CryoET of β-amyloid and tau within postmortem Alzheimer's disease brain

Anti-Alzheimer effects of an HDAC6 inhibitor, WY118, alone and in combination of lithium chloride: Synergistic suppression of ferroptosis via the modulation of tau phosphorylation and MAPK signaling

Alzheimer's disease (AD) is a complex neurodegenerative disorder, and current therapies mainly offer symptomatic relief. Given that the pathophysiology of AD is multifaceted, a multimodal therapeutic strategy targeting multiple molecular pathways implicated in AD-related pathogenesis represents a pragmatic avenue for impeding the advancement of AD. In this study, we evaluated the anti-Alzheimer effects of an HDAC6 inhibitor WY118, both alone and in combination with lithium chloride (LiCl), a GSK-3β inhibitor, to synergistically suppress ferroptosis. The combination of compound WY118 and LiCl demonstrated significant synergistic effects in both cellular models of AD induced by glutamate and streptozotocin. The findings suggest that compound WY118, in particular in combination with LiCl, exhibits potent anti-Alzheimer effects by synergistically suppressing ferroptosis. Studies on the mechanism of action indicated that the combination treatment significantly reduced tau phosphorylation and inhibited p38 MAPK signaling. This combination therapy holds promise for developing more effective treatments for AD.

Extracellular vesicles: translational research and applications in neurology

Over the past few decades, extensive basic, translational and clinical research has been devoted to deciphering the physiological and pathogenic roles of extracellular vesicles (EVs) in the nervous system. The presence of brain cell-derived EVs in the blood, carrying diverse cargoes, has enabled the development of predictive, diagnostic, prognostic, disease-monitoring and treatment-response biomarkers for various neurological disorders. In this Review, we consider how EV biomarkers can bring us closer to understanding the complex pathogenesis of neurological disorders such as Alzheimer disease, Parkinson disease, stroke, traumatic brain injury, amyotrophic lateral sclerosis and multiple sclerosis. We describe how translational research on EVs might unfold bidirectionally, proceeding from basic to clinical studies but also in the opposite direction, with biomarker findings in the clinic leading to novel hypotheses that can be tested in the laboratory. We demonstrate the potential value of EVs across all stages of the therapeutic development pipeline, from identifying therapeutic targets to the use of EVs as reporters in model systems and biomarkers in clinical research. Finally, we discuss how the cargo and physicochemical properties of naturally occurring and custom-engineered EVs can be leveraged as novel treatments and vehicles for drug delivery, potentially revolutionizing neurotherapeutics.

Extracellular particles: emerging insights into central nervous system diseases

Extracellular particles (EPs), including extracellular vesicles (EVs) and non-vesicular extracellular particles (NVEPs), are multimolecular biomaterials released by cells that play a crucial role in intercellular communication. Recently, new subtypes of EPs associated with central nervous system (CNS), such as exophers and supermeres have been identified. These EPs provide new perspectives for understanding the pathological progression of CNS disorders and confer potential diagnostic value for liquid biopsies in neurodegenerative diseases (NDs). Moreover, EPs have emerged as promising drug delivery vehicles and targeted platforms for CNS-specific therapies. In this review, we delineate the landscape of EP subtypes and their roles in the pathophysiology of CNS diseases. We also review the recent advances of EP-based diagnosis in NDs and highlight the importance of analytical platforms with single-particle resolution in the exploitation of potential biomarkers. Furthermore, we summarize the application of engineered EVs in the treatment of CNS diseases and outline the underexplored potential of NVEPs as novel therapeutic agents.

Detecting the Undetectable: Advances in Methods for Identifying Small Tau Aggregates in Neurodegenerative Diseases

Tau, a microtubule-associated protein, plays a critical role in maintaining neuronal structure and function. However, in neurodegenerative diseases such as Alzheimer's disease and other tauopathies, tau misfolds and aggregates into oligomers and fibrils, leading to neuronal damage. Tau oligomers are increasingly recognised as the most neurotoxic species, inducing synaptic dysfunction and contributing to disease progression. Detecting these early-stage aggregates is challenging due to their low concentration and high heterogeneity in biological samples. Traditional methods such as immunostaining and enzyme-linked immunosorbent assay (ELISA) lack the sensitivity and specificity to reliably detect small tau aggregates. Advanced single-molecule approaches, including single-molecule fluorescence resonance energy transfer (smFRET) and single-molecule pull-down (SiMPull), offer improved sensitivity for studying tau aggregation at the molecular level. These emerging tools provide critical insights into tau pathology, enabling earlier detection and characterisation of disease-relevant aggregates, thereby offering potential for the development of targeted therapies and diagnostic approaches for tauopathies.

Uncovering synaptic and cellular nanoarchitecture of brain tissue via seamless in situ trimming and milling for cryo-electron tomography

Cell-cell communication underlies all emergent properties of the brain, including cognition, learning and memory. The physical basis for these communications is the synapse, a multi-component structure requiring coordinated interactions between diverse cell types. However, many aspects of three-dimensional (3D) synaptic organization remain poorly understood. Here, we developed an approach, seamless in situ trimming and milling (SISTM), to reliably fabricate sufficiently thin lamellae for mapping of the 3D nanoarchitecture of synapses in mouse, monkey and human brain tissue under near-native conditions via cryo-electron tomography (cryo-ET). We validated SISTM in a mouse model of Huntington's disease, demonstrating distinct 3D alterations to synaptic vesicles and mitochondria. By successfully applying SISTM to macaque brain, we described the 3D architecture of a tripartite synapse within the cortex. Subtomogram averaging (STA) enabled spatial mapping of astrocyte-neuron contacts within the tripartite synapse, revealing neurexin-neuroligin complexes as potential constituents that tether the two cell types. Finally, we showed that the defining features of synaptic nanoarchitecture were conserved across species and evident in human brain tissue obtained postmortem. Combining SISTM with cryo-ET and STA is a starting point for a new understanding of brain organization, disease-induced structural alterations and the development of rational, structure-guided therapeutics.

Chiral Inorganic Nanomaterial-Based Diagnosis and Treatments for Neurodegenerative Diseases

Chiral nanomaterials are widely investigated over recent decades due to their biocompatibility and unique chiral effects. These key properties have significantly promoted the rapid development of chiral nanomaterials in bioengineering and medicine. In this review, the basic principles of constructing chiral nanomaterials along with the latest progress in research are comprehensively summarized. Then, the application of chiral nanomaterials for the diagnosis of neurodegenerative diseases (NDDs) is systematically described. In addition, the significant potential and broad prospects of chiral nanomaterials in the treatment of NDDs are highlighted from several aspects, including the disaggregation of neurofibrils, the scavenging of reactive oxygen species, regulation of the microbial-gut-brain axis, the elimination of senescent cells, and the promotion of directed differentiation in neural stem cells. Finally, a perspective of the challenges and future development of chiral nanomaterials for the treatment of NDDs is provided.

How is the Amyloid Fold Built? Polymorphism and the Microscopic Mechanisms of Fibril Assembly

For a given protein sequence, many, up to sometimes hundreds of different amyloid fibril folds, can be formed in vitro. Yet, fibrils extracted from, or found in, human tissue, usually at the end of a long disease process, are often structurally homogeneous. Through monitoring of amyloid assembly reactions in vitro, the scientific community has gained a detailed understanding of the kinetic mechanisms of fibril assembly and the rates at which the different processes involved occur. However, how this kinetic information relates to the structural changes as a protein transforms from its initial, native structure to the canonical cross-β structure of amyloid remain obscure. While cryoEM has yielded a plethora of high-resolution information that portray a vast variety of fibril structures, there remains little knowledge of how and why each particular structure resulted. Recent work has demonstrated that fibril structures can change over an assembly time course, despite the different fibril types having similar thermodynamic stability. This points to kinetic control of the fibrils formed, with structures that initiate or elongate faster becoming the dominant products of assembly. Annotating kinetic assembly mechanisms alongside structural analysis of the fibrils formed is required to truly understand the molecular mechanisms of amyloid formation. However, this is a complicated task. In this review, we discuss how embracing this challenge could open new frontiers in amyloid research and new opportunities for therapy.

New insights into the molecular architecture of neurons by cryo-electron tomography

Cryo-electron tomography (cryo-ET) visualizes natively preserved cellular ultrastructure at molecular resolution. Recent developments in sample preparation workflows and image processing tools enable growing applications of cryo-ET in cellular neurobiology. As such, cryo-ET is beginning to unravel the in situ macromolecular organization of neurons using samples of increasing complexity. Here, we highlight advances in cryo-ET technology and review its recent use to study neuronal architecture and its alterations under disease conditions.

Structural glycobiology - from enzymes to organelles

Biological carbohydrate polymers represent some of the most complex molecules in life, enabling their participation in a huge range of physiological functions. The complexity of biological carbohydrates arises from an extensive enzymatic repertoire involved in their construction, deconstruction and modification. Over the past decades, structural studies of carbohydrate processing enzymes have driven major insights into their mechanisms, supporting associated applications across medicine and biotechnology. Despite these successes, our understanding of how multienzyme networks function to create complex polysaccharides is still limited. Emerging techniques such as super-resolution microscopy and cryo-electron tomography are now enabling the investigation of native biological systems at near molecular resolutions. Here, we review insights from classical in vitro studies of carbohydrate processing, alongside recent in situ studies of glycosylation-related processes. While considerable technical challenges remain, the integration of molecular mechanisms with true biological context promises to transform our understanding of carbohydrate regulation, shining light upon the processes driving functional complexity in these essential biomolecules.

Structural biology inside multicellular specimens using electron cryotomography

The electron cryomicroscopy (cryo-EM) resolution revolution has shifted structural biology into a new era, enabling the routine structure determination of macromolecular complexes at an unprecedented rate. Building on this, electron cryotomography (cryo-ET) offers the potential to visualise the native three-dimensional organisation of biological specimens, from cells to tissues and even entire organisms. Despite this huge potential, the study of tissue-like multicellular specimens via cryo-ET still presents numerous challenges, wherein many steps in the workflow are being developed or in urgent need of improvement. In this review, we outline the latest techniques currently utilised for in situ imaging of multicellular specimens, while clearly enumerating their associated limitations. We consider every step in typical workflows employed by various laboratories, including sample preparation, data collection and image analysis, to highlight recent progress and showcase prominent success stories. By considering the entire structural biology workflow for multicellular specimens, we identify which future exciting developments in hardware and software could enable comprehensive in situ structural biology investigations, bringing forth a new age of discovery in molecular structural and cell biology.

Memory engram synapse 3D molecular architecture visualized by cryoCLEM-guided cryoET

Memory is incorporated into the brain as physicochemical changes to engram cells. These are neuronal populations that form complex neuroanatomical circuits, are modified by experiences to store information, and allow for memory recall. At the molecular level, learning modifies synaptic communication to rewire engram circuits, a mechanism known as synaptic plasticity. However, despite its functional role on memory formation, the 3D molecular architecture of synapses within engram circuits is unknown. Here, we demonstrate the use of engram labelling technology and cryogenic correlated light and electron microscopy (cryoCLEM)-guided cryogenic electron tomography (cryoET) to visualize the in-tissue 3D molecular architecture of engram synapses of a contextual fear memory within the CA1 region of the mouse hippocampus. Engram cells exhibited structural diversity of macromolecular constituents and organelles in both pre- and postsynaptic compartments and within the synaptic cleft, including in clusters of membrane proteins, synaptic vesicle occupancy, and F-actin copy number. This 'engram to tomogram' approach, harnessing in vivo functional neuroscience and structural biology, provides a methodological framework for testing fundamental molecular plasticity mechanisms within engram circuits during memory encoding, storage and recall.

Inducers and modulators of protein aggregation in Alzheimer's disease - Critical tools for understanding the foundations of aggregate structures

Amyloidogenic protein aggregation is a pathological hallmark of Alzheimer's Disease (AD). As such, this critical feature of the disease has been instrumental in guiding research on the mechanistic basis of disease, diagnostic biomarkers and preventative and therapeutic treatments. Here we review identified molecular triggers and modulators of aggregation for two of the proteins associated with AD: amyloid beta and tau. We aim to provide an overview of how specific molecular factors can impact aggregation kinetics and aggregate structure to promote disease. Looking toward the future, we highlight some research areas of focus that would accelerate efforts to effectively target protein aggregation in AD.

Leukotriene signaling in neurodegeneration: implications for treatment strategies

Leukotrienes (LTs) are a group of substances that cause inflammation. They are produced by the enzyme 5-lipoxygenase (5-LOX) from arachidonic acid. Cysteinyl LTs are a group of lipid molecules that have a prominent role in inflammatory signaling in the allergic diseases. Although they are traditionally known for their role in allergic disease, current advancements in bio-medical research have shed light on the involvement of these inflammatory mediators in diseases such as in the inflammation related to central nervous system (CNS) disorders. Among the CNS diseases, LTs, along with 5-LOX and their receptors, have been shown to be associated with multiple sclerosis (MS), Alzheimer's disease (AD), and Parkinson's disease (PD). Through a comprehensive review of current research and experimentation, this investigation provides an insight on the biosynthesis, receptors, and biological effects of LTs in the body. Furthermore, implications of leukotriene signaling in CNS and its intricate role in neurodegeneration are also studied. Through the revelation of these insights, our aim is to establish a foundation for the development of enhanced and focused therapeutic approaches in the continuous endeavor to combat neurodegeneration. Furthermore, the pharmacological inhibition of leukotriene signaling with selective inhibitors offers promising prospects for future interventions and treatments for neurodegenerative diseases.

Alzheimer's Disease: Exploring the Landscape of Cognitive Decline

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and impaired daily functioning. The pathology of AD is marked by the accumulation of amyloid beta plaques and tau protein tangles in the brain, along with neuroinflammation and synaptic dysfunction. Genetic factors, such as mutations in APP, PSEN1, and PSEN2 genes, as well as the APOE ε4 allele, contribute to increased risk of acquiring AD. Currently available treatments provide symptomatic relief but do not halt disease progression. Research efforts are focused on developing disease-modifying therapies that target the underlying pathological mechanisms of AD. Advances in identification and validation of reliable biomarkers for AD hold great promise for enhancing early diagnosis, monitoring disease progression, and assessing treatment response in clinical practice in effort to alleviate the burden of this devastating disease. In this paper, we analyze data from the CAS Content Collection to summarize the research progress in Alzheimer's disease. We examine the publication landscape in effort to provide insights into current knowledge advances and developments. We also review the most discussed and emerging concepts and assess the strategies to combat the disease. We explore the genetic risk factors, pharmacological targets, and comorbid diseases. Finally, we inspect clinical applications of products against AD with their development pipelines and efforts for drug repurposing. The objective of this review is to provide a broad overview of the evolving landscape of current knowledge regarding AD, to outline challenges, and to evaluate growth opportunities to further efforts in combating the disease.

Mouse α-synuclein fibrils are structurally and functionally distinct from human fibrils associated with Lewy body diseases

The intricate process of α-synuclein aggregation and fibrillization holds pivotal roles in Parkinson's disease (PD) and multiple system atrophy (MSA). While mouse α-synuclein can fibrillize in vitro, whether these fibrils commonly used in research to induce this process or form can reproduce structures in the human brain remains unknown. Here, we report the first atomic structure of mouse α-synuclein fibrils, which was solved in parallel by two independent teams. The structure shows striking similarity to MSA-amplified and PD-associated E46K fibrils. However, mouse α-synuclein fibrils display altered packing arrangements, reduced hydrophobicity, and heightened fragmentation sensitivity and evoke only weak immunological responses. Furthermore, mouse α-synuclein fibrils exhibit exacerbated pathological spread in neurons and humanized α-synuclein mice. These findings provide critical insights into the structural underpinnings of α-synuclein pathogenicity and emphasize a need to reassess the role of mouse α-synuclein fibrils in the development of related diagnostic probes and therapeutic interventions.

Bridging structural biology and clinical research through in-tissue cryo-electron tomography

This commentary of the Sparks of Science series from the Catalysts program reflects on the contribution of technological advances in cryo-EM to medically relevant studies.

Cryo-electron tomography reveals coupled flavivirus replication, budding and maturation

Flaviviruses replicate their genomes in replication organelles (ROs) formed as bud-like invaginations on the endoplasmic reticulum (ER) membrane, which also functions as the site for virion assembly. While this localization is well established, it is not known to what extent viral membrane remodeling, genome replication, virion assembly, and maturation are coordinated. Here, we imaged tick-borne flavivirus replication in human cells using cryo-electron tomography. We find that the RO membrane bud is shaped by a combination of a curvature-establishing coat and the pressure from intraluminal template RNA. A protein complex at the RO base extends to an adjacent membrane, where immature virions bud. Naturally occurring furin site variants determine whether virions mature in the immediate vicinity of ROs. We further visualize replication in mouse brain tissue by cryo-electron tomography. Taken together, these findings reveal a close spatial coupling of flavivirus genome replication, budding, and maturation.

Cognitive synaptopathy: synaptic and dendritic spine dysfunction in age-related cognitive disorders

Cognitive impairment is a leading component of several neurodegenerative and neurodevelopmental diseases, profoundly impacting on the individual, the family, and society at large. Cognitive pathologies are driven by a multiplicity of factors, from genetic mutations and genetic risk factors, neurotransmitter-associated dysfunction, abnormal connectomics at the level of local neuronal circuits and broader brain networks, to environmental influences able to modulate some of the endogenous factors. Otherwise healthy older adults can be expected to experience some degree of mild cognitive impairment, some of which fall into the category of subjective cognitive deficits in clinical practice, while many neurodevelopmental and neurodegenerative diseases course with more profound alterations of cognition, particularly within the spectrum of the dementias. Our knowledge of the underlying neuropathological mechanisms at the root of this ample palette of clinical entities is far from complete. This review looks at current knowledge on synaptic modifications in the context of cognitive function along healthy ageing and cognitive dysfunction in disease, providing insight into differential diagnostic elements in the wide range of synapse alterations, from those associated with the mild cognitive changes of physiological senescence to the more profound abnormalities occurring at advanced clinical stages of dementia. I propose the term "cognitive synaptopathy" to encompass the wide spectrum of synaptic pathologies associated with higher brain function disorders.