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p62/SQSTM1-KEAP1 complex prevents clearance of ubiquitinated Z alpha-1 antitrypsin and aggravates liver proteotoxicity.

Liver disease in Alpha-1 antitrypsin deficiency (AATD) is caused by the toxic accumulation of mutant Z alpha-1 antitrypsin (Z-AAT) within the endoplasmic reticulum (ER) of hepatocytes. Livers from PiZ transgenic mice expressing the human Z-AAT and AATD patients who are homozygotes for the allele expressing Z-AAT were found to have increased p62/SQSTM1, a multifunctional protein involved in protein homeostasis. The goal of this study was to elucidate the involvement of p62/SQSTM1 in the formation of Z-AAT globules that are responsible for liver injury in AATD. In the present study, we found that p62/SQSTM1 decorated ubiquitin-positive, Periodic-Acid Shiff-diastase-resistant Z-AAT globules and interacted with Z-AAT at the ER-cytosol interface. Genetic ablation of p62/SQSTM1 in PiZ mice (PiZ;p62-/-) led to marked reduction in hepatic Z-AAT globules and polymers, and decreased serum Z-AAT, highlighting a central role for p62/SQSTM1 in disease pathogenesis. Moreover, hepatocyte-specific somatic deletion of the ubiquitin-association (UBA) domain of p62/SQSTM1 reduced Z-AAT aggregation. Furthermore, KEAP1 was identified as a binding partner of p62/SQSTM1-Z-AAT complex, leading to nuclear translocation and activation of NRF2. Inhibition of KEAP1-p62/SQSTM1 interaction reduced the abundance of p62 and phosphorylated p62, decreased intracellular Z-AAT, and redistributed NRF2 to the cytoplasm. In conclusion, this study identifies p62/SQSTM1 as a regulator of Z-AAT proteostasis and link Z-AAT/p62 accumulation to KEAP1 sequestration and NRF2 pathway activation in liver disease due to Z-AAT.

AATD

Puerarin Attenuates Binge Ethanol-Induced Cortical Neurotoxicity in Association with AKT/mTOR Signaling and Autophagy-Related Responses.

Puerarin (Pue), a major isoflavone derived from Pueraria lobata, has demonstrated neuroprotective potential in multiple neurological disorders; however, its effects on ethanol (EtOH)-induced cortical injury and the associated molecular responses remain incompletely understood. In the present study, network pharmacology was combined with in vivo and in vitro experiments to investigate molecular responses associated with the effects of Pue on EtOH-induced neurotoxicity. Public databases were used to predict targets of Pue and alcohol-related brain injury, followed by protein-protein interaction analysis, Gene Ontology annotation, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment. A total of 101 overlapping targets were identified, among which TNF, AKT1, EGFR, TP53, and PPARG emerged as major hub targets, and PI3K-Akt signaling pathway was among the pathways that remained significantly enriched after FDR correction. In a 4-day binge EtOH rat model, Pue attenuated EtOH-associated increases in oxidative stress, neuronal degeneration, and apoptotic markers in cortical tissue. This was accompanied by attenuation of the EtOH-associated reductions in the p-AKT/AKT and p-mTOR/mTOR ratios, as well as an attenuation of EtOH-associated changes in LC3, ATG5, and Beclin-1 expression. In primary cortical neurons, Pue partially attenuated the EtOH-associated loss of neuronal viability and preserved neurite morphology. Bafilomycin A1 (BafA1)-based analysis of LC3-II and p62/SQSTM1 showed an overall BafA1-sensitive increase in LC3-II without a significant treatment-dependent difference in the BafA1 response. Collectively, these findings suggest that Pue attenuates binge EtOH-induced cortical neurotoxicity in association with changes in AKT/mTOR phosphorylation and autophagy-related responses.

AKT/mTOR signaling