During chronic viral infection, virus-specific CD8(+) T cells become exhausted, exhibit poor effector function and lose memory potential. However, exhausted CD8(+) T cells can still contain viral replication in chronic infections, although the mechanism of this containment is largely unknown. Here we show that a subset of exhausted CD8(+) T cells expressing the chemokine receptor CXCR5 has a critical role in the control of viral replication in mice that were chronically infected with lymphocytic choriomeningitis virus (LCMV). These CXCR5(+) CD8(+) T cells were able to migrate into B-cell follicles, expressed lower levels of inhibitory receptors and exhibited more potent cytotoxicity than the CXCR5(-) [corrected] subset. Furthermore, we identified the Id2-E2A signalling axis as an important regulator of the generation of this subset. In patients with HIV, we also identified a virus-specific CXCR5(+) CD8(+) T-cell subset, and its number was inversely correlated with viral load. The CXCR5(+) subset showed greater therapeutic potential than the CXCR5(-) [corrected] subset when adoptively transferred to chronically infected mice, and exhibited synergistic reduction of viral load when combined with anti-PD-L1 treatment. This study defines a unique subset of exhausted CD8(+) T cells that has a pivotal role in the control of viral replication during chronic viral infection.

Follicular regulatory T (Tfr) cells differentiate from conventional regulatory T (Treg) cells and suppress excessive germinal center (GC) responses by acting on both GC B cells and T follicular helper (Tfh) cells. Here, we examined the impact of mTOR, a serine/threonine protein kinase that senses and integrates diverse environmental cues, on the differentiation and functional competency of Tfr cells in response to protein immunization or viral infection. By genetically deleting Rptor or Rictor, essential components for mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), respectively, we found that mTORC1 but not mTORC2 is essential for Tfr differentiation. Mechanistically, mTORC1-mediated phosphorylation of the transcription factor STAT3 induced the expression of the transcription factor TCF-1 by promoting STAT3 binding to the Tcf7 5'-regulatory region. Subsequently, TCF-1 bound to the Bcl6 promoter to induce Bcl6 expression, which launched the Tfr cell differentiation program. Thus, mTORC1 initiates Tfr cell differentiation by activating the TCF-1-Bcl-6 axis during immunization or infection.

SUMMARY Overnutrition activates proinflammatory program in macrophages to induce insulin resistance (IR), but its molecular mechanisms remain incompletely understood. Here we show that saturated fatty acid and lipopolysaccharide, two factors implicated in high-fat diet (HFD)-induced IR, suppress macrophage CGI-58 expression. Macrophage-specific CGI-58 knockout (MaKO) in mice aggravates HFD-induced glucose intolerance and IR, which is associated with augmented systemic/tissue inflammation and proinflammatory activation of adipose tissue macrophages. CGI-58-deficient macrophages exhibit mitochondrial dysfunction due to defective peroxisome proliferator-activated receptor (PPAR)-γ signaling. Consequently they overproduce reactive oxygen species (ROS) to potentiate secretion of proinflammatory cytokines by activating NLRP3 inflammasome. Anti-ROS treatment or NLRP3 silencing prevents CGI-58-deficient macrophages from over-secreting proinflammatory cytokines and from inducing proinflammatory signaling and IR in the co-cultured fat slices. Anti-ROS treatment also prevents exacerbation of inflammation and IR in HFD-fed MaKO mice. Our data thus establish CGI-58 as a suppressor of overnutrition-induced NLRP3 inflammasome activation in macrophages.

SUMMARY How cancer cells shift metabolism to aerobic glycolysis is largely unknown. Here we show that deficiency of α/β-hydrolase domain-containing-5 (Abhd5), an intracellular lipolytic activator that is also known as comparative gene identification-58 (CGI-58), promotes this metabolic shift and enhances malignancies of colorectal carcinomas (CRCs). Silencing of Abhd5 in normal fibroblasts induces malignant transformation. Intestine-specific knockout of Abhd5 in ApcMin/+ mice robustly increases tumorigenesis and malignant transformation of adenomatous polyps. In colon cancer cells, Abhd5 deficiency induces epithelial-mesenchymal transition by suppressing the AMPKα-p53 pathway, which is attributable to increased aerobic glycolysis. In human CRCs, Abhd5 expression falls substantially and correlates negatively with malignant features. Our study is the first to link Abhd5 to CRC pathogenesis. It suggests that cancer cells may develop aerobic glycolysis by suppressing Abhd5-mediated intracellular lipolysis.

Metabolic reprogramming in stromal cells plays an essential role in regulating tumour growth. The metabolic activities of tumour-associated macrophages (TAMs) in colorectal cancer (CRC) are incompletely characterized. Here, we identify TAM-derived factors and their roles in the development of CRC. We demonstrate that ABHD5, a lipolytic co-activator, is ectopically expressed in CRC-associated macrophages. We demonstrate in vitro and in mouse models that macrophage ABHD5 potentiates growth of CRC cells. Mechanistically, ABHD5 suppresses spermidine synthase (SRM)-dependent spermidine production in macrophages by inhibiting the reactive oxygen species-dependent expression of C/EBPɛ, which activates transcription of the srm gene. Notably, macrophage-specific ABHD5 transgene-induced CRC growth in mice can be prevented by an additional SRM transgene in macrophages. Altogether, our results show that the lipolytic factor ABHD5 suppresses SRM-dependent spermidine production in TAMs and potentiates the growth of CRC. The ABHD5/SRM/spermidine axis in TAMs might represent a potential target for therapy.

Mammals store excess triglyceride (TG) in the large lipid droplet (LD) of white adipose tissue . During a period of starvation or increased energy demand, the stored TG is used as an energy source via a process called lipolysis. Excessive lipid accumulation in nonadipose tissues ("ectopic" fat deposition) is lipotoxic ( 1 ). Increased TG accumulation in liver hepatocytes is a hallmark of nonalcoholic fatty liver disease (NAFLD) ( 2, 3 ). NAFLD is the most common liver disease in the United States ( 4-6 ). In the general population, the estimated prevalence of NAFLD is as high as 24% ( 6 ). The highest estimates of NAFLD are among obese individuals after bariatric surgery, which range from 84% to 96% of all patients undergoing this procedure ( 6 ). It is estimated that 17-33% of Americans may have hepatic steatosis ( 5 ), a condition that is often associated with insulin resistance, type 2 diabetes, and central obesity. The prevalence of NAFLD is increasing worldwide and is expected to more than double by the year 2025 ( 5 ).NAFLD includes a spectrum of liver pathological changes ranging from simple hepatic steatosis to advanced abnor-

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The extra domain A (EDA)-containing fibronectin (EDA-FN), an alternatively spliced form of the extracellular matrix protein fibronectin, is predominantly expressed in various malignancies but not in normal tissues. In the present study, we investigated the potential pro-lymphangiogenesis effects of extra domain A (EDA)-mediated vascular endothelial growth factor-C (VEGF-C) secretion in colorectal carcinoma (CRC). We detected the expressions of EDA and VEGF-C in 52 human colorectal tumor tissues and their surrounding mucosae by immunohistochemical analysis, and further tested the correlation between the expressions of these two proteins in aforementioned CRC tissues. Both EDA and VEGF-C were abundantly expressed in the specimens of human CRC tissues. And VEGF-C was associated with increased expression of EDA in human CRC according to linear regression analysis. Besides, EDA expression was significantly correlated with lymph node metastasis, tumor differentiation and clinical stage by clinicopathological analysis of tissue microarrays containing tumor tissues of 115 CRC patients. Then, human CRC cell SW480 was transfected with lentivectors to elicit expression of shRNA against EDA (shRNA-EDA), and SW620 was transfected with a lentiviral vector to overexpress EDA (pGC-FU-EDA), respectively. We confirmed that VEGF-C was upregulated in EDA-overexpressed cells, and downregulated in shRNA-EDA cells. Moreover, a PI3K-dependent signaling pathway was found to be involved in EDA-mediated VEGF-C secretion. The in vivo result demonstrated that EDA could promote tumor growth and tumor-induced lymphangiogenesis in mouse xenograft models. Our findings provide evidence that EDA could play a role in tumor-induced lymphangiogenesis via upregulating autocrine secretion of VEGF-C in colorectal cancer, which is associated with the PI3K/Akt-dependent pathway.