This may point to differentiated use of LUBAC components in immune cells. mice. A homozygous hypomorphic mutation in human causes a potentially fatal autoinflammatory condition termed OTULIN-related autoinflammatory syndrome (ORAS). Four impartial OTULIN mouse models reveal that OTULIN deficiency in immune cells results in cell-type-specific effects, ranging from over-production of inflammatory cytokines and autoimmunity due to accumulation of M1-linked polyubiquitin and spontaneous NF-B activation in myeloid cells to downregulation of M1-polyubiquitin signaling by degradation of LUBAC in B and T?cells. Amazingly, treatment with anti-TNF neutralizing antibodies ameliorates inflammation in ORAS patients and rescues mouse phenotypes. Hence, OTULIN is critical for restraining?life-threatening spontaneous inflammation and maintaining immune homeostasis. Graphical Abstract Open in a separate window Highlights ? Mutation of OTULIN causes OTULIN-related autoinflammatory syndrome (ORAS) in humans ? Anti-TNF treatment reverses inflammation in ORAS individual and OTULIN-deficient mice ? OTULIN deficiency deregulates M1-polyUb Lapatinib (free base) signaling and causes sterile inflammation ? Loss of OTULIN has cell-type-specific effects on LUBAC large quantity and signaling A homozygous hypomorphic mutation in the deubiquitinase OTULIN causes a potentially fatal autoinflammatory disorder, which is reconciled in mouse models. Introduction Protein ubiquitination regulates virtually every aspect of cellular homeostasis, in large part through structurally and functionally distinct polyubiquitin (polyUb) signals (Komander and Rape, 2012). PolyUb chains can be linked via one of seven Ub Lys (K) residues (e.g., K63-linked chains) or via Ub Met1 (M1), forming M1-linked (also known as linear) chains. The latter have important roles in regulating the immune system, in which they contribute to regulating nuclear factor-B (NF-B) transcription factors that orchestrate immune responses (Bonizzi and Karin, 2004). Ub chains regulate canonical NF-B activation by mediating timed degradation of the inhibitor of B (IB) proteins but also serve as a scaffolding, recruitment, and activation platform in receptor signaling complexes. Non-degradative K63- and M1-linked chains mediate the key upstream event of recruiting the TGF-activated kinase (TAK1) and the IB kinase (IKK) Mouse monoclonal to LAMB1 complexes, respectively (Jiang and Chen, 2012). K63 and M1 linkages occur in the same Ub polymers (Emmerich et?al., 2013), facilitating TAK1 and IKK co-localization and cross-activation. M1-linked chains are generated by the linear ubiquitin chain assembly complex (LUBAC) consisting Lapatinib (free base) of HOIP, HOIL-1, and SHARPIN (Fiil and Gyrd-Hansen, 2014, Iwai et?al., 2014). LUBAC is recruited to many immune receptors, including TNF-R1, IL-1R, CD40, TLRs, and NOD2, in a Ub-dependent manner. At the receptors, LUBAC ubiquitinates a host of targets, including RIPK1, RIPK2, MyD88, IRAKs, and NEMO, directly or on pre-existing Ub chains (Fiil and Gyrd-Hansen, 2014, Iwai et?al., 2014). Genetic loss of LUBAC components leads to immunodeficiency Lapatinib (free base) (MacDuff et?al., 2015) and inflammatory phenotypes in mice (Gerlach et?al., 2011, Ikeda et?al., 2011, Tokunaga et?al., 2011, Tokunaga et?al., 2009), which can be rescued by co-deletion of TNF-R1 (Gerlach et?al., 2011, Kumari et?al., 2014, Peltzer et?al., 2014, Rickard et?al., 2014). Mutations in LUBAC components also cause inflammatory conditions in humans (Boisson et?al., 2015, Boisson et?al., 2012). Hence, loss of M1-linked chains imbalances immune signaling. Several deubiquitinating enzymes (DUBs), including A20, CYLD, and Cezanne, act as negative regulators of NF-B signaling and are essential for resolving inflammation and the return to homeostasis (Harhaj and Dixit, 2012). OTULIN (also known as FAM105B or Gumby) is the only DUB known to specifically cleave M1 linkages (Keusekotten et?al., 2013, Rivkin et?al., 2013). OTULIN directly binds the LUBAC component HOIP, and knockdown of OTULIN in human cell lines increases M1-linked chains on LUBAC and its substrates (Elliott et?al., 2014, Fiil et?al., 2013, Keusekotten et?al., 2013, Rivkin et?al., 2013, Schaeffer et?al., 2014). Strikingly, while LUBAC translocates to receptor signaling complexes (RSCs), OTULIN is not stably associated with TNF or NOD2 RSCs (Draber et?al., 2015), and how it regulates signaling complexes, e.g., TNF signaling, is unclear (Hrdinka et?al., 2016). Indeed, the physiological role of OTULIN in Lapatinib (free base) the immune system has remained unstudied, since OTULIN loss-of-function mutations lead to early embryonic lethality (E12.5CE14) in mice due to defective Wnt signaling and angiogenesis (Rivkin et?al., 2013). Here, we describe that a homozygous hypomorphic OTULIN mutation in a consanguineous family causes a potentially fatal autoinflammatory disorder Lapatinib (free base) termed OTULIN-related autoinflammatory syndrome (ORAS), which can be managed by Infliximab (anti-TNF neutralizing antibody)..