USP50 Inhibitors

Chemical inhibitors of USP50 operate through various mechanisms to impair the protein's ability to process ubiquitinated substrates. E-64 serves as a potent, irreversible inhibitor by covalently binding to the active site cysteine residue of USP50, thus blocking its protease activity. Similarly, N-Ethylmaleimide targets the thiol groups of active site cysteine residues, modifying them and preventing the deubiquitination process. Another approach to inhibit USP50 is by restricting its access to ubiquitin-tagged proteins. Ubistatin A achieves this by binding ubiquitin moieties on substrates, which inhibits the cleavage of ubiquitin from these proteins by USP50. PYR-41 inhibits the ubiquitin-activating enzyme E1, leading to reduced ubiquitin conjugation and substrate availability for USP50, thereby limiting its function. VLX1570 and b-AP15 both act by inhibiting proteasomal deubiquitinases, causing an accumulation of polyubiquitinated proteins that saturate USP50 due to competitive inhibition.

Continuing with the theme of competitive inhibition, HBX 19818 and NSC697923 inhibit USP7 and USP47, respectively. The inhibition of these deubiquitinating enzymes leads to an increased concentration of ubiquitin-conjugated proteins, which competes with USP50 for substrates. P5091, while selective for USP7 and USP47, also contributes to an indirect functional inhibition of USP50 in a similar manner. The inhibition of these DUBs causes a buildup of ubiquitinated proteins that could overwhelm USP50, restricting its activity. IU1, targeting USP14, prevents the disassembly of ubiquitin chains, thereby increasing the ubiquitinated protein load and indirectly restricting USP50's capacity to function effectively. Lastly, WP1130 disrupts deubiquitinating enzymes, including USP50, by promoting their degradation, which results in the accumulation of ubiquitinated substrates that can inhibit USP50 through competitive interactions.