The influence of signals transmitted by the phosphatase calcineurin and the transcription factor NFAT on the development and function of natural killer T (NKT) cells is unclear. In this report, we demonstrate that the transcription factor early growth response 2 (Egr2), a target gene of NFAT, was specifically required for the ontogeny of NKT cells but not that of conventional CD4 + or CD8 + T cells. NKT cells developed normally in the absence of Egr1 or Egr3, which suggests that Egr2 is a specific regulator of NKT cell differentiation. We found that Egr2 was important in the selection, survival and maturation of NKT cells. Our findings emphasize the importance of the calcineurin-NFAT-Egr2 pathway in the development of the NKT lymphocyte lineage.Mouse natural killer T (NKT) cells that express an invariant T cell antigen receptor (TCR) α-chain composed of variable α-chain region 14 (V α 14) and joining α-chain region 18 (J α 18) gene segments (V α 14i) constitute a distinct lymphocyte subset that coexpresses TCRαβ and markers of the NK cell lineage. NKT cells function in the first line of defense against infectious agents, contribute to the development of asthma and chronic obstructive pulmonary disease, potently promote the regression of transplanted tumors, and influence the maintenance of immunological tolerance 1-3 . Unlike conventional T lymphocytes, which express a diverse repertoire of TCRα and TCRβ, NKT cells combine the V α 14i TCRα chain (V α 24-J α 18 in humans) with a restricted repertoire of TCRβ proteins that contain V β 8, V β 7 or V β 2 segments (V β 11 in humans). Also in contrast to conventional T lymphocytes, which recognize peptides bound to major histocompatibility complex molecules and are selected by thymic stromal cells that present complexes of peptide and major histocompatibility complex, NKT cells are

Background: Induced mammalian target of rapamycin (mTOR)-dependent autophagy can restrict mycobacterial growth. Results: Mycobacterial lipids stimulate macrophage autophagy and mTOR signaling. Conclusion: Mycobacteria naturally induce autophagy in an mTOR-independent manner. Significance: This work will impact the development of therapeutic strategies for Mycobacteria tuberculosis infection.

The Ras small GTPase functions as a signaling node and is activated by extracellular stimuli. Upon activation, Ras interacts with a spectrum of functionally diverse downstream effectors and stimulates multiple cytoplasmic signaling cascades that regulate cellular proliferation, differentiation, and apoptosis. In addition to the association of Ras with the plasma membrane, recent studies have established an association of Ras with Golgi membranes. Whereas the effectors of signal transduction by activated, plasma membranelocalized Ras are well characterized, very little is known about the effectors used by Golgi-localized Ras. In this study, we report the identification of a novel Ras-interacting protein, Rain, that may serve as an effector for endomembrane-associated Ras. Rain does not share significant sequence similarity with any known mammalian proteins, but contains a Ras-associating domain that is found in RalGDS, AF-6, and other characterized Ras effectors. Rain interacts with Ras in a GTP-dependent manner in vitro and in vivo, requires an intact Ras core effector-binding domain for this interaction, and thus fits the definition of a Ras effector. Unlike other Ras effectors, however, Rain is localized to perinuclear, juxta-Golgi vesicles in intact cells and is recruited to the Golgi by activated Ras. Finally, we found that Rain cooperates with activated Raf and causes synergistic transformation of NIH3T3 cells. Taken together, these observations support a role for Rain as a novel protein that can serve as an effector of endomembrane-localized Ras.

The importance of regulated AP-1 activity during T cell development was assessed using transgenic mice overexpressing BATF, a basic leucine zipper transcription factor and an AP-1 inhibitor. BATF transgenic animals possess normal thymic cellularity and all major T cell subsets, but show impaired thymocyte proliferation in vitro and no induction of IL-2, IL-4, IL-5, IL-10, and IL-13 expression. Since NKT cells are largely responsible for cytokine production in the thymus, this population was examined by detection of the Vα14-Jα281 TCR, flow cytometry of NK1.1+ TCRβ+ cells, and analysis of cytokine production by heat-stable Aglow thymocytes and peripheral NKT cells stimulated in vivo. Results show a severe under-representation of NKT cells in BATF transgenic animals, providing the first evidence that the precise control of AP-1-mediated transcription is critical for the proper emergence of thymus-derived NKT cells in the mouse.