p62 as a therapeutic target for tumor.

p62/SQSTM1 (hereafter as p62) is a stress-inducible cellular protein, which interacts with various signaling proteins to regulate a variety of cellular functions. Growing lines of evidence supported a critical role of p62 in tumorigenesis, and p62 may become a therapeutic target for tumor. In this review, we summarize biological functions of structural domains of p62, reported bioactive molecules targeting p62, and the relationship between p62 and tumorigenesis.

CPUY192018, a potent inhibitor of the Keap1-Nrf2 protein-protein interaction, alleviates renal inflammation in mice by restricting oxidative stress and NF-κB activation.

The Keap1-Nrf2-ARE pathway regulates the constitutive and inducible transcription of various genes that encode detoxification enzymes, antioxidant proteins and anti-inflammatory proteins and has pivotal roles in the defence against cellular oxidative stress. In this study, we investigated the therapeutic potential of CPUY192018, a potent small-molecule inhibitor of the Keap1-Nrf2 protein-protein interaction (PPI), in renal inflammation. In human proximal tubular epithelial HK-2 cells, CPUY192018 treatment significantly increased Nrf2 protein level and Nrf2 nuclear translocation, which enhanced Nrf2-ARE transcription capacity and the downstream protein content in a Nrf2 dependent manner. In lipopolysaccharide (LPS)-challenged human HK-2 cells, CPUY192018 exhibited cytoprotective effects by enhancing the Nrf2-ARE regulated antioxidant system and diminished the LPS-induced inflammatory response by hindering the ROS-mediated activation of the NF-κB pathway. In the LPS-induced mouse model of chronic renal inflammation, by activating Nrf2, CPUY192018 treatment balanced renal oxidative stress and suppressed inflammatory responses. Hence, administration of CPUY192018 reduced kidney damage and ameliorated pathological alterations of the glomerulus. Taken together, our study suggested that small-molecule Keap1-Nrf2 PPI inhibitors can activate the Nrf2-based cytoprotective system and protect the kidney from inflammatory injury, raising a potential application of Keap1-Nrf2 PPI inhibitors in the treatment of inflammatory kidney disorders.

The total alkaloids from Coptis chinensis Franch improve cognitive deficits in type 2 diabetic rats.

BACKGROUND: Coptis chinensis Franch is extensively used in traditional Chinese medicine to treat diabetes and dementia. Alkaloids are the main active ingredients of C. chinensis. PURPOSE: This study was designed to probe the effects and possible mechanisms of the total alkaloids from C. chinensis (TAC) on cognitive deficits in type 2 diabetic rats. METHODS: Cognitive deficits were induced in rats by streptozotocin and high glucose/high fat diet. After treatment with TAC (80, 120, and 180 mg/kg) for 24 weeks, the behavioral parameters of each rat were assessed by Morris water maze and Y-maze tests. The indexes of glucose and lipid metabolism, pathological changes of brain tissue, and the phosphorylation levels of insulin signaling related proteins were also evaluated. RESULTS: The type 2 diabetic rats showed significantly elevated levels of fasting blood glucose, glycosylated hemoglobin and glycosylated serum protein, as well as apolipoprotein B, free fatty acid, triglyceride and total cholesterol but decreased the content of apolipoprotein A1, and TAC treatment dose-dependently reversed these abnormal changes. Furthermore, the behavioral results showed that TAC alleviated the cognitive deficits in type 2 diabetic rats. Moreover, immunohistochemical and histopathologic examinations indicated that the diabetic rats showed significant Aß deposition, and neuronal damage and loss, which can be reversed by TAC treatment. The western blot results showed that TAC treatment markedly increased the phosphorylation of IRS, PI3K, and Akt, and inhibited the overactivation of GSK3ß in the brain of type 2 diabetic rats. CONCLUSION: These findings conclude that TAC prevents diabetic cognitive deficits, most likely by ameliorating the disorder of glucose and lipid metabolism, attenuating Aß deposition, and enhancing insulin signaling.

Discovery of a Keap1-dependent peptide PROTAC to knockdown Tau by ubiquitination-proteasome degradation pathway.

Induced protein degradation by PROTACs has emerged as a promising strategy to target nonenzymatic proteins inside the cell. The aim of this study was to identify Keap1, a substrate adaptor protein for ubiquitin E3 ligase involved in oxidative stress regulation, as a novel candidate for PROTACs that can be applied in the degradation of the nonenzymatic protein Tau. A peptide PROTAC by recruiting Keap1-Cul3 ubiquitin E3 ligase was developed and applied in the degradation of intracellular Tau. Peptide 1 showed strong in vitro binding with Keap1 and Tau. With proper cell permeability, peptide 1 was found to colocalize with cellular Keap1 and resulted in the coimmunoprecipitation of Tau and Keap1. The results of flow cytometry and western blotting assays showed that peptide 1 can downregulate the intracellular Tau level in both time- and concentration-dependent manner. The application of Keap1 siRNA silencing and the proteasome inhibitor MG132 confirmed that peptide 1 could promote the Keap1-dependent poly-ubiquitination and proteasome-dependent degradation of Tau. The results suggested that using PROTACs to recruit Keap1 to induce the degradation of Tau may show promising character in the treatment of neurodegenerative disease. Besides, our research demonstrated that Keap1 should be a promising E3 ligase adaptor to be used in the design of novel PROTACs.