Targeted truncation of the ADAM17 cytoplasmic domain in mice results in protein destabilization and a hypomorphic phenotype

A disintegrin and metalloprotease 17 (ADAM17) is a cell-surface metalloprotease that serves as the principle sheddase for tumor necrosis factor α (TNFα), interleukin-6 receptor (IL-6R), and several ligands of the epidermal growth factor receptor (EGFR), regulating these crucial signaling pathways. ADAM17 activation requires its transmembrane domain, but not its cytoplasmic domain, and little is known about the role of this domain in vivo. To investigate, we used CRISPR-Cas9 to mutate the endogenous Adam17 locus in mice to produce a mutant ADAM17 lacking its cytoplasmic domain (Adam17Δcyto). Homozygous Adam17Δcyto animals were born at a Mendelian ratio and survived into adulthood with slightly wavy hair and curled whiskers, consistent with defects in ADAM17/EGFR signaling. At birth, Adam17Δcyto mice resembled Adam17−/− mice in that they had open eyes and enlarged semilunar heart valves, but they did not have bone growth plate defects. The deletion of the cytoplasmic domain resulted in strongly decreased ADAM17 protein levels in all tissues and cells examined, providing a likely cause for the hypomorphic phenotype. In functional assays, Adam17Δcyto mouse embryonic fibroblasts and bone-marrow-derived macrophages had strongly reduced ADAM17 activity, consistent with the reduced protein levels. Nevertheless, ADAM17Δcyto could be stimulated by PMA, a well-characterized posttranslational activator of ADAM17, corroborating that the cytoplasmic domain of endogenous ADAM17 is not required for its rapid response to PMA. Taken together, these results provide the first evidence that the cytoplasmic domain of ADAM17 plays a pivotal role in vivo in regulating ADAM17 levels and function.

Abstract B179: Mechanism of antitumor activity of BET inhibitors in models of lymphomas and leukemia

Proteins of the BET family bind to acetylated histones and promote gene expression by recruiting transcriptional activators. We developed BET inhibitors and demonstrated a strong association between biochemical inhibition of BET-chromatin binding, MYC suppression and reduced proliferation in hematopoietic cancer cells. We assessed the gene loci affected by BET inhibition by integrating ChipSeq and gene expression profiling, and identified genes that are directly regulated by BRD4 binding, most notably MYC, or genes that are targets of MYC. BET inhibition resulted in robust suppression of MYC expression in tumor xenograft models. Moreover, based on the PK/PD relationships established for these compounds we designed dosing regimens that resulted in significant anti-tumor efficacy in xenograft models of Burkitt's lymphoma and acute leukemia. Compound doses and schedules resulting in sustained MYC suppression were most effective in inhibiting tumor growth and were well tolerated.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B179.

The progamic phase of an early-divergent angiosperm, Annona cherimola (Annonaceae)

BACKGROUND AND AIMS

Recent studies of reproductive biology in ancient angiosperm lineages are beginning to shed light on the early evolution of flowering plants, but comparative studies are restricted by fragmented and meagre species representation in these angiosperm clades. In the present study, the progamic phase, from pollination to fertilization, is characterized in Annona cherimola, which is a member of the Annonaceae, the largest extant family among early-divergent angiosperms. Beside interest due to its phylogenetic position, this species is also an ancient crop with a clear niche for expansion in subtropical climates.

METHODS

The kinetics of the reproductive process was established following controlled pollinations and sequential fixation. Gynoecium anatomy, pollen tube pathway, embryo sac and early post-fertilization events were characterized histochemically.

KEY RESULTS

A plesiomorphic gynoecium with a semi-open carpel shows a continuous secretory papillar surface along the carpel margins, which run from the stigma down to the obturator in the ovary. The pollen grains germinate in the stigma and compete in the stigma-style interface to reach the narrow secretory area that lines the margins of the semi-open stylar canal and is able to host just one to three pollen tubes. The embryo sac has eight nuclei and is well provisioned with large starch grains that are used during early cellular endosperm development.

CONCLUSIONS

A plesiomorphic simple gynoecium hosts a simple pollen-pistil interaction, based on a support-control system of pollen tube growth. Support is provided through basipetal secretory activity in the cells that line the pollen tube pathway. Spatial constraints, favouring pollen tube competition, are mediated by a dramatic reduction in the secretory surface available for pollen tube growth at the stigma-style interface. This extramural pollen tube competition contrasts with the intrastylar competition predominant in more recently derived lineages of angiosperms.

Differential expression of inflammatory chemokines by Th1- and Th2-cell promoting dendritic cells: a role for different mature dendritic cell populations in attracting appropriate effector cells to peripheral sites of inflammation

Protective immunity to pathogens depends on efficient immune responses adapted to the type of pathogen and the infected tissue. Dendritic cells (DC) play a pivotal role in directing the effector T cell response to either a protective T helper type 1 (Th1) or type 2 (Th2) phenotype. Human monocyte-derived DC can be differentiated into Th1-, Th2- or Th1/Th2-promoting DC in vitro upon activation with microbial compounds or cytokines. Host defence is highly dependent on mobile leucocytes and cell trafficking is largely mediated by the interactions of chemokines with their specific receptors expressed on the surface of leucocytes. The production of chemokines by mature effector DC remains elusive. Here we assess the differential production of both inflammatory and homeostatic chemokines by monocyte-derived mature Th1/Th2-, Th1- or Th2-promoting DC and its regulation in response to CD40 ligation, thereby mimicking local engagement with activated T cells. We show that mature Th1- and Th1/Th2-, but not Th2-promoting DC, selectively express elevated levels of the inflammatory chemokines CCL2/MCP-1, CCL3/MIP-1alpha, CCL4/MIP-1beta and CCL5/RANTES, as well as the homeostatic chemokine CCL19/MIP-3beta. CCL21/6Ckine is preferentially expressed by Th2-promoting DC. Production of the Th1-attracting chemokines, CXCL9/Mig, CXCL10/IP-10 and CXCL11/I-TAC, is restricted to Th1-promoting DC. In contrast, expression of Th2-associated chemokines does not strictly correlate with the Th2-promoting DC phenotype, except for CCL22/MDC, which is preferentially expressed by Th2-promoting DC. Because inflammatory chemokines and Th1-associated chemokines are constitutively expressed by mature Th1-promoting DC and CCL22/MDC is constitutively expressed by mature Th2-promoting DC, we propose a novel role for mature DC present in inflamed peripheral tissues in orchestrating the immune response by recruiting appropriate leucocyte populations to the site of pathogen entry.

PK1/EG-VEGF induces monocyte differentiation and activation

Macrophages exist as sentinels in innate immune response and react by expressing proinflammatory cytokines and up-regulating antigen-presenting and costimulatory molecules. We report a novel function for prokineticin-1 (PK1)/endocrine gland-derived vascular endothelial growth factor. Screening of murine tissue sections and cells for specific binding site leads to the identification of macrophages as an in vivo cellular target for PK1. We demonstrate PK1 induces differentiation of murine and human bone marrow cells into the monocyte/macrophage lineage. Human peripheral blood monocytes respond to PK1 by morphological changes and down-regulation of B7-1, CD14, CC chemokine receptor 5, and CXC chemokine receptor 4. Monocytes treated with PK1 have elevated interleukin (IL)-12 and tumor necrosis factor alpha and down-regulated IL-10 production in response to lipopolysaccharide. PK1 induces a distinct monocyte-derived cell population, which is primed for release of proinflammatory cytokines that favor a T helper cell type 1 response.

The murine CCR3 receptor regulates both the role of eosinophils and mast cells in allergen-induced airway inflammation and hyperresponsiveness

CCR3 is a chemokine receptor initially thought specific to eosinophils but subsequently identified on TH2 cell subsets, basophils, mast cells, neural tissue, and some epithelia. Because of the prominent role of these cells in allergic disease, including asthma, we generated mice deficient in CCR3 to determine its contribution in a model of allergic airway disease. Here we show that CCR3 is important for the basal trafficking of eosinophils to the intestinal mucosa but not the lung. In contrast, CCR3 disruption significantly curtails eosinophil recruitment to the lung after allergen challenge, with the majority of the eosinophils being arrested in the subendothelial space. Further, a role for CCR3 in mast cell homing has been identified; after sensitization and allergen challenge, we find increased numbers of intraepithelial mast cells in the trachea of knockout mice. Physiologically, we find that the net result of these complex cell fates after sensitization and allergen challenge is a paradoxical increase in airway responsiveness to cholinergic stimulation. These data underscore a more complex role for CCR3 in allergic disease than was anticipated.

ICOS is critical for T helper cell-mediated lung mucosal inflammatory responses

We examined the requirement for and cooperation between CD28 and inducible costimulator (ICOS) in effective T helper (TH) cell responses in vivo. We found that both CD28 and ICOS were critical in determining the outcome of an immune response; cytolytic T lymphocyte-associated antigen 4-immunoglobulin (CTLA-4-Ig), ICOS-Ig and/or a neutralizing ICOS monoclonal antibody attenuated T cell expansion, TH2 cytokine production and eosinophilic inflammation. CD28-dependent signaling was essential during priming, whereas ICOS-B7RP-1 regulated TH effector responses, and the up-regulation of chemokine receptors that determine T cell migration. Our data suggests a scenario whereby both molecules regulate the outcome of the immune response but play separate key roles: CD28 primes T cells and ICOS regulates effector responses.

Urbanisation of yellow fever in Santa Cruz, Bolivia

BACKGROUND

Reinvasion by Aedes aegypti of cities in the Americas poses a threat of urbanisation of yellow fever. After detection of yellow-fever infection in a resident of the city of Santa Cruz, Bolivia, in December, 1997, we investigated all subsequent suspected cases.

METHODS

We introduced active surveillance of yellow fever in the Santa Cruz area. Hospitals and selected urban and rural health centres reported all suspected cases. Patients were serologically screened for yellow fever, dengue, hepatitis A and B, and leptospirosis. We collected clinical and epidemiological information from patients' records and through interviews. We also carried out a population-based serosurvey in the neighbourhood of one case.

FINDINGS

Between December, 1997, and June, 1998, symptomatic yellow-fever infection was confirmed in six residents of Santa Cruz, five of whom died. Five lived in the southern sector of the city. Two had not left the city during the incubation period, and one had visited only an area in which sylvatic transmission was deemed impossible. Of the 281 people covered in the serosurvey 16 (6%) were positive for IgM antibody to yellow fever. Among five people for whom this result could not be explained by recent vaccination, there were two pairs of neighbours.

INTERPRETATION

Urban transmission of yellow fever in Santa Cruz was limited in space and time. Low yellow-fever immunisation coverage and high infestation with A. aegypti in the city, and the existence of endemic areas in the region present a risk for future urban outbreaks. We recommend immediate large-scale immunisation of the urban population, as well as tightened surveillance and appropriate vector control.