Highlights d Lipophilic statins and lipophilic bisphosphonates are potent vaccine adjuvants d Modulation of post-translational protein prenylation confers adjuvanticity d Decreased protein prenylation augments antigen preservation and presentation d Statin-or bisphosphonate-mediated vaccination synergizes with anti-PD1 against cancer

Graphical Abstract Highlights d The crystal structure of HMBPP-bound intracellular BTN3A1 was determined at 1.97 Å d HMBPP forms hydrogen bonds with H 351 for efficient Vg9Vd2 T cell activation d An asymmetric intracellular dimer is involved in HMBPPmediated gd T cell activation d HMBPP doubles the binding force between extracellular BTN3A and Vg9Vd2 TCR SUMMARYHuman Vg9Vd2 T cells respond to microbial infections and malignancy by sensing diphosphate-containing metabolites called phosphoantigens, which bind to the intracellular domain of butyrophilin 3A1, triggering extracellular interactions with the Vg9Vd2 T cell receptor (TCR). Here, we examined the molecular basis of this ''inside-out'' triggering mechanism. Crystal structures of intracellular butyrophilin 3A proteins alone or in complex with the potent microbial phosphoantigen HMBPP or a synthetic analog revealed key features of phosphoantigens and butyrophilins required for gd T cell activation. Analyses with chemical probes and molecular dynamic simulations demonstrated that dimerized intracellular proteins cooperate in sensing HMBPP to enhance the efficiency of gd T cell activation. HMBPP binding to butyrophilin doubled the binding force between a gd T cell and a target cell during ''outside'' signaling, as measured by single-cell force microscopy. Our findings provide insight into the ''inside-out'' triggering of Vg9Vd2 T cell activation by phosphoantigen-bound butyrophilin, facilitating immunotherapeutic drug design.

Polyethylene terephthalate (PET) is among the most extensively produced plastics, but huge amounts of PET wastes that have accumulated in the environment have become a serious threat to the ecosystem. Applying PET hydrolytic enzymes to depolymerize PET is an attractive measure to manage PET pollution, and searching for more effective enzymes is a prerequisite to achieve this goal. A thermostable cutinase that originates from the leaf-branch compost termed ICCG is the most effective PET hydrolase reported so far. Here, we illustrated the crystal structure of ICCG in complex with the PET analogue, mono­(2-hydroxyethyl)­terephthalic acid, to reveal the enzyme–substrate interaction network. Furthermore, we applied structure-based engineering to modify ICCG and screened for variants that exhibit higher efficacy than the parental enzyme. As a result, several variants with the measured melting temperature approaching 99 °C and elevated PET hydrolytic activity were obtained. Finally, crystallographic analyses were performed to reveal the structural stabilization effects mediated by the introduced mutations. These results are of importance in the context of understanding the mechanism of action of the thermostable PET hydrolytic enzyme and shall be beneficial to the development of PET biodegradation platforms.

KRAS mutation occurs in nearly 30% of human cancers, yet the most prevalent and oncogenic KRAS(G12D) variant still lacks inhibitors. Herein, we designed a series of potent inhibitors that can form a salt bridge with KRAS’s Asp12 residue. Our ITC results show that these inhibitors have similar binding affinity with both GDP-bound and GTP-bound KRAS(G12D), and our crystallographic studies reveal the structural basis of inhibitor binding-induced switch-II pocket in KRAS(G12D), experimentally confirming the formation of a salt bridge between the piperazine moiety of the inhibitors and the Asp12 residue of the mutant protein. Among KRAS family proteins and mutants, both ITC and enzymatic assays demonstrate the selectivity of the inhibitors for KRAS(G12D); and the inhibitors disrupt the KRAS–CRAF interaction. We also observed the inhibition of cancer cell proliferation as well as MAPK signaling by a representative inhibitor (TH-Z835). However, since the inhibition was not fully dependent on KRAS mutation status, it is possible that our inhibitors may have off-target effects via targeting non-KRAS small GTPases. Experiments with mouse xenograft models of pancreatic cancer showed that TH-Z835 significantly reduced tumor volume and synergized with an anti-PD-1 antibody. Collectively, our study demonstrates proof-of-concept for a strategy based on salt-bridge and induced-fit pocket formation for KRAS(G12D) targeting, which warrants future medicinal chemistry efforts for optimal efficacy and minimized off-target effects.