Bingwei Lu

Sleep deprivation (SD), together with inevitable stress inherent to conventional SD protocols, can induce oxidative stress and inflammation, thereby increasing the risk of premature death. However, the source and signaling pathways underlying reactive oxygen species (ROS) generation remain unclear. Here, we demonstrate that both mechanical and thermogenetic SD, along with possible stress induced by both protocols, lead to initial ROS accumulation in Drosophila gut subregions, including the proventriculus (PV) and PV-resident hemocytes, via upregulation of dopamine (DA) biosynthesis. Intriguingly, DA acts unconventionally by activating mitochondrial reverse electron transfer (RET), presumably through modifying interactions between the respiratory complex I proteins NDUFV1 and NDUFS3. RET-ROS elicits hemolymphatic IMD/Relish-mediated antibacterial defense. However, during chronic SD, downregulation of the Drosophila APOE/D ortholog Neural Lazarillo promotes the recruitment of hemocytes to the central brain and, together with this process, leads to widespread neuronal ROS accumulation in an Alzheimer’s disease (AD) fly model. Inhibiting RET or hemocytic DA levels extends the survival of animals under chronic SD. Our work reveals DA-driven RET-ROS in innate immune cells during SD, highlights the pivotal role of a gut-innate immune-brain crosstalk in mediating the effect of SD manipulation on aging and AD pathogenesis, and suggests ways to lessen the consequence of SD, a profound health issue in modern society.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are progressive neurodegenerative disorders characterized by motor neuron degeneration, leading to muscle weakness, atrophy, and cognitive impairments. A defining pathological hallmark of ALS/FTD is the cytosolic mislocalization and accumulation of TAR DNA-binding protein 43 (TDP-43), highlighting its critical role in ALS pathogenesis. However, the molecular mechanisms underlying TDP-43 proteostasis remain poorly understood. Through a genetic screening approach, we identify inositol-requiring enzyme 1 (IRE1), an endoplasmic reticulum-resident transmembrane protein, as a potent suppressor of TDP-43 protein levels. Furthermore, we show that ribosome-associated quality control (RQC) factors play a crucial role in regulating TDP-43 proteostasis and cellular toxicity. Activation of the RQC pathway prevents excessive accumulation of TDP-43 and associated toxicity. Mechanistically, our findings suggest that IRE1 regulates TDP-43 protein level by promoting the degradation of aberrant TDP-43 translation product through the RQC pathway. IRE1 acts canonically to enhance the transcription of the RQC core component Clbn/NEMF and noncanonically to physically interact with Clbn/NEMF, thereby ameliorating TDP-43-induced proteotoxicity. Moreover, ectopic expression or pharmacological activation of IRE1 alleviates TDP-43 pathology and restores cognitive function in the TDP-43 A315T ALS mouse models. Collectively, our study identifies a role for IRE1 in the translational quality control of TDP-43 and establishes its potential as a therapeutic target for ALS/FTD.

Hyperphosphorylation and aggregation of the microtubule-associated protein tau are recognized as pathological hallmarks of tauopathies; however, the biological activity of tau that drives its pathophysiological effects remains poorly understood ^1–6 . Mitochondrial dysfunction is a common feature of tauopathies ^7,8 . Despite this, the mechanistic link between tau abnormalities and mitochondrial dysfunction, as well as its relationship to tau’s physiological function, remains unclear. Here, we demonstrate that tau regulates mitochondrial reverse electron transport (RET), which produces excess ROS, reduces the NAD ⁺ /NADH ratio, and is activated by aging or stress. In flies, mice, and human induced pluripotent stem cells (hiPSC)-derived neurons, tau depletion eliminates stress-induced RET and confers significant stress resistance. Mechanistically, tau enters mitochondria and directly interacts with the mitochondrial complex I (C-I) subunit NDUFS3, enhancing RET activation in a phosphorylation-dependent manner that correlates with tau pathogenicity. Elevated RET further drives tau hyperphosphorylation, establishing a self-perpetuating pathological loop. Blocking tau entry into mitochondria or disrupting tau/NDUFS3 interaction reduces tau-induced RET. Genetic or pharmacological inhibition of RET protects against tau-induced neurodegeneration across species. RET regulation represents a previously unrecognized normal function of tau that becomes pathological in disease, providing a therapeutic target for conditions characterized by tau abnormalities and mitochondrial dysfunction.

Loss of fragile X messenger ribonucleoprotein (FMRP) causes fragile X syndrome (FXS), an inherited neurodevelopmental disorder resulting in intellectual disability and autism spectrum disorder; however, the molecular function of FMRP remains uncertain. Here, using cell lines and fibroblasts and induced pluripotent stem cell–derived neurons from healthy individuals and patients with FXS, we showed that FMRP regulates collided ribosomes by recruiting activating signal cointegrator 1 complex subunit 3 (ASCC3), an early-acting ribosome-associated quality control (RQC) factor to collided ribosomes, and either positively or negatively regulating translation, depending on transcript context. Disease-associated ASCC3 variants that perturbed ASCC3-FMRP interaction were also found to be defective in ribosome association and handling of collided ribosomes. In cells of a patient with FXS and the Fmr1 KO mouse model, ASCC3 abundance was reduced, and overexpression of ASCC3 in the brains of fetal Fmr1 KO mice promoted neuronal migration. In addition, CRISPR-mediated activation of ASCC3 by lateral ventricular injection of adeno-associated virus (AAV) ameliorated synaptic defects and improved locomotor activity, cognitive deficits, obsessive-compulsive–like behavior, and social interaction deficits after 1 month in 2-month-old Fmr1 KO mice compared with untreated Fmr1 KO controls. In conclusion, these data implicated FMRP in the handling of collided ribosomes to maintain protein homeostasis during neurodevelopment and synaptogenesis and demonstrated proof of concept that targeting RQC may offer alternative treatment strategies for FXS.

It is well established that DNA Damage Regulated Autophagy Modulator 1 (DRAM1), a lysosomal protein and a target of p53, participates in autophagy. The cellular functions of DRAM1 beyond autophagy remain elusive. Here, we show p53-dependent upregulation of DRAM1 in mitochondrial damage–induced Parkinson’s disease (PD) models and exacerbation of disease phenotypes by DRAM1. We find that the lysosomal location of DRAM1 relies on its intact structure including the cytosol-facing C-terminal domain. Excess DRAM1 disrupts endoplasmic reticulum (ER) structure, triggers ER stress, and induces protective ER-phagy. Mechanistically, DRAM1 interacts with stromal interacting molecule 1 (STIM1) to tether lysosomes to the ER and perturb STIM1 function in maintaining intracellular calcium homeostasis. STIM1 overexpression promotes cellular health by restoring calcium homeostasis, ER stress response, ER-phagy, and AMP-activated protein kinase (AMPK)-Unc-51 like autophagy activating kinase 1 (ULK1) signaling in cells with excess DRAM1. Thus, by promoting organelle contact between lysosomes and the ER, DRAM1 modulates ER structure and function and cell survival under stress. Our results suggest that DRAM1 as a lysosomal protein performs diverse roles in cellular homeostasis and stress response. These findings may have significant implications for our understanding of the role of the p53/DRAM1 axis in human diseases, from cancer to neurodegenerative diseases.