The Catalytically Inactive Mutation of the Ubiquitin-Conjugating Enzyme CDC34 Affects its Stability and Cell Proliferation

Dauricine inhibits human pancreatic carcinoma cell proliferation through regulating miRNAs

Pancreatic cancer is one of the most malignant digestive tract tumors with the worst prognosis. Dauricine (Dau) can inhibit the proliferation of the pancreatic cancer cell line, and has the potential to be used as an adjuvant drug against pancreatic cancer; however, the working mechanism of Dau has not been elucidated. To unravel the effects and mechanisms of Dau on proteins and metabolic pathways, we evaluated the mRNA and microRNA expression in BxPC3 cells treated with Dau. The differences in the gene expression were compared using principal component analysis using mRNA and miRNA data to detect and analyze the sample discrimination. 187 miRNA and 907 mRNA that were significantly differentially expressed were identified using Python programming. On comparing genes and miRNAs in the DISEASES database, 79 known miRNA and 47 mRNA were found to be affected by Dau. The up-regulated and down-regulated genes were annotated with GO biological processes to determine the functional effect. Interactions between mRNA and mRNA were analyzed using the STRING database and the miRBase database was queried to obtain experimentally verified interactions between miRNA and mRNA as edges of miRNA and mRNA in the network. Finally, 413 sites and 2125 sides of the network were obtained, including 1 up-regulated and 18 down-regulated miRNAs. The expression of 19 miRNAs was identified by qPCR. The analysis of the protein-protein interaction network, using the Molecular Complex Detection (MCODE) plug-in of cytoscape, helped in identifying 12 important sub-networks. Most subnets are indirectly or directly related to specific miRNAs. This study provides evidence for the anticancer effect of Dau as a potential anticancer compound.

The Molecular Basis of Ubiquitin-Conjugating Enzymes (E2s) as a Potential Target for Cancer Therapy

Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

Beyond repression of Nrf2: An update on Keap1

Nrf2 (NFE2L2 - nuclear factor (erythroid-derived 2)-like 2) is a transcription factor, which is repressed by interaction with a redox-sensitive protein Keap1 (Kelch-like ECH-associated protein 1). Deregulation of Nrf2 transcriptional activity has been described in the pathogenesis of multiple diseases, and the Nrf2/Keap1 axis has emerged as a crucial modulator of cellular homeostasis. Whereas the significance of Nrf2 in the modulation of biological processes has been well established and broadly discussed in detail, the focus on Keap1 rarely goes beyond the regulation of Nrf2 activity and redox sensing. However, recent studies and scrutinized analysis of available data point to Keap1 as an intriguing and potent regulator of cellular function. This review aims to shed more light on Keap1 structure, interactome, regulation and non-canonical functions, thereby enhancing its significance in cell biology. We also intend to highlight the impact of balance between Keap1 and Nrf2 in the maintenance of cellular homeostasis.

Identifying the Potential Substrates of the Depalmitoylation Enzyme Acyl-protein Thioesterase 1

BACKGROUND

The homeostasis of palmitoylation and depalmitoylation is involved in various cellular processes, the disruption of which induces severe physiological consequences. Acyl-protein thioesterase (APT) and palmitoyl-protein thioesterases (PPT) catalyze the depalmitoylation process. The natural mutation in human PPT1 caused neurodegenerative disease, yet the understanding of APT1 remains to be elucidated. While the deletion of APT1 in mice turned out to be potentially embryonically lethal, the decoding of its function strictly relied on the identification of its substrates.

OBJECTIVE

To determine the potential substrates of APT1 by using the generated human APT1 knockout cell line.

METHODS

The combined techniques of palmitoyl-protein enrichment and massspectrometry were used to analyze the different proteins. Palmitoyl-proteins both in HEK293T and APT1-KO cells were extracted by resin-assisted capture (RAC) and data independent acquisition (DIA) quantitative method of proteomics for data collection.

RESULTS

In total, 382 proteins were identified. The gene ontology classification segregated these proteins into diverse biological pathways e.g. endoplasmic reticulum process and ubiquitin-mediated proteolysis. A few potential substrates were selected for verification; indeed, major proteins were palmitoylated. Importantly, their levels of palmitoylation were clearly changed in APT1-KO cells. Interestingly, the proliferation of APT1-KO cells escalated dramatically as compared to that of the WT cells, which could be rescued by APT1 overexpression.

CONCLUSION

Our study provides a large scale of potential substrates of APT1, thus facilitating the understanding of its intervened molecular functions.