Adipocytes possess remarkable adaptive capacity to respond to nutrient excess, fasting or cold exposure, and they are thus an important cell type for the maintenance of proper metabolic health. Although the endoplasmic reticulum (ER) is a critical organelle for cellular homeostasis, the mechanisms that mediate adaptation of the ER to metabolic challenges in adipocytes are unclear. Here we show that brown adipose tissue (BAT) thermogenic function requires an adaptive increase in proteasomal activity to secure cellular protein quality control, and we identify the ER-localized transcription factor nuclear factor erythroid 2-like 1 (Nfe2l1, also known as Nrf1) as a critical driver of this process. We show that cold adaptation induces Nrf1 in BAT to increase proteasomal activity and that this is crucial for maintaining ER homeostasis and cellular integrity, specifically when the cells are in a state of high thermogenic activity. In mice, under thermogenic conditions, brown-adipocyte-specific deletion of Nfe2l1 (Nrf1) resulted in ER stress, tissue inflammation, markedly diminished mitochondrial function and whitening of the BAT. In mouse models of both genetic and dietary obesity, stimulation of proteasomal activity by exogenously expressing Nrf1 or by treatment with the proteasome activator PA28α in BAT resulted in improved insulin sensitivity. In conclusion, Nrf1 emerges as a novel guardian of brown adipocyte function, providing increased proteometabolic quality control for adapting to cold or to obesity.
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http://dx.doi.org/10.1038/nm.4481 | DOI Listing |
Nat Cell Biol
January 2025
Department of Biochemistry and Molecular Biology, the Institute for Medical Research Israel-Canada, the Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel.
The protein homeostasis (proteostasis) network encompasses a myriad of mechanisms that maintain the integrity of the proteome by controlling various biological functions, including protein folding and degradation. Alas, ageing-associated decline in the efficiency of this network enables protein aggregation and consequently the development of late-onset neurodegenerative disorders, such as Alzheimer's disease. Accordingly, the maintenance of proteostasis through late stages of life bears the promise to delay the emergence of these devastating diseases.
View Article and Find Full Text PDFAlzheimers Dement
December 2024
Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
Background: The proteasome plays key roles in synaptic plasticity and memory by regulating protein turnover, quality control, and elimination of oxidized/misfolded proteins. Here, we investigate proteasome function and localization at synapses in Alzheimer's disease (AD) post-mortem brain tissue and in experimental models.
Method: We used primary hippocampal cultures, amyloid-β oligomers (AβO)-injected or transgenic animal models, and human brain tissue to determine brain proteasome function and subcellular localization.
Alzheimers Dement
December 2024
University of California San Francisco, San Francisco, CA, USA.
Background: The direct and chaperone-associated interactions of E3 ubiquitin ligase CHIP with tau in Alzheimer's disease and other tauopathies, regulates tau turnover, by directly linking it to ubiquitination and proteasomal degradation, as well as through suppression of tau aggregation. Modulation of these CHIP-driven tau clearance mechanisms can be an effective treatment strategy. Antigen-binding antibody fragments (Fabs) are potent tools that can highly-selectively engage target proteins and act as functional probes or inhibitors.
View Article and Find Full Text PDFAlzheimers Dement
December 2024
Columbia University Medical Center, New York, NY, USA.
Background: The ubiquitin-proteasome system (UPS) is the primary protein degrading mechanism in eukaryotes, and is essential for cellular homeostasis. Dysregulation of the UPS has been linked to neurodegeneration through two hallmarks, pathogenic protein aggregation and aberrant proteostasis. However, the molecular changes that alter proteasome functioning in AD are poorly understood.
View Article and Find Full Text PDFAlzheimers Dement
December 2024
Physiopathology in Aging Laboratory (LIM-22), University of São Paulo Medical School, São Paulo, São Paulo, Brazil.
Background: Understanding the molecular mechanisms underlying selective neuronal vulnerability is crucial for developing effective treatments for Alzheimer's disease (AD). Our group has shown that RORB/CDH9-positive excitatory neurons in the entorhinal cortex (EC) display selective vulnerability as early as Braak stage (BB) 2. However, not all RORB/CDH9-positive neurons are vulnerable.
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