MALT1 Small Molecule Inhibitors Specifically Suppress ABC-DLBCL In Vitro and In Vivo

SummaryMALT1 cleavage activity is linked to the pathogenesis of activated B cell-like diffuse large B cell lymphoma (ABC-DLBCL), a chemoresistant form of DLBCL. We developed a MALT1 activity assay and identified chemically diverse MALT1 inhibitors. A selected lead compound, MI-2, featured direct binding to MALT1 and suppression of its protease function. MI-2 concentrated within human ABC-DLBCL cells and irreversibly inhibited cleavage of MALT1 substrates. This was accompanied by NF-κB reporter activity suppression, c-REL nuclear localization inhibition, and NF-κB target gene downregulation. Most notably, MI-2 was nontoxic to mice, and displayed selective activity against ABC-DLBCL cell lines in vitro and xenotransplanted ABC-DLBCL tumors in vivo. The compound was also effective against primary human non-germinal center B cell-like DLBCLs ex vivo

Asymmetric Structure of the Yeast F1 ATPase in the Absence of Bound Nucleotides*

The crystal structure of nucleotide-free yeast F1 ATPase has been determined at a resolution of 3.6 Å. The overall structure is very similar to that of the ground state enzyme. In particular, the βDP and βTP subunits both adopt the closed conformation found in the ground state structure despite the absence of bound nucleotides. This implies that interactions between the γ and β subunits are as important as nucleotide occupancy in determining the conformational state of the β subunits. Furthermore, this result suggests that for the mitochondrial enzyme, there is no state of nucleotide occupancy that would result in more than one of the β subunits adopting the open conformation. The adenine-binding pocket of the βTP subunit is disrupted in the apoenzyme, suggesting that the βDP subunit is responsible for unisite catalytic activity

Dedicator of cytokinesis 8 regulates signal transducer and activator of transcription 3 activation and promotes T(H)17 cell differentiation

WOS: 000389542700018PubMed ID: 27350570Background: The autosomal recessive hyper-IgE syndrome (HIES) caused by dedicator of cytokinesis 8 (DOCK8) deficiency shares clinical features with autosomal dominant HIES because of signal transducer and activator of transcription 3 (STAT3) mutations, including recurrent infections and mucocutaneous candidiasis, which are suggestive of T(H)17 cell dysfunction. The mechanisms underlying this phenotypic overlap are unclear. Objective: We sought to elucidate common mechanisms operating in the different forms of HIES. Methods: We analyzed the differentiation of CD4(+) T-H cell subsets in control and DOCK8-deficient subjects. We also examined the role of DOCK8 in regulating STAT3 activation in T cells. T-H cell differentiation was analyzed by ELISA, flow cytometry, and real-time PCR measurements of cytokines and T-H cell transcription factors. The interaction of DOCK8 and STAT3 signaling pathways was examined by using flow cytometry, immunofluorescence, coimmunoprecipitation, and gene expression analysis. Results: There was a profound block in the differentiation of DOCK8-deficient naive CD4(+) T cells into T(H)17 cells. A missense mutation that disrupts DOCK8 guanine nucleotide exchange factor (GEF) activity while sparing protein expression also impaired T(H)17 cell differentiation. DOCK8 constitutively associated with STAT3 independent of GEF activity, whereas it regulated STAT3 phosphorylation in a GEF activity-dependent manner. DOCK8 also promoted STAT3 translocation to the nucleus and induction of STAT3-dependent gene expression. Conclusion: DOCK8 interacts with STAT3 and regulates its activation and the outcome of STAT3-dependent TH17 differentiation. These findings might explain the phenotypic overlap between DOCK8 deficiency and autosomal dominant HIES.National Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [5R01AI065617]; Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [1059B191300622]Supported by the National Institutes of Health (5R01AI065617, to T.A.C.) and a grant from the Scientific and Technological Research Council of Turkey (1059B191300622 to S.K.)

Novel features of the rotary catalytic mechanism revealed in the structure of yeast F(1) ATPase

The crystal structure of yeast mitochondrial F(1) ATPase contains three independent copies of the complex, two of which have similar conformations while the third differs in the position of the central stalk relative to the α(3)β(3) sub-assembly. All three copies display very similar asymmetric features to those observed for the bovine enzyme, but the yeast F(1) ATPase structures provide novel information. In particular, the active site that binds ADP in bovine F(1) ATPase has an ATP analog bound and therefore this structure does not represent the ADP-inhibited form. In addition, one of the complexes binds phosphate in the nucleotide-free catalytic site, and comparison with other structures provides a picture of the movement of the phosphate group during initial binding and subsequent catalysis. The shifts in position of the central stalk between two of the three copies of yeast F(1) ATPase and when these structures are compared to those of the bovine enzyme give new insight into the conformational changes that take place during rotational catalysis