Fig. 7

Zebrafish and human LGP2s promote MDA5 signaling under low concentrations of poly(I:C) and downregulate RIG-I/MDA5 signaling mainly under high concentrations of poly(I:C) in mammalian cells (A, B) DrLGP2 and HsLGP2 promoted human IFNβ activation by HsMDA5 at a high dose and downregulated IFN response by HsRIG-I at a high dose in mammalian cells. HEK293T cells seeded in 24-wells plates were transfected with HsIFNβpro-luc, DrLGP2 or HsLGP2 at increasing doses, together with HsRIG-I (A) or HsMAD5 (B) (200 ng each). 24 h later, cells were transfected again with or without poly(I:C) (2 μg/ml) for another 24 h, followed by luciferase assays. P values were calculated using ANOVA. **P<0.01. (C, D) HsLGP2 negatively regulated zebrafish RIG-I signaling in mammalian cells. HEK293T cells seeded in 24-wells plates were transfected as in A with the indicated plasmids. (E–G) Titration of HsLGP2 expression revealed differential regulation of RIG-I- and MDA5-triggered IFN signaling by HsLGP2 in the presence of poly(I:C) in mammalian cells. HEK293T cells seeded in 24-wells plates were transfected with HsIFNβpro-luc, HsLGP2 at increasing doses, together with HsRIG-I (E) or HsMAD5 (F, G) (200 ng each). 24 h later, cells were transfected with or without poly (I:C) at 2 μg/ml (E, F) or at 4 ng/ml (G) for another 24 h, followed by luciferase assays. P values were calculated using ANOVA. **P<0.01. (H–K) Titration of HsMDA5/MsRIG-I showed that HsLGP2 promoted HsMDA5 signaling under low concentrations of poly (I:C) and downregulate HsRIG-I signaling mainly under high concentrations of poly (I:C) in mammalian cells. HEK293T cells seeded in 24-wells plates were transfected with HsIFNβpro-luc, HsLGP2, together with increasing doses of HsMDA5 (H, K) or HsRIG-I (J, K). 24 h later, cells were transfected with or without poly (I:C) at 4 ng/ml (H, J) or 2 μg/ml (I K) for another 24 h, followed by luciferase assays.