ABSTRACT
The Ddi1/DDI2 proteins are ubiquitin shuttling factors, implicated in a variety of cellular functions. In addition to ubiquitin-binding and ubiquitin-like domains, they contain a conserved region with similarity to retroviral proteases, but whether and how DDI2 functions as a protease has remained unknown. Here, we show that DDI2 knockout cells are sensitive to proteasome inhibition and accumulate high-molecular weight, ubiquitylated proteins that are poorly degraded by the proteasome. These proteins are targets for the protease activity of purified DDI2. No evidence for DDI2 acting as a de-ubiquitylating enzyme was uncovered, which could suggest that it cleaves the ubiquitylated protein itself. In support of this idea, cleavage of transcription factor NRF1 is known to require DDI2 activity in vivo. We show that DDI2 is indeed capable of cleaving NRF1 in vitro but only when NRF1 protein is highly poly-ubiquitylated. Together, these data suggest that DDI2 is a ubiquitin-directed endoprotease.
Subject(s)
Aspartic Acid Proteases/metabolism , Nuclear Respiratory Factor 1/metabolism , Ubiquitin/metabolism , Aspartic Acid Proteases/genetics , Binding Sites , CRISPR-Cas Systems , Cell Line , Gene Knockout Techniques , HEK293 Cells , Humans , Protein Biosynthesis , ProteolysisABSTRACT
The identification of novel, potent, non-steroidal/small molecule functional GR antagonist GSK1564023A selective over PR is described. Associated structure-activity relationships and the process of optimisation of an initial HTS hit are also described.
Subject(s)
Receptors, Glucocorticoid/antagonists & inhibitors , Receptors, Glucocorticoid/metabolism , Small Molecule Libraries/chemistry , Small Molecule Libraries/pharmacology , Animals , Rats , Small Molecule Libraries/metabolism , Structure-Activity RelationshipABSTRACT
New kinase inhibitors can be found by synthesis of targeted arrays of compounds designed using system-based knowledge as well as through screening focused or diverse compounds. Most array strategies aim to add functionality to a fragment that binds in the purine subpocket of the ATP-site. Here, an alternative pharmacophore-guided array approach is described which set out to discover novel purine subpocket-binding groups. Results are shown for p38alpha and cFMS kinase, for which multiple distinct series with nanomolar potency were discovered. Some of the compounds showed potency in cell-based assays and good pharmacokinetic properties.
