Targeting proteasomal deubiquitinases USP14 and UCHL5 with b-AP15 reduces 5-fluorouracil resistance in colorectal cancer cells.

5-Fluorouracil (5-FU) is the first-line treatment for colorectal cancer (CRC) patients, but the development of acquired resistance to 5-FU remains a big challenge. Deubiquitinases play a key role in the protein degradation pathway, which is involved in cancer development and chemotherapy resistance. In this study, we investigated the effects of targeted inhibition of the proteasomal deubiquitinases USP14 and UCHL5 on the development of CRC and resistance to 5-FU. By analyzing GEO datasets, we found that the mRNA expression levels of USP14 and UCHL5 in CRC tissues were significantly increased, and negatively correlated with the survival of CRC patients. Knockdown of both USP14 and UCHL5 led to increased 5-FU sensitivity in 5-FU-resistant CRC cell lines (RKO-R and HCT-15R), whereas overexpression of USP14 and UCHL5 in 5-FU-sensitive CRC cells decreased 5-FU sensitivity. B-AP15, a specific inhibitor of USP14 and UCHL5, (1-5 µM) dose-dependently inhibited the viability of RKO, RKO-R, HCT-15, and HCT-15R cells. Furthermore, treatment with b-AP15 reduced the malignant phenotype of CRC cells including cell proliferation and migration, and induced cell death in both 5-FU-sensitive and 5-FU-resistant CRC cells by impairing proteasome function and increasing reactive oxygen species (ROS) production. In addition, b-AP15 inhibited the activation of NF-κB pathway, suppressing cell proliferation. In 5-FU-sensitive and 5-FU-resistant CRC xenografts nude mice, administration of b-AP15 (8 mg·kg-1·d-1, intraperitoneal injection) effectively suppressed the growth of both types of tumors. These results demonstrate that USP14 and UCHL5 play an important role in the development of CRC and resistance to 5-FU. Targeting USP14 and UCHL5 with b-AP15 may represent a promising therapeutic strategy for the treatment of CRC.

Lysine butyrylation of HSP90 regulated by KAT8 and HDAC11 confers chemoresistance.

Posttranslational modification dramatically enhances protein complexity, but the function and precise mechanism of novel lysine acylation modifications remain unknown. Chemoresistance remains a daunting challenge to successful treatment. We found that lysine butyrylation (Kbu) is specifically upregulated in chemoresistant tumor cells and tissues. By integrating butyrylome profiling and gain/loss-of-function experiments, lysine 754 in HSP90 (HSP90 K754) was identified as a substrate for Kbu. Kbu modification leads to overexpression of HSP90 in esophageal squamous cell carcinoma (ESCC) and its further increase in relapse samples. Upregulation of HSP90 contributes to 5-FU resistance and can predict poor prognosis in cancer patients. Mechanistically, HSP90 K754 is regulated by the cooperation of KAT8 and HDAC11 as the writer and eraser, respectively; SDCBP increases the Kbu level and stability of HSP90 by binding competitively to HDAC11. Furthermore, SDCBP blockade with the lead compound V020-9974 can target HSP90 K754 to overcome 5-FU resistance, constituting a potential therapeutic strategy.

K235 acetylation couples with PSPC1 to regulate the m6A demethylation activity of ALKBH5 and tumorigenesis.

N6-methyladenosine (m6A) modification plays important roles in bioprocesses and diseases. AlkB homolog 5 (ALKBH5) is one of two m6A demethylases. Here, we reveal that ALKBH5 is acetylated at lysine 235 (K235) by lysine acetyltransferase 8 and deacetylated by histone deacetylase 7. K235 acetylation strengthens the m6A demethylation activity of ALKBH5 by increasing its recognition of m6A on mRNA. RNA-binding protein paraspeckle component 1 (PSCP1) is a regulatory subunit of ALKBH5 and preferentially interacts with K235-acetylated ALKBH5 to recruit and facilitate the recognition of m6A mRNA by ALKBH5, thereby promoting m6A erasure. Mitogenic signals promote ALKBH5 K235 acetylation. K235 acetylation of ALKBH5 is upregulated in cancers and promotes tumorigenesis. Thus, our findings reveal that the m6A demethylation activity of ALKBH5 is orchestrated by its K235 acetylation and regulatory subunit PSPC1 and that K235 acetylation is necessary for the m6A demethylase activity and oncogenic roles of ALKBH5.

Lysine 2-hydroxyisobutyrylation of NAT10 promotes cancer metastasis in an ac4C-dependent manner.

Posttranslational modifications add tremendous complexity to proteomes; however, gaps remain in knowledge regarding the function and regulatory mechanism of newly discovered lysine acylation modifications. Here, we compared a panel of non-histone lysine acylation patterns in metastasis models and clinical samples, and focused on 2-hydroxyisobutyrylation (Khib) due to its significant upregulation in cancer metastases. By the integration of systemic Khib proteome profiling in 20 paired primary esophageal tumor and metastatic tumor tissues with CRISPR/Cas9 functional screening, we identified N-acetyltransferase 10 (NAT10) as a substrate for Khib modification. We further showed that Khib modification at lysine 823 in NAT10 functionally contribute to metastasis. Mechanistically, NAT10 Khib modification enhances its interaction with deubiquitinase USP39, resulting in increased NAT10 protein stability. NAT10 in turn promotes metastasis by increasing NOTCH3 mRNA stability in an N4-acetylcytidine-dependent manner. Furthermore, we discovered a lead compound #7586-3507 that inhibited NAT10 Khib modification and showed efficacy in tumor models in vivo at a low concentration. Together, our findings bridge newly identified lysine acylation modifications with RNA modifications, thus providing novel insights into epigenetic regulation in human cancer. We propose that pharmacological inhibition of NAT10 K823 Khib modification constitutes a potential anti-metastasis strategy.

Pharmacological characterization of a novel metal-based proteasome inhibitor Na-AuPT for cancer treatment.

The ubiquitin-proteasome system (UPS) is essential for maintaining cell homeostasis by orchestrating the protein degradation, but is impaired in various diseases, including cancers. Several proteasome inhibitors, such as bortezomib, are currently used in cancer treatment, but associated toxicity limits their widespread application. Recently metal complex-based drugs have attracted great attention in tumor therapy; however, their application is hindered by low water-solubility and poor absorbency. Herein, we synthesized a new type of gold (I) complex named Na-AuPT, and further characterized its anticancer activity. Na-AuPT is highly water-soluble (6 mg/mL), and it was able to potently inhibit growth of a panel of 11 cancer cell lines (A549, SMMC7721, H460, HepG2, BEL7402, LNCap, PC3, MGC-803, SGC-7901, U266, and K562). In A549 and SMMC7721 cells, Na-AuPT (in a range of 2.5-20 µM) inhibited the UPS function in a dose-dependent fashion by targeting and inhibiting both 20 S proteasomal proteolytic peptidases and 19 S proteasomal deubiquitinases. Furthermore, Na-AuPT induced caspase-dependent apoptosis in A549 and SMMC7721 cells, which was prevented by the metal chelator EDTA. Administration of Na-AuPT (40 mg · kg-1 · d-1, ip) in nude mice bearing A549 or SMMC7721 xenografts significantly inhibited the tumor growth in vivo, accompanied by increased levels of total ubiquitinated proteins, cleaved caspase 3 and Bax protein in tumor tissue. Moreover, Na-AuPT induced cell death of primary mononuclear cells from 5 patients with acute myeloid leukemia ex vivo with an average IC50 value of 2.46 µM. We conclude that Na-AuPT is a novel metal-based proteasome inhibitor that may hold great potential for cancer therapy.

TRIM25 activates AKT/mTOR by inhibiting PTEN via K63-linked polyubiquitination in non-small cell lung cancer.

The PTEN/AKT/mTOR signaling pathway is frequently dysregulated in non-small cell lung cancer (NSCLC), but the mechanisms are not well-understood. The present study found that the ubiquitin ligase TRIM25 is highly expressed in NSCLC tissues and promotes NSCLC cell survival and tumor growth. Mechanistic studies revealed that TRIM25 binds to PTEN and mediates its K63-linked ubiquitination at K266. This modification prevents the plasma membrane translocation of PTEN and reduces its phosphatase activity therefore accumulating PI(3,4,5)P3. TRIM25 thus activates the AKT/mTOR signaling. Moreover, we found that the antibacterial nitroxoline can activate PTEN by reducing its K63-linked polyubiquitination and sensitizes NSCLC to cisplatin-induced apoptosis. This study thus identified a novel modulation on the PTEN signaling pathway by TRIM25 and provides a potential target for NSCLC treatment.

Study on the molecular mechanism of BuShenHuoXue capsule in treatment of steroid-induced osteonecrosis of the femoral head.

BACKGROUND: Steroid-induced osteonecrosis of the femoral head (SONFH) is the pathological process caused by the death of the active components of the head of the femur due to the high dose of hormones, which has become a common public health problem. BuShenHuoXue capsule (BSHXC) has been clinically proven to be effective against the SONFH, the main pharmacological action of BSHXC is tonifying kidney and promoting blood circulation, but the mechanism remains to be explored. METHODS: We established a rat SONFH model by injecting Methylprednisolone (MPS) into the right gluteus muscle 30 mg/kg/d, 3 days of continuous injection every week, 4 weeks in total. According to the clinical dosage of BSHXC (Herba epimedium 3 g, Eucommia ulmoides 15 g, Salvia miltiorrhizae 30 g, Chuanxiong 15 g, Paeonia lactiflora Pall 15 g, Poria cocos 12 g, Achyranthes bidentata 12 g, antler gum 10 g, Cyperus rotundus L. Nine g and Radix Glycyrrhizae 9 g), it was converted into the equivalent dose of rats, and gavage was performed at the weight of 10 mL/kg, once per day. The BSHXC was subjected to experiments in vivo, SONFH pharmacodynamics, bioinformatics, and network of pharmacology to determine the active ingredients, and its protective role against SONFH, Enrichment analysis was performed to explore the possible mechanism of BSHXC, and cell experiments were undertaken to analyze the impact of BSHXC on the hormones associated with bone marrow mesenchymal stem cells (BMSCs) between osteogenesis and apoptosis. RESULTS: Experiments confirmed that BSHXC could effectively reduce bone loss in SONFH rat models. From bioinformatics and a network constructed from 10 drugs-208 pharmacology-126 targets, the enrichment analysis showed that the core targets were inflammatory reaction, steroid hormones, estrogen receptors, osteoporosis, and adjustment of osteogenesis and osteoclast differentiation, among others. The cell proliferation and staining supported that the mechanism of BSHXC promoted osteogenesis and intervening in apoptosis. CONCLUSIONS: The BSHXC reduced the inflammatory response, changed steroid response, regulated estrogen receptors, delayed osteoporosis, regulated osteoblast and osteoclast differentiation by regulating related targets, and improved the local microenvironment by a multi-component, multi-target, and multi-link process to delay or reverse the progression of SONFH.

Rapid Discovery of Potential Drugs for Osteonecrosis of Femoral Head Based on Gene Expression Omnibus Database and Connectivity Map.

OBJECTIVE: To use Gene Expression Omnibus (GEO) database coupled with Connectivity Map (CMap) databases to screen potential therapeutic drugs for osteonecrosis of femoral head (ONFH) rapidly. METHODS: Raw genetic data with accession number GSE74089 that contained eight hip articular cartilage specimens from four ONFH patients and four healthy controls were obtained from the Gene Expression Omnibus (GEO) database and were then integrated using R to identify differentially expressed genes (DEGs). Subsequently, to identify several potential small molecular compounds that were most strongly negatively correlated with ONFH, a search query of DEGs was explored by using CMap. RESULTS: Filtering revealed 1937 DEGs with log (fold-change) ≥1 and adjust P value < 0.001. Finally, a network of candidate targets for ONFH with 135 nodes and 660 edges was constructed through network topology analysis, including 96 up-regulated genes and 39 down-regulated genes. Several significant gene functions and signaling pathways associated with pathological processes of ONFH were identified via gene enrichment analysis. Based on the CMap database, some potential small molecular components that may be possible to counteract the effects of molecular signal imbalance for ONFH were identified. Neostigmine bromide with low CMap score and P value and specificity score was predicted to be the most candidate compound, involved in the "positive regulation of stem cell proliferation," "regulation of protein autophosphorylation," "VEGF signaling pathway," and "ECM-receptor interaction." CONCLUSIONS: The GEO and CMap databases can be effectively used in understanding the molecular changes in ONFH and provide a systematic manner to identify potential drugs for ONFH prevention and treatment. However, additional clinical and experimental research of the candidate compound is warranted.

Intrasarcoplasmic amyloidosis impairs proteolytic function of proteasomes in cardiomyocytes by compromising substrate uptake.

The presence of increased ubiquitinated proteins and amyloid oligomers in failing human hearts strikingly resembles the characteristic pathology in the brain of many neurodegenerative diseases. The ubiquitin-proteasome system (UPS) is responsible for degradation of most cellular proteins and plays essential roles in virtually all cellular processes. UPS impairment by aberrant protein aggregation was previously shown in cell culture but remains to be demonstrated in intact animals. Mechanisms underlying the impairment are poorly understood. We report here that UPS proteolytic function is severely impaired in the heart of a mouse model of intrasarcoplasmic amyloidosis caused by cardiac-restricted expression of a human desmin-related myopathy-linked missense mutation of alphaB-crystallin (CryAB(R120G)). The UPS impairment was detected before cardiac hypertrophy, and failure became discernible, suggesting that defective protein turnover likely contributes to cardiac remodeling and failure in this model. Further analyses reveal that the impairment is likely attributable to insufficient delivery of substrate proteins into the 20S proteasomes, and depletion of key components of the 19S subcomplex may be responsible. The derangement is likely caused by aberrant protein aggregation rather than loss of function of the CryAB gene because UPS malfunction was not evident in CryAB-null hearts and inhibition of aberrant protein aggregation by Congo red or a heat shock protein significantly attenuated CryAB(R120G)-induced UPS malfunction in cultured cardiomyocytes. Because of the central role of the UPS in cell regulation and the high intrasarcoplasmic amyloidosis prevalence in failing human hearts, our data suggest a novel pathogenic process in cardiac disorders with abnormal protein aggregation.

[Experimental study on effect of gastrodia in inducing the differentiation of mesenchymal stem cells into neuron-like cells].

OBJECTIVE: To investigate the effect of gastrodia in extracorporeal oriented inducing the differentiation of mesenchymal stem cells into neuron-like cells. METHODS: Mesenchymal stem cells were separated from bone marrow of rats by wall sticking method, amplifying cultured in vitro, and differentiated into neuron-like cells by oriented induction with gastrodia. The morphology of cells was observed under light microscopy, neuro-specific enolase (NSE), nestin and glial fibrillary acidic protein (GFAP) were detected by immunocytochemistry. RESULTS: Rats mesenchymal stem cells could be separated and amplified in vitro. After being induced by gastrodia for 2 hrs, most of the cells would be differentiated into meuron-like cells, revealing cytodendrite. By immunochemical staining, cells showed positive of NSE, nestin, and negative of GFAP. CONCLUSION: Rats' mesenchymal stem cells could be induced to differentiate into neuron-like cells.