Search

INTRODUCTION: As aggregation underpins Tau toxicity, aggregation inhibitor peptides may have disease‐modifying potential. They are therefore currently being designed and target either the 306VQIVYK311 aggregation‐promoting hotspot found in all Tau isoforms or the 275VQIINK280 aggregation‐promoting hotspot found in 4R isoforms. However, for any Tau aggregation inhibitor to potentially be clinically relevant for other tauopathies, it should target both hotspots to suppress aggregation of Tau isoforms, be stable, cross the blood‐brain barrier, and rescue aggregation‐dependent Tau phenotypes in vivo. METHODS: We developed a retro‐inverso, stable D‐amino peptide, RI‐AG03 [Ac‐rrrrrrrrGpkyk(ac)iqvGr‐NH2], based on the 306VQIVYK311 hotspots which exhibit these disease‐relevant attributes. RESULTS: Unlike other aggregation inhibitors, RI‐AG03 effectively suppresses aggregation of multiple Tau species containing both hotspots in vitro and in vivo, is non‐toxic, and suppresses aggregation‐dependent neurodegenerative and behavioral phenotypes. DISCUSSION: RI‐AG03 therefore meets many clinically relevant requirements for an anti‐aggregation Tau therapeutic and should be explored further for its disease‐modifying potential for Tauopathies. Highlights: Our manuscript describes the development of a novel peptide inhibitor of Tau aggregation, a retro‐inverso, stable D‐amino peptide called RI‐AG03 that displays many clinically relevant attributes. We show its efficacy in preventing Tau aggregation in both in vitro and in vivo experimental models while being non‐toxic to cells. RI‐AG03 also rescues a biosensor cell line that stably expresses Tau repeat domains with the P301S mutation fused to Cer/Clo and rescues aggregation‐dependent phenotypes in vivo, suppressing neurodegeneration and extending lifespan.Collectively our data describe several properties and attributes of RI‐AG03 that make it a promising disease‐modifying candidate to explore for reducing pathogenic Tau aggregation in Tauopathies such as Alzheimer's disease. Given the real interest in reducing Tau aggregation and the potential clinical benefit of using such agents in clinical practice, RI‐AG03 should be investigated further for the treatment of Tauopathies after validation in mammalian models.Tau aggregation inhibitors are the obvious first choice as Tau‐based therapies as much of Tau‐mediated toxicity is aggregation dependent. Indeed, there are many research efforts focusing on this therapeutic strategy with aggregation inhibitors being designed against one of the two aggregation‐promoting hotspots of the Tau protein. To our knowledge, RI‐AG03 is the only peptide aggregation inhibitor that inhibits aggregation of Tau by targeting both aggregation‐promoting hotspot motifs simultaneously. As such, we believe that our study will have a significant impact on drug discovery efforts in this arena. [ABSTRACT FROM AUTHOR]

Author(s): Manuel Schweighauser [sup.1] , Yang Shi [sup.1] , Airi Tarutani [sup.2] [sup.3] , Fuyuki Kametani [sup.2] , Alexey G. Murzin [sup.1] , Bernardino Ghetti [sup.4] , Tomoyasu Matsubara [sup.5] [...], Synucleinopathies, which include multiple system atrophy (MSA), Parkinson's disease, Parkinson's disease with dementia and dementia with Lewy bodies (DLB), are human neurodegenerative diseases.sup.1. Existing treatments are at best symptomatic. These diseases are characterized by the presence of, and believed to be caused by the formation of, filamentous inclusions of [alpha]-synuclein in brain cells.sup.2,3. However, the structures of [alpha]-synuclein filaments from the human brain are unknown. Here, using cryo-electron microscopy, we show that [alpha]-synuclein inclusions from the brains of individuals with MSA are made of two types of filament, each of which consists of two different protofilaments. In each type of filament, non-proteinaceous molecules are present at the interface of the two protofilaments. Using two-dimensional class averaging, we show that [alpha]-synuclein filaments from the brains of individuals with MSA differ from those of individuals with DLB, which suggests that distinct conformers or strains characterize specific synucleinopathies. As is the case with tau assemblies.sup.4-9, the structures of [alpha]-synuclein filaments extracted from the brains of individuals with MSA differ from those formed in vitro using recombinant proteins, which has implications for understanding the mechanisms of aggregate propagation and neurodegeneration in the human brain. These findings have diagnostic and potential therapeutic relevance, especially because of the unmet clinical need to be able to image filamentous [alpha]-synuclein inclusions in the human brain. Cryo-electron microscopy reveals the structures of [alpha]-synuclein filaments from the brains of individuals with multiple system atrophy.

Author(s): Wenjuan Zhang [sup.1] , Airi Tarutani [sup.2] , Kathy L. Newell [sup.3] , Alexey G. Murzin [sup.1] , Tomoyasu Matsubara [sup.4] , Benjamin Falcon [sup.1] , Ruben Vidal [sup.3] [...], Corticobasal degeneration (CBD) is a neurodegenerative tauopathy--a class of disorders in which the tau protein forms insoluble inclusions in the brain--that is characterized by motor and cognitive disturbances.sup.1-3. The H1 haplotype of MAPT (the tau gene) is present in cases of CBD at a higher frequency than in controls.sup.4,5, and genome-wide association studies have identified additional risk factors.sup.6. By histology, astrocytic plaques are diagnostic of CBD.sup.7,8; by SDS-PAGE, so too are detergent-insoluble, 37 kDa fragments of tau.sup.9. Like progressive supranuclear palsy, globular glial tauopathy and argyrophilic grain disease.sup.10, CBD is characterized by abundant filamentous tau inclusions that are made of isoforms with four microtubule-binding repeats.sup.11-15. This distinguishes such '4R' tauopathies from Pick's disease (the filaments of which are made of three-repeat (3R) tau isoforms) and from Alzheimer's disease and chronic traumatic encephalopathy (CTE) (in which both 3R and 4R isoforms are found in the filaments).sup.16. Here we use cryo-electron microscopy to analyse the structures of tau filaments extracted from the brains of three individuals with CBD. These filaments were identical between cases, but distinct from those seen in Alzheimer's disease, Pick's disease and CTE.sup.17-19. The core of a CBD filament comprises residues lysine 274 to glutamate 380 of tau, spanning the last residue of the R1 repeat, the whole of the R2, R3 and R4 repeats, and 12 amino acids after R4. The core adopts a previously unseen four-layered fold, which encloses a large nonproteinaceous density. This density is surrounded by the side chains of lysine residues 290 and 294 from R2 and lysine 370 from the sequence after R4. Cyro-electron microscopy of tau filaments from people with corticobasal degeneration reveals a previously unseen four-layered fold, distinct from the filament structures seen in Alzheimer's disease, Pick's disease and chronic traumatic encephalopathy.

N -methyl-D-aspartate receptors (NMDARs) respond to glutamate to allow the influx of calcium ions and the signaling to the mitogen-activated protein kinase (MAPK) cascade. Both MAPK- and Ca2+-mediated events are important for both neurotransmission and neural cell function and fate. Using a heterologous expression system, we demonstrate that NMDAR may interact with the EF-hand calcium-binding proteins calmodulin, calneuron-1, and NCS1 but not with caldendrin. NMDARs were present in primary cultures of both neurons and microglia from cortex and hippocampus. Calmodulin in microglia, and calmodulin and NCS1 in neurons, are necessary for NMDA-induced MAP kinase pathway activation. Remarkably, signaling to the MAP kinase pathway was blunted in primary cultures of cortical and hippocampal neurons and microglia from wild-type animals by proteins involved in neurodegenerative diseases: α-synuclein, Tau, and p-Tau. A similar blockade by pathogenic proteins was found using samples from the APPSw,Ind transgenic Alzheimer’s disease model. Interestingly, a very marked increase in NMDAR–NCS1 complexes was identified in neurons and a marked increase of both NMDAR–NCS1 and NMDAR–CaM complexes was identified in microglia from the transgenic mice. The results show that α-synuclein, Tau, and p-Tau disrupt the signaling of NMDAR to the MAPK pathway and that calcium sensors are important for NMDAR function both in neurons and microglia. Finally, it should be noted that the expression of receptor–calcium sensor complexes, specially those involving NCS1, is altered in neural cells from APPSw,Ind mouse embryos/pups. [ABSTRACT FROM AUTHOR]

The degeneration of pyramidal tracts has been reported in frontotemporal lobar degeneration with TDP-43 (TAR DNA-binding protein 43) pathology (FTLD-TDP) type C. Herein, we examined the detailed pathology of the primary motor area and pyramidal tracts in the central nervous system in four autopsy cases of FTLD-TDP type C, all of which were diagnosed by neuropathological, biochemical, and genomic analyses. Three patients showed right dominant atrophy of the frontal and temporal lobes, while the other patient showed left dominant atrophy. All four patients showed motor symptoms, and two patients had episodes of repeated aspiration. In the primary motor area, phosphorylated TDP-43 (p-TDP-43) or annexin A11-immunoreactive long dystrophic neurites were observed in all cases, and neuronophagia of the Betz cells was frequently observed in two of four cases. In the lower motor system, p-TDP-43 or annexin A11-positive dystrophic neurites were detected in the anterior horn of the spinal cord. Immuno-electron microscopy of the insoluble fraction extracted from all cases showed p-TDP-43 or annexin A11-labelled filaments. In FTLD-TDP type C, neurodegeneration with TDP and annexin A11 pathology was observed mainly in the upper motor neurons of both patients with right- and left predominant temporal atrophy and a short disease duration. Furthermore, a combination of TDP-43 and annexin A11 pathology was visible in the lower motor neurons, albeit less frequently. In summary, we reported the TDP-43 and annexin A11-associated involvement of anterior horn cells of the spinal cord for the first time. The degeneration of the motor system could contribute to dysphagia and aspiration pneumonia at the late stage of FTLD-TDP type C. Little or no TDP pathology was found in the corticospinal tract, unlike in FTLD-TDP type B, suggesting the occurrence of secondary degeneration in FTLD-TDP type C., (© 2025 Japanese Society of Neuropathology.)

Introduction: As aggregation underpins Tau toxicity, aggregation inhibitor peptides may have disease-modifying potential. They are therefore currently being designed and target either the 306 VQIVYK 311 aggregation-promoting hotspot found in all Tau isoforms or the 275 VQIINK 280 aggregation-promoting hotspot found in 4R isoforms. However, for any Tau aggregation inhibitor to potentially be clinically relevant for other tauopathies, it should target both hotspots to suppress aggregation of Tau isoforms, be stable, cross the blood-brain barrier, and rescue aggregation-dependent Tau phenotypes in vivo., Methods: We developed a retro-inverso, stable D-amino peptide, RI-AG03 [Ac-rrrrrrrrGpkyk(ac)iqvGr-NH2], based on the 306 VQIVYK 311 hotspots which exhibit these disease-relevant attributes., Results: Unlike other aggregation inhibitors, RI-AG03 effectively suppresses aggregation of multiple Tau species containing both hotspots in vitro and in vivo, is non-toxic, and suppresses aggregation-dependent neurodegenerative and behavioral phenotypes., Discussion: RI-AG03 therefore meets many clinically relevant requirements for an anti-aggregation Tau therapeutic and should be explored further for its disease-modifying potential for Tauopathies., Highlights: Our manuscript describes the development of a novel peptide inhibitor of Tau aggregation, a retro-inverso, stable D-amino peptide called RI-AG03 that displays many clinically relevant attributes. We show its efficacy in preventing Tau aggregation in both in vitro and in vivo experimental models while being non-toxic to cells. RI-AG03 also rescues a biosensor cell line that stably expresses Tau repeat domains with the P301S mutation fused to Cer/Clo and rescues aggregation-dependent phenotypes in vivo, suppressing neurodegeneration and extending lifespan. Collectively our data describe several properties and attributes of RI-AG03 that make it a promising disease-modifying candidate to explore for reducing pathogenic Tau aggregation in Tauopathies such as Alzheimer's disease. Given the real interest in reducing Tau aggregation and the potential clinical benefit of using such agents in clinical practice, RI-AG03 should be investigated further for the treatment of Tauopathies after validation in mammalian models. Tau aggregation inhibitors are the obvious first choice as Tau-based therapies as much of Tau-mediated toxicity is aggregation dependent. Indeed, there are many research efforts focusing on this therapeutic strategy with aggregation inhibitors being designed against one of the two aggregation-promoting hotspots of the Tau protein. To our knowledge, RI-AG03 is the only peptide aggregation inhibitor that inhibits aggregation of Tau by targeting both aggregation-promoting hotspot motifs simultaneously. As such, we believe that our study will have a significant impact on drug discovery efforts in this arena., (© 2024 The Author(s). Alzheimer's & Dementia published by Wiley Periodicals LLC on behalf of Alzheimer's Association.)

Intracellular α-synuclein (α-syn) inclusions are a neuropathological hallmark of Lewy body disease (LBD) and multiple system atrophy (MSA), both of which are termed synucleinopathies. LBD is defined by Lewy bodies and Lewy neurites in neurons, while MSA displays glial cytoplasmic inclusions in oligodendrocytes. Pathological α-syn adopts an ordered filamentous structure with a 5-10 nm filament diameter, and this conformational change has been suggested to be involved in the disease onset and progression. Synucleinopathies also exhibit characteristic ultrastructural and biochemical properties of α-syn filaments, and α-syn strains with distinct conformations have been identified. Numerous experimental studies have supported the idea that pathological α-syn self-amplifies and spreads throughout the brain, during which processes the conformation of α-syn filaments may drive the disease specificity. In this review, we summarize the ultrastructural features and heterogeneity of α-syn filaments in the brains of patients with synucleinopathy and in experimental models of seeded α-syn aggregation.

Pathological tau protein accumulated in the brain of patients with tauopathies undergoes structural changes into amyloid-like filaments and forms the intracellular deposits that characterize the disease. Structural and biochemical classification of pathogenic tau extracted from patients' brains supports the hypothesis that structural polymorphisms of tau filaments occur in the brain. Additionally, disease-specific tau pathologies are recapitulated in in vitro and in vivo experimental models that mimic tau aggregation and dissemination and indicate that conformation of tau filaments is a key contributor to the pathological diversity in tauopathy. In this review, we describe the structural and biochemical features of pathological tau extracted from the brain of patients with tauopathies and discuss the possible mechanisms underlying amplification and dissemination of pathological tau in the brain.

α-Synuclein (α-syn) is a major component of abnormal protein deposits observed in the brains of patients with synucleinopathies, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy (MSA). The synaptic protein α-syn is water-soluble under normal physiological conditions, but in these patients' brains, we see accumulation of insoluble amyloid-like α-syn fibrils with prion-like properties. Intracerebral accumulation of these fibrils is correlated with disease onset and progression. Recombinant α-syn protein also forms amyloid-like fibrils that are structurally akin to those extracted from patients' brains. Recent cryo-electron microscopic studies have identified the core structures of synthetic α-syn fibrils and α-syn fibrils extracted from the brains of patients with MSA at the atomic level. In this chapter, we describe negative staining and immunoelectron microscopy protocols for ultrastructural characterization of synthetic α-syn fibrils and pathological α-syn fibrils.

N -methyl-D-aspartate receptors (NMDARs) respond to glutamate to allow the influx of calcium ions and the signaling to the mitogen-activated protein kinase (MAPK) cascade. Both MAPK- and Ca 2+ -mediated events are important for both neurotransmission and neural cell function and fate. Using a heterologous expression system, we demonstrate that NMDAR may interact with the EF-hand calcium-binding proteins calmodulin, calneuron-1, and NCS1 but not with caldendrin. NMDARs were present in primary cultures of both neurons and microglia from cortex and hippocampus. Calmodulin in microglia, and calmodulin and NCS1 in neurons, are necessary for NMDA-induced MAP kinase pathway activation. Remarkably, signaling to the MAP kinase pathway was blunted in primary cultures of cortical and hippocampal neurons and microglia from wild-type animals by proteins involved in neurodegenerative diseases: α-synuclein, Tau, and p-Tau. A similar blockade by pathogenic proteins was found using samples from the APP Sw,Ind transgenic Alzheimer's disease model. Interestingly, a very marked increase in NMDAR-NCS1 complexes was identified in neurons and a marked increase of both NMDAR-NCS1 and NMDAR-CaM complexes was identified in microglia from the transgenic mice. The results show that α-synuclein, Tau, and p-Tau disrupt the signaling of NMDAR to the MAPK pathway and that calcium sensors are important for NMDAR function both in neurons and microglia. Finally, it should be noted that the expression of receptor-calcium sensor complexes, specially those involving NCS1, is altered in neural cells from APP Sw,Ind mouse embryos/pups.

Intracellular abnormal protein deposits, such as tau, α-synuclein and TDP-43, are the hallmark of many neurodegenerative diseases, and the distributions of these pathological proteins are closely correlated with disease symptoms and progression. A growing body of evidence strongly suggests that these abnormal proteins have prion-like properties: they convert normal proteins into abnormal forms, self-propagate through neuronal networks, and then spread in the brain. This prion-like propagation of abnormal proteins may account for the diversity, selective degeneration and disease progression seen in neurodegenerative diseases, although the molecular mechanism remains uncertain the molecular details of this mechanism. This review describes recent studies on prion-like properties of abnormal proteins in vitro, in cells and in animal experimental models.