E3 Ubiquitin Ligase FBXW7 Promotes TMPD Induced Systemic Lupus Erythematosus And The Mechanism Research

Systemic lupus erythematosus(SLE)is a systemic autoimmune disease,leading to multi-organ dysfunction with the main feature of lupus nephritis and autoantibody production.By far,the pathogenesis has not been fully elaborated,which made it crucial to build the SLE model and explore the mechanism.As a tumor suppresser gene,the role of E3 ubiquitin ligase FBXW7 has been well characterized in cancer.FBXW7 can promote the ubiquitination and subsequent degradation of various oncoproteins including c-Myc,Cyclin E1 and Notch through ubiquitin-proteasome system.Whereas,the potential role of FBXW7 in inflammation,especially in autoimmune diseases has not been reported.Our previous work demonstrated that FBXW7 could positively regulate type Ⅰ interferon production in antivral innate imuunity,which intreated us to explore the potential role of FBXW7 in inflammatory autoimmune diseases.We built mice SLE model with TMPD to investigate the effection of FBXW7 deficiency in myeloid cells in mice SLE.First we constructed myeloid-cell-specific FBXW7 deficient(Lysm+FBXW7f/f)C57BL/6 mice and built FBXW7f/f and Lysm+FBXW7f/fmice SLE model with peritoneal injection of TMPD.Six months later,mice were sacrificed and found that anti-Sm/RNP,anti-AN A antibody levels in Lysm+FBXW7f/f mice serum were lower than that of FBXW7f/f mice,similar results were observed with immune complex accumulation in kidneys.Lysm+FBXW7f/f mice showed decreased glomerulonephritis,glomerular mesangial cell proliferation and base-membrane thickness than FBXW7f/f mice.By flow cytometry,we found that the accumulation of monocytes/macrophages and neutrophils in kidneys was also lower in Lysm+FBXW7f/f mice than FBXW7f/f mice.Two weeks later,flow cytometry analysis of peritoneal cells showed that Lysm+FBXW7f/f mice recruited less CD11b+Ly6Chi inflammatory monocytes into peritoneal cavity than FBXW7f/f mice.Consistently,IFN-a,IL-6,TNF-a and CCL2 levels in peritoneal lavage fluids were also lower in Lysm+FBXW7f/f mice compared with FBXW7f/f mice.We also found that FBXW7 deficiency does not affect cells chemotaxis ability or TLR7 triggered innate immune responses in vitro and in vivo.Meanwhile,we noticed that the apoptotic cells in peritoneal cavity of Lysm+FBXW7f/f mice were dramatically decreased compared with FBXW7f/f mice.It has been reported that intraperitoneal injection with TMPD could induce cell apoptosis,which had been considered as a critical event in the pathogenesis of mice lupus.This mechanism was similar to pathogenesis of clinic SLE.Therefore,we focused our attention on the regulation of FBXW7 in TMPD induced cell apoptosis.In primary macrophages,we found that the proportions of apoptotic cells in FBXW7 deficient macrophages were significantly decreased than FBXW7f/f macrophages in response to TMPD treatment,as well as caspase-3 activation.Overexpression of FBXW7 in Hela cells could significantly increase cell apoptosis in the present of TMPD.Mechanically,MCL1 has been reported as an anti-apoptotic factor which belongs to BCL2 family,and it is one of the substrates of E3 ubiquitin ligase FBXW7.We found that FBXW7 could interact with MCL1 and promote MCL1 degradation by K48-linked ubiquitination which ultimately relieved MCL1 regulation in TMPD induced apoptosis.The present study revealed that FBXW7 played crucial role in mice SLE by promoting TMPD induced cell apoptosis,which eventually cause inflammation and autoimmune responses.Our work may provide novel ideas and theoretical support in understanding SLE pathogenesis.