A potent and selective inhibitor for the UBLCP1 proteasome phosphatase

Bioorg Med Chem. 2015 Jun 15;23(12):2798-809. doi: 10.1016/j.bmc.2015.03.066. Epub 2015 Mar 31.


The ubiquitin-like domain-containing C-terminal domain phosphatase 1 (UBLCP1) has been implicated as a negative regulator of the proteasome, a key mediator in the ubiquitin-dependent protein degradation. Small molecule inhibitors that block UBLCP1 activity would be valuable as research tools and potential therapeutics for human diseases caused by the cellular accumulation of misfold/damaged proteins. We report a salicylic acid fragment-based library approach aimed at targeting both the phosphatase active site and its adjacent binding pocket for enhanced affinity and selectivity. Screening of the focused libraries led to the identification of the first potent and selective UBLCP1 inhibitor 13. Compound 13 exhibits an IC50 of 1.0μM for UBLCP1 and greater than 5-fold selectivity against a large panel of protein phosphatases from several distinct families. Importantly, the inhibitor possesses efficacious cellular activity and is capable of inhibiting UBLCP1 function in cells, which in turn up-regulates nuclear proteasome activity. These studies set the groundwork for further developing compound 13 into chemical probes or potential therapeutic agents targeting the UBLCP1 phosphatase.

Keywords: Fragment-based drug discovery; Inhibitor development; Protein phosphatase; UBLCP1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cell Line
  • Enzyme Inhibitors / chemistry*
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Molecular Docking Simulation
  • Molecular Sequence Data
  • Nuclear Proteins / antagonists & inhibitors*
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / metabolism
  • Phosphoprotein Phosphatases / antagonists & inhibitors*
  • Phosphoprotein Phosphatases / chemistry
  • Phosphoprotein Phosphatases / metabolism
  • Salicylic Acid / chemistry*
  • Salicylic Acid / pharmacology*
  • Small Molecule Libraries / chemistry
  • Small Molecule Libraries / pharmacology


  • Enzyme Inhibitors
  • Nuclear Proteins
  • Small Molecule Libraries
  • Phosphoprotein Phosphatases
  • UBLCP1 protein, human
  • Salicylic Acid