Activation of T cells accompanies remarkable enhancement of metabolism. Sufficient and continuous nutrient supply is therefore important to support immune reaction in T cells. However, the mechanism of the promotion of nutrient incorporation in activated T cells has not been elucidated. In this study, we show that L-type amino acid transporter 1 (LAT1) is a major transporter for essential amino acids into activated human T cells. CD3/CD28 stimulation in primary human T cells triggered dramatic induction of LAT1 expression mediated by NF-κB and AP-1. Functional disturbance of LAT1 by a specific inhibitor and by small interfering RNA in human T cells suppressed essential amino acid uptake and induced a stress response mediated by DNA damage–inducible transcript 3 to attenuate cytokine production via inhibition of NF-κB and NFAT activities. These results uncover the previously unknown mechanism by which T cells accelerate essential amino acid uptake upon activation and adapt to essential amino acid starvation. Our results also raise the possibility for application of an LAT1 inhibitor as a new drug for therapy of disease caused by exaggerated immune response.

Protein kinase C-theta (PKCθ) is a member of the novel, Ca 2+ -independent PKC subfamily, which plays an important and non-redundant role in several aspects of T cell biology. Much progress has been accomplished in understanding the function of PKCθ in the immune system and its unique translocation to the immunological synapse in Ag-stimulated T lymphocytes. Biochemical and genetic approaches revealed that PKCθ is required for the activation of mature T cells as well as for their survival. Mutation of the PKCθ gene leads to impaired receptor-induced stimulation of the transcription factors AP-1, NF-κB and NFAT, which results in defective T cell activation, and to aberrant expression of apoptosis-related proteins, resulting in poor T cell survival. Furthermore, PKCθ-deficient mice display defects in the differentiation of T helper subsets, particularly in Th2 and Th17-mediated inflammatory responses. Therefore, PKCθ is a critical enzyme that regulates T cell function at multiple stages, and it represents an attractive drug target for allergic and autoimmune diseases.

13513 Background: MicroRNAs (miRNAs) are small non-cording RNAs (∼ 22 nucleotide) that regulate gene expression by suppressing their target mRNAs at post-transcriptional level. Previous studies from our group have identified a number of dis-regulated miRNAs due to the loss of p53 tumor suppressor in cancer cell lines. As part of the efforts to further investigate the in vivo biological significance of these miRNAs, the expression of both hsa-let-7g and hsa-miR-200c were investigated using formalin-fixed paraffin embedded (FFPE) colon cancer specimens to evaluate the potential correlation with chemosensitivity and tumorigenesis. Methods: Forty-six patients with recurrent or residual colon cancer lesion assessable were treated with 5-FU based antimetabolite S-1. This includes twenty-one pair of tumor and normal samples. Total RNAs were isolated from these samples FFPE specimens (contains either > 90% normal or > 90% tumor tissue). cDNAs were synthesized using primers specific for hsa-let-7g, hsa-miR-200c and internal control 5S. The expression levels of each particular miRNAs were quantified using real time qRT-PCR analysis. The expression level of each miRNAs was quantified by measuring the difference of threshold cycle (CT) of candidate miRNAs and internal control 5S (Δ-CT). Results: The expression level of hsa-let-7g was significantly higher in tumor tissues compare to normal tissues (p=0.0026; Wilcoxon test). In the forty-six tumor tissues, the expression level of hsa-let-7g in disease response group (patients group of complete response, partial response and no change after chemotherapy) was significantly lower than the disease progression group (p=0.03; Mann-Whitney test). The expression of hsa-miR-200c was significantly over-expressed in tumor tissues compare to normal tissues (p=0.0001; Wilcoxon test). Although hsa-let-7g is strongly associated with patient’s response to S-1 treatment, it is not a prognostic factor for predicting survival. Conclusion: hsa-let-7g and hsa-miR-200c may be associated with tumorigenesis in colon cancer. In addition, hsa-let-7g may be a significant indicator for chemoresponse to S-1 based chemotherapy. No significant financial relationships to disclose.

Differentiation of naive CD4+ T cells into helper T (Th) cells is controlled by a combination of several transcriptional factors. In this study, we examined the functional role of the Runx1 transcription factor in Th cell differentiation. Naive T cells from transgenic mice expressing a dominant interfering form of Runx1 exhibited enhanced interleukin 4 production and efficient Th2 differentiation. In contrast, transduction of Runx1 into wild-type T cells caused a complete attenuation of Th2 differentiation and was accompanied by the cessation of GATA3 expression. Furthermore, endogenous expression of Runx1 in naive T cells declined after T cell receptor stimulation, at the same time that expression of GATA3 increased. We conclude that Runx1 plays a novel role as a negative regulator of GATA3 expression, thereby inhibiting the Th2 cell differentiation.

The molecular basis of T cell anergy is not completely understood. We show that in antigen-primed anergic murine CD4(+) T cells the linker for activation of T cells (LAT) is hypophosphorylated upon CD3/CD28 restimulation. Signaling events downstream of LAT (PLCgamma1 phosphorylation and p85 [PI3-K] association) were impaired, whereas upstream events (CD3zeta and ZAP-70 phosphorylation) remained intact. LAT recruitment to the immunological synapse and its localization in detergent-resistant membrane (DRM) fractions were defective in anergic T cells. These defects resulted from impaired palmitoylation of LAT and were selective since the DRM localization and palmitoylation of Fyn were intact. This LAT defect was independent of Cbl-b and did not reflect enhanced LAT degradation. These results identify LAT as the most upstream target of anergy induction; moreover, they suggest that regulation of the amount of LAT in the immunological synapse and DRM by posttranslational palmitoylation contributes to the induction of T cell anergy.