TMEM203 is a binding partner and regulator of STING-mediated inflammatory signaling in macrophages.

Regulation of IFN signaling is critical in host recognition and response to pathogens while its dysregulation underlies the pathogenesis of several chronic diseases. STimulator of IFN Genes (STING) has been identified as a critical mediator of IFN inducing innate immune pathways, but little is known about direct coregulators of this protein. We report here that TMEM203, a conserved putative transmembrane protein, is an intracellular regulator of STING-mediated signaling. We show that TMEM203 interacts, functionally cooperates, and comigrates with STING following cell stimulation, which in turn leads to the activation of the kinase TBK1, and the IRF3 transcription factor. This induces target genes in macrophages, including IFN-ß. Using Tmem203 knockout bone marrow-derived macrophages and transient knockdown of TMEM203 in human monocyte-derived macrophages, we show that TMEM203 protein is required for cGAMP-induced STING activation. Unlike STING, TMEM203 mRNA levels are elevated in T cells from patients with systemic lupus erythematosus, a disease characterized by the overexpression of type I interferons. Moreover, TMEM203 mRNA levels are associated with disease activity, as assessed by serum levels of the complement protein C3. Identification of TMEM203 sheds light into the control of STING-mediated innate immune responses, providing a potential novel mechanism for therapeutic interventions in STING-associated inflammatory diseases.

The combination of a synthetic promoter and a CMV promoter improves foreign gene expression efficiency in myocytes.

Skeletal muscle is becoming an attractive target tissue for gene therapy. Nevertheless, the low level of gene therapeutic expression in this tissue is the major limitation to it becoming an ideal target for gene transfer. The promoter is important element for gene transcription; however, the gene expression efficiencies and specificities of viral promoters and skeletal muscle-specific promotors are in themselves limiting factors. In this study, we established a dual-promoters system in skeletal muscle using a cytomegalovirus (CMV) promoter and a skeletal muscle-specific synthetic promoter. Mouse myoblast cell line C2C12 cells were transfected with the system. We demonstrated that the dual-promoters system could significantly improve exogenous gene expression rate in vitro when compared with a single CMV promoter system and a skeletal muscle-specific synthetic promoter system in C2C12 cell line, by 69.48% and 41.93%, respectively. Next, we evaluated the system efficiency in vivo, the results showed that the dual-promoters system increased gene expression in mice 1.23-fold and 1.60-fold, respectively compared with expression controlled by the two single promoter vectors. Finally, we tested the dual-promoters system in growth hormone-releasing hormone (GHRH) gene therapy, and revealed that when these two promoters co-drove the GHRH gene expression in vivo animal growth was enhanced significantly. All these results indicate that use of the dual-promoter vector was more efficient for gene expression in skeletal muscle tissue than use of the single promoter vectors. These finding could, hopefully, lead to the development of a high efficiency expression system in myocytes and form an ideal approach for gene therapy.