Interplay of Energetics and ER Stress Exacerbates Alzheimer's Amyloid-β (Aβ) Toxicity in Yeast

Simple model systems reveal conserved mechanisms of Alzheimer's disease and related tauopathies

The lack of effective therapies that slow the progression of Alzheimer's disease (AD) and related tauopathies highlights the need for a more comprehensive understanding of the fundamental cellular mechanisms underlying these diseases. Model organisms, including yeast, worms, and flies, provide simple systems with which to investigate the mechanisms of disease. The evolutionary conservation of cellular pathways regulating proteostasis and stress response in these organisms facilitates the study of genetic factors that contribute to, or protect against, neurodegeneration. Here, we review genetic modifiers of neurodegeneration and related cellular pathways identified in the budding yeast Saccharomyces cerevisiae, the nematode Caenorhabditis elegans, and the fruit fly Drosophila melanogaster, focusing on models of AD and related tauopathies. We further address the potential of simple model systems to better understand the fundamental mechanisms that lead to AD and other neurodegenerative disorders.

Alzheimer's Disease: Significant Benefit from the Yeast-Based Models

Alzheimer's disease (AD) is an age-related, multifaceted neurological disorder associated with accumulation of aggregated proteins (amyloid Aβ and hyperphosphorylated tau), loss of synapses and neurons, and alterations in microglia. AD was recognized by the World Health Organization as a global public health priority. The pursuit of a better understanding of AD forced researchers to pay attention to well-defined single-celled yeasts. Yeasts, despite obvious limitations in application to neuroscience, show high preservation of basic biological processes with all eukaryotic organisms and offer great advantages over other disease models due to the simplicity, high growth rates on low-cost substrates, relatively simple genetic manipulations, the large knowledge base and data collections, and availability of an unprecedented amount of genomic and proteomic toolboxes and high-throughput screening techniques, inaccessible to higher organisms. Research reviewed above clearly indicates that yeast models, together with other, more simple eukaryotic models including animal models, C. elegans and Drosophila, significantly contributed to understanding Aβ and tau biology. These models allowed high throughput screening of factors and drugs that interfere with Aβ oligomerization, aggregation and toxicity, and tau hyperphosphorylation. In the future, yeast models will remain relevant, with a focus on creating novel high throughput systems to facilitate the identification of the earliest AD biomarkers among different cellular networks in order to achieve the main goal-to develop new promising therapeutic strategies to treat or prevent the disease.

Dataset for suppressors of amyloid-β toxicity and their functions in recombinant protein production in yeast

The production of recombinant proteins at high levels often induces stress-related phenotypes by protein misfolding or aggregation. These are similar to those of the yeast Alzheimer's disease (AD) model in which amyloid-β peptides (Aβ42) were accumulated [1], [2]. We have previously identified suppressors of Aβ42 cytotoxicity via the genome-wide synthetic genetic array (SGA) [3] and here we use them as metabolic engineering targets to evaluate their potentiality on recombinant protein production in yeast Saccharomyces cerevisiae. In order to investigate the mechanisms linking the genetic modifications to the improved recombinant protein production, we perform systems biology approaches (transcriptomics and proteomics) on the resulting strain and intermediate strains. The RNAseq data are preprocessed by the nf-core/RNAseq pipeline and analyzed using the Platform for Integrative Analysis of Omics (PIANO) package [4]. The quantitative proteome is analyzed on an Orbitrap Fusion Lumos mass spectrometer interfaced with an Easy-nLC1200 liquid chromatography (LC) system. LC-MS data files are processed by Proteome Discoverer version 2.4 with Mascot 2.5.1 as a database search engine. The original data presented in this work can be found in the research paper titled “Suppressors of Amyloid-β Toxicity Improve Recombinant Protein Production in yeast by Reducing Oxidative Stress and Tuning Cellular Metabolism”, by Chen et al. [5].

UBB+1 reduces amyloid-β cytotoxicity by activation of autophagy in yeast

UBB+1 is a mutated version of ubiquitin B peptide caused by a transcriptional frameshift due to the RNA polymerase II "slippage". The accumulation of UBB+1 has been linked to ubiquitin-proteasome system (UPS) dysfunction and neurodegeneration. Alzheimer's disease (AD) is defined as a progressive neurodegeneration and aggregation of amyloid-β peptides (Aβ) is a prominent neuropathological feature of AD. In our previous study, we found that yeast cells expressing UBB+1 at lower level display an increased resistance to cellular stresses under conditions of chronological aging. In order to examine the molecular mechanisms behind, here we performed genome-wide transcriptional analyses and molecular/cellular biology assays. We found that low UBB+1 expression activated the autophagy pathway, increased vacuolar activity, and promoted transport of autophagic marker ATG8p into vacuole. Furthermore, we introduced low UBB+1 expression to our humanized yeast AD models, that constitutively express Aβ42 and Aβ40 peptide, respectively. The co-expression of UBB+1 with Aβ42 or Aβ40 peptide led to reduced intracellular Aβ levels, ameliorated viability, and increased chronological life span. In an autophagy deficient background strain (atg1Δ), intracellular Aβ levels were not affected by UBB+1 expression. Our findings offer insights for reducing intracellular Aβ toxicity via autophagy-dependent cellular pathways under low level of UBB+1 expression.

Development of a method for heat shock stress assessment in yeast based on transcription of specific genes

All living cells, including yeast cells, are challenged by different types of stresses in their environments and must cope with challenges such as heat, chemical stress, or oxidative damage. By reversibly adjusting the physiology while maintaining structural and genetic integrity, cells can achieve a competitive advantage and adapt environmental fluctuations. The yeast Saccharomyces cerevisiae has been extensively used as a model for study of stress responses due to the strong conservation of many essential cellular processes between yeast and human cells. We focused here on developing a tool to detect and quantify early responses using specific transcriptional responses. We analyzed the published transcriptional data on S. cerevisiae DBY strain responses to 10 different stresses in different time points. The principal component analysis (PCA) and the Pearson analysis were used to assess the stress response genes that are highly expressed in each individual stress condition. Except for these stress response genes, we also identified the reference genes in each stress condition, which would not be induced under stress condition and show stable transcriptional expression over time. We then tested our candidates experimentally in the CEN.PK strain. After data analysis, we identified two stress response genes (UBI4 and RRP) and two reference genes (MEX67 and SSY1) under heat shock (HS) condition. These genes were further verified by real-time PCR at mild (42°C), severe (46°C), to lethal temperature (50°C), respectively.

Microbial Pathogenesis and Pathophysiology of Alzheimer's Disease: A Systematic Assessment of Microorganisms' Implications in the Neurodegenerative Disease

Microbial infections have been linked to the pathogenesis and pathophysiology of Alzheimer's disease (AD) and other neurodegenerative diseases. The present study aimed to synthesise and assess global evidence of microbial pathogenesis and pathophysiology in AD (MPP-AD) and associated neurodegenerative conditions using integrated science mapping and content analytics to explore the associated research landscape. Relevant MPP-AD documents were retrieved from Web of Science and Scopus according to PRISMA principles and analysed for productivity/trend linked to authors/countries, thematic conceptual framework, and international collaborative networks. A total of 258 documents published from 136 sources to 39.42 average citations/document were obtained on MPP-AD. The co-authors per document were 7.6, and the collaboration index was 5.71. The annual research outputs increased tremendously in the last 6 years from 2014 to 2019, accounting for 66% compared with records in the early years from 1982 to 1990 (16%). The USA (n = 71, freq. = 30.34%), United Kingdom (n = 32, freq. = 13.68%) and China (n = 27, 11.54%) ranked in first three positions in term of country's productivity. Four major international collaboration clusters were found in MPP-AD research. The country collaboration network in MPP-AD was characteristic of sparse interaction and acquaintanceship (density = 0.11, diameter = 4). Overall, international collaboration is globally inadequate [centralisation statistics: degree (40.5%), closeness (4%), betweenness (23%), and eigenvector (76.7%)] against the robust authors' collaboration index of 5.71 in MPP-AD research. Furthermore, four conceptual thematic frameworks (CTF) namely, CTF#1, roles of microbial/microbiome infection and dysbiosis in cognitive dysfunctions; CTF#2, bacterial infection specific roles in dementia; CTF#3, the use of yeast as a model system for studying MPP-AD and remediation therapy; and CFT#4, flow cytometry elucidation of amyloid-beta and aggregation in Saccharomyces cerevisiae model. Finally, aetiology-based mechanisms of MPP-AD, namely, gut microbiota, bacterial infection, and viral infection, were comprehensively discussed. This study provides an overview of MPP-AD and serves as a stepping stone for future preparedness in MPP-AD-related research.

A Toxic Synergy between Aluminium and Amyloid Beta in Yeast

Alzheimer’s disease (AD), the most prevalent, age-related, neurodegenerative disease, is associated with the accumulation of amyloid beta (Aβ) and oxidative stress. However, the sporadic nature of late-onset AD has suggested that other factors, such as aluminium may be involved. Aluminium (Al³⁺) is the most ubiquitous neurotoxic metal on earth, extensively bioavailable to humans. Despite this, the link between Al³⁺ and AD has been debated for decades and remains controversial. Using Saccharomyces cerevisiae as a model organism expressing Aβ42, this study aimed to examine the mechanisms of Al³⁺ toxicity and its interactions with Aβ42. S. cerevisiae cells producing Aβ42 treated with varying concentrations of Al³⁺ were examined for cell viability, growth inhibition, and production of reactive oxygen species (ROS). Al³⁺ caused a significant reduction in cell viability: cell death in yeast producing green fluorescent protein tagged with Aβ42 (GFP–Aβ42) was significantly higher than in cells producing green fluorescent protein (GFP) alone. Additionally, Al³⁺ greatly inhibited the fermentative growth of yeast producing GFP–Aβ42, which was enhanced by ferric iron (Fe³⁺), while there was negligible growth inhibition of GFP cells. Al³⁺- induced ROS levels in yeast expressing native Aβ42 were significantly higher than in empty vector controls. These findings demonstrate Al³⁺ has a direct, detrimental toxic synergy with Aβ42 that can be influenced by Fe³⁺, causing increased oxidative stress. Thus, Al³⁺ should be considered as an important factor, alongside the known characteristic hallmarks of AD, in the development and aetiology of the disease.

Protein Homeostasis Networks and the Use of Yeast to Guide Interventions in Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive multifactorial age-related neurodegenerative disorder that causes the majority of deaths due to dementia in the elderly. Although various risk factors have been found to be associated with AD progression, the cause of the disease is still unresolved. The loss of proteostasis is one of the major causes of AD: it is evident by aggregation of misfolded proteins, lipid homeostasis disruption, accumulation of autophagic vesicles, and oxidative damage during the disease progression. Different models have been developed to study AD, one of which is a yeast model. Yeasts are simple unicellular eukaryotic cells that have provided great insights into human cell biology. Various yeast models, including unmodified and genetically modified yeasts, have been established for studying AD and have provided significant amount of information on AD pathology and potential interventions. The conservation of various human biological processes, including signal transduction, energy metabolism, protein homeostasis, stress responses, oxidative phosphorylation, vesicle trafficking, apoptosis, endocytosis, and ageing, renders yeast a fascinating, powerful model for AD. In addition, the easy manipulation of the yeast genome and availability of methods to evaluate yeast cells rapidly in high throughput technological platforms strengthen the rationale of using yeast as a model. This review focuses on the description of the proteostasis network in yeast and its comparison with the human proteostasis network. It further elaborates on the AD-associated proteostasis failure and applications of the yeast proteostasis network to understand AD pathology and its potential to guide interventions against AD.

Biophysical studies of protein misfolding and aggregation in in vivo models of Alzheimer's and Parkinson's diseases

Neurodegenerative disorders, including Alzheimer's (AD) and Parkinson's diseases (PD), are characterised by the formation of aberrant assemblies of misfolded proteins. The discovery of disease-modifying drugs for these disorders is challenging, in part because we still have a limited understanding of their molecular origins. In this review, we discuss how biophysical approaches can help explain the formation of the aberrant conformational states of proteins whose neurotoxic effects underlie these diseases. We discuss in particular models based on the transgenic expression of amyloid-β (Aβ) and tau in AD, and α-synuclein in PD. Because biophysical methods have enabled an accurate quantification and a detailed understanding of the molecular mechanisms underlying protein misfolding and aggregation in vitro, we expect that the further development of these methods to probe directly the corresponding mechanisms in vivo will open effective routes for diagnostic and therapeutic interventions.

FMN reduces Amyloid-β toxicity in yeast by regulating redox status and cellular metabolism

Alzheimer's disease (AD) is defined by progressive neurodegeneration, with oligomerization and aggregation of amyloid-β peptides (Aβ) playing a pivotal role in its pathogenesis. In recent years, the yeast Saccharomyces cerevisiae has been successfully used to clarify the roles of different human proteins involved in neurodegeneration. Here, we report a genome-wide synthetic genetic interaction array to identify toxicity modifiers of Aβ42, using yeast as the model organism. We find that FMN1, the gene encoding riboflavin kinase, and its metabolic product flavin mononucleotide (FMN) reduce Aβ42 toxicity. Classic experimental analyses combined with RNAseq show the effects of FMN supplementation to include reducing misfolded protein load, altering cellular metabolism, increasing NADH/(NADH + NAD⁺) and NADPH/(NADPH + NADP⁺) ratios and increasing resistance to oxidative stress. Additionally, FMN supplementation modifies Htt103QP toxicity and α-synuclein toxicity in the humanized yeast. Our findings offer insights for reducing cytotoxicity of Aβ42, and potentially other misfolded proteins, via FMN-dependent cellular pathways.

Protective effects of tanshinone IIA on SH-SY5Y cells against oAβ1-42-induced apoptosis due to prevention of endoplasmic reticulum stress

Endoplasmic reticulum (ER) stress caused by β-amyloid protein (Aβ) may play an important role in the pathogenesis of Alzheimer disease (AD). Our previous data have indicated that tanshinone IIA (tan IIA) protected primary neurons from Aβ induced neurotoxicity. To further explore the neuroprotection of tan IIA, here we study the effects of tan IIA on the ER stress response in oligomeric Aβ_1-42 (oAβ_1-42)-induced SH-SY5Y cell injury. Our data showed that tan IIA pretreatment could increase cell viability and inhibit apoptosis caused by oAβ_1-42. Furthermore, tan IIA markedly suppressed ER dilation and prevented oAβ_1-42-induced abnormal expression of glucose regulated protein 78 (GRP78), initiation factor 2α (eIF2α), activating transcription factor 6 (ATF6), as well as inhibited the activation of C/EBP homologous protein (CHOP) and c-Jun N-terminal kinase (JNK) pathways. Moreover, tan IIA ameliorated oAβ_1-42-induced Bcl-2/Bax ratio reduction, prevented cytochrome c translocation into cytosol from mitochondria, reduced oAβ_1-42-induced cleavage of caspase-9 and caspase-3, suppressed caspase-3/7 activity, and increased mitochondrial membrane potential (MMP) and ATP content. Meanwhile, oAβ_1-42-induced cell apoptosis and activation of ER stress can also be attenuated by the inhibitor of ER stress 4-phenylbutyric acid (4-PBA). Taken together, these data indicated that tan IIA protects SH-SY5Y cells against oAβ_1-42-induced apoptosis through attenuating ER stress, modulating CHOP and JNK pathways, decreasing the expression of cytochrome c, cleaved caspase-9 and cleaved caspase-3, as well as increasing the ratio of Bcl-2/Bax, MMP and ATP content. Our results strongly suggested that tan IIA may be effective in treating AD associated with ER stress.

The Impact of ESCRT on Aβ1-42 Induced Membrane Lesions in a Yeast Model for Alzheimer's Disease

Aβ metabolism plays a pivotal role in Alzheimer’s disease. Here, we used a yeast model to monitor Aβ₄₂ toxicity when entering the secretory pathway and demonstrate that processing in, and exit from the endoplasmic reticulum (ER) is required to unleash the full Aβ₄₂ toxic potential. Consistent with previously reported data, our data suggests that Aβ₄₂ interacts with mitochondria, thereby enhancing formation of reactive oxygen species and eventually leading to cell demise. We used our model to search for genes that modulate this deleterious effect, either by reducing or enhancing Aβ₄₂ toxicity, based on screening of the yeast knockout collection. This revealed a reduced Aβ₄₂ toxicity not only in strains hampered in ER-Golgi traffic and mitochondrial functioning but also in strains lacking genes connected to the cell cycle and the DNA replication stress response. On the other hand, increased Aβ₄₂ toxicity was observed in strains affected in the actin cytoskeleton organization, endocytosis and the formation of multivesicular bodies, including key factors of the ESCRT machinery. Since the latter was shown to be required for the repair of membrane lesions in mammalian systems, we studied this aspect in more detail in our yeast model. Our data demonstrated that Aβ₄₂ heavily disturbed the plasma membrane integrity in a strain lacking the ESCRT-III accessory factor Bro1, a phenotype that came along with a severe growth defect and enhanced loading of lipid droplets. Thus, it appears that also in yeast ESCRT is required for membrane repair, thereby counteracting one of the deleterious effects induced by the expression of Aβ₄₂. Combined, our studies once more validated the use of yeast as a model to investigate fundamental mechanisms underlying the etiology of neurodegenerative disorders.

Exploiting Post-mitotic Yeast Cultures to Model Neurodegeneration

Over the last few decades, the budding yeast Saccharomyces cerevisiae has been extensively used as a valuable organism to explore mechanisms of aging and human age-associated neurodegenerative disorders. Yeast models can be used to study loss of function of disease-related conserved genes and to investigate gain of function activities, frequently proteotoxicity, exerted by non-conserved human mutant proteins responsible for neurodegeneration. Most published models of proteotoxicity have used rapidly dividing cells and suffer from a high level of protein expression resulting in acute growth arrest or cell death. This contrasts with the slow development of neurodegenerative proteotoxicity during aging and the characteristic post-mitotic state of the affected cell type, the neuron. Here, we will review the efforts to create and characterize yeast models of neurodegeneration using the chronological life span model of aging, and the specific information they can provide regarding the chronology of physiological events leading to neurotoxic proteotoxicity-induced cell death and the identification of new pathways involved.

An Apoptotic and Endosymbiotic Explanation of the Warburg and the Inverse Warburg Hypotheses

Otto Warburg, a Nobel prize winner, observed that cancer cells typically “switch” from aerobic to anaerobic respiration. He hypothesized that mitochondrial damage induces neoplastic transformation. In contrast, pathological aging is observed mainly in neuron cells in neurodegenerative diseases. Oxidative respiration is particularly active in neurons. There is inverse comorbidity between cancer and neurodegenerative diseases. This led to the creation of the “inverse Warburg hypothesis”, according to which excessive mitochondrial activity induces pathological aging. The findings of our studies suggest that both the Warburg effect and the “inverse Warburg hypothesis” can be elucidated by the activation or suppression of apoptosis through oxidative respiration. The key outcome of our phylogenetic studies was the discovery that apoptosis and apoptosis-like cell death evolved due to an evolutionary “arms race” conducted between “prey” protomitochondrion and “predator” primitive eukaryotes. The ancestral protomitochondrial machinery produces and releases toxic mitochondrial proteins. Extant apoptotic factors evolved from these toxins. Our experiments indicate that the mitochondrial machinery is directly involved in adaptation to aerobic conditions. Additionally, our hypothesis is supported by the fact that different apoptotic factors are directly involved in respiration.

Global rewiring of cellular metabolism renders Saccharomyces cerevisiae Crabtree negative

Saccharomyces cerevisiae is a Crabtree-positive eukaryal model organism. It is believed that the Crabtree effect has evolved as a competition mechanism by allowing for rapid growth and production of ethanol at aerobic glucose excess conditions. This inherent property of yeast metabolism and the multiple mechanisms underlying it require a global rewiring of the entire metabolic network to abolish the Crabtree effect. Through rational engineering of pyruvate metabolism combined with adaptive laboratory evolution (ALE), we demonstrate that it is possible to obtain such a global rewiring and hereby turn S. cerevisiae into a Crabtree-negative yeast. Using integrated systems biology analysis, we identify that the global rewiring of cellular metabolism is accomplished through a mutation in the RNA polymerase II mediator complex, which is also observed in cancer cells expressing the Warburg effect.

Reducing aerobic ethanol production, a phenomenon referred to as the Crabtree effect, may open up new perspectives for using yeast as a cell factory. Here, the authors turn the Crabtree-positive yeast into Crabtree negative by combined engineering of cytosolic acetyl-CoA metabolism and mutating the RNA polymerase II mediator complex.

Gut microbiota influences Alzheimer's disease pathogenesis by regulating acetate in Drosophila model

AIM

The aim of present study is to investigate the relationship between gut microbiota and Alzheimer's disease (AD) using Drosophila model.

MATERIALS & METHODS

The microbiota was characterized by Illumina sequencing of 16S rRNA gene. Gas chromatography-mass spectrometer was performed to measure the level of short-chain fatty acids (SCFAs), metabolites of the commensal microbiota.

RESULTS

The diversity of the gut microbiota increased in AD Drosophila. As the most enriched bacteria at genus level, the proportions of Acetobacter and Lactobacillus decreased dramatically. Acetate was the most abundant SCFA derived from the dysregulated microbiota and markedly downregulated in AD Drosophila.

CONCLUSION

Our study on Drosophila model suggests that dysregulation of gut microbiota may participate in AD pathogenesis by influencing SCFA level.

Recent Insights on Alzheimer's Disease Originating from Yeast Models

In this review article, yeast model-based research advances regarding the role of Amyloid-β (Aβ), Tau and frameshift Ubiquitin UBB+1 in Alzheimer’s disease (AD) are discussed. Despite having limitations with regard to intercellular and cognitive AD aspects, these models have clearly shown their added value as complementary models for the study of the molecular aspects of these proteins, including their interplay with AD-related cellular processes such as mitochondrial dysfunction and altered proteostasis. Moreover, these yeast models have also shown their importance in translational research, e.g., in compound screenings and for AD diagnostics development. In addition to well-established Saccharomyces cerevisiae models, new upcoming Schizosaccharomyces pombe, Candida glabrata and Kluyveromyces lactis yeast models for Aβ and Tau are briefly described. Finally, traditional and more innovative research methodologies, e.g., for studying protein oligomerization/aggregation, are highlighted.

Different Expression Levels of Human Mutant Ubiquitin B+1 (UBB+1) Can Modify Chronological Lifespan or Stress Resistance of Saccharomyces cerevisiae

The ubiquitin-proteasome system (UPS) is the main pathway responsible for the degradation of misfolded proteins, and its dysregulation has been implicated in several neurodegenerative diseases, including Alzheimer's disease (AD). UBB⁺¹, a mutant variant of ubiquitin B, was found to accumulate in neurons of AD patients and it has been linked to UPS dysfunction and neuronal death. Using the yeast Saccharomyces cerevisiae as a model system, we constitutively expressed UBB⁺¹ to evaluate its effects on proteasome function and cell death, particularly under conditions of chronological aging. We showed that the expression of UBB⁺¹ caused inhibition of the three proteasomal proteolytic activities (caspase-like (β1), trypsin-like (β2) and chymotrypsin-like (β5) activities) in yeast. Interestingly, this inhibition did not alter cell viability of growing cells. Moreover, we showed that cells expressing UBB⁺¹ at lower level displayed an increased capacity to degrade induced misfolded proteins. When we evaluated cells during chronological aging, UBB⁺¹ expression at lower level, prevented cells to accumulate reactive oxygen species (ROS) and avert apoptosis, dramatically increasing yeast life span. Since proteasome inhibition by UBB⁺¹ has previously been shown to induce chaperone expression and thus protect against stress, we evaluated our UBB⁺¹ model under heat shock and oxidative stress. Higher expression of UBB⁺¹ caused thermotolerance in yeast due to induction of chaperones, which occurred to a lesser extent at lower expression level of UBB⁺¹ (where we observed the phenotype of extended life span). Altering UPS capacity by differential expression of UBB⁺¹ protects cells against several stresses during chronological aging. This system can be valuable to study the effects of UBB⁺¹ on misfolded proteins involved in neurodegeneration and aging.

Calcium Dysregulation in Alzheimer's Disease: A Target for New Drug Development

Alzheimer's disease (AD) is a devastating neurodegenerative disorder and the most common cause of dementia among aged people whose population is rapidly increasing. AD not only seriously affects the patient's physical health and quality of life, but also adds a heavy burden to the patient's family and society. It is urgent to understand AD pathogenesis and develop the means of prevention and treatment. AD is a chronic devastating neurodegenerative disease without effective treatment. Current approaches for management focus on helping patients relieve or delay the symptoms of cognitive dysfunction. The calcium ion (Ca²⁺) is an important second messenger in the function and structure of nerve cell circuits in the brain such as neuronal growth, exocytosis, as well as in synaptic and cognitive function. Increasing numbers of studies suggested that disruption of intracellular Ca²⁺ homeostasis, especially the abnormal and excessive Ca²⁺ release from the endoplasmic reticulum (ER) via the ryanodine receptor (RYR), plays important roles in orchestrating the dynamic of the neuropathology of AD and associated memory loss, cognitive dysfunction. Dantrolene, a known antagonist of the RYR and a clinically available drug to treat malignant hyperthermia, can ameliorate the abnormal Ca²+ release from the RYR in AD and the subsequent pathogenesis, such as increased β-secretase and γ-secretase activities, production of Amyloid-β 42 (Aβ 42) and its oligomer, impaired autophagy, synapse dysfunction, and memory loss. However, more studies are needed to confirm the efficacy and safety repurposing dantrolene as a therapeutic drug in AD.