Meditation-induced bloodborne factors as an adjuvant treatment to COVID-19 disease.

The COVID-19 pandemic has resulted in significant morbidity and mortality worldwide. Management of the pandemic has relied mainly on SARS-CoV-2 vaccines, while alternative approaches such as meditation, shown to improve immunity, have been largely unexplored. Here, we probe the relationship between meditation and COVID-19 disease and directly test the impact of meditation on the induction of a blood environment that modulates viral infection. We found a significant inverse correlation between length of meditation practice and SARS-CoV-2 infection as well as accelerated resolution of symptomology of those infected. A meditation "dosing" effect was also observed. In cultured human lung cells, blood from experienced meditators induced factors that prevented entry of pseudotyped viruses for SARS-CoV-2 spike protein of both the wild-type Wuhan-1 virus and the Delta variant. We identified and validated SERPINA5, a serine protease inhibitor, as one possible protein factor in the blood of meditators that is necessary and sufficient for limiting pseudovirus entry into cells. In summary, we conclude that meditation can enhance resiliency to viral infection and may serve as a possible adjuvant therapy in the management of the COVID-19 pandemic.

Fibril polymorphism affects immobilized non-amyloid flanking domains of huntingtin exon1 rather than its polyglutamine core.

Polyglutamine expansion in the huntingtin protein is the primary genetic cause of Huntington's disease (HD). Fragments coinciding with mutant huntingtin exon1 aggregate in vivo and induce HD-like pathology in mouse models. The resulting aggregates can have different structures that affect their biochemical behaviour and cytotoxic activity. Here we report our studies of the structure and functional characteristics of multiple mutant htt exon1 fibrils by complementary techniques, including infrared and solid-state NMR spectroscopies. Magic-angle-spinning NMR reveals that fibrillar exon1 has a partly mobile α-helix in its aggregation-accelerating N terminus, and semi-rigid polyproline II helices in the proline-rich flanking domain (PRD). The polyglutamine-proximal portions of these domains are immobilized and clustered, limiting access to aggregation-modulating antibodies. The polymorphic fibrils differ in their flanking domains rather than the polyglutamine amyloid structure. They are effective at seeding polyglutamine aggregation and exhibit cytotoxic effects when applied to neuronal cells.

Polyglutamine amyloid core boundaries and flanking domain dynamics in huntingtin fragment fibrils determined by solid-state nuclear magnetic resonance.

In Huntington's disease, expansion of a polyglutamine (polyQ) domain in the huntingtin (htt) protein leads to misfolding and aggregation. There is much interest in the molecular features that distinguish monomeric, oligomeric, and fibrillar species that populate the aggregation pathway and likely differ in cytotoxicity. The mechanism and rate of aggregation are greatly affected by the domains flanking the polyQ segment within exon 1 of htt. A "protective" C-terminal proline-rich flanking domain inhibits aggregation by inducing polyproline II structure (PPII) within an extended portion of polyQ. The N-terminal flanking segment (htt(NT)) adopts an α-helical structure as it drives aggregation, helps stabilize oligomers and fibrils, and is seemingly integral to their supramolecular assembly. Via solid-state nuclear magnetic resonance (ssNMR), we probe how, in the mature fibrils, the htt flanking domains impact the polyQ domain and in particular the localization of the ß-structured amyloid core. Using residue-specific and uniformly labeled samples, we find that the amyloid core occupies most of the polyQ domain but ends just prior to the prolines. We probe the structural and dynamical features of the remarkably abrupt ß-sheet to PPII transition and discuss the potential connections to certain htt-binding proteins. We also examine the htt(NT) α-helix outside the polyQ amyloid core. Despite its presumed structural and demonstrated stabilizing roles in the fibrils, quantitative ssNMR measurements of residue-specific dynamics show that it undergoes distinct solvent-coupled motion. This dynamical feature seems reminiscent of molten-globule-like α-helix-rich features attributed to the nonfibrillar oligomeric species of various amyloidogenic proteins.

Identification of novel potentially toxic oligomers formed in vitro from mammalian-derived expanded huntingtin exon-1 protein.

Huntington disease is a genetic neurodegenerative disorder that arises from an expanded polyglutamine region in the N terminus of the HD gene product, huntingtin. Protein inclusions comprised of N-terminal fragments of mutant huntingtin are a characteristic feature of disease, though are likely to play a protective role rather than a causative one in neurodegeneration. Soluble oligomeric assemblies of huntingtin formed early in the aggregation process are candidate toxic species in HD. In the present study, we established an in vitro system to generate recombinant huntingtin in mammalian cells. Using both denaturing and native gel analysis, we have identified novel oligomeric forms of mammalian-derived expanded huntingtin exon-1 N-terminal fragment. These species are transient and were not previously detected using bacterially expressed exon-1 protein. Importantly, these species are recognized by 3B5H10, an antibody that recognizes a two-stranded hairpin conformation of expanded polyglutamine believed to be associated with a toxic form of huntingtin. Interestingly, comparable oligomeric species were not observed for expanded huntingtin shortstop, a 117-amino acid fragment of huntingtin shown previously in mammalian cell lines and transgenic mice, and here in primary cortical neurons, to be non-toxic. Further, we demonstrate that expanded huntingtin shortstop has a reduced ability to form amyloid-like fibrils characteristic of the aggregation pathway for toxic expanded polyglutamine proteins. Taken together, these data provide a possible candidate toxic species in HD. In addition, these studies demonstrate the fundamental differences in early aggregation events between mutant huntingtin exon-1 and shortstop proteins that may underlie the differences in toxicity.

A compact beta model of huntingtin toxicity.

Huntington disease results from an expanded polyglutamine region in the N terminus of the huntingtin protein. HD pathology is characterized by neuronal degeneration and protein inclusions containing N-terminal fragments of mutant huntingtin. Structural information is minimal, though it is believed that mutant huntingtin polyglutamine adopts ß structure upon conversion to a toxic form. To this end, we designed mammalian cell expression constructs encoding compact ß variants of Htt exon 1 N-terminal fragment and tested their ability to aggregate and induce toxicity in cultured neuronal cells. In parallel, we performed molecular dynamics simulations, which indicate that constructs with expanded polyglutamine ß-strands are stabilized by main-chain hydrogen bonding. Finally, we found a correlation between the reactivity to 3B5H10, an expanded polyglutamine antibody that recognizes a compact ß rich hairpin structure, and the ability to induce cell toxicity. These data are consistent with an important role for a compact ß structure in mutant huntingtin-induced cell toxicity.

Baicalein reduces E46K alpha-synuclein aggregation in vitro and protects cells against E46K alpha-synuclein toxicity in cell models of familiar Parkinsonism.

The E46K is a point mutation in alpha-synuclein (alpha-syn) that causes familial Parkinsonism with Lewy body dementia. We have now generated a cell model of Parkinsonism/Parkinson's disease (PD) and demonstrated cell toxicity after expression of E46K in the differentiated PC12 cells. E46K alpha-syn inhibited proteasome activity and induced mitochondrial depolarization in the cell model. Baicalein has been reported to inhibit fibrillation of wild type alpha-syn in vitro, and to protect neurons against several chemical-induced models of PD. We now report that baicalein significantly attenuated E46K-induced mitochondrial depolarization and proteasome inhibition, and protected cells against E46K-induced toxicity in a cell model of PD. Baicalein also reduced E46K fibrilization in vitro, with a concentration-dependent decrease in beta sheet conformation, though it increased some oligomeric species, and decreased formation of E46K alpha-syn-induced aggregates and rescued toxicity in N2A cells. Taken together, these data indicate that mitochondrial dysfunction, proteasome inhibition and specific aspects of abnormal E46K aggregation accompany E46K alpha-syn-induced cell toxicity, and baicalein can protect as well as altering aggregation properties. Baicalein has potential as a tool to understand the relation between different aggregation species and toxicity, and might be a candidate compound for further validation by using in vivo alpha-syn genetic PD models.

The chaperonin TRiC blocks a huntingtin sequence element that promotes the conformational switch to aggregation.

Aggregation of proteins containing polyglutamine (polyQ) expansions characterizes many neurodegenerative disorders, including Huntington's disease. Molecular chaperones modulate the aggregation and toxicity of the huntingtin (Htt) protein by an ill-defined mechanism. Here we determine how the chaperonin TRiC suppresses Htt aggregation. Unexpectedly, TRiC does not physically block the polyQ tract itself, but rather sequesters a short Htt sequence element, N-terminal to the polyQ tract, that promotes the amyloidogenic conformation. The residues of this element essential for rapid Htt aggregation are directly bound by TRiC. Our findings illustrate how molecular chaperones, which recognize hydrophobic determinants, can prevent aggregation of polar polyQ tracts associated with neurodegenerative diseases. The observation that short endogenous sequence elements can accelerate the switch of polyQ tracts to an amyloidogenic conformation provides a novel target for therapeutic strategies.

ATF3 plays a protective role against toxicity by N-terminal fragment of mutant huntingtin in stable PC12 cell line.

Huntington's disease is a progressive neurodegenerative disorder caused by a polyglutamine expansion near the N-terminus of huntingtin. The mechanisms of polyglutamine neurotoxicity, and cellular responses are not fully understood. We have studied gene expression profiles by short oligo array using an inducible PC12 cell model expressing an N-terminal huntingtin fragment with expanded polyglutamine (Htt-N63-148Q). Mutant huntingtin Htt-N63 induced cell death and increased the mRNA and protein levels of activating transcription factor 3 (ATF3). Mutant Htt-N63 also significantly enhanced ATF3 transcriptional activity by a promoter-based reporter assay. Overexpression of ATF3 protects against mutant Htt-N63 toxicity and knocking down ATF3 expression reduced Htt-N63 toxicity in a stable PC12 cell line. These results indicated that ATF3 plays a critical role in toxicity induced by mutant Htt-N63 and may lead to a useful therapeutic target.

Mutant huntingtin N-terminal fragments of specific size mediate aggregation and toxicity in neuronal cells.

Huntingtin proteolysis is implicated in Huntington disease pathogenesis, yet, the nature of huntingtin toxic fragments remains unclear. Huntingtin undergoes proteolysis by calpains and caspases within an N-terminal region between amino acids 460 and 600. We have focused on proteolytic steps producing shorter N-terminal fragments, which we term cp-1 and cp-2 (distinct from previously described cp-A/cp-B). We used HEK293 cells to express the first 511 residues of huntingtin and further define the cp-1 and cp-2 cleavage sites. Based on epitope mapping with huntingtin-specific antibodies, we found that cp-1 cleavage occurs between residues 81 and 129 of huntingtin. Affinity and size exclusion chromatography were used to further purify huntingtin cleavage products and enrich for the cp-1/cp-2 fragments. Using mass spectrometry, we found that the cp-2 fragment is generated by cleavage of huntingtin at position Arg(167). This site was confirmed by deletion analysis and specific detection with a custom-generated cp-2 site neo-epitope antibody. Furthermore, alterations of this cleavage site resulted in a decrease in toxicity and an increase in aggregation of huntingtin in neuronal cells. These data suggest that cleavage of huntingtin at residue Arg(167) may mediate mutant huntingtin toxicity in Huntington disease.

Depletion of CBP is directly linked with cellular toxicity caused by mutant huntingtin.

Huntington's disease is a neurodegenerative disease caused by an expanded polyglutamine stretch within the huntingtin protein. Transfection of mutant huntingtin causes cell toxicity and depletion of CREB binding protein (CBP) or its recruitment into huntingtin aggregates. However, the role of CBP has been controversial and the relationship between polyglutamine-induced toxicity and CBP depletion has not been examined on an individual cell basis. Using a single-cell based assay, we found that, in HT22 cells or primary neurons transfected with mutant huntingtin, cell toxicity was accompanied by CBP depletion, rather than merely recruitment. Transfection with a htt exon1 construct containing uninterrupted polyglutamine or a polyglutamine region engineered to form a compact beta structure resulted in cell toxicity. CBP depletion was accompanied by histone hypo-acetylation. CBP overexpression rescued both acetylated histone levels and cell toxicity. These data suggest that CBP dysfunction and altered gene transcription contribute to mutant htt-induced neurotoxicity.

Opinion: What is the role of protein aggregation in neurodegeneration?

Neurodegenerative diseases typically involve deposits of inclusion bodies that contain abnormal aggregated proteins. Therefore, it has been suggested that protein aggregation is pathogenic. However, several lines of evidence indicate that inclusion bodies are not the main cause of toxicity, and probably represent a cellular protective response. Aggregation is a complex multi-step process of protein conformational change and accretion. The early species in this process might be most toxic, perhaps through the exposure of buried moieties such as main chain NH and CO groups that could serve as hydrogen bond donors or acceptors in abnormal interactions with other cellular proteins. This model implies that the pathogenesis of diverse neurodegenerative diseases arises by common mechanisms, and might yield common therapeutic targets.

A structure-based analysis of huntingtin mutant polyglutamine aggregation and toxicity: evidence for a compact beta-sheet structure.

Huntington's disease (HD) arises from an expanded polyglutamine (polyQ) in the N-terminus of the huntingtin (htt) protein. Neuronal degeneration and inclusions containing N-terminal fragments of mutant htt are present in the cortex and striatum of HD brain. Recently, a model of polyQ aggregate structure has been proposed on the basis of studies with synthetic polyQ peptides and includes an alternating beta-strand/beta-turn structure with seven glutamine residues per beta-strand. We tested this model in the context of the htt exon-1 N-terminal fragment in both mammalian cell culture and cultured primary cortical neurons. We found our data support this model in the htt protein and provide a better understanding of the structural basis of polyQ aggregation in toxicity in HD.

Protein aggregation and neurodegenerative disease.

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and prion diseases are increasingly being realized to have common cellular and molecular mechanisms including protein aggregation and inclusion body formation. The aggregates usually consist of fibers containing misfolded protein with a beta-sheet conformation, termed amyloid. There is partial but not perfect overlap among the cells in which abnormal proteins are deposited and the cells that degenerate. The most likely explanation is that inclusions and other visible protein aggregates represent an end stage of a molecular cascade of several steps, and that earlier steps in the cascade may be more directly tied to pathogenesis than the inclusions themselves. For several diseases, genetic variants assist in explaining the pathogenesis of the more common sporadic forms and developing mouse and other models. There is now increased understanding of the pathways involved in protein aggregation, and some recent clues have emerged as to the molecular mechanisms of cellular toxicity. These are leading to approaches toward rational therapeutics.

Huntingtin spheroids and protofibrils as precursors in polyglutamine fibrilization.

The pathology of Huntington's disease is characterized by neuronal degeneration and inclusions containing N-terminal fragments of mutant huntingtin (htt). To study htt aggregation, we examined purified htt fragments in vitro, finding globular and protofibrillar intermediates participating in the genesis of mature fibrils. These intermediates were high in beta-structure. Furthermore, Congo Red, a dye that stains amyloid fibrils, prevented the assembly of mutant htt into mature fibrils, but not the formation of protofibrils. Other proteins capable of forming ordered aggregates, such as amyloid beta and alpha-synuclein, form similar intermediates, suggesting that the mechanisms of mutant htt aggregation and possibly htt toxicity may overlap with other neurodegenerative disorders.