Project description:Squestosome 1 (SQSTM1), also known as p62, is a multi-functional adaptor protein known for its pleotropic roles in autophagy, proteostasis, inflammation and cancer. Recently, p62 has emerged as an important modulator of protein quality control and aging. However, its role in the heart is not well understood. Our understanding of the role of p62 in the heart has been limited to the indirect assessment of its function in the setting of autophagy inhibition or proteotoxic stress. However, whether p62 is required to maintain cardiac function at rest or in response to stress has not been explored. Here we investigated the functional consequence of cardiac p62 deletion in the absence of other contributing phenotypic and systemic factors observed in the whole-body p62 deleted mice. Lack of cardiomyocytes p62 precipitated cardiac aging in mice and was associated with reduced contractile function and a progressive development of cardiac hypertrophy and fibrosis. Transcriptomic analysis of p62-deleted heart revealed a selective impairment in Nrf2 transcription, which was confirmed in the hearts of p62cKO mice. We further showed that absence of p62 in adult mice resulted in excessive oxidative stress and cell death when mice were rendered hypoxic. To gain mechanistic insights, we employed loss and gain of p62 function in H9c2 cardiomyoblasts and showed a sustained reduction in Nrf2 protein expression, nuclear translocation and transcriptional activity in p62-deficient cells. Mechanistically, p62-deficient cells exhibited an increase in proteasome-mediated Nrf2 degradation. In contrast, gain of p62 function led to Nrf2 stabilization and transcriptional activity.
Project description:p62/SQSTM1 is a ubiquitin-binding autophagy receptor and signaling protein that accumulates in premalignant liver diseases and most hepatocellular carcinomas (HCC). Although p62 was proposed to participate in formation of benign adenomas in autophagy-deficient livers, its role in HCC initiation was not explored. Here we show that p62 is necessary and sufficient for HCC induction in mice and that its high expression level in non-tumor human liver predicts rapid HCC recurrence after curative ablation. High p62 expression is needed for activation of NRF2 and mTORC1, c-Myc induction and protection of HCC-initiating cells from oxidative stress-induced death.
Project description:Neurodegenerative disorders are an increasingly common and irreversible burden on society, often affecting the ageing population, but their aetiology and disease mechanisms are poorly understood. Studying monogenic neurodegenerative diseases, with known genetic cause, provides an opportunity to understand cellular mechanisms also affected in more complex disorders. We recently reported that loss-of-function mutations in the autophagy adaptor protein, SQSTM1/p62, lead to a slowly progressive neurodegenerative disease presenting in childhood. To further elucidate the neuronal involvement, we studied the cellular consequences of loss of p62 in a neuroepithelial stem (NES) cell model and differentiated neurones, derived from reprogrammed p62 patient cells, or by CRISPR/Cas9-directed gene editing in NES cells. Transcriptomic and proteomic analyses suggest that p62 is essential for neuronal differentiation by controlling the metabolic shift from aerobic glycolysis to oxidative phosphorylation required for neuronal maturation. This shift is blocked by the failure to sufficiently downregulate lactate dehydrogenase expression due to the loss of p62, possibly through impaired Hif-1α downregulation and increased sensitivity to oxidative stress. The findings implicate an important role for p62 in neuronal energy metabolism and particularly in the regulation of the shift between glycolysis and oxidative phosphorylation, required for normal neurodifferentiation.
Project description:Impaired protective autophagy contributes to idiopathic pulmonary fibrosis (IPF), yet therapeutic strategies that restore this process remain limited. Here, we identify SKLB-39b, a BRD4-BD1-selective inhibitor that restores protective autophagy and attenuates pulmonary fibrosis. SKLB-39b exhibits over 100-fold selectivity for BRD4-BD1 relative to BRD4-BD2 and nearly 10-fold greater affinity for BRD4-BD1 than for BRD2/3-BD1. Mechanistically, we identify a BRD4-BD1-p62 interaction that links BET bromodomain function to autophagy regulation. By engaging Leu92 and Ile146 through a hydrophobic binding mode, SKLB-39b disrupts this interaction, restores ULK1-dependent autophagy, and provides a structural framework for BD1-selective inhibitor design. SKLB-39b outperformed JQ-1 in suppressing fibroblast activation, epithelial-mesenchymal transition, and collagen deposition in experimental fibrosis while showing favorable pharmacokinetic exposure and no overt toxicity in the mouse studies performed. These findings establish the BRD4-BD1-p62 interface as a druggable target for restoring protective autophagy in IPF.
Project description:Impaired protective autophagy contributes to idiopathic pulmonary fibrosis (IPF), yet therapeutic strategies that restore this process remain limited. Here, we identify SKLB-39b, a BRD4-BD1-selective inhibitor that restores protective autophagy and attenuates pulmonary fibrosis. SKLB-39b exhibits over 100-fold selectivity for BRD4-BD1 relative to BRD4-BD2 and nearly 10-fold greater affinity for BRD4-BD1 than for BRD2/3-BD1. Mechanistically, we identify a BRD4-BD1-p62 interaction that links BET bromodomain function to autophagy regulation. By engaging Leu92 and Ile146 through a hydrophobic binding mode, SKLB-39b disrupts this interaction, restores ULK1-dependent autophagy, and provides a structural framework for BD1-selective inhibitor design. SKLB-39b outperformed JQ-1 in suppressing fibroblast activation, epithelial-mesenchymal transition, and collagen deposition in experimental fibrosis while showing favorable pharmacokinetic exposure and no overt toxicity in the mouse studies performed. These findings establish the BRD4-BD1-p62 interface as a druggable target for restoring protective autophagy in IPF.
Project description:These are the results of the iCLIP experiment for p62/SQSTM1 in Human Huh-7 cells treated with DMSO. We used iCLIP method to identify the RNA targets of p62 and nucleotide positions of the p62 interaction on RNA. We used 2 replicates and 2 different antibodies against endogenous p62 to enrich protein/RNA complexes. cDNAs were tagged with iCLIP composite barcodes (e.g. NNNTTGTNN) which contain 4 sample-encoding bases (e.g. TTGT) and and 5 random bases (noted with N in NNNTTGTNN example) which serve as unique molecular identifiers to post-filter PCR duplicates. These composite barcodes are found in the read headers (after last colon ':' character) of submitted fastq files.