Discovery of a potent and selective covalent inhibitor and activity-based probe for UCHL1, with anti-fibrotic activity

Ubiquitin carboxy-terminal hydrolase L1 (UCHL1) is a deubiquitinating enzyme (DUB) that is very highly expressed in human brain. UCHL1 has been proposed as a potential therapeutic target in neurodegeneration, cancer, and liver and lung fibrosis, however bona fide molecular functions of UCHL1 are yet to be elucidated. Herein we characterize a potent and selective inhibitor and activity-based probe (IMP-1710) for UCHL1 based on a covalent inhibitor scaffold, and its application to identify and quantify target proteins in intact human cells. IMP-1710 stereoselectively labels the catalytic cysteine of UCHL1 at low nanomolar concentration, and we show that a previously claimed UCHL1 inhibitor (LDN-57444) fails to engage UCHL1 in cells. We further demonstrate that potent UCHL1 inhibitors selectively block pro-fibrotic responses in a cellular model of idiopathic pulmonary fibrosis (IPF), supporting a potential therapeutic role for UCHL1 inhibition.