Age-associated Neurodegenerative Diseases Research Articles

Guideline "Parkinson's disease" of the German Society of Neurology (Deutsche Gesellschaft für Neurologie): concepts of care.

In 2023, the German Society of Neurology published a new guideline on Parkinson's disease. An important section dealt with PD care concepts, which represent a particularly dynamic field of PD research, including their implementation in clinical practice. Parkinson's disease is the second most common age-associated neurodegenerative disease. Current estimates of the number of cases in the population describe a significant increase in prevalence in Germany by 2030 with higher proportions in rural areas, which also have a lack of sufficient PD care resources. In comparison with other international guidelines, which have so far mentioned palliative care and Parkinson's nurses in particular, the German S2k guideline expands the recommended concepts of PD care to include PD day clinics, inpatient complex treatment, and PD networks. Concepts of PD care guidelines are necessary because of the complex and rapidly evolving field of PD care provision. If applied appropriately, the potential for optimized care can be exploited and both the patient burden and the economic burden can be reduced. Given that modern care concepts have so far only been applied in a few regions, it is often impossible to generate broad evidence-based data, so that the evaluation of PD care concepts is partly dependent on expert opinion.

Overexpression of mitochondrial fission or mitochondrial fusion genes enhances resilience and extends longevity.

The dynamicity of the mitochondrial network is crucial for meeting the ever-changing metabolic and energy needs of the cell. Mitochondrial fission promotes the degradation and distribution of mitochondria, while mitochondrial fusion maintains mitochondrial function through the complementation of mitochondrial components. Previously, we have reported that mitochondrial networks are tubular, interconnected, and well-organized in young, healthy C. elegans, but become fragmented and disorganized with advancing age and in models of age-associated neurodegenerative disease. In this work, we examine the effects of increasing mitochondrial fission or mitochondrial fusion capacity by ubiquitously overexpressing the mitochondrial fission gene drp-1 or the mitochondrial fusion genes fzo-1 and eat-3, individually or in combination. We then measured mitochondrial function, mitochondrial network morphology, physiologic rates, stress resistance, and lifespan. Surprisingly, we found that overexpression of either mitochondrial fission or fusion machinery both resulted in an increase in mitochondrial fragmentation. Similarly, both mitochondrial fission and mitochondrial fusion overexpression strains have extended lifespans and increased stress resistance, which in the case of the mitochondrial fusion overexpression strains appears to be at least partially due to the upregulation of multiple pathways of cellular resilience in these strains. Overall, our work demonstrates that increasing the expression of mitochondrial fission or fusion genes extends lifespan and improves biological resilience without promoting the maintenance of a youthful mitochondrial network morphology. This work highlights the importance of the mitochondria for both resilience and longevity.

P7C3 suppresses astrocytic senescence to protect dopaminergic neurons: Implication in the mouse model of Parkinson's disease.

Astrocytic senescence is inextricably linked to aging and neurodegenerative disorders, including Parkinson's disease (PD). P7C3 is a small, neuroprotective aminopropyl carbazole compound that exhibits anti-inflammatory properties. However, the effects of P7C3 on astrocytic senescence in PD remain to be elucidated. An invitro, long culture-induced, replicative senescence cell model and a 1-methyl-4-phenylpyridinium (MPP+)/rotenone-induced premature senescence cell model were used to investigate the effects of P7C3 on astrocytic senescence. An invivo, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse PD model was used to study the role of P7C3 in astrocytic senescence. Immunoblotting, real-time quantitative RT-PCR (qPCR), immunofluorescence, subcellular fractionation assays, and immunohistochemistry were utilized to confirm the effects of P7C3 on astrocytic senescence and elucidate its underlying mechanisms. This study determined that P7C3 suppressed the senescence-associated secretory phenotype (SASP) in both cell models, as demonstrated by the reduction in the critical senescence marker p16 and proinflammatory factors (IL-6, IL-1β, CXCL10, and MMP9) and increased laminB1 levels, implying that P7C3 inhibited replicative astrocytic senescence and MPP+/rotenone-induced premature astrocytic senescence, Most importantly, we demonstrated that P7C3 prevented the death of dopamine (DA) neurons and reduced the behavioral deficits in the MPTP-induced mouse model of PD, which is accompanied by a decrease in senescent astrocytes in the substantia nigra compacta (SNc). Mechanistically, P7C3 promoted Nrf2/Sirt3-mediated mitophagy and reduced mitochondrial reactive oxygen species (mitoROS) generation, which contributed to the suppression of astrocytic senescence. Furthermore, Sirt3 deficiency obviously abolished the inhibitory effects of P7C3 on astrocytic senescence. This study revealed that P7C3 inhibited astrocytic senescence via increased Nrf2/Sirt3-mediated mitophagy and suppression of mitoROS, which further protected against DA neuronal loss. These observations provide a prospective theoretical basis for P7C3 in the treatment of age-associated neurodegenerative diseases, such as PD.

In vivo cyclic overexpression of Yamanaka factors restricted to neurons reverses age-associated phenotypes and enhances memory performance

In recent years, there has been success in partially reprogramming peripheral organ cells using cyclic Yamanaka transcription factor (YF) expression, resulting in the reversal of age-related pathologies. In the case of the brain, the effects of partial reprogramming are scarcely known, and only some of its effects have been observed through the widespread expression of YF. This study is the first to exclusively partially reprogram a specific subpopulation of neurons in the cerebral cortex of aged mice. The in vivo model demonstrate that YF expression in postmitotic neurons does not dedifferentiate them, and it avoids deleterious effects observed with YF expression in other cell types. Additionally, our study demonstrates that only cyclic, not continuous, expression of YF result in a noteworthy enhancement of cognitive function in adult mice. This enhancement is closely tied to increased neuronal activation in regions related to memory processes, reversed aging-related epigenetic markers and to increased plasticity, induced by the reorganization of the extracellular matrix. These findings support the therapeutic potential of targeted partial reprogramming of neurons in addressing age-associated phenotypes and neurodegenerative diseases correlated with aging.

Downregulation of miR-181c-5p in Alzheimer’s disease weakens the response of microglia to Aβ phagocytosis

Alzheimer’s disease (AD) is an age-associated neurodegenerative disease. Recently, studies have demonstrated the potential involvement of microRNA-181c-5p (miR-181c-5p) in AD. However, the mechanism through which miR-181c-5p is responsible for the onset and progression of this disease remains unclear, and our study aimed to explore this problem. Differential expression analysis of the AD dataset was performed to identify dysregulated genes. Based on hypergeometric analysis, AD differential the upstream regulation genes miR-181c-5p was found. We constructed a model where SH-SY5Y and BV2 cells were exposed to Aβ1-42 to simulate AD. Levels of tumor necrosis factor-alpha, interleukin-6, and IL-1β were determined using enzyme-linked immunosorbent assay or reverse transcription quantitative polymerase chain reaction. Phosphorylation levels of p-P38 and P38 were detected by Western blot. The level of apoptosis in BV2 cells under Aβ1-42 stress was exacerbated by miR-181c-5p mimic. Downregulated miR-181c-5p impaired the phagocytosis and degradation of Aβ by BV2 cells. The release of proinflammatory cytokines in BV2 cells with Aβ1-42 stress was alleviated by miR-181c-5p upregulation. Additionally, miR-181c-5p downregulation alleviated the phosphorylation of P38 in Aβ1-42-induced SH-SY5Y cells. In conclusion, miR-181c-5p improves the phagocytosis of Aβ by microglial cells in AD patients, thereby reducing neuroinflammation.

Human iPSC 4R tauopathy model uncovers modifiers of tau propagation

Tauopathies are age-associated neurodegenerative diseases whose mechanistic underpinnings remain elusive, partially due to a lack of appropriate human models. Here, we engineered human induced pluripotent stem cell (hiPSC)-derived neuronal lines to express 4R Tau and 4R Tau carrying the P301S MAPT mutation when differentiated into neurons. 4R-P301S neurons display progressive Tau inclusions upon seeding with Tau fibrils and recapitulate features of tauopathy phenotypes including shared transcriptomic signatures, autophagic body accumulation, and reduced neuronal activity. A CRISPRi screen of genes associated with Tau pathobiology identified over 500 genetic modifiers of seeding-induced Tau propagation, including retromer VPS29 and genes in the UFMylation cascade. In progressive supranuclear palsy (PSP) and Alzheimer's Disease (AD) brains, the UFMylation cascade is altered in neurofibrillary-tangle-bearing neurons. Inhibiting the UFMylation cascade invitro and invivo suppressed seeding-induced Tau propagation. This model provides a robust platform to identify novel therapeutic strategies for 4R tauopathy.

Metformin normalizes mitochondrial function to delay astrocyte senescence in a mouse model of Parkinson’s disease through Mfn2-cGAS signaling

BackgroundSenescent astrocytes play crucial roles in age-associated neurodegenerative diseases, including Parkinson’s disease (PD). Metformin, a drug widely used for treating diabetes, exerts longevity effects and neuroprotective activities. However, its effect on astrocyte senescence in PD remains to be defined.MethodsLong culture-induced replicative senescence model and 1-methyl-4-phenylpyridinium/α-synuclein aggregate-induced premature senescence model, and a mouse model of PD were used to investigate the effect of metformin on astrocyte senescence in vivo and in vitro. Immunofluorescence staining and flow cytometric analyses were performed to evaluate the mitochondrial function. We stereotactically injected AAV carrying GFAP-promoter-cGAS-shRNA to mouse substantia nigra pars compacta regions to specifically reduce astrocytic cGAS expression to clarify the potential molecular mechanism by which metformin inhibited the astrocyte senescence in PD.ResultsWe showed that metformin inhibited the astrocyte senescence in vitro and in PD mice. Mechanistically, metformin normalized mitochondrial function to reduce mitochondrial DNA release through mitofusin 2 (Mfn2), leading to inactivation of cGAS-STING, which delayed astrocyte senescence and prevented neurodegeneration. Mfn2 overexpression in astrocytes reversed the inhibitory role of metformin in cGAS-STING activation and astrocyte senescence. More importantly, metformin ameliorated dopamine neuron injury and behavioral deficits in mice by reducing the accumulation of senescent astrocytes via inhibition of astrocytic cGAS activation. Deletion of astrocytic cGAS abolished the suppressive effects of metformin on astrocyte senescence and neurodegeneration.ConclusionsThis work reveals that metformin delays astrocyte senescence via inhibiting astrocytic Mfn2-cGAS activation and suggest that metformin is a promising therapeutic agent for age-associated neurodegenerative diseases.

Dementia and depression: Biological connections with amyloid β protein.

Dementia is an umbrella term for a broad group of age-associated neurodegenerative diseases. It is estimated that dementia affects 50 million people worldwide and that Alzheimer's disease (AD) is responsible for up to 75% of cases. Small extracellular senile plaques composed of filamentous aggregates of amyloid β (Aβ) protein tend to bind to neuronal receptors, affecting cholinergic, serotonergic, dopaminergic and noradrenergic neurotransmission, leading to neuroinflammation, among other pathophysiologic processes and subsequent neuronal death, followed by dementia. The amyloid cascade hypothesis points to a pathological process in the cleavage of the amyloid precursor protein (APP), resulting in pathological Aβ. There is a close relationship between the pathologies that lead to dementia and depression. It is estimated that depression is prevalent in up to 90% of individuals diagnosed with Parkinson's disease, with varying severity, and in 20 to 30% of cases of Alzheimer's disease. The hypothalamic pituitary adrenal (HPA) axis is the great intermediary between the pathophysiological mechanisms in neurodegenerative diseases and depression. This review discusses the role of Aβ protein in the pathophysiological mechanisms of dementia and depression, considering the HPA axis, neuroinflammation, oxidative stress, signalling pathways and neurotransmission.

Functional aspects of the brain lymphatic drainage system in aging and neurodegenerative diseases.

The phenomenon of an aging population is advancing at a precipitous rate. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common age-associated neurodegenerative diseases, both of which are primarily characterized by the accumulation of toxic proteins and the progressive demise of neuronal structures. Recent discoveries about the brain lymphatic drainage system have precipitated a growing body of investigations substantiating its novel roles, including the clearance of macromolecular waste and the trafficking of immune cells. Notably, aquaporin 4-mediated glymphatic transport, crucial for maintaining neural homeostasis, becomes disrupted during the aging process and is further compromised in the pathogenesis of AD and PD. Functional meningeal lymphatic vessels, which facilitate the drainage of cerebrospinal fluid into the deep cervical lymph nodes, are integral in bridging the central nervous system with peripheral immune responses. Dysfunction in these meningeal lymphatic vessels exacerbates pathological trajectory of the age-related neurodegenerative disease. This review explores modulatory influence of the glymphatic system and meningeal lymphatic vessels on the aging brain and its associated neurodegenerative disorders. It also encapsulates the insights of potential mechanisms and prospects of the targeted non-pharmacological interventions.

Elucidating Multimodal Imaging Patterns in Accelerated Brain Aging: Heterogeneity through a Discriminant Analysis Approach Using the UK Biobank Dataset.

Accelerated brain aging (ABA) intricately links with age-associated neurodegenerative and neuropsychiatric diseases, emphasizing the critical need for a nuanced exploration of heterogeneous ABA patterns. This investigation leveraged data from the UK Biobank (UKB) for a comprehensive analysis, utilizing structural magnetic resonance imaging (sMRI), diffusion magnetic resonance imaging (dMRI), and resting-state functional magnetic resonance imaging (rsfMRI) from 31,621 participants. Pre-processing employed tools from the FMRIB Software Library (FSL, version 5.0.10), FreeSurfer, DTIFIT, and MELODIC, seamlessly integrated into the UKB imaging processing pipeline. The Lasso algorithm was employed for brain-age prediction, utilizing derived phenotypes obtained from brain imaging data. Subpopulations of accelerated brain aging (ABA) and resilient brain aging (RBA) were delineated based on the error between actual age and predicted brain age. The ABA subgroup comprised 1949 subjects (experimental group), while the RBA subgroup comprised 3203 subjects (control group). Semi-supervised heterogeneity through discriminant analysis (HYDRA) refined and characterized the ABA subgroups based on distinctive neuroimaging features. HYDRA systematically stratified ABA subjects into three subtypes: SubGroup 2 exhibited extensive gray-matter atrophy, distinctive white-matter patterns, and unique connectivity features, displaying lower cognitive performance; SubGroup 3 demonstrated minimal atrophy, superior cognitive performance, and higher physical activity; and SubGroup 1 occupied an intermediate position. This investigation underscores pronounced structural and functional heterogeneity in ABA, revealing three subtypes and paving the way for personalized neuroprotective treatments for age-related neurological, neuropsychiatric, and neurodegenerative diseases.

Telomere shortening induces aging-associated phenotypes in hiPSC-derived neurons and astrocytes

Telomere shortening is a well-established hallmark of cellular aging. Telomerase reverse transcriptase (TERT) plays a crucial role in maintaining the length of telomeres, which are specialised protective caps at the end of chromosomes. The lack of in vitro aging models, particularly for the central nervous system (CNS), has impeded progress in understanding aging and age-associated neurodegenerative diseases. In this study, we aimed to explore the possibility of inducing aging-associated features in cell types of the CNS using hiPSC (human induced pluripotent stem cell) technology. To achieve this, we utilised CRISPR/Cas9 to generate hiPSCs with a loss of telomerase function and shortened telomeres. Through directed differentiation, we generated motor neurons and astrocytes to investigate whether telomere shortening could lead to age-associated phenotypes. Our findings revealed that shortened telomeres induced age-associated characteristics in both motor neurons and astrocytes including increased cellular senescence, heightened inflammation, and elevated DNA damage. We also observed cell-type specific age-related morphology changes. Additionally, our study highlighted the fundamental role of TERT and telomere shortening in neural progenitor cell (NPC) proliferation and neuronal differentiation. This study serves as a proof of concept that telomere shortening can effectively induce aging-associated phenotypes, thereby providing a valuable tool to investigate age-related decline and neurodegenerative diseases.Graphical abstract

Caenorhabditis elegans: A transgenic model for studying age-associated neurodegenerative diseases.

Neurodegenerative diseases (NDs) are a heterogeneous group of aging-associated ailments characterized by interrupting cellular proteostasic machinery and the misfolding of distinct proteins to form toxic aggregates in neurons. Neurodegenerative diseases, which include Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), and others, are becoming an increasing threat to human health worldwide. The degeneration and death of certain specific groups of neurons are the hallmarks of these diseases. Over the past decades, Caenorhabditis eleganshas beenwidely used as a transgenic model to investigate biological processes related to health and disease. The nematode Caenorhabditis elegans (C. elegans) has developed as a powerful tool for studying disease mechanisms due to its ease of genetic handling and instant cultivation while providing a whole-animal system amendable to several molecular and biochemical techniques. In this review, we elucidate the potential of C. elegans as a versatile platform for systematic dissection of the molecular basis of human disease, focusing on neurodegenerative disorders, and may help better our understanding of the disease mechanisms and search for new therapeutics for these devastating diseases.

Uncovering the Achilles heel of genetic heterogeneity: machine learning-based classification and immunological properties of necroptosis clusters in Alzheimer's disease.

Alzheimer's disease (AD) is an age-associated neurodegenerative disease, and the currently available diagnostic modalities and therapeutic agents are unsatisfactory due to its high clinical heterogeneity. Necroptosis is a common type of programmed cell death that has been shown to be activated in AD. In this study, we first investigated the expression profiles of necroptosis-related genes (NRGs) and the immune landscape of AD based on GSE33000 dataset. Next, the AD samples in the GSE33000 dataset were extracted and subjected to consensus clustering based upon the differentially expressed NRGs. Key genes associated with necroptosis clusters were identified using Weighted Gene Co-Expression Network Analysis (WGCNA) algorithm, and then intersected with the key gene related to AD. Finally, we developed a diagnostic model for AD by comparing four different machine learning approaches. The discrimination performance and clinical relevance of the diagnostic model were assessed using various evaluation metrics, including the nomogram, calibration plot, decision curve analysis (DCA), and independent validation datasets. Aberrant expression patterns of NRGs and specific immune landscape were identified in the AD samples. Consensus clustering revealed that patients in the GSE33000 dataset could be classified into two necroptosis clusters, each with distinct immune landscapes and enriched pathways. The Extreme Gradient Boosting (XGB) was found to be the most optimal diagnostic model for the AD based on the predictive ability and reliability of the models constructed by four machine learning approaches. The five most important variables, including ACAA2, BHLHB4, CACNA2D3, NRN1, and TAC1, were used to construct a five-gene diagnostic model. The constructed nomogram, calibration plot, DCA, and external independent validation datasets exhibited outstanding diagnostic performance for AD and were closely related with the pathologic hallmarks of AD. This work presents a novel diagnostic model that may serve as a framework to study disease heterogeneity and provide a plausible mechanism underlying neuronal loss in AD.

An engineered Sox17 induces somatic to neural stem cell fate transitions independently from pluripotency reprogramming.

Advanced strategies to interconvert cell types provide promising avenues to model cellular pathologies and to develop therapies for neurological disorders. Yet, methods to directly transdifferentiate somatic cells into multipotent induced neural stem cells (iNSCs) are slow and inefficient, and it is unclear whether cells pass through a pluripotent state with full epigenetic reset. We report iNSC reprogramming from embryonic and aged mouse fibroblasts as well as from human blood using an engineered Sox17 (eSox17FNV). eSox17FNV efficiently drives iNSC reprogramming while Sox2 or Sox17 fail. eSox17FNV acquires the capacity to bind different protein partners on regulatory DNA to scan the genome more efficiently and has a more potent transactivation domain than Sox2. Lineage tracing and time-resolved transcriptomics show that emerging iNSCs do not transit through a pluripotent state. Our work distinguishes lineage from pluripotency reprogramming with the potential to generate more authentic cell models for aging-associated neurodegenerative diseases.

Stressing the role of a short linear motif in ataxin-2 condensation

Ataxin-2, an RNA-binding protein that is conserved across eukaryotes, is involved in stress granule assembly and age-associated neurodegenerative diseases. In this issue of Molecular Cell, Boeynaems etal.1 identify a short linear motif in ataxin-2 as a condensation switch, providing molecular insights into its essential role in cellular stress response.

Antioxidant Compounds from Edible Mushrooms as Potential Candidates for Treating Age-Related Neurodegenerative Diseases.

The last century has seen an increase in our life expectancy. As a result, various age-related diseases, such as neurodegenerative diseases (NDs), have emerged, representing new challenges to society. Oxidative stress (OS), a condition of redox imbalance resulting from excessive production of reactive oxygen species, represents a common feature that characterizes the brains of elderly people, thus contributing to NDs. Consequently, antioxidant supplementation or dietary intake of antioxidant-containing foods could represent an effective preventive and therapeutic intervention to maintain the integrity and survival of neurons and to counteract the neurodegenerative pathologies associated with aging. Food contains numerous bioactive molecules with beneficial actions for human health. To this purpose, a wide range of edible mushrooms have been reported to produce different antioxidant compounds such as phenolics, flavonoids, polysaccharides, vitamins, carotenoids, ergothioneine, and others, which might be used for dietary supplementation to enhance antioxidant defenses and, consequently, the prevention of age-related neurological diseases. In this review, we summarized the role of oxidative stress in age-related NDs, focusing on the current knowledge of the antioxidant compounds present in edible mushrooms, and highlighting their potential to preserve healthy aging by counteracting age-associated NDs.

Geroprotective interventions in the 3xTg mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is an age-associated neurodegenerative disease. As the population ages, the increasing prevalence of AD threatens massive healthcare costs in the coming decades. Unfortunately, traditional drug development efforts for AD have proven largely unsuccessful. A geroscience approach to AD suggests that since aging is the main driver of AD, targeting aging itself may be an effective way to prevent or treat AD. Here, we discuss the effectiveness of geroprotective interventions on AD pathology and cognition in the widely utilized triple-transgenic mouse model of AD (3xTg-AD) which develops both β-amyloid and tau pathologies characteristic of human AD, as well as cognitive deficits. We discuss the beneficial impacts of calorie restriction (CR), the gold standard for geroprotective interventions, and the effects of other dietary interventions including protein restriction. We also discuss the promising preclinical results of geroprotective pharmaceuticals, including rapamycin and medications for type 2 diabetes. Though these interventions and treatments have beneficial effects in the 3xTg-AD model, there is no guarantee that they will be as effective in humans, and we discuss the need to examine these interventions in additional animal models as well as the urgent need to test if some of these approaches can be translated from the lab to the bedside for the treatment of humans with AD.

Visually Driven Behavior Assays to Study Functionality and Recovery after Damage of the Aged African Turquoise Killifish Visual System.

Loss of vision is a prominent feature of aging and vision is considered by many to be the most valuable sense to be lost. In our graying society, we are increasingly challenged by age-related deterioration of the central nervous system (CNS), as well as by age-associated neurodegenerative diseases and brain injuries, all often affecting the visual system and thus its performance. Here, we describe two visually driven behavior assays to evaluate visual performance upon aging or CNS damage in the fast-aging killifish. The first test, the optokinetic response (OKR), measures the reflexive eye movement triggered by motion in the visual field and allows assessment of visual acuity. The second assay, the dorsal light reflex (DLR), evaluates the swimming angle based on input of light coming from above. The OKR can be used to study the effect of aging on visual acuity as well as visual improvement and recovery after rejuvenation therapy or visual system injury or disease, whereas the DLR is best used to assess functional repair after a unilateral optic nerve crush.

The Optic Nerve Crush Injury Paradigm in African Turquoise Killifish to Study Axonal Regeneration in an Aged Environment.

In our graying world population, we are increasingly facing brain injuries and age-associated neurodegenerative diseases, which are often characterized by axonal pathology. Here, we propose the killifish visual/retinotectal system as a model for investigating central nervous system repair, more specifically axonal regeneration, in an aging context. We first describe an optic nerve crush (ONC) injury paradigm in killifish to induce and study both de- and regeneration of retinal ganglion cells (RGCs) and their axons. Subsequently, we summarize several methods for mapping different steps of the regenerative process-namely, axonal regrowth and synapse reformation-using retro- and anterograde tracing methods, (immuno)histochemistry, and morphometrical analyses.

DAmFRET measures saturating concentrations and toxicities of protein phase transitions in vivo.

Protein phase transitions broadly govern protein function and dysfunction. However, analyzing the consequences of specific phase transitions in cells is hindered by the low throughput and limited resolution of fluorescence microscopy, and this problem is compounded for proteins with complex phase behavior such as those implicated in age-associated neurodegenerative diseases. As one solution to this problem, we incorporated an orthogonally fluorescence proxy of total protein expression to adjust for effective cell volume differences in a flow cytometric assay for protein self-association-Distributed Amphifluoric FRET (DAmFRET)-thereby allowing the intracellular saturating concentrations of different proteins to be precisely compared in single experiments. We further found that the effective cell volume decreased in cells experiencing proteotoxicity, which provided a simple way to assign toxicity to specific phases of ectopically expressed proteins.