It should also be noted that there were no significant differences for any of the observed phenotypes between male and female ABIN1[D485N] mice. T cell activation, and inflammatory cytokine release.1 Multiple factors contribute to the immune response in SLE, including genetic, epigenetic, immunoregulatory, environmental, and hormonal factors.1 Lupus nephritis (LN) occurs in about 50% of patients with SLE and is a major cause of morbidity and mortality.2 The incidence of LN varies among different ethnic groups, suggesting that genetic factors play an important role in the pathogenesis. Patients with African ancestry are at increased risk for LN.3 Immunosuppressive treatment is effective in only about 50% of patients with LN,4 and that therapy is associated with undesirable short- and long-term adverse effects. Thus, identifying the molecular mechanisms responsible for the pathogenesis of LN is necessary to define more specific diagnostic and therapeutic targets. However, the complex interactions of genetic risks, environmental factors, and molecular events that contribute to the development of LN are only beginning to be defined. The transcription factor nuclear factor-B (NF-B) regulates the expression of hundreds of genes that control cell proliferation and survival, the cellular stress response, innate immunity, and inflammation. Dysregulation of NF-B activity is usually associated with many human diseases, especially those including chronic inflammation, and recent studies suggest that NF-B plays a role in the incidence and severity of LN as well. 5C9 Immunohistochemistry-based studies have shown enhanced glomerular and tubular expression of NF-B, NF-B regulatory proteins, and NF-B target proinflammatory cytokines in renal biopsy specimens from patients with LN compared with normal controls and patients with minimal-change disease.8,9 Another report found that pharmacologic inhibition of NF-B reduced the development of autoantibodies and renal impairment in SLE-susceptible FcRIIb-deficient mice.5 Treatment of spontaneous SLECdeveloping SWRxNZB mice with a flavonoid, apigenin, inhibited NF-BCmediated events in T cells and suppressed serum IgG levels, resulting in delayed appearance of nephritis.6 NF-B is activated by a variety of immune, inflammatory, and stress stimuli through cytokine and toll-like receptors (TLRs) and regulated through a complex interplay of proteins (recently reviewed).10 In resting cells, NF-B is sequestered in the cytoplasm in an inactive state by binding to inhibitor of B (IB) proteins.11,12 Following activation, the IB is phosphorylated, polyubiquitinated through Lys48 linkages, and then degraded by the proteasome. This releases an active NF-B complex to translocate to the nucleus and drive target gene expression. In the canonical NF-B pathway, phosphorylation of IB is usually mediated by the IB kinase (IKK) complex, which consists of , , and subunits.13 IKK is the regulatory subunit also referred to as NF-B essential modulator (NEMO). Activation of IKK is usually mediated by TGF-Cactivated kinase 1 (TAK1), and recruitment of TAK1 to IKK is usually regulated by an integral complex of proteins that is put together through protein-protein interactions BGB-102 to lysine 63-linked polyubiquitin chains.14 NEMO binding to head-to-tail linked linear polyubiquitin chains or the linear ubiquitin assembly complex also activates the canonical NF-B pathway.15C17 The ubiquitin-editing protein, A20, and ubiquitin-binding protein, A20 binding inhibitor of NF-B 1 (ABIN1) have important inhibitory functions in NF-B signaling.18,19 ABIN1 binds to lysine 63-linked and linear polyubiquitin chains and contains the same ubiquitin-binding domain as NEMO that facilitates binding to other regulatory proteins, such as TRAF2/6, RIP1, and IRAK1.16,20C22 It is not obvious how ABIN1 inhibits NF-B activity, but two possible mechanisms have been proposed. One is that ABIN1 binding competes BGB-102 with NEMO binding to proteins required for activation of IKK, and the second is that ABIN1 recruits A20 to the IKK regulatory complex,23 where A20 disrupts the interactions needed for IKK activation by removing lysine 63- Keratin 18 antibody or linear polyubiquitin moieties from regulatory proteins.24 A20 has also been reported to mediate proteasomal degradation of ubiquitin processing proteins that mediate IKK activation.25 We previously reported that ABIN1[D485N] transgenic mice with disrupted ABIN1 lysine 63 and linear polyubiquitin binding have enhanced NF-B and mitogen-activated protein kinase (MAPK) signaling in B cells, bone marrowCderived macrophages, and dendritic cells after stimulation with TLR agonists and developed an SLE-like autoimmune disease with enlarged spleens and lymph nodes and autoantibodies in the serum.26 Crossing ABIN1[D485N] mice with mice deficient for the TLR/IL-1R adaptor protein MyD88 suppressed the autoimmunity, indicating that a function for ABIN1 in autoimmunity is TLR/IL-1R-dependent. In the present study, we show that ABIN1[D485N] mice develop diffuse proliferative GN similar to class III and IV human LN. We also found that two BGB-102 SNPs in gene could be mechanistically involved in LN disrupted regulation.