CD28 is one of the most important costimulatory receptors necessary for full T lymphocyte activation. The CD28 receptor can enhance T cell antigen receptor (TCR) signals, as well as deliver independent signals. Indeed, CD28 engagement by B7 can generate TCR-independent signals leading to I B kinase and NF-B activation. Here we demonstrate that the TCR-independent CD28 signal leads to the selective transcription of survival (Bcl-xL) and inflammatory (IL-8 and B cell activation factor, but not proliferative (IL-2), genes, in a NF-Bdependent manner. CD28-stimulated T cells actively secrete IL-8, and Bcl-xL up-regulation protects T cells from radiation-induced apoptosis. The transcription of CD28-induced genes is mediated by the specific recruitment of RelA and p52 NF-B subunits to target promoters. In contrast, p50 and c-Rel, which preferentially bind NF-B sites on the IL-2 gene promoter after anti-CD3 stimulation, are not involved. Thus, we identify CD28 as a key regulator of genes important for both survival and inflammation. C D28 is one of the most important costimulatory receptors necessary for full T lymphocyte activation. Early studies on CD28 demonstrated that it provides a potent signal for the upregulation of several cytokines, acting at the level of both transcription and message stability. More recent studies have evidenced that CD28 plays a key role in enhancing T cell activation by the T cell antigen receptor (TCR) (1). As an integral component of the immunological synapse, CD28 plays a critical role in the recruitment of signaling molecules to the TCR (2). In particular, it has been recently demonstrated that CD28 enhances close contact between T cells and antigen-presenting cells and facilitates TCR signal transduction by amplifying phospholipase C␥1 activation and Ca 2ϩ response (3). The consequence of this action is an augmentation of early TCR-mediated signal (4). Recent evidence showing that CD28 can mediate adhesion signals beyond costimulatory ones (3) has led to new interest and induced a new wave of investigation of the intriguing problems concerning the molecular mechanisms as well as the targets of CD28 as an independent signaling unit. CD28 stimulation can induce cytoskeletal rearrangements in T cells (5) or up-regulate IL-2-4 only when Vav and the adapter SLP-76 are overexpressed (6). However, the mediators and the molecular mechanisms, which govern the process whereby CD28 may deliver an autonomous signal, remain unknown. We have recently demonstrated that CD28 engagement by B7 can generate TCRindependent signals leading to I B kinase (IKK) and NF-B activation (7) and that Vav-1 acts as the upstream regulator of this signaling pathway (8).NF-B͞Rel transcription factors are critical regulators of the positioning of immune responses to integrate information from both innate and adaptive immune signaling pathways. In mammals, this family consists of five members that form homo-and heterodimeric complexes including NF-B1 (p50 and its precursor p105), NF-B2 (p52 and its precursor p100), RelA...

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Tumor necrosis factor ␣-converting enzyme (TACE, also known as ADAM17) was recently involved in the pathogenesis of insulin resistance. We observed that TACE activity was significantly higher in livers of mice fed a high-fat diet (HFD) for 1 month, and this activity was increased in liver > white adipose tissue > muscle after 5 months compared with chow control. In mouse hepatocytes, C 2 C 12 myocytes, and 3T3F442A adipocytes, TACE activity was triggered by palmitic acid, lipolysaccharide, high glucose, and high insulin. TACE overexpression significantly impaired insulin-dependent phosphorylation of AKT, GSK3, and FoxO1 in mouse hepatocytes. To test the role of TACE activation in vivo, we used tissue inhibitor of metalloproteinase 3 (Timp3) null mice, because Timp3 is the specific inhibitor of TACE and Timp3 ؊/؊ mice have higher TACE activity compared with wild-type (WT) mice. Timp3 ؊/؊ mice fed a HFD for 5 months are glucose-intolerant and insulin-resistant; they showed macrovesicular steatosis and ballooning degeneration compared with WT mice, which presented only microvesicular steatosis. Shotgun proteomics analysis revealed that Timp3 ؊/؊ liver showed a significant differential expression of 38 proteins, including lower levels of adenosine kinase, methionine adenosysltransferase I/III, and glycine N-methyltransferase and higher levels of liver fatty acid-binding protein 1. These changes in protein levels were also observed in hepatocytes infected with adenovirus encoding TACE. All these proteins play a role in fatty acid uptake, triglyceride synthesis, and methionine metabolism, providing a molecular explanation for the increased hepatosteatosis observed in Timp3 ؊/؊ compared with WT mice. Conclusion: We have identified novel mechanisms, governed by the TACE-Timp3 interaction, involved in the determination of insulin resistance and liver steatosis during overfeeding in mice. (HEPATOLOGY 2010;51:103-110.) P andemic obesity is now considered the underlying basis for the increasing prevalence of chronic metabolic-inflammatory diseases including type 2 diabetes, nonalcoholic fatty liver disease (NAFLD) and atherosclerosis. 1 Although NAFLD is an emerging metabolic complication of obesity, its pathogenic mechanisms are still unclear. 1 The contribution of insulin resistance to the development of fatty liver occurs in part by deficient control of lipid storage in white adipose tissue and in part by altered

Neuroblastoma is one of the most aggressive solid tumors in the childhood. Therapy resistance to anticancer drugs represents the major limitation to the effectiveness of clinical treatment. To better understand the mechanisms underlying cisplatin resistance, we performed a comparative proteomic study of the human neuroblastoma cell line SH-SY5Y and its cisplatin resistant counterpart by both the classical 2-DE electrophoresis coupled to mass spectrometry and the more innovative label-free nLC-MS(E). The differentially expressed proteins were classified by bioinformatic tools according to their biological functions and their involvement in several cellular processes. Moreover, a meta-mining investigation of protein ontologies was also performed on available data from previously published proteomics studies to highlight the modulation of significant cellular pathways, which may regulate the sensitivity of neuroblastoma to cisplatin. In particular, we hypothesized a major role of the transcription factor nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. Confocal microscopy experiments, enzyme assay, and Western blotting of proteins regulated by Nrf2 provided evidences that this pathway, playing a protective role in normal cells, may represent a potential novel target to control cisplatin resistance in neuroblastoma.