br Acknowledgments The authors thank Dr
Acknowledgments The authors thank Dr. Tai-Sheng Cheng, Yu-Wen Huang and Ting-Wei Gau for technical assistance. This work was supported by the National Science Council of TaiwanNSC 98-2320-B-024-002-MY3 and National University of TainanAB102-216. This information is available free of charge via the Internet at http://pubs.acs.org.
Restenosis after angioplasty remains a remarkable challenge, although drug-eluting stents have reduced the incidence of restenosis considerably . Vascular smooth muscle (S)-10-Hydroxycamptothecin (VSMCs) play a pivotal role in the development of intimal thickening and restenosis. VSMCs proliferate and migrate from the media to the intima , . Thus, finding new targets against VSMCs is important. The ubiquitin proteasome system is the main intracellular protein degradation route by which cells get rid of excess and mis-folded proteins. A growing body of evidence has implicated the ubiquitin proteasome system (UPS) as being involved in the regulation of the complex cell signaling processes that are fundamental to atherosclerotic diseases. Recent studies have identified the contribution that the UPS makes to the initiation and complication of atherosclerosis via the regulation of vascular inflammation, apoptosis, oxidative stress and cholesterol metabolism . An increased activity in ubiquitination-proteasome in neointimal areas and the role of ubiquitin gene expression in these settings have been mentioned . Furthermore, the effects of proteasome inhibition on neointima formation have been well characterized, and the proteosome is considered as a therapeutic target , . However, the consequences of blocking protein degradation by inhibiting the apex of protein ubiquitination remain largely unknown. Here, we used chemical and genetic approaches to investigate the inhibition of protein ubiquitination in VSMCs both in vitro and in vivo. The ubiquitin moiety is generally attached via an E1-E2-E3 multi-enzyme cascade. In the first step, the ubiquitin-activating enzyme E1, UBA1 (E1), binds ATP·Mg and ubiquitin and catalyses C-terminal ubiquitin acyl-adenylation and the binding of a molecule . This ubiquitin is then available to be transferred to one of the E2 ubiquitin conjugating enzymes. E2 enzymes then interact with one of the hundreds of ubiquitin E3 ligases to transfer the ubiquitin to the ε-amino group of a lysine residue in the target protein. After several cycles, four or more ubiquitins linked via lysine-48 of ubiquitin (K48) are attached to the target protein. The K48-linked polyubiquitination chain is the canonical ubiquitin chain that targets the ubiquitinated protein for degradation by the proteasome enzyme complex . Monoubiquitination with a single ubiquitin conjugated to a protein regulates DNA repair, nuclear export and histone regulation rather than protein degradation , . To date, dozens of E2 enzymes and hundreds of E3 enzymes have been identified, whereas only two ubiquitin E1 enzymes have been discovered, of which E1 is the predominant isoform in the UPS pathway. Because the inhibition of the proteasome effectively reduces neointima formation in vivo, we hypothesized that inhibition of UBA1, the apex of the UPS, would also effectively block the UPS pathway (A), as do proteasome inhibition, and may thus attenuate neointimal hyperplasia.
Introduction With the increasing eutrophication and global warming, harmful cyanobacterial blooms (HCB) have become a major threat to human health and ecological system because HCB have increased all over the world during recent decades and they are possibly expanding further in the recent future. Several approaches have been developed to control HCB, including (1) physical methods, such as nutrient management by phosphorus-binding clays, high-frequency sonication for disrupting cell membranes and retarding photosynthetic activity; (2) biological methods, such as viruses, bacteria or fungi; (3) chemical methods, such as herbicides (e.g. diuron) and copper-based compounds (e.g. copper sulfate)5, 6. Among these approaches, chemical methods could rapidly eradicate HCB and have been used for many decades. However, these chemical compounds are no longer recommended because of their lengthy environmental persistence and toxic effect on both cyanobacteria and other non-target aquatic organisms5, 6. Therefore, it is very necessary and urgent to develop novel selective and safe algicides targeting cyanobacteria.