Summary In humans, Vγ9Vδ2 T cells detect tumor cells and microbial infections including Mycobacterium tuberculosis through recognition of small pyrophosphate containing organic molecules known as phosphoantigens (pAgs). Key to pAg-mediated activation of Vγ9Vδ2 T cells is the butyrophilin 3A1 (BTN3A1) protein that contains an intracellular B30.2 domain critical to pAg reactivity. Here, we have demonstrated through structural, biophysical and functional approaches that the intracellular B30.2 domain of BTN3A1 directly binds pAg through a positively-charged surface pocket. Charge-reversal of pocket residues abrogates binding and Vγ9Vδ2 T cell activation. We have also identified a gain-of-function mutation within this pocket that when introduced into B30.2 domain of the non-stimulatory BTN3A3 isoform, transfers pAg binding ability and Vγ9Vδ2 T cell activation. These studies demonstrate that internal sensing of changes in pAg metabolite concentrations by BTN3A1 molecules is a critical step in Vγ9Vδ2 T cell detection of infection and tumorigenesis.

Aquaporin (AQP) 4 is the predominant water channel in the mammalian brain, abundantly expressed in the blood-brain and braincerebrospinal fluid interfaces of glial cells. Its function in cerebral water balance has implications in neuropathological disorders, including brain edema, stroke, and head injuries. The 1.8-Å crystal structure reveals the molecular basis for the water selectivity of the channel. Unlike the case in the structures of water-selective AQPs AqpZ and AQP1, the asparagines of the 2 Asn-Pro-Ala motifs do not hydrogen bond to the same water molecule; instead, they bond to 2 different water molecules in the center of the channel. Molecular dynamics simulations were performed to ask how this observation bears on the proposed mechanisms for how AQPs remain totally insulating to any proton conductance while maintaining a single file of hydrogen bonded water molecules throughout the channel.brain edema ͉ inhibitor discovery ͉ NPA motif

Inflammasomes are multi-protein platforms that initiate innate immunity by recruitment and activation of Caspase-1. The NLRP1B inflammasome is activated upon direct cleavage by the anthrax lethal toxin protease. However, the mechanism by which cleavage results in NLRP1B activation is unknown. Here we find that cleavage results in proteasome-mediated degradation of the N-terminal domains of NLRP1B, liberating a C-terminal fragment that is a potent Caspase-1 activator. Proteasome-mediated degradation of NLRP1B is both necessary and sufficient for NLRP1B activation. Consistent with our “functional degradation” model, we identify IpaH7.8, a Shigella flexneri ubiquitin ligase secreted effector, as an enzyme that induces NLRP1B degradation and activation. Our results provide a unified mechanism for NLRP1B activation by diverse pathogen-encoded enzymatic activities.

Background: Phosphoisoprenoid stimulation of V␥9V␦2 T cells can be modulated by anti-BTNA3 antibodies. Results: Agonist and antagonist antibodies associate differently with BTN3A structurally and biophysically. Conclusion: Differential binding of antibodies to BTN3A modulates its oligomerization on the cell surface. Significance: Defining how ␥␦ T cells recognize antigen is critical for understanding their functions in the immune response.