Project description:We describe a previously unappreciated role for Bruton's tyrosine kinase (BTK) in fungal immune surveillance against aspergillosis, an unforeseen complication of BTK inhibitors (BTKi) used for treating B-cell lymphoid malignancies. We studied BTK-dependent fungal responses in neutrophils from diverse populations, including healthy donors, BTKi-treated patients, and X-linked agammaglobulinemia patients. Upon fungal exposure, BTK was activated in human neutrophils in a TLR2-, Dectin-1-, and FcgR-dependent manner, triggering the oxidative burst. BTK inhibition selectively impeded neutrophil-mediated damage to Aspergillus hyphae, primary granule release, and the fungus-induced oxidative burst by abrogating NADPH oxidase subunit p40phox and GTPase RAC2 activation. Moreover, neutrophil-specific Btk deletion in mice enhanced aspergillosis susceptibility by impairing neutrophil function, not recruitment nor lifespan. Conversely, GM-CSF partially mitigated these deficits by enhancing p47phox activation. Our findings underline the crucial role of BTK signaling in neutrophils for antifungal immunity and provide a rationale for GM-CSF use to offset these deficits in susceptible patients.
Project description:Bruton’s tyrosine kinase (BTK) is targeted in the treatment of B-cell disorders including leukemias and lymphomas. Currently approved BTK inhibitors, including Ibrutinib, a first-in-class covalent inhibitor of BTK, bind directly to the kinase active site. While effective at blocking the catalytic activity of BTK, consequences of drug binding on the global conformation of full-length BTK are unknown. Here we uncover a range of conformational effects in full-length BTK induced by a panel of active site inhibitors, including unexpected shifts in the conformational equilibria of the regulatory domains. Additionally, we find that a remote Ibrutinib resistance mutation, T316A in the BTK SH2 domain, drives spurious BTK activity by destabilizing the compact autoinhibitory conformation of full-length BTK, shifting the conformational ensemble away from the autoinhibited form. Future development of BTK inhibitors will need to consider long-range allosteric consequences of inhibitor binding, including the emerging application of these BTK inhibitors in treating COVID-19.
Project description:Full-length BTK has been refractory to structural analysis. The nearest full-length structure of BTK to date consists of the autoinhibited SH3-SH2-kinase core. Precisely how the BTK N-terminal domains (the Pleckstrin homology/Tec homology (PHTH) domain and the long linker that includes proline-rich regions (PRR)) contribute to BTK regulation remains unclear. Here we produce crystals of full-length BTK for the first time. Despite efforts to stabilize the autoinhibited state, the diffraction data still reveals only the SH3-SH2-kinase core with no electron density visible for the PHTH-PRR segment. CryoEM data, on the other hand, provides a glimpse of the PHTH domain. CryoEM reconstructions support conformational heterogeneity in the PHTH-PRR region; the globular PHTH domain adopts a range of states arrayed around the autoinhibited SH3-SH2-kinase core. Upon disassembly of the SH3-SH2-kinase core, an autoinhibitory site on the kinase domain becomes available for PHTH domain binding. This PHTH/kinase autoinhibitory contact is then lost upon interaction of PHTH with PIP3. Membrane-induced dimerization activates BTK and here we solve a structure of an activation loop swapped BTK kinase domain dimer that likely represents the conformational state leading to trans-autophosphorylation. Together, these data provide the first structural insight into full-length BTK and allow a deeper understanding of allosteric control over the BTK kinase domain during distinct stages of activation.
Project description:Neutrophil abscess formation is critical in innate immunity against many pathogens. Here, the mechanism of neutrophil abscess formation was investigated using a mouse model of Staphylococcus aureus cutaneous infection. Gene expression analysis of S. aureus-infected skin revealed that induction of neutrophil recruitment genes was largely dependent upon IL-1beta/IL-1R activation. Unexpectedly, using IL 1beta reporter mice, neutrophils were identified as the primary source of IL-1beta at the site of infection. Furthermore, IL-1beta-producing neutrophils were necessary and sufficient for abscess formation and bacterial clearance. S. aureus-induced IL 1beta production by neutrophils required TLR2, NOD2, FPRs and the ASC/NLRP3 inflammasome. Taken together, IL-1beta and neutrophil abscess formation during an infection are functionally, spatially and temporally linked as a consequence of direct IL-1beta production by neutrophils. Lesional skin biopsies obtained from C57BL/6J WT mice or IL-1R-deficient mice at 4 hours post-infection with Staphylococcus aureus. Uninfected skin biopsies were also collected from WT and IL-1R-deficient mice.
Project description:Using the novel BTK inhibitor PF-303, we model the clinical phenotype of BTK inhibition by systematically examining the impact of PF-303 on the mature immune system in mice autoimmune indications. However, our current knowledge of the role of BTK in immune competence has been gathered in the context of genetic inactivation of btk in both mice and man. Using the novel BTK inhibitor PF-303, we model the clinical phenotype of BTK inhibition by systematically examining the impact of PF-303 on the mature immune system in mice. We implicate BTK in tonic BCR signaling, demonstrate dependence of the T3 B cell subset and IgM surface expression on BTK activity, and find that B1 cells survive and function independently of BTK. While BTK inhibition does not impact humoral memory survival, antigen-driven clonal expansion of memory B cells and antibody secreting cell generation are inhibited. These data define the role of BTK in the mature immune system and mechanistically predict the clinical phenotype of BTK inhibition. We used Affymetrix genechips to profile the transcriptional changes downstream of BTK inhibition after in vivo B-cell activation by anti-IgD Mice were injected with the novel BTK inhibitor PF-303 2 hours prior to anti-IgD mediated in vivo B-cell activation; B-cells where harvested 2 hours after anti-IgD activation and RNA isolated.
Project description:Bruton's tyrosine kinase (Btk) is important for B lymphocyte development. To identify genes that are differentially expressed in primary B cells lacking functional Btk, splenocytes from X-linked immunodeficiency (Xid), Btk knockout (KO) and immunocompetent CBA mice, were used in microarrays containing more than 12,000 genes and expressed sequence tags (ESTs). We found 4515 transcripts expressed in duplicate experiments in all three strains. Out of these, 38 were differentially expressed genes (21 up-regulated >2 fold and 17 down-regulated <-2 fold) between CBA and Btk defective mice. Ten out of these genes were selected and quantitative Real-Time PCR was conducted for validation and further investigation. Real-Time experiments correlated nicely with the microarray data. No definitive phenotypic difference has previously been reported between Xid and Btk KO mice. We found 7 genes, whose expression differed (>2 fold) between the two strains. Moreover, when the 38 genes, which differed between immunocompetent CBA and Btk defective mice were ranked according to fold-increase, the levels in Btk KO mice were significantly more altered. This suggests that the defect in Btk KO mice is more severe and demonstrates that the mutant Btk protein in Xid mice does not generally function as dominant negative form. Experiment Overall Design: 6 Affymetrix U74Av2 GeneChip arrays was run. Three initially with CBA, Xid and Btk KO mice and then additional three chips with new RNA preperations from new CBA, Xid and Btk KO mice.
Project description:Proteome analysis reveals that the tumor suppressor kinase DAPK3 drives tumor-intrinsic immunity through the STING-IFNb pathway Proteome
Project description:B cell linker protein (BLNK) is a pivotal adaptor protein that interfaces the B cell receptor (BCR)-associated spleen tyrosine kinase (Syk) to regulate B cell function and development. However, it is still not well understood whether BLNK is involved in Syk-coupled C-type lectin receptor (CLR) signaling in myeloid cells, particularly in the context of antifungal immunity. Here, we show that stimulation with fungi-derived β-glucans or α-mannans induced the phosphorylation of BLNK in macrophages, which was significantly impaired due to the deficiency of CLRs including Dectin-1 and Dectin-2, as well as their downstream mediators Syk and Fc-receptor gamma-chain (FcRγ). Furthermore, BLNK is induced to be interacted with casitas B-lineage lymphoma (c-Cbl), which is completely dependent on the engagement of Dectin-1 and Dectin-2. Notably, BLNK deficiency facilitates CLR-mediated recruitment of c-Cbl/phosphatidylinositol 3-kinase (PI3K) complex to F-actin cytoskeleton, thereby promoting macrophage migration. Consequently, mice with monocyte-specific deficiency of BLNK are highly resistant to the infection with Candida albicans, a major human fungal pathogen, through increasing the infiltration of Ly6C+macrophages into kidneys. Together, our data indicate that BLNK functions downstream of Syk-coupled CLRs to negatively regulate antifungal immunity against C. albicans infection. These findings unravel a previously unidentified role of BLNK that negatively regulates macrophage migration through inhibiting CLR-mediated recruitment of c-Cbl/PI3K complex to the cytoskeleton.