Fig. 5: The cGAS–STING pathway inhibits cAMP-PKA signaling by activating PDE.

a Representative immunoblot analysis of UCP1 expression, and phosphorylation of PKA substrates, HSL, and TBK1 in brown adipocytes treated with 10 nM 2′3′-cGAMP at different time points as indicated. Representative immunoblot analysis of UCP1 expression, and the phosphorylation of PKA substrates, HSL and TBK1 in b STING RNAi or c cGAS RNAi brown adipocytes treated with 10 nM 2′3′-cGAMP, 10 μM ABT-737 or 4 μM nigericin for 12 h. Representative immunoblot analysis of UCP1 expression, and the phosphorylation of PKA substrates, HSL, and TBK1 in d cGAS-, e STING-, or f TBK1/IKKε-suppressed brown adipocytes treated with or without 10 nM 2′3′-cGAMP or 10 μM H89 for 12 h. g cAMP levels in scramble and DsbA-L-suppressed brown adipocytes treated with or without 250 μM IBMX or 10 μM zardaverine (Zarda) for 15 min (n = 3 for each group). h cAMP levels in brown adipocytes treated with or without 10 nM 2′3′-cGAMP for 6 h followed by treatment with or without 250 μM IBMX or 10 μM zardaverine (Zarda) for 15 min (n = 3 for each group). cAMP levels in primary adipocytes isolated from iWAT of wild-type and STING-deficient mice (STING^gt) (n = 3 for each group) treated with or without 10 nM 2′3′-cGAMP for 6 h followed by treatment of 10 μM zardaverine (Zarda) for 15 min in the i absence or j presence of CL316243. PDE activities were measured in primary adipocytes isolated from iWAT of k STING^gt or l cGAS^−/− mice (n = 3 for each group) treated with or without 10 nM 2′3′-cGAMP for 6 h. Data are presented as mean ± SEM of biologically independent samples, *p < 0.05, **p < 0.01, and ***p < 0.001 by unpaired two-tailed t-test (for comparison between two groups) or one-way ANOVA (for comparison of multiple groups).