Fig. 6: Intracellular SP induce ER stress activation ERAD pathway degrading STING protein.

A GSEA bubble plot of GO enrichment in Mock and SP group (n = 4) in HCT116 cells. B TEM showing SP (red row) and ER (yellow row) in HCT116 cells (based on Fig. 1F). C Representative of IF showing ER treated 24 h with or without SP (MOI = 0.01) in HCT116 cells; Nucleus, DAPI, red; Light blue, ER; SP is without GFP marker; White row, points to ER stress (ER swelling); Scale bar = 15 μm. D Representative of IF showing p-STING in HCT116. p-STING, STING phosphorylate; Nucleus, DAPI, red; Vehicle, without treating 4 h with cGAMP. Mock, without treating SP; SP, treating 24 h with SP (MOI = 0.01); SP is without GFP marker. E, F Quantification of ER stress and p-STING in HCT116 corresponding to (C, D). Data are mean ± SEM from n = 4. G WB analysis p-PERK, PERK, IRE1a, ATF6, and XBP1s protein with SP (MOI = 0.01) for 48 hours in HCT116 cells. H–J WB analysis of STING protein with CHX, MG132, CB5083, BafA1 or chloroquine after SP treatment. K Co-IP analysis interaction STING with SEL1L, treated by SP (MOI = 0.01) and MG132 (25 µM), for 48 h in HCT116 cells; IP, STING. L WB analysis STING protein, treated by SP (MOI = 0.01) and SEL1L-KO, for 48 h in HCT116 cells. SEL1L-KO, SEL1L knockout in HCT116 cells. M WB analysis p-PERK, PERK, IRE1a, ATF6, and XBP1s protein with SP (MOI = 0.01) for 48 h in WT or SEL1L-KO HCT116 cells. N ELISA analysis IFNβ secretion in WT or KO HCT116 cells treated with cGAMP for 3 h after infected SP (MOI = 0.01) for 48 h. Data are mean ± SEM from n = 3. O Schematic diagram for coculture SP with SEL1L-KO MC38 in vivo. P Proportion (left) and flow cytometry image (right) of MHC-II⁺ macrophage. Data are mean ± SEM from n = 3 P values were determined by unpaired two-tailed t-tests unless otherwise specified (one-way ANOVA was used to multiple group comparisons). *p < 0.05, **p < 0.01, ***p < 0.001. Source data are provided as a Source data file.