Dorsomorphin Reduces Type Ⅰ Interferon Expression By Inhibiting CGAMP Production

Cyclic GMP-AMP(cGAMP)synthase(cGAS)has attracted much attention since it was discovered as a DNA recognition receptor.It can induce the expression of type I interferon by recognizing dsDNA,and activate the immune response.cGAS gene knockout studies have shown that the inhibition of cGAS may be used as an effective strategy for treating autoimmune diseases such as Aicardi-Goutieres syndrome(AGS)and systemic lupus erythematosus(SLE).However,the development of cGAS inhibitors has not been very successful.Dorsomorphin(Compound C)is a potent,selective and reversible inhibitor of AMPK.But In this dissertation,we discovered a new function of Dorsomorphin.It can reduce type I interferon expression by inhibiting the production of cGAMP,and may have therapeutic effect on autoimmune diseases.Firstly,we detected the expression of IFNβ by qRT-PCR and ELISA,and determined that Dorsomorphin could inhibit the dsDNA-induced type I interferon expression,which is not dependent on cGAMP or dsRNA-mediated signaling reactions.Next,we validated whether the inhibition of type I interferon expression by Dorsomorphin was associated with AMPK in AMPK knockout cells.The results showed that AMPK-deficient did not affect the Dorsomorphin-mediated inhibitory effect of type I interferon expression.To explore the role of Dorsomorphin in the cGAS-STING signaling pathway,we first examined the effect of Dorsomorphin on the activity of cGAS enzyme in vitro,and found that Dorsomorphin had no effect on the function of cGAS in recognizing dsDNA and utilizing ATP.Then,we introduced the plasmids overexpressing TBK1 and IRF3 into STING-deleted cells,qRT-PCR and Western Blot data showed that Dorsomorphin did not inhibit the expression of TBK1 and IRF3-induced type I interferon,indicating that Dorsomorphin did not target on these two proteins which are downstream of STING.Based on the above experimental results,we believe that Dorsomorphin reduces the expression of type I interferon by inhibiting the production of cGAMP.To test this hypothesis we examined the cGAMP production by in vitro and in vitro measures.In vitro assayed and LC-MS data showed that Dorsomorphin had the capability of reducing cGAMP synthesis by 50% at 10 μM.In addition,we validated the feasibility of Dorsomorphin in treating autoimmune diseases in TREX1 knockout cell lines and MFFcells derived from knockout mice,and found that Dorsomorphin could effectively reduce the expression of type I interferon and ISGs caused by TREX1-deficiency.These data demonstrate a new and inverse correlation between Dorsomorphin and type I interferon production in dsDNA signaling,and suggest that Dorsomorphin may serve as a small molecule drug for future autoimmune therapies.