Mettl3-mediated mRNA m6A methylation promotes dendritic cell activation

Huamin Wang,Lijia Ma,Xiang Hu,Yan Gu,Juan Liu,Xuetao Cao,Mingyan Huang,Qi Zhou

doi:10.1038/s41467-019-09903-6

Abstract

N6-methyladenosine (m6A) modification plays important roles in various cellular responses by regulating mRNA biology. However, how m6A modification is involved in innate immunity via affecting the translation of immune transcripts remains to be further investigated. Here we report that RNA methyltransferase Mettl3-mediated mRNA m6A methylation promotes dendritic cell (DC) activation and function. Specific depletion of Mettl3 in DC resulted in impaired phenotypic and functional maturation of DC, with decreased expression of co-stimulatory molecules CD40, CD80 and cytokine IL-12, and reduced ability to stimulate T cell responses both in vitro and in vivo. Mechanistically, Mettl3-mediated m6A of CD40, CD80 and TLR4 signaling adaptor Tirap transcripts enhanced their translation in DC for stimulating T cell activation, and strengthening TLR4/NF-κB signaling-induced cytokine production. Our findings identify a new role for Mettl3-mediated m6A modification in increasing translation of certain immune transcripts for physiological promotion of DC activation and DC-based T cell response.

Highlights

N6-methyladenosine (m6A) modification plays important roles in various cellular responses by regulating mRNA biology
We found that Tirap mRNA level was similar in Mettl3KO dendritic cell (DC) compared with Mettl3WT DC (Fig. 5a), CD40 and CD80 had similar mRNA level but decreased protein level in Mettl3KO DC (Fig. 5a)
These results indicated that the mRNA of Tirap, CD80, and CD40 had a decreased translation efficiency in Mettl3KO mature DC (maDC) in vivo

Summary

55 KD 60 KD

Overexpression of M3_Wt, but not M3_Mut, in OVA(323–339)-pulsed Mettl3WT and Mettl3KO DC both induced a larger amount of CD45.2+CD4+ T cells in the recipient mice (Fig. 3c) These data indicate that Mettl[3] is required for DC function in promoting T- cell proliferation via its m6A catalytic activity, both in vitro and in vivo. Consistent with our observations, deficiency of Mettl[3] caused downregulation of the downstream effector molecules of the TLR4/NF-κB pathway, such as MHC class II molecule H2-Eb2, cytokines IL-6 and IL-12b mRNA level (Fig. 4a), which was validated by qPCR (Fig. 4b) In both replicates of RNA-seq, the downregulated transcripts (Supplementary Table 1) in Mettl3KO DC compared with Mettl3WT DC were enriched in immune responses, especially the innate

70 KD 45 KD

46 KD 43 KD p65 p-Erk Erk p-Jnk

Discussion

55–70 KD 45 KD

Methods