Foxp3 regulatory T (Treg) cells, which suppress immune responses, are highly proliferative in vivo. However, it remains unclear how the active replication of Treg cells is maintained in vivo. Here, we show that branched-chain amino acids (BCAAs), including isoleucine, are required for maintenance of the proliferative state of Treg cells via the amino acid transporter Slc3a2-dependent metabolic reprogramming. Mice fed BCAA-reduced diets showed decreased numbers of Foxp3 Treg cells with defective in vivo proliferative capacity. Mice lacking Slc3a2 specifically in Foxp3 Treg cells showed impaired in vivo replication and decreased numbers of Treg cells. Slc3a2-deficient Treg cells showed impaired isoleucine-induced activation of the mTORC1 pathway and an altered metabolic state. Slc3a2 mutant mice did not show an isoleucine-induced increase of Treg cells in vivo and exhibited multi-organ inflammation. Taken together, these findings demonstrate that BCAA controls Treg cell maintenance via Slc3a2-dependent metabolic regulation.

Extracellular ATP is released from live cells in controlled conditions, as well as dying cells in inflammatory conditions, and, thereby, regulates T cell responses, including Th17 cell induction. The level of extracellular ATP is closely regulated by ATP hydrolyzing enzymes, such as ecto-nucleoside triphosphate diphosphohydrolases (ENTPDases). ENTPDase1/CD39, which is expressed in immune cells, was shown to regulate immune responses by downregulating the ATP level. In this study, we analyzed the immunomodulatory function of ENTPDase7, which is preferentially expressed in epithelial cells in the small intestine. The targeted deletion of Entpd7 encoding ENTPDase7 in mice resulted in increased ATP levels in the small intestinal lumen. The number of Th17 cells was selectively increased in the small intestinal lamina propria in Entpd7−/− mice. Th17 cells were decreased by oral administration of antibiotics or the ATP antagonist in Entpd7−/− mice, indicating that commensal microbiota-dependent ATP release mediates the enhanced Th17 cell development in the small intestinal lamina propria of Entpd7−/− mice. In accordance with the increased number of small intestinal Th17 cells, Entpd7−/− mice were resistant to oral infection with Citrobacter rodentium. Entpd7−/− mice suffered from severe experimental autoimmune encephalomyelitis, which was associated with increased numbers of CD4+ T cells producing both IL-17 and IFN-γ. Taken together, these findings demonstrate that ENTPDase7 controls the luminal ATP level and, thereby, regulates Th17 cell development in the small intestine.

Crosslinking of the immunoglobulin receptor FcεRI activates basophils and mast cells to induce immediate and chronic allergic inflammation. However, it remains unclear how the chronic allergic inflammation is regulated. Here, we showed that ecto-nucleotide pyrophosphatase-phosphodiesterase 3 (E-NPP3), also known as CD203c, rapidly induced by FcεRI crosslinking, negatively regulated chronic allergic inflammation. Basophil and mast cell numbers increased in Enpp3(-/-) mice with augmented serum ATP concentrations. Enpp3(-/-) mice were highly sensitive to chronic allergic pathologies, which was reduced by ATP blockade. FcεRI crosslinking induced ATP secretion from basophils and mast cells, and ATP activated both cells. ATP clearance was impaired in Enpp3(-/-) cells. Enpp3(-/-)P2rx7(-/-) mice showed decreased responses to FcεRI crosslinking. Thus, ATP released by FcεRI crosslinking stimulates basophils and mast cells for further activation causing allergic inflammation. E-NPP3 decreases ATP concentration and suppresses basophil and mast cell activity.

Although LT can be successful for treating end-stage liver disease in children, some patients develop fibrosis around the central vein area (PCF). This raises the possibility that PCF could lead to later cirrhosis and graft failure. Here, we report a retrospective immunohistochemical study of 28 patients who received a live donor liver transplant. We assessed the incidence and etiology of PCF using CD3, CD20, HLA-DR, and C4d-specific antibodies. Histological evidence of PCF was found in 13 cases (46.4%), of which 11 (84.6%) had experienced ACR and/or CP events post-transplant. Immunohistochemical evaluation revealed significantly stronger staining with these antibodies in the central vein area in PCF, especially for CD20 and C4d. This implies humoral immunopathology and suggests involvement of humoral immunity in the development of PCF. These results further imply that suppression of cellular immunity alone is insufficient to prevent PCF. We therefore suggest that suppression of both humoral and cellular immunity in combination would be required for prevention of PCF.

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Under conditions of heat shock at 42 degrees C, mRNAs of HSP (heat shock protein) genes are exported out of the nucleus, whereas bulk poly(A)(+) (polyadenylated) mRNA shows a nuclear accumulation in Saccharomyces cerevisiae. Such a selective mRNA export seems an efficacious strategy of yeast cells to adapt rapidly to stress. Although ethanol stress (10%, v/v) as well as heat shock blocks the export of bulk poly(A)(+) mRNA, the differences and/or similarity between heat shock and ethanol stress in the mechanisms of selective mRNA export still remain to be clarified. We found that ethanol stress induced transcriptional activation of a subset of yeast HSP genes; however, intriguingly, most such transcripts remained in the nucleus in a hyperadenylated state and, as a consequence, were not translated into HSPs. Elimination of ethanol resulted in a rapid shortening of the poly(A) tails of HSP mRNAs, loss of their nuclear retention, and the coincidental synthesis of the respective HSPs. Since HSP mRNAs are selectively exported from the nucleus in heat-shocked cells, yeast cells respond differently to ethanol stress and heat shock in the 3'-processing and transport of HSP mRNAs. Furthermore, these results also suggest that hyperadenylation and nuclear retention of mRNAs might be used as a means to control eukaryotic gene expression under stressed conditions.

Streptomyces castaneoglobisporus HUT6202 overproduces a diffusible melanin-like pigment. An operon, designated mel, containing a gene that encodes tyrosinase, which is involved in the synthesis of melanin pigment, was cloned from the chromosomal DNA of the microorganism into the high-copy plasmid pAK114 and expressed in S. lividans. The tyrosinase activity of the transformed cells was at approximately a 110-fold higher level than that of the same host carrying the plasmid pIJ702, which has the same replication origin as pAK114 and carries the mel operon from S. antibioticus. The sequence analysis of the S. castaneoglobisporus mel operon revealed that an open-reading frame consisting of 378 base pairs(bp), designated ORF378, was found upstream of the tyrosinase gene (TYRC) consisting of 819 bp. In the present study, we constructed a chimeric mel operon consisting of ORF378 from S. castaneoglobisporus and the tyrosinase gene (TYRA) from S. antibioticus. The chimeric mel operon or the S. antibioticus mel operon, which consists of ORF438 and TYRA, expressed the tyrosinase activity in Escherichia coli intracellularly when located under the control of lacZ promoter, and the tyrosinase activity from the former was at a 30-fold higher level than that from the latter. This suggests that the gene contributing to the high expression of the tyrosinase activity in S. castaneoglobisporus is ORF378, rather than TYRC.