Targeting the deubiquitinase STAMBP inhibits NALP7 inflammasome activity

Abstract

Inflammasomes regulate innate immune responses by facilitating maturation of inflammatory cytokines, interleukin (IL)-1β and IL-18. NACHT, LRR and PYD domains-containing protein 7 (NALP7) is one inflammasome constituent, but little is known about its cellular handling. Here we show a mechanism for NALP7 protein stabilization and activation of the inflammasome by Toll-like receptor (TLR) agonism with bacterial lipopolysaccharide (LPS) and the synthetic acylated lipopeptide Pam3CSK4. NALP7 is constitutively ubiquitinated and recruited to the endolysosome for degradation. With TLR ligation, the deubiquitinase enzyme, STAM-binding protein (STAMBP) impedes NALP7 trafficking to lysosomes to increase NALP7 abundance. STAMBP deubiquitinates NALP7 and STAMBP knockdown abrogates LPS or Pam3CSK4-induced increases in NALP7 protein. A small-molecule inhibitor of STAMBP deubiquitinase activity, BC-1471, decreases NALP7 protein levels and suppresses IL-1β release after TLR agonism. These findings describe a unique pathway of inflammasome regulation with the identification of STAMBP as a potential therapeutic target to reduce pro-inflammatory stress.

Design, synthesis, and structure–activity relationships of 2-benzylidene-1-indanone derivatives as anti-inflammatory agents for treatment of acute lung injury

“… 25 , 26 Evidence from experimental and clinical studies shows that these proinflammatory cytokines play a significant role in accelerated inflammation-mediated ALI pathogenesis. 27 All the synthesized 2-benzylidene-1-indanone derivatives were evaluated for their in vitro anti-inflammatory activity toward TNF-α and IL-6 release in LPS-stimulated MPMs, and XAN was used as a positive control. The macrophages were preincubated for 30 min with 10 µM test compounds, XAN, and DMSO, which was used as the control medium.…”

Small molecules that target the ubiquitin system

“…But it was found to inhibit both UCHL1 and UCHL3 with IC 50 values of 0.67 ± 1.0 μM and 6.4 ± 1.1 μM, respectively [109]. A more selective and potent UCHL1 inhibitor (35a) [118], as well as a structurally related activity-based probe (35b) [110], were reported to label UCHL1 in [117] living cells at low micromolar concentrations, and block pro-fibrotic responses in IPF cellular models without substantial associated cytotoxicity. The cell permeable small molecules 6RK73 (36) and 8RK64 (37) were found to target UCHL1 but no other DUBs [111].…”

“…STAMBP (or AMSH), is a K63-specific JAMM-type DUB that protects endosome cargo proteins from lysosomal degradation and also controls the levels of ubiquitination of ESCRT proteins. BC-1471 (43) was discovered as a specific STAMBP inhibitor (IC 50 = 0.33 μM) that selectively blocked deubiquitination of Ub-NALP7 by recombinant STAMBP [117] but did not significantly inhibit the activity of a panel of 38 different DUBs at the concentration tested.…”

The Role of Deubiquitinating Enzymes in Acute Lung Injury and Acute Respiratory Distress Syndrome

“…Protein kinase JNK1 catalyzes NLRP3 phosphorylation at S194 within NLRP3, which is critical for NLRP3 deubiquitination and facilitates its self-association and the subsequent inflammasome assembly [99]. Another inflammasome component NALP7 is regulated by the deubiquitinating enzyme STAM-binding protein (STAMBP), targeting the STAMBP with a small molecule that inhibits NALP7 inflammasome activity [95].…”