The deubiquitinase MYSM1 dampens NOD2-mediated inflammation and tissue damage by inactivating the RIP2 complex

Abstract

NOD2 is essential for antimicrobial innate immunity and tissue homeostasis, but require tight regulation to avert pathology. A focal point of NOD2 signaling is RIP2, which upon polyubiquitination nucleates the NOD2:RIP2 complex, enabling signaling events leading to inflammation, yet the precise nature and the regulation of the polyubiquitins coordinating this process remain unclear. Here we show that NOD2 signaling involves conjugation of RIP2 with lysine 63 (K63), K48 and M1 polyubiquitin chains, as well as with non-canonical K27 chains. In addition, we identify MYSM1 as a proximal deubiquitinase that attenuates NOD2:RIP2 complex assembly by selectively removing the K63, K27 and M1 chains, but sparing the K48 chains. Consequently, MYSM1 deficient mice have unrestrained NOD2-mediated peritonitis, systemic inflammation and liver injury. This study provides a complete overview of the polyubiquitins in NOD2:RIP2 signaling and reveal MYSM1 as a central negative regulator restricting these polyubiquitins to prevent excessive inflammation.

XIAP controls RIPK2 signaling by preventing its deposition in speck-like structures

“…Mechanistically this was proposed to involve aberrant ubiquitination of RIPK1/3, raising the question which ubiquitination events play a role in RIPK2 complex formation. As RIPK2 is mainly regulated by ubiquitination on K209 via covalent attachment of different linkage-types of ubiquitin (Hasegawa et al, 2008, Panda & Gekara, 2018 this site might play a role in RIPosome formation as well.…”

“…Some insight on this controversy was provided by the recent identification that RIPK2 inhibitors can also block interaction of RIPK2 with the E3 ubiquitin ligase X-linked inhibitor of apoptosis (XIAP), which is essential for RIPK2-mediated NF-κB activation (Goncharov, Hedayati et al, 2018). RIPK2 is modified by K63-, K27 and M1-linked ubiquitination at K209, located in its kinase domain (Hasegawa, Fujimoto et al, 2008, Panda & Gekara, 2018. XIAP is the essential E3 for RIPK2 ubiquitination and interacts with RIPK2 through its baculoviral IAP-repeat (BIR) 2 domain (Krieg, Correa et al, 2009).…”

Deubiquitinase MYSM1 in the Hematopoietic System and beyond: A Current Review

“…Histone H2A, monoubiquitinated at K119, was the first substrate of MYSM1 to be described (H2AK119ub) [7]. More recently MYSM1 was also demonstrated to cleave K63-polyubiquitin chains on cytosolic substrates TRAF3, TRAF6, and RIP2 [3,8]. MYSM1 catalytic activity against polyubiquitin chains of different geometries [9] was subsequently tested using in vitro assays, and MYSM1 was shown to cleave M1, K6, and K27 chains, but was catalytically inactive against K11, K29, K33, and K48 chains [8].…”

“…More recently MYSM1 was also demonstrated to cleave K63-polyubiquitin chains on cytosolic substrates TRAF3, TRAF6, and RIP2 [3,8]. MYSM1 catalytic activity against polyubiquitin chains of different geometries [9] was subsequently tested using in vitro assays, and MYSM1 was shown to cleave M1, K6, and K27 chains, but was catalytically inactive against K11, K29, K33, and K48 chains [8]. This suggests that our knowledge of MYSM1 substrates remains incomplete and further targets of its catalytic activity may be discovered in the future.…”

“…Recent studies indicated an alternative function for MYSM1 as a regulator of the signal transduction pathways of innate immunity in the cytosol, independent of MYSM1-mediated regulation of gene expression at chromatin [3,8]. Thus, a cytosolic pool of MYSM1 protein is produced transiently in mouse macrophages, in response to inflammatory stimulation or infection, involving de novo protein synthesis and subsequent proteasomal degradation [3].…”