Selective Inhibition of the Immunoproteasome by Ligand‐Induced Crosslinking of the Active Site

Abstract

The concept of proteasome inhibition ranks among the latest achievements in the treatment of blood cancer and represents a promising strategy for modulating autoimmune diseases. In this study, we describe peptidic sulfonyl fluoride inhibitors that selectively block the catalytic β5 subunit of the immunoproteasome by inducing only marginal cytotoxic effects. Structural and mass spectrometric analyses revealed a novel reaction mechanism involving polarity inversion and irreversible crosslinking of the proteasomal active site. We thus identified the sulfonyl fluoride headgroup for the development and optimization of immunoproteasome selective compounds and their possible application in autoimmune disorders.

One-pot palladium-catalyzed synthesis of sulfonyl fluorides from aryl bromides

“…The ability to quickly prepare peptide-based sulfonyl fluoride probes could lead to increased exploration of protein binding pockets containing nucleophilic residues such as cysteine, tyrosine, lysine, serine and threonine 3 a or for use as irreversible inhibitors. 18 …”

Proteasome inhibition by new dual warhead containing peptido vinyl sulfonyl fluorides

“…Mechanism of covalent inhibition of the proteasome by peptido sulfonyl fluorides (PSF) [8] and proposed mechanism for inhibition by peptido vinylsulfonyl fluorides (PVSF). The threonine depicted in red represents the N-terminal threonine of the proteasome.…”

“…[8] It was found that selective inhibition of the immunoproteasome occurred by ligand-induced cross-linking of the active site (Scheme 2). With respect to this, comparison with other warheads highlights the peptido sulfonyl fluoride as a promising motif for 5i targeting.…”

“…To a stirred solution of oxalyl chloride (5.45 mL, 63.0 mmol) in CH2Cl2 (100 mL), under N2 atmosphere and cooled at -78 °C, were subsequently added dropwise a solution of DMSO (9.0 mL, 126 mmol) in CH2Cl2 (20 mL) and a solution of Cbz-Leucinol (38.2 mmol) [8] in CH2Cl2 (27 mL). After 10 min stirring at -78 °C a solution of DiPEA (40 mL, 230 mmol) in CH2Cl2 (100 mL) was added dropwise, and stirring was continued at -78 °C for 30 min.…”

“…[4,5] Increasingly, established proteasome inhibitors are evaluated as anti-inflammatory immunoproteasome inhibitors leading to new therapeutic strategies for treatment of autoimmune diseases such as rheumatoid arthritis and multiple sclerosis [6,7] Recently, in collaboration with Groll et al, we have achieved selective inhibition of the immunoproteasome by crosslinking of the active site effected by a peptido sulfonyl fluoride ligand (PSF). [8] Most proteasome inhibitors contain a single electrophilic moiety capable of covalently interacting with the threonine active site residue. [9] For example, the Michael acceptor electrophile containing proteasome inhibitors, especially the vinyl sulfones containing ones have been subject of intense investigations (Scheme 1).…”