Halogen Substituents in the Isoquinoline Scaffold Switches the Selectivity of Inhibition between USP2 and USP7

The discovery of potent USP2/USP8 dual-target inhibitors for the treatment of breast cancer via structure guided optimization of ML364

USP2 and USP8 are crucial in the development and progression of breast cancer, primarily through the stabilization of protein substrates such as Her2 and ERα. The dual-target inhibitor ML364, targeting both USP2 and USP8, has garnered significant interest in recent research. In this study, we developed a series of ML364 derivatives using ligand-based drug design strategies. The standout compound, LLK203, demonstrated enhanced inhibitory activity, showing a 4-fold increase against USP2 and a 9-fold increase against USP8, compared to the parent molecule. In MCF-7 breast cancer cells, LLK203 effectively degraded key proteins involved in cancer progression and notably inhibited cell proliferation. Moreover, LLK203 exhibited potent in vivo efficacy in the 4T1 homograft model, while maintaining a low toxicity profile. These results underscore the potential of LLK203 as a promising dual-target inhibitor of USP2/USP8 for breast cancer treatment.

Advances in the Development Ubiquitin-Specific Peptidase (USP) Inhibitors

Ubiquitylation and deubiquitylation are reversible protein post-translational modification (PTM) processes involving the regulation of protein degradation under physiological conditions. Loss of balance in this regulatory system can lead to a wide range of diseases, such as cancer and inflammation. As the main members of the deubiquitinases (DUBs) family, ubiquitin-specific peptidases (USPs) are closely related to biological processes through a variety of molecular signaling pathways, including DNA damage repair, p53 and transforming growth factor-β (TGF-β) pathways. Over the past decade, increasing attention has been drawn to USPs as potential targets for the development of therapeutics across diverse therapeutic areas. In this review, we summarize the crucial roles of USPs in different signaling pathways and focus on advances in the development of USP inhibitors, as well as the methods of screening and identifying USP inhibitors.

Enhanced Live-Cell Delivery of Synthetic Proteins Assisted by Cell-Penetrating Peptides Fused to DABCYL

Live-cell delivery of a fully synthetic protein having selectivity towards a particular target is a promising approach with potential applications for basic research and therapeutics. Cell-penetrating peptides (CPPs) allow the cellular delivery of proteins but mostly result in endosomal entrapment, leading to lack of bioavailability. Herein, we report the design and synthesis of a CPP fused to 4-((4-(dimethylamino)phenyl)azo)benzoic acid (DABCYL) to enhance cellular uptake of fluorescently labelled synthetic protein analogues in low micromolar concentration. The attachment of cyclic deca-arginine (cR10) modified with a single lysine linked to DABCYL to synthetic ubiquitin (Ub) and small ubiquitin-like modifier-2 (SUMO-2) scaffolds resulted in a threefold higher uptake efficacy in live cells compared to the unmodified cR10. We could also achieve cR10DABCYL-assisted delivery of Ub and a Ub variant (Ubv) based activity-based probes for functional studies of deubiquitinases in live cells.

Semisynthesis of Ubiquitin and SUMO-Rhodamine 110-Glycine through Aminolysis of Boc-Protected Thioester Counterparts

Ubiquitin (Ub)-based fluorescent reagents are crucial to explore the activity of deubiquitinases (DUBs). Ub-Rho110-G is one of the preferred tools, whereas the current synthetic route is time-consuming. Here, we report a new semisynthetic strategy to produce Ub-Rho110-G through direct aminolysis of Boc-protected Ub-Mesna using bisglycyl-rhodamine 110. We also applied this strategy to synthesize active SUMO2-Rho110-G for the first time. Biochemical analysis demonstrated that semisynthetic Ub or SUMO-Rho110-G can be effectively used for the detection of the activity of DUBs or SUMO-specific enzymes.