β-Catenin functions in both cell–cell adhesion and as a transcriptional coactivator in the canonical Wnt pathway. Nuclear accumulation of β-catenin is the hallmark of active Wnt signaling and is frequently observed in human cancers. Although β-catenin shuttles in and out of the nucleus, the molecular mechanisms underlying its translocation remain poorly understood. Chibby (Cby) is an evolutionarily conserved molecule that inhibits β-catenin–mediated transcriptional activation. Here, we identified 14-3-3ε and 14-3-3ζ as Cby-binding partners using affinity purification/mass spectrometry. 14-3-3 proteins specifically recognize serine 20 within the 14-3-3–binding motif of Cby when phosphorylated by Akt kinase. Notably, 14-3-3 binding results in sequestration of Cby into the cytoplasm. Moreover, Cby and 14-3-3 form a stable tripartite complex with β-catenin, causing β-catenin to partition into the cytoplasm. Our results therefore suggest a novel paradigm through which Cby acts in concert with 14-3-3 proteins to facilitate nuclear export of β-catenin, thereby antagonizing β-catenin signaling.

In recent models of decision-making, cognitive scientists have examined the relationship between option generation and successful performance. These models suggest that those who are successful at decision-making generate few courses of action and typically choose the first, often best, option. Scientists working in the area of expert performance, on the other hand, have demonstrated that the ability to generate and prioritize task-relevant options during situation assessment is associated with successful performance. In the current study, we measured law enforcement officers' performance and thinking in a simulated task environment to examine the option generation strategies used during decision-making in a complex domain. The number of options generated during assessment (i.e., making decisions about events in the environment) and intervention (i.e., making decisions about personal courses of action) phases of decision-making interact to produce a successful outcome. The data are explained with respect to the development of a situational representation and long-term working memory skills capable of supporting both option generation processes.

Agonists of TLR have been explored as vaccine adjuvants for tumor immunotherapy. However, their immunological consequences are not fully understood. Although TLR signaling increases the functional potential of dendritic cells (DCs) for priming T cells, coinduction of potentially negative immunoregulatory capacities may impair effector T cell generation. We examined the expression and function of B7 family costimulatory molecules on DCs after activation with the TLR3 agonist, polyinosinic:polycytidylic acid. We demonstrated that polyinosinic:polycytidylic acid consistently up-regulated both B7-2 and B7-H1 molecules on resident, migratory DCs from spleen and lymph nodes. Depletion or blockade of B7-H1 on activated DCs increased the magnitude of effector CD8 T cell expansion. DC-based or protein-based tumor vaccines, in combination with B7-H1 blockade, induced strong effector CD8 T cell responses, resulting in protective immunity against newly established tumors. Our studies suggest that TLR3 signaling has the potential to up-regulate both positive and negative coregulatory molecules on APCs. Selective blockade of negative regulatory molecules in combination with TLR3 agonist may be an effective strategy for increasing the efficacy of tumor vaccines.

An immuno-inhibitory role of B7-H1 expressed by non-T cells has been established, however, the function of B7-H1 expressed by T cells is not clear. Peak expression of B7-H1 on antigen-primed CD8 T cells was observed during the contraction phase of an immune response. Unexpectedly, B7-H1 blockade at this stage reduced the numbers of effector CD8 T cells, suggesting B7-H1 blocking antibody may disturb an unknown function of B7-H1 expressed by CD8 T cells. To exclusively examine the role of B7-H1 expressed by T cells, we introduced B7-H1 deficiency into TCR transgenic (OT-1) mice. Naive B7-H1 deficient CD8 T cells proliferated normally following antigen stimulation, however once activated, they underwent more robust contraction in vivo and more apoptosis in vitro. In addition, B7-H1 deficient CD8 T cells were more sensitive to Ca-dependent and Fas ligand-dependent killing by cytotoxic T lymphocytes. Activation-induced Bcl-xL expression was lower in activated B7-H1 deficient CD8 T cells, while Bcl-2 and Bim expression were comparable to the wild type. Transfer of effector B7-H1 deficient CD8 T cells failed to suppress tumor growth in vivo. Thus, up-regulation of B7-H1 on primed T cells helps effector T cells survive the contraction phase and consequently generate optimal protective immunity.

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