accelerate fibril formation, which likely involves hetero-oligomerization. Accordingly, native MS analysis revealed pairwise oligomerization between all variants, with the formation of heterodimers and heterotrimers. Interestingly, IM-MS indicates that hetero-oligomers containing longer Aβ variants are enriched in conformers with lower collision cross-sections when compared to their homo-oligomer counterparts. This suggests that Aβ42 and Aβ43 are capable of remodeling the oligomer structure toward a higher compaction level. Altogether, our findings provide a mechanistic description for the hetero-oligomerization of Aβ variants implicated in AD, contributing to rationalizing their in vivo proteotoxic interplay.

Intrinsically disordered proteins (IDPs) are closely associated with a number of neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease. Due to the highly dynamic nature of IDPs, their structural determination and conformational exploration pose significant challenges for both experimental and computational research. Recently, the integration of machine learning with molecular dynamics (MD) simulations has emerged as a promising methodology for efficiently exploring the conformation spaces of IDPs. In this viewpoint, we briefly review recently developed autoencoder-based models designed to enhance the conformational exploration of IDPs through embedding and latent sampling. We highlight the capability of autoencoders in expanding the conformations sampled by MD simulations and discuss their limitations due to the non-Gaussian latent space distribution and the limited conformational diversity of training conformations. Potential strategies to overcome these limitations are also discussed.

Aggregation of TDP-43 is linked to the pathogenesis of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Notably, electrostatic point mutations such as D169G and P112H, located within the highly conserved functional tandem RNA recognition motif (RRM) domains of the TDP-43 protein (TDP-43^tRRM), have been identified in diseased patients as well. In this study, we address how the electrostatic mutations alter both the native state stability and aggregation propensity of TDP-43^tRRM. The mutants D169G and P112H show increased chemical stability compared to the TDP-43^tRRM at physiological pH. However, at low pH, both the mutants undergo a conformational change to form amyloid-like fibrils, though with variable rates─the P112H mutant being substantially faster than the other two sequences (TDP-43^tRRM and D169G mutant) showing comparable rates. Moreover, among the three sequences, only the P112H mutant undergoes a strong ionic strength-dependent aggregability trend. These observations signify the substantial contribution of the excess charge of the P112H mutant to its unique aggregation process. Complementary simulated observables with atomistic resolution assign the experimentally observed sequence-, pH-, and ionic strength-dependent aggregability pattern to the degree of thermal lability of the mutation site-containing RRM1 domain and its extent of dynamical anticorrelation with the RRM2 domain whose combination eventually dictate the extent of generation of aggregation-prone partially unfolded conformational ensembles. Our choice of a specific charge-modulated pathogenic mutation-based experiment-simulation-combination approach unravels the otherwise hidden residue-wise contribution to the individual steps of this extremely complicated multistep aggregation process.

The aberrant aggregation of TAR DNA-binding protein 43 kDa (TDP-43) in cells leads to the pathogenesis of multiple fatal neurodegenerative diseases. Decoding the proposed initial transition between its functional dimeric and aggregation-prone monomeric states can potentially design a viable therapeutic strategy, which is presently limited by the lack of structural detail of the full-length TDP-43. To achieve a complete understanding of such a delicate phase space, we employed a multiscale simulation approach that unearths numerous crucial features, broadly summarized in two categories: (1) state-independent features that involve inherent chain collapsibility, rugged polymorphic landscape dictated by the terminal domains, high β-sheet propensity, structural integrity preserved by backbone-based intrachain hydrogen bonds and electrostatic forces, the prominence of the C-terminal domain in the intrachain cross-domain interfaces, and equal participation of hydrophobic and hydrophilic (charged and polar) residues in cross-domain interfaces; and (2) dimerization-modulated characteristics that encompass slower collapsing dynamics, restricted polymorphic landscape, the dominance of side chains in interchain hydrogen bonds, the appearance of the N-terminal domain in the dimer interface, and the prominence of hydrophilic (specifically polar) residues in interchain homo- and cross-domain interfaces. In our work, the ill-known C-terminal domain appears as the most crucial structure-dictating domain, which preferably populates a compact conformation with a high β-sheet propensity in its isolated state stabilized by intrabackbone hydrogen bonds, and these signatures are comparatively faded in its integrated form. Validation of our simulated observables by a complementary spectroscopic approach on multiple counts ensures the robustness of the computationally predicted features of the TDP-43 aggregation landscape.