Project description:Protein homeostasis and lipid metabolism are crucial cellular processes that are dysregulated in neurodegeneration. However, their connection in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) remains unexplored. Ubiquilin 2 (UBQLN2) is a protein quality control factor linked to familial ALS/FTD and broader neurodegeneration. Here, we idetified UBQLN2 as an essential regulator for intracellular lipid metabolism, the biological processes of which are impaired by ALS/FTD-linked mutations in UBQLN2. Using transcriptome analysis, we profiled the molecular changes in motor neurons derived from isogenic control and UBQLN2-mutant iPSCs under ALS/FTD-associated metabolic stress, glucose deficiency. We found that biological processes related to cell survival and metabolism were greately affected by the disease-linked mutations in UBQLN2, suggesting that the impaired metabolic role of UBQLN2 by the disease-linked mutations is involved in the pathogenesis of relative neurodegeneration.
Project description:Missense mutations in UBQLN2, a protein quality control factor, are associated with neurodegenerative diseases amyotrophic lateral sclerosis (ALS) overlapping with frontotemporal dementia (FTD). The mechanisms by which these mutations lead to neurodegeneration are not fully understood. Here we describe a critical role for UBQLN2 in regulating cellular lipid metabolism, which is crucial for cell survival under nutrient stress. The stress dependent regulation of lipid metabolism by UBQLN2 is mediated by ILVBL, a UBQLN2 substrate and a key enzyme in lipid turnover. The function of UBQLN2 in promoting ILVBL degradation and maintaining intracellular lipids was compromised by ALS/FTD-linked mutations in UBQLN2. As a result of the lipid dysregulation, synaptic vesicles were deficient and neuronal death was exacerbated in mutant UBQLN2 transgenic mice or human iPSCs derived motor neurons and cortical organoids. Replenishing lipids or restoring UBQLN2 function could reverse the deficits in the UBQLN2 mutant neurons under nutrient stress. Our study reveals UBQLN2 essential role in lipid metabolism and suggests metabolic imbalance underlying ALS/FTD and related neurodegenerative conditions.
Project description:Apolipoprotein E (APOE) is a strong genetic risk factor for late-onset Alzheimer’s disease (AD) with APOE4 increasing and APOE2 decreasing risk relative to APOE3. In the P301S mouse model of tauopathy, ApoE4 increases tau pathology and neurodegeneration when compared to ApoE3 or the absence of ApoE. However, the role of ApoE isoforms in regulating lipid metabolism in the setting of tauopathy is unknown. Here, by using targeted lipidomics coupled with histological analysis, we demonstrate that in P301S tau mice, ApoE4 strongly promotes glial lipid accumulation along with significant perturbations in cholesterol metabolism and lysosomal function. Increasing lipid efflux in glia via administration of the LXR agonist GW3965 reduces lipid droplet accumulation in primary E4 microglia in vitro and GW3965 or Abca1 overexpression strongly attenuates tau pathology, neurodegeneration, and synapse loss in P301S/ApoE4 mice. By immunostaining, bulk and snRNA sequencing, we demonstrate reductions in reactive astrocytes and microglia as well as significant changes in cholesterol biosynthesis and metabolism in glia of tauopathy mice in response to LXR activation. These data suggest that promoting efflux of glial lipids via Abca1 could serve as a therapeutic approach to ameliorate tau and ApoE4-linked neurodegeneration.
Project description:Apolipoprotein E (APOE) is a strong genetic risk factor for late-onset Alzheimer’s disease (AD) with APOE4 increasing and APOE2 decreasing risk relative to APOE3. In the P301S mouse model of tauopathy, ApoE4 increases tau pathology and neurodegeneration when compared to ApoE3 or the absence of ApoE. However, the role of ApoE isoforms in regulating lipid metabolism in the setting of tauopathy is unknown. Here, by using targeted lipidomics coupled with histological analysis, we demonstrate that in P301S tau mice, ApoE4 strongly promotes glial lipid accumulation along with significant perturbations in cholesterol metabolism and lysosomal function. Increasing lipid efflux in glia via administration of the LXR agonist GW3965 reduces lipid droplet accumulation in primary E4 microglia in vitro and GW3965 or Abca1 overexpression strongly attenuates tau pathology, neurodegeneration, and synapse loss in P301S/ApoE4 mice. By immunostaining, bulk and snRNA sequencing, we demonstrate reductions in reactive astrocytes and microglia as well as significant changes in cholesterol biosynthesis and metabolism in glia of tauopathy mice in response to LXR activation. These data suggest that promoting efflux of glial lipids via Abca1 could serve as a therapeutic approach to ameliorate tau and ApoE4-linked neurodegeneration.
Project description:While the activities of certain proteases promote proteostasis and prevent neurodegeneration-associated phenotypes, the protease cathepsin B (CTSB) enhances proteotoxicity in Alzheimer’s disease (AD) model mice, and its levels are elevated in brains of AD patients. How CTSB exacerbates the toxicity of the AD-causing Amyloid β (Aβ), is controversial. Using an activity based probe, aging-altering interventions and the nematode C. elegans we discovered that the CTSB CPR-6 promotes Aβ proteotoxicity but mitigates the toxicity of polyQ stretches. While the knockdown of cpr-6 does not affect lifespan, it alleviates Aβ toxicity by reducing the expression of swsn-3 and elevating the level of the protein SMK-1, both involved in the regulation of aging. These observations unveil a novel mechanism by which CTSB aggravates Aβ–mediated toxicity, indicate that it plays opposing roles in the face of distinct proteotoxic insults and highlight the importance of tailoring specific remedies for distinct neurodegenerative disorders.