Fig. 5: Macrophage AMPK regulates IL-1β by phosphorylating SUCLA2.

a Schematic representation of the potential substrate of AMPK in succinate formation, and this image was created in BioRender. Zang, Y. (2025) https://BioRender.com/e16k510. Co-immunoprecipitation analysis of the interaction of AMPKα with SUCLA2 (b) or SUCLG2 (c) in RAW 264.7 cells. d Immunoblot analysis of indicated proteins in BMDMs that are transfected with siRNA for 30 h followed by stimulation with 100 ng/mL LPS for an additional 12 h. e Immunoblot analysis of indicated proteins in AMPKα^fl/fl BMDMs (Flox) and LysM-Cre, AMPKα^fl/fl BMDMs (MKO) that are transfected with siRNA for 18 h followed by stimulation with 100 ng/mL LPS for an additional 12 h. f Immunoblot analysis of the expression of SUCLG1 and SUCLA2 after AMPKα was knocked down by siRNA for 48 h in RAW 264.7 cells. g The relative enzymatic activity of SUCLA2 (the direction from succinyl-CoA to succinate) was detected after AMPKα was knocked down by siRNA for 36 h followed by stimulation with 100 ng/mL LPS for an additional 12 h in RAW264.7 cells (n = 3 biological replicates). h In vitro phosphorylation analysis was performed by mixing purified His-CAMKKβ, His-AMPKα1β1γ1 and His-SUCLA2 in the presence of ATP-g-S, and immunoblot analysis of indicated proteins with indicated antibodies. i Venn diagram was used to integrate the phosphorylation site that was detected by mass spectrometry and predicted by GPS 5.0 (http://gps.biocuckoo.cn/) or HPRD. j Protein sequence alignment indicated the conservation of SUCLA2 at Ser60 across multiple species. k Immunoblot analysis of indicated proteins in the in vitro kinase assay that mixed the purified His-CAMKKβ, His-AMPKα1β1γ1 with His-SUCLA2 (WT) or His-SUCLA2 (S60A). l Immunoblot analysis of indicated proteins in BMDMs after incubation with 200 µM A-769662 for 3 h. m In vitro phosphorylation analysis was performed by mixing purified His-CAMKKβ, His-AMPKα1β1γ1 and His-SUCLA2 (WT) or His-SUCLA2 (S60A) in the presence of ATP-g-S, and immunoblot analysis of indicated proteins with indicated antibodies. The enzymatic activity (the direction from succinyl-CoA to succinate) of purified WT-SUCLA2 (n) or S60A-SUCLA2 (o) after incubation with AMPK in vitro (n = 3 biological replicates). p The enzymatic activity (the direction from succinyl-CoA to succinate) of purified WT-SUCLA2, S60A-SUCLA2, and S60D-SUCLA2 in the same protein content (n = 4 biological replicates). q–r The relative gene expression of IL-1β in RAW264.7 cells that overexpress human WT-SUCLA2, S60A-SUCLA2 and S60D-SUCLA2 through lentivirus infection for 48 h followed the treatment by 100 ng/mL LPS for 6 h in the condition of glutamine replete (q) or deprived (r) condition (n = 4 biological replicates). The relative gene expression of IL-1β in RAW264.7 cells that overexpress human WT-SUCLA2 with S60A-SUCLA2 (s) or S60D-SUCLA2 (t) through lentivirus infection for 48 h, the cells were treated with 200 µM A-769662 for 3 h in advance followed by 100 ng/mL LPS for 6 h (n = 4 biological replicates). Data are presented as the mean ± SEM, groups were compared by the unpaired two-tailed Student’s t test (g) or one-way ANOVA followed by Bonferroni’s multiple-comparisons test (q, r) or two-way ANOVA followed by Bonferroni’s multiple-comparisons test (n, o, p, s, t), representative data are shown from one of the three independent experiments (b–f, h, k–m). P < 0.05 was considered to be statistically significant.