Lecanemab in Early Alzheimer's Disease.

BACKGROUND: The accumulation of soluble and insoluble aggregated amyloid-beta (Aß) may initiate or potentiate pathologic processes in Alzheimer's disease. Lecanemab, a humanized IgG1 monoclonal antibody that binds with high affinity to Aß soluble protofibrils, is being tested in persons with early Alzheimer's disease. METHODS: We conducted an 18-month, multicenter, double-blind, phase 3 trial involving persons 50 to 90 years of age with early Alzheimer's disease (mild cognitive impairment or mild dementia due to Alzheimer's disease) with evidence of amyloid on positron-emission tomography (PET) or by cerebrospinal fluid testing. Participants were randomly assigned in a 1:1 ratio to receive intravenous lecanemab (10 mg per kilogram of body weight every 2 weeks) or placebo. The primary end point was the change from baseline at 18 months in the score on the Clinical Dementia Rating-Sum of Boxes (CDR-SB; range, 0 to 18, with higher scores indicating greater impairment). Key secondary end points were the change in amyloid burden on PET, the score on the 14-item cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog14; range, 0 to 90; higher scores indicate greater impairment), the Alzheimer's Disease Composite Score (ADCOMS; range, 0 to 1.97; higher scores indicate greater impairment), and the score on the Alzheimer's Disease Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment (ADCS-MCI-ADL; range, 0 to 53; lower scores indicate greater impairment). RESULTS: A total of 1795 participants were enrolled, with 898 assigned to receive lecanemab and 897 to receive placebo. The mean CDR-SB score at baseline was approximately 3.2 in both groups. The adjusted least-squares mean change from baseline at 18 months was 1.21 with lecanemab and 1.66 with placebo (difference, -0.45; 95% confidence interval [CI], -0.67 to -0.23; P<0.001). In a substudy involving 698 participants, there were greater reductions in brain amyloid burden with lecanemab than with placebo (difference, -59.1 centiloids; 95% CI, -62.6 to -55.6). Other mean differences between the two groups in the change from baseline favoring lecanemab were as follows: for the ADAS-cog14 score, -1.44 (95% CI, -2.27 to -0.61; P<0.001); for the ADCOMS, -0.050 (95% CI, -0.074 to -0.027; P<0.001); and for the ADCS-MCI-ADL score, 2.0 (95% CI, 1.2 to 2.8; P<0.001). Lecanemab resulted in infusion-related reactions in 26.4% of the participants and amyloid-related imaging abnormalities with edema or effusions in 12.6%. CONCLUSIONS: Lecanemab reduced markers of amyloid in early Alzheimer's disease and resulted in moderately less decline on measures of cognition and function than placebo at 18 months but was associated with adverse events. Longer trials are warranted to determine the efficacy and safety of lecanemab in early Alzheimer's disease. (Funded by Eisai and Biogen; Clarity AD ClinicalTrials.gov number, NCT03887455.).

Trial of Solanezumab in Preclinical Alzheimer's Disease.

BACKGROUND: Trials of monoclonal antibodies that target various forms of amyloid at different stages of Alzheimer's disease have had mixed results. METHODS: We tested solanezumab, which targets monomeric amyloid, in a phase 3 trial involving persons with preclinical Alzheimer's disease. Persons 65 to 85 years of age with a global Clinical Dementia Rating score of 0 (range, 0 to 3, with 0 indicating no cognitive impairment and 3 severe dementia), a score on the Mini-Mental State Examination of 25 or more (range, 0 to 30, with lower scores indicating poorer cognition), and elevated brain amyloid levels on 18F-florbetapir positron-emission tomography (PET) were enrolled. Participants were randomly assigned in a 1:1 ratio to receive solanezumab at a dose of up to 1600 mg intravenously every 4 weeks or placebo. The primary end point was the change in the Preclinical Alzheimer Cognitive Composite (PACC) score (calculated as the sum of four z scores, with higher scores indicating better cognitive performance) over a period of 240 weeks. RESULTS: A total of 1169 persons underwent randomization: 578 were assigned to the solanezumab group and 591 to the placebo group. The mean age of the participants was 72 years, approximately 60% were women, and 75% had a family history of dementia. At 240 weeks, the mean change in PACC score was -1.43 in the solanezumab group and -1.13 in the placebo group (difference, -0.30; 95% confidence interval, -0.82 to 0.22; P = 0.26). Amyloid levels on brain PET increased by a mean of 11.6 centiloids in the solanezumab group and 19.3 centiloids in the placebo group. Amyloid-related imaging abnormalities (ARIA) with edema occurred in less than 1% of the participants in each group. ARIA with microhemorrhage or hemosiderosis occurred in 29.2% of the participants in the solanezumab group and 32.8% of those in the placebo group. CONCLUSIONS: Solanezumab, which targets monomeric amyloid in persons with elevated brain amyloid levels, did not slow cognitive decline as compared with placebo over a period of 240 weeks in persons with preclinical Alzheimer's disease. (Funded by the National Institute on Aging and others; A4 ClinicalTrials.gov number, NCT02008357.).

Inhibitory Roles of Apolipoprotein E Christchurch Astrocytes in Curbing Tau Propagation Using Human Pluripotent Stem Cell-Derived Models.

Genetic variants in the apolipoprotein E (APOE) gene affect the onset and progression of Alzheimer's disease (AD). The APOE Christchurch (APOE Ch) variant has been identified as the most prominent candidate for preventing the onset and progression of AD. In this study, we generated isogenic APOE3Ch/3Ch human-induced pluripotent stem cells (iPSCs) from APOE3/3 healthy control female iPSCs and induced them into astrocytes. RNA expression analysis revealed the inherent resilience of APOE3Ch/3Ch astrocytes to induce a reactive state in response to inflammatory cytokines. Moreover, cytokine treatment changed astrocytic morphology with more complexity in APOE3/3 astrocytes, but not in APOE3Ch/3Ch astrocytes, indicating resilience of the rare variant to a reactive state. Interestingly, we observed robust morphological alterations containing more intricate processes when cocultured with iPSC-derived cortical neurons, in which APOE3Ch/3Ch astrocytes reduced complexity compared with APOE3/3 astrocytes. To assess the impacts of tau propagation effects, we next developed a sophisticated and sensitive assay utilizing cortical neurons derived from human iPSCs, previously generated from donors of both sexes. We showed that APOE3Ch/3Ch astrocytes effectively mitigated tau propagation within iPSC-derived neurons. This study provides important experimental evidence of the characteristic functions exhibited by APOE3Ch/3Ch astrocytes, thereby offering valuable insights for the advancement of novel clinical interventions in AD research.

Phosphorylation of Rab29 at Ser185 regulates its localization and role in the lysosomal stress response in concert with LRRK2.

Rab proteins are small GTPases that regulate a myriad of intracellular membrane trafficking events. Rab29 is one of the Rab proteins phosphorylated by leucine-rich repeat kinase 2 (LRRK2), a Parkinson's disease-associated kinase. Recent studies suggest that Rab29 regulates LRRK2, whereas the mechanism by which Rab29 is regulated remained unclear. Here, we report a novel phosphorylation in Rab29 that is not mediated by LRRK2 and occurs under lysosomal overload stress. Mass spectrometry analysis identified the phosphorylation site of Rab29 as Ser185, and cellular expression studies of phosphomimetic mutants of Rab29 at Ser185 unveiled the involvement of this phosphorylation in counteracting lysosomal enlargement. PKCα and PKCδ were deemed to be involved in this phosphorylation and control the lysosomal localization of Rab29 in concert with LRRK2. These results implicate PKCs in the lysosomal stress response pathway comprised of Rab29 and LRRK2, and further underscore the importance of this pathway in the mechanisms underlying lysosomal homeostasis.

Involvement of the glymphatic/meningeal lymphatic system in Alzheimer's disease: insights into proteostasis and future directions.

BACKGROUND:  Alzheimer's disease (AD) is pathologically characterized by the abnormal accumulation of Aß and tau proteins. There has long been a keen interest among researchers in understanding how Aß and tau are ultimately cleared in the brain. The discovery of this glymphatic system introduced a novel perspective on protein clearance and it gained recognition as one of the major brain clearance pathways for clearing these pathogenic proteins in AD. This finding has sparked interest in exploring the potential contribution of the glymphatic/meningeal lymphatic system in AD. Furthermore, there is a growing emphasis and discussion regarding the possibility that activating the glymphatic/meningeal lymphatic system could serve as a novel therapeutic strategy against AD. OBJECTIVES:  Given this current research trend, the primary focus of this comprehensive review is to highlight the role of the glymphatic/meningeal lymphatic system in the pathogenesis of AD. The discussion will encompass future research directions and prospects for treatment in relation to the glymphatic/meningeal lymphatic system.

Alzheimer's Targeted Treatments: Focus on Amyloid and Inflammation.

Alzheimer's disease (AD) is the major cause of dementia that is now threatening the lives of billions of elderly people on the globe, and recent progress in the elucidation of the pathomechanism of AD is now opening venue to tackle the disease by developing and implementing "disease-modifying therapies" that directly act on the pathophysiology and slow down the progression of neurodegeneration. A recent example is the success of clinical trials of anti-amyloid b antibody drugs, whereas other therapeutic targets, e.g., inflammation and tau, are being actively investigated. In this dual perspective session, we plan to have speakers from leading pharmas in the field representing distinct investments in the AD space, which will be followed by the comment from scientific leadership of the Alzheimer's Association who will speak on behalf of all stakeholders. Neuroscientists participating in the Society for Neuroscience may be able to gain insights into the cutting edge of the therapeutic approaches to AD and neurodegenerative disorders, and discuss future contribution of neuroscience to this field.

Genetic Reduction of Insulin Signaling Mitigates Amyloid-ß Deposition by Promoting Expression of Extracellular Matrix Proteins in the Brain.

The insulin/IGF-1 signaling (IIS) regulates a wide range of biological processes, including aging and lifespan, and has also been implicated in the pathogenesis of Alzheimer's disease (AD). We and others have reported that reduced signaling by genetic ablation of the molecules involved in IIS (e.g., insulin receptor substrate 2 [IRS-2]) markedly mitigates amyloid plaque formation in the brains of mouse models of AD, although the molecular underpinnings of the amelioration remain unsolved. Here, we revealed, by a transcriptomic analysis of the male murine cerebral cortices, that the expression of genes encoding extracellular matrix (ECM) was significantly upregulated by the loss of IRS-2. Insulin signaling activity negatively regulated the phosphorylation of Smad2 and Smad3 in the brain, and suppressed TGF-ß/Smad-dependent expression of a subset of ECM genes in brain-derived cells. The ECM proteins inhibited Aß fibril formation in vitro, and IRS-2 deficiency suppressed the aggregation process of Aß in the brains of male APP transgenic mice as revealed by injection of aggregation seeds in vivo Our results propose a novel mechanism in AD pathophysiology whereby IIS modifies Aß aggregation and amyloid pathology by altering the expression of ECM genes in the brain.SIGNIFICANCE STATEMENT The insulin/IGF-1 signaling (IIS) has been recognized as a regulator of aging, a leading risk factor for the onset of Alzheimer's disease (AD). In AD mouse models, genetic deletion of key IIS molecules markedly reduces the amyloid plaque formation in the brain, although the molecular underpinnings of this amelioration remain elusive. We found that the deficiency of insulin receptor substrate 2 leads to an increase in the expression of various extracellular matrices (ECMs) in the brain, potentially through TGF-ß/Smad signaling. Furthermore, some of those ECMs exhibited the potential to inhibit amyloid plaque accumulation by disrupting the formation of Aß fibrils. This study presents a novel mechanism by which IIS regulates Aß accumulation, which may involve altered brain ECM expression.

Development of disease-modifying therapies against Alzheimer's disease.

To successfully develop disease-modifying therapies (DMT) against Alzheimer's disease (AD), it is important to target the mild stage of the disease, before the pathological changes progress and dementia symptoms are fully manifested. To this end, the AD Neuroimaging Initiative (ADNI), a large-scale observational study, was initiated in the U.S. with the goal of development of DMT that are effective in the early stages of mild cognitive impairment (MCI) by utilizing imaging and biomarkers. In Japan, J-ADNI enrolled and followed up 537 patients, mainly with MCI, and established a platform for evaluation including amyloid PET, and demonstrated a high similarity in the clinical course of amyloid-positive MCI (prodromal AD) in Japan and the U.S. In 2023, the anti-Aß antibody lecanemab successfully completed a Phase III clinical trial for early AD (prodromal AD + mild AD dementia) and was granted regulatory approval and made available both in the US and Japan. Also, phase III trial of donanemab was completed successful. The J-TRC study was initiated in Japan as a "trial ready cohort (TRC)" consisting of participants who met the eligibility criteria for participation in preclinical and prodromal AD trials. Based on such a platform, the development of DMT for AD will progress more rapidly in the future.

Chronic Neuronal Hyperexcitation Exacerbates Tau Propagation in a Mouse Model of Tauopathy.

The intracerebral spread of tau is a critical mechanism associated with functional decline in Alzheimer's disease (AD) and other tauopathies. Recently, a hypothesis has emerged suggesting that tau propagation is linked to functional neuronal connections, specifically driven by neuronal hyperactivity. However, experimental validation of this hypothesis remains limited. In this study, we investigated how tau propagation from the entorhinal cortex to the hippocampus, the neuronal circuit most susceptible to tau pathology in AD, is affected by the selective stimulation of neuronal activity along this circuit. Using a mouse model of seed-induced propagation combined with optogenetics, we found that the chronic stimulation of this neuronal connection over a 4-week period resulted in a significant increase in insoluble tau accumulation in both the entorhinal cortex and hippocampus. Importantly, the ratio of tau accumulation in the hippocampus relative to that in the entorhinal cortex, serving as an indicator of transcellular spreading, was significantly higher in mice subjected to chronic stimulation. These results support the notion that abnormal neuronal activity promotes tau propagation, thereby implicating it in the progression of tauopathy.

Casein kinase 1δ/ε phosphorylates fused in sarcoma (FUS) and ameliorates FUS-mediated neurodegeneration.

Aberrant cytoplasmic accumulation of an RNA-binding protein, fused in sarcoma (FUS), characterizes the neuropathology of subtypes of ALS and frontotemporal lobar degeneration, although the effects of post-translational modifications of FUS, especially phosphorylation, on its neurotoxicity have not been fully characterized. Here, we show that casein kinase 1δ (CK1δ) phosphorylates FUS at 10 serine/threonine residues in vitro using mass spectrometric analyses. We also show that phosphorylation by CK1δ or CK1ε significantly increased the solubility of FUS in human embryonic kidney 293 cells. In transgenic Drosophila that overexpress wt or P525L ALS-mutant human FUS in the retina or in neurons, we found coexpression of human CK1δ or its Drosophila isologue Dco in the photoreceptor neurons significantly ameliorated the observed retinal degeneration, and neuronal coexpression of human CK1δ extended fly life span. Taken together, our data suggest a novel regulatory mechanism of the assembly and toxicity of FUS through CK1δ/CK1ε-mediated phosphorylation, which could represent a potential therapeutic target in FUS proteinopathies.

Outcome measures for Alzheimer's disease: A global inter-societal Delphi consensus.

INTRODUCTION: We aim to provide guidance on outcomes and measures for use in patients with Alzheimer's clinical syndrome. METHODS: A consensus group of 20 voting members nominated by 10 professional societies, and a non-voting chair, used a Delphi approach and modified GRADE criteria. RESULTS: Consensus was reached on priority outcomes (n = 66), measures (n = 49) and statements (n = 37) across nine domains. A number of outcomes and measurement instruments were ranked for: Cognitive abilities; Functional abilities/dependency; Behavioural and neuropsychiatric symptoms; Patient quality of life (QoL); Caregiver QoL; Healthcare and treatment-related outcomes; Medical investigations; Disease-related life events; and Global outcomes. DISCUSSION: This work provides indications on the domains and ideal pertinent measurement instruments that clinicians may wish to use to follow patients with cognitive impairment. More work is needed to develop instruments that are more feasible in the context of the constraints of clinical routine.

ALS-linked cytoplasmic FUS assemblies are compositionally different from physiological stress granules and sequester hnRNPA3, a novel modifier of FUS toxicity.

Formation of cytoplasmic RNA-protein structures called stress granules (SGs) is a highly conserved cellular response to stress. Abnormal metabolism of SGs may contribute to the pathogenesis of (neuro)degenerative diseases such as amyotrophic lateral sclerosis (ALS). Many SG proteins are affected by mutations causative of these conditions, including fused in sarcoma (FUS). Mutant FUS variants have high affinity to SGs and also spontaneously form de novo cytoplasmic RNA granules. Mutant FUS-containing assemblies (mFAs), often called "pathological SGs", are proposed to play a role in ALS-FUS pathogenesis. However, structural differences between mFAs and physiological SGs remain largely unknown therefore it is unclear whether mFAs can functionally substitute for SGs and how they affect cellular stress responses. Here we used affinity purification to isolate mFAs and physiological SGs and compare their protein composition. We found that proteins within mFAs form significantly more physical interactions than those in SGs however mFAs fail to recruit many factors involved in signal transduction. Furthermore, we found that proteasome subunits and certain nucleocytoplasmic transport factors are depleted from mFAs, whereas translation elongation, mRNA surveillance and splicing factors as well as mitochondrial proteins are enriched in mFAs, as compared to SGs. Validation experiments for a mFA-specific protein, hnRNPA3, confirmed its RNA-dependent interaction with FUS and its sequestration into FUS inclusions in cultured cells and in a FUS transgenic mouse model. Silencing of the Drosophila hnRNPA3 ortholog was deleterious and potentiated human FUS toxicity in the retina of transgenic flies. In conclusion, we show that SG-like structures formed by mutant FUS are structurally distinct from SGs, prone to persistence, likely cannot functionally replace SGs, and affect a spectrum of cellular pathways in stressed cells. Results of our study support a pathogenic role for cytoplasmic FUS assemblies in ALS-FUS.

The Amyloid-ß Pathway in Alzheimer's Disease.

Breakthroughs in molecular medicine have positioned the amyloid-ß (Aß) pathway at the center of Alzheimer's disease (AD) pathophysiology. While the detailed molecular mechanisms of the pathway and the spatial-temporal dynamics leading to synaptic failure, neurodegeneration, and clinical onset are still under intense investigation, the established biochemical alterations of the Aß cycle remain the core biological hallmark of AD and are promising targets for the development of disease-modifying therapies. Here, we systematically review and update the vast state-of-the-art literature of Aß science with evidence from basic research studies to human genetic and multi-modal biomarker investigations, which supports a crucial role of Aß pathway dyshomeostasis in AD pathophysiological dynamics. We discuss the evidence highlighting a differentiated interaction of distinct Aß species with other AD-related biological mechanisms, such as tau-mediated, neuroimmune and inflammatory changes, as well as a neurochemical imbalance. Through the lens of the latest development of multimodal in vivo biomarkers of AD, this cross-disciplinary review examines the compelling hypothesis- and data-driven rationale for Aß-targeting therapeutic strategies in development for the early treatment of AD.

Calcium-responsive transactivator (CREST) toxicity is rescued by loss of PBP1/ATXN2 function in a novel yeast proteinopathy model and in transgenic flies.

Proteins associated with familial neurodegenerative disease often aggregate in patients' neurons. Several such proteins, e.g. TDP-43, aggregate and are toxic when expressed in yeast. Deletion of the ATXN2 ortholog, PBP1, reduces yeast TDP-43 toxicity, which led to identification of ATXN2 as an amyotrophic lateral sclerosis (ALS) risk factor and therapeutic target. Likewise, new yeast neurodegenerative disease models could facilitate identification of other risk factors and targets. Mutations in SS18L1, encoding the calcium-responsive transactivator (CREST) chromatin-remodeling protein, are associated with ALS. We show that CREST is toxic in yeast and forms nuclear and occasionally cytoplasmic foci that stain with Thioflavin-T, a dye indicative of amyloid-like protein. Like the yeast chromatin-remodeling factor SWI1, CREST inhibits silencing of FLO genes. Toxicity of CREST is enhanced by the [PIN+] prion and reduced by deletion of the HSP104 chaperone required for the propagation of many yeast prions. Likewise, deletion of PBP1 reduced CREST toxicity and aggregation. In accord with the yeast data, we show that the Drosophila ortholog of human ATXN2, dAtx2, is a potent enhancer of CREST toxicity. Downregulation of dAtx2 in flies overexpressing CREST in retinal ganglion cells was sufficient to largely rescue the severe degenerative phenotype induced by human CREST. Overexpression caused considerable co-localization of CREST and PBP1/ATXN2 in cytoplasmic foci in both yeast and mammalian cells. Thus, co-aggregation of CREST and PBP1/ATXN2 may serve as one of the mechanisms of PBP1/ATXN2-mediated toxicity. These results extend the spectrum of ALS associated proteins whose toxicity is regulated by PBP1/ATXN2, suggesting that therapies targeting ATXN2 may be effective for a wide range of neurodegenerative diseases.

Evaluation of major national dementia policies and health-care system preparedness for early medical action and implementation.

With population growth and aging, the number of people with dementia and related disorders will grow substantially in the years ahead, bringing with it significant societal, health-care, and economic challenges. Here, we analyze dementia policies of seven major countries in Asia/Pacific, Europe, and North America to identify opportunities for early actions to mitigate disease burden. We find that most countries are addressing this need by including a specific focus on early action in their national dementia strategies (five of seven countries), implementing public health initiatives for risk reduction, prevention, and early detection and diagnosis (six of seven countries); supporting enabling research for early detection and risk reduction (six of seven countries); and enacting a system for early, regular brain health screening (one of seven). We discuss risks and opportunities for integrating early action policies and conducting additional systematic research to understand the potential benefits and impacts of these policies.

State-of-the-art of lumbar puncture and its place in the journey of patients with Alzheimer's disease.

Recent advances in developing disease-modifying therapies (DMT) for Alzheimer's disease (AD), and the recognition that AD pathophysiology emerges decades before clinical symptoms, necessitate a paradigm shift of health-care systems toward biomarker-guided early detection, diagnosis, and therapeutic decision-making. Appropriate incorporation of cerebrospinal fluid biomarker analysis in clinical practice is an essential step toward system readiness for accommodating the demand of AD diagnosis and proper use of DMTs-once they become available. However, the use of lumbar puncture (LP) in individuals with suspected neurodegenerative diseases such as AD is inconsistent, and the perception of its utility and safety differs considerably among medical specialties as well as among regions and countries. This review describes the state-of-the-art evidence concerning the safety profile of LP in older adults, discusses the risk factors for LP-associated adverse events, and provides recommendations and an outlook for optimized use and global implementation of LP in individuals with suspected AD.

Correction: Koh et al. Targeting MicroRNA-485-3p Blocks Alzheimer's Disease Progression. Int. J. Mol. Sci. 2021, 22, 13136.

The authors wish to make the following corrections to this paper [...].

Differential involvement of insulin receptor substrate (IRS)-1 and IRS-2 in brain insulin signaling is associated with the effects on amyloid pathology in a mouse model of Alzheimer's disease.

Insulin signaling has been implicated in the metabolism as well as aging and longevity. Type 2 diabetes mellitus and its core pathology, insulin resistance, has also been implicated in the development of Alzheimer's disease (AD) and amyloid-ß deposition in humans. By contrast, genetic ablation of the insulin/IGF-1 signaling (IIS) pathway components, e.g. insulin receptor substrate (IRS)-2, has been documented to suppress amyloid-ß accumulation in the brains of transgenic mice overexpressing AD mutant ß-amyloid precursor protein (APP). Therefore, the brain IIS may be a key modifiable molecular target in the pathophysiology of AD. IRS-1 and IRS-2 are critical nodes in IIS as substrates for insulin receptor and IGF-1 receptor, although the functional differences between IRS-1 and IRS-2 in the adult brain are yet to be explored. To examine their relative contribution to the brain IIS activity and AD pathomechanism, we generated APP transgenic mice lacking either IRS-1 or IRS-2. IRS-1 deficiency had little effects on the brain IIS pathway associated with compensatory activation of IRS-2, whereas IRS-2 deficiency was not fully compensated by activation of IRS-1, and the downstream activation of Akt also was significantly compromised. Pathological analyses of the cortical tissues showed that the biochemical levels of soluble and insoluble amyloid-ß, the amyloid-ß histopathology, and tau phosphorylation were not affected by the absence of IRS-1, in contrast to the marked alteration in IRS-2 deleted mice. These results suggest the predominance of IRS-2 in the brain IIS, and support the hypothesis that reduced IIS exerts anti-amyloid effects in the brain.

Long non-coding RNA NEAT1_1 ameliorates TDP-43 toxicity in in vivo models of TDP-43 proteinopathy.

Pathological changes involving TDP-43 protein ('TDP-43 proteinopathy') are typical for several neurodegenerative diseases, including frontotemporal lobar degeneration (FTLD). FTLD-TDP cases are characterized by increased binding of TDP-43 to an abundant lncRNA, NEAT1, in the cortex. However it is unclear whether enhanced TDP-43-NEAT1 interaction represents a protective mechanism. We show that accumulation of human TDP-43 leads to upregulation of the constitutive NEAT1 isoform, NEAT1_1, in cultured cells and in the brains of transgenic mice. Further, we demonstrate that overexpression of NEAT1_1 ameliorates TDP-43 toxicity in Drosophila and yeast models of TDP-43 proteinopathy. Thus, NEAT1_1 upregulation may be protective in TDP-43 proteinopathies affecting the brain. Approaches to boost NEAT1_1 expression in the CNS may prove useful in the treatment of these conditions.

LRRK2 and its substrate Rab GTPases are sequentially targeted onto stressed lysosomes and maintain their homeostasis.

Leucine-rich repeat kinase 2 (LRRK2) has been associated with a variety of human diseases, including Parkinson's disease and Crohn's disease, whereas LRRK2 deficiency leads to accumulation of abnormal lysosomes in aged animals. However, the cellular roles and mechanisms of LRRK2-mediated lysosomal regulation have remained elusive. Here, we reveal a mechanism of stress-induced lysosomal response by LRRK2 and its target Rab GTPases. Lysosomal overload stress induced the recruitment of endogenous LRRK2 onto lysosomal membranes and activated LRRK2. An upstream adaptor Rab7L1 (Rab29) promoted the lysosomal recruitment of LRRK2. Subsequent family-wide screening of Rab GTPases that may act downstream of LRRK2 translocation revealed that Rab8a and Rab10 were specifically accumulated on overloaded lysosomes dependent on their phosphorylation by LRRK2. Rab7L1-mediated lysosomal targeting of LRRK2 attenuated the stress-induced lysosomal enlargement and promoted lysosomal secretion, whereas Rab8 stabilized by LRRK2 on stressed lysosomes suppressed lysosomal enlargement and Rab10 promoted lysosomal secretion, respectively. These effects were mediated by the recruitment of Rab8/10 effectors EHBP1 and EHBP1L1. LRRK2 deficiency augmented the chloroquine-induced lysosomal vacuolation of renal tubules in vivo. These results implicate the stress-responsive machinery composed of Rab7L1, LRRK2, phosphorylated Rab8/10, and their downstream effectors in the maintenance of lysosomal homeostasis.