Methotrexate-based PROTACs as DHFR-specific chemical probes

Methotrexate (MTX) is a tight-binding dihydrofolate reductase (DHFR) inhibitor, used as both an antineoplastic and immunosuppressant therapeutic. MTX, like folate undergoes folylpolyglutamate synthetase-mediated γ-glutamylation, which affects cellular retention and target specificity. Mechanisms of MTX resistance in cancers include a decrease in MTX poly-γ-glutamylation and an upregulation of DHFR. Here, we report a series of potent MTX-based proteolysis targeting chimeras (PROTACs) to investigate DHFR degradation pharmacology and one-carbon biochemistry. These on-target, cell-active PROTACs show proteasome- and E3 ligase-dependent activity, and selective degradation of DHFR in multiple cancer cell lines. By comparison, treatment with MTX increases cellular DHFR protein expression. Importantly, these PROTACs produced distinct, less-lethal phenotypes compared to MTX. The chemical probe set described here should complement conventional DHFR inhibitors and serve as useful tools for studying one-carbon biochemistry and dissecting complex polypharmacology of MTX and related drugs. Such compounds may also serve as leads for potential autoimmune and antineoplastic therapeutics.

In vivo quantitative high-throughput screening for drug discovery and comparative toxicology

Quantitative high-throughput screening (qHTS) pharmacologically evaluates chemical libraries for therapeutic uses, toxicological risk and, increasingly, for academic probe discovery. Phenotypic high-throughput screening assays interrogate molecular pathways, often relying on cell culture systems, historically less focused on multicellular organisms. Caenorhabditis elegans has served as a eukaryotic model organism for human biology by virtue of genetic conservation and experimental tractability. Here, a paradigm enabling C. elegans qHTS using 384-well microtiter plate laser-scanning cytometry is described, in which GFP-expressing organisms revealing phenotype-modifying structure-activity relationships guide subsequent life-stage and proteomic analyses, and Escherichia coli bacterial ghosts, a non-replicating nutrient source, allow compound exposures over two life cycles, mitigating bacterial overgrowth complications. We demonstrate the method with libraries of anti-infective agents, or substances of toxicological concern. Each was tested in seven-point titration to assess the feasibility of nematode-based in vivo qHTS, and examples of follow-up strategies were provided to study organism-based chemotype selectivity and subsequent network perturbations with a physiological impact. We anticipate that this qHTS approach will enable analysis of C. elegans orthologous phenotypes of human pathologies to facilitate drug library profiling for a range of therapeutic indications.

Magnetosphere-Ionosphere-Thermosphere Coupling Study at Jupiter Based on Juno's First 30 Orbits and Modeling Tools

The dynamics of the Jovian magnetosphere is controlled by the interplay of the planet's fast rotation, its solar-wind interaction and its main plasma source at the Io torus, mediated by coupling processes involving its magnetosphere, ionosphere, and thermosphere. At the ionospheric level, these processes can be characterized by a set of parameters including conductances, field-aligned currents, horizontal currents, electric fields, transport of charged particles along field lines including the fluxes of electrons precipitating into the upper atmosphere which trigger auroral emissions, and the particle and Joule heating power dissipation rates into the upper atmosphere. Determination of these key parameters makes it possible to estimate the net transfer of momentum and energy between Jovian upper atmosphere and equatorial magnetosphere. A method based on a combined use of Juno multi-instrument data and three modeling tools was developed by Wang et al. (2021, https://doi.org/10.1029/2021ja029469) and applied to an analysis of the first nine orbits to retrieve these parameters along Juno's magnetic footprint. We extend this method to the first 30 Juno science orbits and to both hemispheres. Our results reveal a large variability of these parameters from orbit to orbit and between the two hemispheres. They also show dominant trends. Southern current systems are consistent with the generation of a region of sub-corotating ionospheric plasma flows, while both super-corotating and sub-corotating plasma flows are found in the north. These results are discussed in light of the previous space and ground-based observations and currently available models of plasma convection and current systems, and their implications are assessed.

A Perspective on Substorm Dynamics Using 10 Years of Auroral Kilometric Radiation Observations From Wind

We study 10 years (1995-2004 inclusive) of auroral kilometric radiation (AKR) radio emission data from the Wind spacecraft to examine the link between AKR and terrestrial substorms. We use substorm lists based on parameters including ground magnetometer signatures and geosynchronous particle injections as a basis for superposed epoch analyses of the AKR data. The results for each list show a similar, clear response of the AKR power around substorm onset. For nearly all event lists, the average response shows that the AKR power begins to increase around 20 min prior to expansion phase onset, as defined by the respective lists. The analysis of the spectral parameters of AKR bursts show that this increase in power is due to an extension of the source region to higher altitudes, which also precedes expansion phase onset by 20 min. Our observations show that the minimum frequency channel that observes AKR at this time, on average, is 60 kHz. AKR visibility is highly sensitive to observing spacecraft location, and the biggest radio response to substorm onset is seen in the 21:00-03:00 hr local time sector.

Structure-activity relationship of ipglycermide binding to phosphoglycerate mutases

Catalysis of human phosphoglycerate mutase is dependent on a 2,3-bisphosphoglycerate cofactor (dPGM), whereas the nonhomologous isozyme in many parasitic species is cofactor independent (iPGM). This mechanistic and phylogenetic diversity offers an opportunity for selective pharmacologic targeting of glycolysis in disease-causing organisms. We previously discovered ipglycermide, a potent inhibitor of iPGM, from a large combinatorial cyclic peptide library. To fully delineate the ipglycermide pharmacophore, herein we construct a detailed structure–activity relationship using 280 substituted ipglycermide analogs. Binding affinities of these analogs to immobilized Caenorhabditis elegans iPGM, measured as fold enrichment relative to the index residue by deep sequencing of an mRNA display library, illuminated the significance of each amino acid to the pharmacophore. Using cocrystal structures and binding kinetics, we show that the high affinity of ipglycermide for iPGM orthologs, from Brugia malayi, Onchocerca volvulus, Dirofilaria immitis, and Escherichia coli, is achieved by a codependence between (1) the off-rate mediated by the macrocycle Cys14 thiolate coordination to an active-site Zn²⁺ in the iPGM phosphatase domain and (2) shape complementarity surrounding the macrocyclic core at the phosphotransferase–phosphatase domain interface. Our results show that the high-affinity binding of ipglycermide to iPGMs freezes these structurally dynamic enzymes into an inactive, stable complex.

Auroral emissions from Uranus and Neptune

Uranus and Neptune possess highly tilted/offset magnetic fields whose interaction with the solar wind shapes unique twin asymmetric, highly dynamical, magnetospheres. These radiate complex auroral emissions, both reminiscent of those observed at the other planets and unique to the ice giants, which have been detected at radio and ultraviolet (UV) wavelengths to date. Our current knowledge of these radiations, which probe fundamental planetary properties (magnetic field, rotation period, magnetospheric processes, etc.), still mostly relies on Voyager 2 radio, UV and in situ measurements, when the spacecraft flew by each planet in the 1980s. These pioneering observations were, however, limited in time and sampled specific solar wind/magnetosphere configurations, which significantly vary at various timescales down to a fraction of a planetary rotation. Since then, despite repeated Earth-based observations at similar and other wavelengths, only the Uranian UV aurorae have been re-observed at scarce occasions by the Hubble Space Telescope. These observations revealed auroral features radically different from those seen by Voyager 2, diagnosing yet another solar wind/magnetosphere configuration. Perspectives for the in-depth study of the Uranian and Neptunian auroral processes, with implications for exoplanets, include follow-up remote Earth-based observations and future orbital exploration of one or both ice giant planetary systems. This article is part of a discussion meeting issue 'Future exploration of ice giant systems'.

A homogeneous SIRPα-CD47 cell-based, ligand-binding assay: Utility for small molecule drug development in immuno-oncology

CD47 is an immune checkpoint protein that downregulates both the innate and adaptive anti-tumor immune response via its counter receptor SIRPα. Biologics, including humanized CD47 monoclonal antibodies and decoy SIRPα receptors, that block the SIRPα-CD47 interaction, are currently being developed as cancer immunotherapy agents. However, adverse side effects and limited penetration of tumor tissue associated with their structure and large size may impede their clinical application. We recently developed a quantitative high throughput screening assay platform to identify small molecules that disrupt the binding of SIRPα and CD47 as an alternative approach to these protein-based therapeutics. Here, we report on the development and optimization of a cell-based binding assay to validate active small molecules from our biochemical screening effort. This assay has a low volume, high capacity homogenous format that relies on laser scanning cytometry (LSC) and associated techniques to enhance signal to noise measurement of cell surface binding. The LSC assay is specific, concentration dependent, and validated for the two major human SIRPα variants (V1 and V2), with results that parallel those of our biochemical data as well as published studies. We also utilized the LSC assay to confirm published studies showing that the inhibition of amino-terminal pyroglutamate formation on CD47 using the glutaminyl cyclase inhibitor SEN177 disrupts SIRPα binding. The SIRPα-CD47 interaction could be quantitatively measured in live and fixed tumor cells. Use of fixed cells reduces the burden of cell maintenance and provides stable cell standards to control for inter- and intra-assay variations. We also demonstrate the utility of the assay to characterize the activity of the first reported small molecule antagonists of the SIRPα-CD47 interaction. This assay will support the screening of thousands of compounds to identify or validate active small molecules as hits, develop structure activity relationships and assist in the optimization of hits to leads by a typical iterative medicinal chemistry campaign.

The H3+ ionosphere of Uranus: decades-long cooling and local-time morphology

The upper atmosphere of Uranus has been observed to be slowly cooling between 1993 and 2011. New analysis of near-infrared observations of emission from H3+ obtained between 2012 and 2018 reveals that this cooling trend has continued, showing that the upper atmosphere has cooled for 27 years, longer than the length of a nominal season of 21 years. The new observations have offered greater spatial resolution and higher sensitivity than previous ones, enabling the characterization of the H3+ intensity as a function of local time. These profiles peak between 13 and 15 h local time, later than models suggest. The NASA Infrared Telescope Facility iSHELL instrument also provides the detection of a bright H3+ signal on 16 October 2016, rotating into view from the dawn sector. This feature is consistent with an auroral signal, but is the only of its kind present in this comprehensive dataset. This article is part of a discussion meeting issue 'Advances in hydrogen molecular ions: H3+, H5+ and beyond'.

Quantitative high-throughput screening assays for the discovery and development of SIRPα-CD47 interaction inhibitors

CD47 is an immune checkpoint molecule that downregulates key aspects of both the innate and adaptive anti-tumor immune response via its counter receptor SIRPα, and it is expressed at high levels in a wide variety of tumor types. This has led to the development of biologics that inhibit SIRPα engagement including humanized CD47 antibodies and a soluble SIRPα decoy receptor that are currently undergoing clinical trials. Unfortunately, toxicological issues, including anemia related to on-target mechanisms, are barriers to their clinical advancement. Another potential issue with large biologics that bind CD47 is perturbation of CD47 signaling through its high-affinity interaction with the matricellular protein thrombospondin-1 (TSP1). One approach to avoid these shortcomings is to identify and develop small molecule molecular probes and pretherapeutic agents that would (1) selectively target SIRPα or TSP1 interactions with CD47, (2) provide a route to optimize pharmacokinetics, reduce on-target toxicity and maximize tissue penetration, and (3) allow more flexible routes of administration. As the first step toward this goal, we report the development of an automated quantitative high-throughput screening (qHTS) assay platform capable of screening large diverse drug-like chemical libraries to discover novel small molecules that inhibit CD47-SIRPα interaction. Using time-resolved Förster resonance energy transfer (TR-FRET) and bead-based luminescent oxygen channeling assay formats (AlphaScreen), we developed biochemical assays, optimized their performance, and individually tested them in small-molecule library screening. Based on performance and low false positive rate, the LANCE TR-FRET assay was employed in a ~90,000 compound library qHTS, while the AlphaScreen oxygen channeling assay served as a cross-validation orthogonal assay for follow-up characterization. With this multi-assay strategy, we successfully eliminated compounds that interfered with the assays and identified five compounds that inhibit the CD47-SIRPα interaction; these compounds will be further characterized and later disclosed. Importantly, our results validate the large library qHTS for antagonists of CD47-SIRPα interaction and suggest broad applicability of this approach to screen chemical libraries for other protein-protein interaction modulators.

The low-frequency source of Saturn’s kilometric radiation

Understanding how auroral radio emissions are produced by magnetized bodies requires in situ measurements within their source region. Saturn’s kilometric radiation (SKR) has been widely used as a remote proxy of Saturn’s magnetosphere. We present wave and plasma measurements from the Cassini spacecraft during its ring-grazing high-inclination orbits, which passed three times through the high-altitude SKR emission region. Northern dawn-side, narrow-banded radio sources were encountered at frequencies of 10 to 20 kilohertz, within regions of upward currents mapping to the ultraviolet auroral oval. The kilometric waves were produced on the extraordinary mode by the cyclotron maser instability from 6– to 12–kilo–electron volt electron beams and radiated quasi-perpendicularly to the auroral magnetic field lines. The SKR low-frequency sources appear to be strongly controlled by time-variable magnetospheric electron densities.

Baseline mutational patterns and sustained MRD negativity in patients with high-risk smoldering myeloma

Early results of a prospective phase 2 clinical trial of carfilzomib, lenalidomide, and dexamethasone followed by lenalidomide maintenance in high-risk smoldering myeloma showed promising results that were previously published. Here, we provide novel insights into the genetic landscape of high-risk smoldering myeloma and information on sustained minimal residual disease (MRD) negativity with an expanded cohort of patients. Eighteen patients with high-risk smoldering myeloma were enrolled between 29 May 2012, and 14 January 2014. We included patients with newly diagnosed multiple myeloma enrolled in a parallel trial who received the same therapy (reference group). The overall response rate was 100%. With median potential follow-up of 43.3 months, 10 (63%) remain in MRD negativity, and the estimated 4-year progression-free and overall survival rates are 71% and 100%, respectively. Importantly, we report differences in mutational patterns in patients with high-risk smoldering myeloma and newly diagnosed multiple myeloma, reflected in a lower frequency of mutations in significant myeloma genes (6.6% vs 45%) and NFKB pathway genes (6.6% vs 25%). Treatment with carfilzomib, lenalidomide, and dexamethasone followed by lenalidomide maintenance was associated with a 100% response rate and 63% MRD negativity with a safety profile consistent with previous reports for this regimen. This study had a small numbers of participants, but there seemed to be important differences in the genetic landscape of patients with high-risk smoldering myeloma and those with newly diagnosed multiple myeloma, suggestive of a more treatment-responsive biology in early disease.

Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft

We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions-a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ∼27 and 51 R_S . An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection.

KEY POINTS

We observe evidence for reconnection in the cusp plasma at SaturnWe present evidence that the reconnection process can be pulsed at SaturnSaturn's cusp shows similar characteristics to the terrestrial cusp.

Control of autophagic cell death by caspase-10 in multiple myeloma

We performed a loss-of-function RNA interference screen to define therapeutic targets in multiple myeloma, a genetically diverse plasma cell malignancy. Unexpectedly, we discovered that all myeloma lines require caspase-10 for survival irrespective of their genetic abnormalities. The transcription factor IRF4 induces both caspase-10 and its associated protein cFLIPL in myeloma, generating a protease that does not induce apoptosis but rather blocks an autophagy-dependent cell death pathway. Caspase-10 inhibits autophagy by cleaving the BCL2-interacting protein BCLAF1, itself a strong inducer of autophagy that acts by displacing beclin-1 from BCL2. While myeloma cells require a basal level of autophagy for survival, caspase-10 tempers this response to avoid cell death. Drugs that disrupt this vital balance may have therapeutic potential in myeloma.

Cooperative epigenetic modulation by cancer amplicon genes

Chromosome band 9p24 is frequently amplified in primary mediastinal B cell lymphoma (PMBL) and Hodgkin lymphoma (HL). To identify oncogenes in this amplicon, we screened an RNA interference library targeting amplicon genes and thereby identified JAK2 and the histone demethylase JMJD2C as essential genes in these lymphomas. Inhibition of JAK2 and JMJD2C cooperated in killing these lymphomas by decreasing tyrosine 41 phosphorylation and increasing lysine 9 trimethylation of histone H3, promoting heterochromatin formation. MYC, a major target of JAK2-mediated histone phosphorylation, was silenced after JAK2 and JMJD2C inhibition, with a corresponding increase in repressive chromatin. Hence, JAK2 and JMJD2C cooperatively remodel the PMBL and HL epigenome, offering a mechanistic rationale for the development of JAK2 and JMJD2C inhibitors in these diseases.

Chronic active B-cell-receptor signalling in diffuse large B-cell lymphoma

A role for B-cell-receptor (BCR) signalling in lymphomagenesis has been inferred by studying immunoglobulin genes in human lymphomas and by engineering mouse models, but genetic and functional evidence for its oncogenic role in human lymphomas is needed. Here we describe a form of 'chronic active' BCR signalling that is required for cell survival in the activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL). The signalling adaptor CARD11 is required for constitutive NF-kappaB pathway activity and survival in ABC DLBCL. Roughly 10% of ABC DLBCLs have mutant CARD11 isoforms that activate NF-kappaB, but the mechanism that engages wild-type CARD11 in other ABC DLBCLs was unknown. An RNA interference genetic screen revealed that a BCR signalling component, Bruton's tyrosine kinase, is essential for the survival of ABC DLBCLs with wild-type CARD11. In addition, knockdown of proximal BCR subunits (IgM, Ig-kappa, CD79A and CD79B) killed ABC DLBCLs with wild-type CARD11 but not other lymphomas. The BCRs in these ABC DLBCLs formed prominent clusters in the plasma membrane with low diffusion, similarly to BCRs in antigen-stimulated normal B cells. Somatic mutations affecting the immunoreceptor tyrosine-based activation motif (ITAM) signalling modules of CD79B and CD79A were detected frequently in ABC DLBCL biopsy samples but rarely in other DLBCLs and never in Burkitt's lymphoma or mucosa-associated lymphoid tissue lymphoma. In 18% of ABC DLBCLs, one functionally critical residue of CD79B, the first ITAM tyrosine, was mutated. These mutations increased surface BCR expression and attenuated Lyn kinase, a feedback inhibitor of BCR signalling. These findings establish chronic active BCR signalling as a new pathogenetic mechanism in ABC DLBCL, suggesting several therapeutic strategies.

A library of gene expression signatures to illuminate normal and pathological lymphoid biology

Genomics has provided a lever to pry open lymphoid cells and examine their regulatory biology. The large body of available gene expression data has also allowed us to define the of coordinately expressed genes, termed gene expression signatures, which characterize the states of cellular physiology that reflect cellular differentiation, activation of signaling pathways, and the action of transcription factors. Gene expression signatures that reflect the action of individual transcription factors can be defined by perturbing transcription factor function using RNA interference (RNAi), small-molecule inhibition, and dominant-negative approaches. We have used this methodology to define gene expression signatures of various transcription factors controlling B-cell differentiation and activation, including BCL-6, B lymphocyte-induced maturation protein-1 (Blimp-1), X-box binding protein-1 (XBP1), nuclear factor-kappaB (NF-kappaB), and c-myc. We have also curated a wide variety of gene expression signatures from the literature and assembled these into a signature database. Statistical methods can define whether any signature in this database is differentially expressed in independent biological samples, an approach we have used to gain mechanistic insights into the origin and clinical behavior of B-cell lymphomas. We also discuss the use of genomic-scale RNAi libraries to identify genes and pathways that may serve as therapeutic targets in B-cell malignancies.

Interactions between CD47 and Thrombospondin Reduce Inflammation

CD47 on the surface of T cells was shown in vitro to mediate either T cell activation or, in the presence of high amounts of thrombospondin (TSP), T cell apoptosis. We report here that CD47-deficient mice, as well as TSP-1 or TSP-2-deficient mice, sustain oxazolone-induced inflammation for more than four days, whereas wild-type mice reduce the inflammation within 48 h. We observe that prolonged inflammation in CD47-, TSP-1-, or TSP-2-deficient mice is accompanied by a local deficiency of T cell apoptosis. Finally, we show that upon activation normal T cells increase the expression of the proapoptotic Bcl-2 family member BNIP3 (Bcl-2/adenovirus E1B 19-kDa interacting protein) and undergo CD47-mediated apoptosis. This finding is consistent with our previous demonstration of a physical interaction between BNIP3 and CD47 that inhibits BNIP3 degradation by the proteasome, sensitizing T cells to CD47-induced apoptosis. Overall, these results reveal an important role in vivo for this new CD47/BNIP3 pathway in limiting inflammation by controlling the number of activated T cells.

A loss-of-function RNA interference screen for molecular targets in cancer

The pursuit of novel therapeutic agents in cancer relies on the identification and validation of molecular targets. Hallmarks of cancer include self-sufficiency in growth signals and evasion from apoptosis; genes that regulate these processes may be optimal for therapeutic attack. Here we describe a loss-of-function screen for genes required for the proliferation and survival of cancer cells using an RNA interference library. We used a doxycycline-inducible retroviral vector for the expression of small hairpin RNAs (shRNAs) to construct a library targeting 2,500 human genes. We used retroviral pools from this library to infect cell lines representing two distinct molecular subgroups of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like DLBCL and germinal centre B-cell-like DLBCL. Each vector was engineered to contain a unique 60-base-pair 'bar code', allowing the abundance of an individual shRNA vector within a population of transduced cells to be measured using microarrays of the bar-code sequences. We observed that a subset of shRNA vectors was depleted from the transduced cells after three weeks in culture only if shRNA expression was induced. In activated B-cell-like DLBCL cells, but not germinal centre B-cell-like DLBCL cells, shRNAs targeting the NF-kappaB pathway were depleted, in keeping with the essential role of this pathway in the survival of activated B-cell-like DLBCL. This screen uncovered CARD11 as a key upstream signalling component responsible for the constitutive IkappaB kinase activity in activated B-cell-like DLBCL. The methodology that we describe can be used to establish a functional taxonomy of cancer and help reveal new classes of therapeutic targets distinct from known oncogenes.

Cholera toxin B-subunit prevents activation and proliferation of human CD4+ T cells by activation of a neutral sphingomyelinase in lipid rafts

The inhibition of human CD4+ T lymphocyte activation and proliferation by cholera toxin B-subunit (CTB) is a well-established phenomenon; nevertheless, the exact mechanism remained unclear. In the present study, we propose an explanation for the rCTB-induced inhibition of CD4+ T lymphocytes. rCTB specifically binds to GM1, a raft marker, and strongly modifies the lipid composition of rafts. First, rCTB inhibits sphingomyelin synthesis; second, it enhances phosphatidylcholine synthesis; and third, it activates a raft-resident neutral sphingomyelinase resembling to neutral sphingomyelinase type 1, thus generating a transient ceramide production. We demonstrated that these ceramides inhibit protein kinase Calpha phosphorylation and its translocation into the modified lipid rafts. Furthermore, we show that rCTB-induced ceramide production activate NF-kappaB. Combined all together: raft modification in terms of lipids, ceramide production, protein kinase Calpha inhibition, and NF-kappaB activation lead to CD4+ T cell inhibition.

CD47 and the 19 kDa interacting protein-3 (BNIP3) in T cell apoptosis

CD47 is a surface receptor that induces either coactivation or apoptosis in lymphocytes, depending on the ligand(s) bound. Interestingly, the apoptotic pathway is independent of caspase activation and cytochrome c release and is accompanied by early mitochondrial dysfunction with suppression of mitochondrial membrane potential (Deltapsim). Using CD47 as bait in a yeast two-hybrid system, we identified the Bcl-2 homology 3 (BH3)-only protein 19 kDa interacting protein-3 (BNIP3), a pro-apoptotic member of the Bcl-2 family, as a novel partner. Interaction between CD47 and the BH3-only protein was confirmed by immunoprecipitation analysis, and CD47-induced apoptosis was inhibited by attenuating BNIP3 expression with antisense oligonucleotides. Finally, we showed that the C-terminal domain of thrombospondin-1 (TSP-1), but not signal-regulatory protein (SIRPalpha1), is the ligand for CD47 involved in inducing cell death. Immunofluorescence analysis of CD47 and BNIP3 revealed a partial colocalization of both molecules under basal conditions. After T cell stimulation via CD47, BNIP3 translocates to the mitochondria to induce apoptosis. These results show that the BH3-dependent apoptotic pathways, previously shown to be activated by intracellular pro-apoptotic events, can also be turned on by surface receptors. This new pathway results in a fast induction of cell death resembling necrosis, which is likely to play an important role in lymphocyte regulation at inflammatory sites and/or in the vicinity of thrombosis.

Signaling through ZAP-70 is required for CXCL12-mediated T-cell transendothelial migration

Transendothelial migration of activated lymphocytes from the blood into the tissues is an essential step for immune functions. The housekeeping chemokine CXCL12 (or stroma cell-derived factor-1alpha), a highly efficient chemoattractant for T lymphocytes, drives lymphocytes to sites where they are highly likely to encounter antigens. This suggests that cross-talk between the T-cell receptor (TCR) and CXCR4 (the CXCL12 receptor) might occur within these sites. Here we show that the zeta-associated protein 70 (ZAP-70), a key element in TCR signaling, is required for CXCR4 signal transduction. The pharmacologic inhibition of ZAP-70, or the absence of ZAP-70 in Jurkat T cells and in primary CD4(+) T cells obtained from a patient with ZAP deficiency, resulted in an impairment of transendothelial migration that was rescued by the transfection of ZAP-70. Moreover, the overexpression of mutated forms of ZAP-70, whose kinase domain was inactivated, also abrogated the migratory response of Jurkat T cells to CXCL12. In contrast, no involvement of ZAP-70 in T-cell arrest on inflammatory endothelium under flow conditions or in CXCL12-induced actin polymerization was observed. Furthermore, CXCL12 induced time-dependent phosphorylation of ZAP-70, Vav1, and extracellular signal-regulated kinases (ERKs); the latter were reduced in the absence of functional ZAP-70. However, though a dominant-negative Vav1 mutant (Vav1 L213A) blocked CXCL12-induced T-cell migration, pharmacologic inhibition of the ERK pathway did not affect migration, suggesting that ERK activation is dispensable for T-cell chemotaxis. We conclude that cross-talk between the ZAP-70 signaling pathway and the chemokine receptor CXCR4 is required for T-cell migration.

Integrin-associated protein (CD47/IAP) contributes to T cell arrest on inflammatory vascular endothelium under flow

Integrin-associated protein (CD47/IAP) is a pentaspan molecule that regulates integrin functions. We prepared a CD47-deficient Jurkat T cell line to assess its role in the arrest of T cells on inflammatory endothelium. Under flow conditions, constitutive arrest of CD47-deficient cells is strongly decreased as compared to the original cell line, whereas reexpression of CD47 reestablishes their ability to stop. Moreover, cells transfected with a chimera made with the extracellular portion of CD47 and the transmembrane domain of CD7 or several truncated forms of CD47 show that the first transmembrane domain and a short cytoplasmic loop are sufficient for this process. CD47 effect is indirect and depends mainly on the alpha4beta1/VCAM-1 pathway, as shown by blocking antibodies. We detected on endothelium the two CD47 counter receptors known to date: thrombospondin and SIRP1alpha. Blocking experiments show that both are involved. Overall, CD47 participates in the constitutive arrest of T lymphocytes on inflamed vascular endothelium by up-regulating alpha 4beta1 integrins.

The hemagglutinating adhesin HA-Ag2 of Bacteroides gingivalis is distinct from fimbrilin

We carried out a series of immunoblots with antigenic preparations from the periodontal pathogen Bacteroides gingivalis using antisera of restricted specificity for the hemagglutinating adhesin HA-Ag2, and for the major structural subunit of the fimbriae (fimbrilin). We have been able to show that these 2 antigens are distinct. The fimbrilin subunit had an apparent molecular weight of 42 kDa in all of the bacterial preparations tested. HA-Ag2 occurred as a pair of bands at 43 and 49 kDa in outer membranes prepared as extracellular vesicles, and at 33 and 38 kDa in glass-bead-EDTA extracted antigens and in sheared-cell outer membranes prepared in the presence of EDTA. No HA-Ag2 was found in an enriched fimbrial preparation. The 2 antigens could thus be distinguished on the basis of their behaviour when subjected to different extraction techniques. The lower apparent molecular weight of HA-Ag2 (a pair of bands at 33 and 38 kDa) was invariably associated with the presence of EDTA in the buffers used to prepare the extracts, and the effect could be partially prevented by adding MgCl2 to the extraction buffer. The difference in apparent molecular weight of HA-Ag2 in the different extracts can thus be attributed either to an EDTA-sensitive tertiary conformation of its component polypeptides, or to an EDTA-sensitive linkage of each of these polypeptides to an unknown component of approximately 10 kDa.

Modulation of egg-white lysozyme activity by viscosity intensifier additives

The activity of egg-white lysozyme was measured in the presence of carbohydrate additives in the reaction medium. These additives show a significant affinity for water. They depress water activity and increase the viscosity of the medium. Solute-solvent interactions in aqueous solutions of the additives are characterized by properties such as the intrinsic viscosity, Huggins constant apparent molar volume and hydration number. It was found that, despite the lowering of enzyme activity when the concentration of additive is increased, the behavior remains Michaelian and neither modification of Km nor inhibition by excess substrate is observed. On the other hand, the effect of the viscosity of the medium on enzyme activity was determined. This effect is independent of the nature of the additive at high viscosities (greater than 4 mPa s-1) for which enzyme activity is very low and appears to vary according to the kind of additive in dilute solution at low viscosities (less than 2 mPa s-1).

Lysozyme kinetics in low water activity media. A possible hydration memory

The influence of water activity on initial lysozyme kinetics is studied. Enzyme catalytic capacity exponentially increases with thermodynamical water activity of the reactant medium; this relation seems independent of the chemical structure of the water activity depressors but dependent on the structuration of water molecules they induce. This influence of water organization on initial enzyme activity is immediate and may be preserved even after a large dilution, thus lysozyme presents a "hydration memory" phenomenon. This effect is in accordance with sorption/desorption isotherms, an hysteresis loop being observed.

[Ectopic ureter ending in the seminal vesicle in adults. Apropos of a case and review of the literature]

The authors report a 38 years old patient in whom an intravenous pyelogram was performed for moderate arterial hypertension. This showed a large filling defect in the right lower part of the bladder without renal function on that side. Endoscopic separation of the jet coming from the right half of the trigone showed a liquid containing numerous spermatozoa. A cystogram opacified by reflux a cavity in the genital system via this, the right ureter. With the diagnosis of ectopic ureter ending in the genital system, a nephro-ureterectomy demonstrated the attachment of the ureter into a pouch which communicated with the bladder and the seminal vesicle. A view of the normal embryology insists on the fact that contrary to the classic view, the pronephros disappears entirely and that the metanephros is at the origin of the Woffian canal which opens on the posterior wall of the urogenital sinus at the 28th day when the ureter springs from a ureteral bud. Since 1960 this would be the 34th case in the literature, seminal ectopia (24%) coming after ectopia in the prostatic urethra (54%). Epididymitis is a frequent presenting symptom (44%). The workup shows: absence of renal function (100%), raising of the ipsilateral trigone by a cystic swelling (76%), absence of the meatus on that side on endoscopy, presence of an ipsilateral mass above the prostate on rectal examination (30%). The diagnosis is confirmed by vasography where the ureter is opacified by the seminal vesicle or by systography after endoscopic incision of the mass. Excision of the seminal vesicle was done in conjunction with total nephroureterectomy in 17% of cases.

Inhibition of respiration and of respiratory development by different doses of chloramphenicol in frog embryos (Rana pipiens)

High doses of chloramphenicol (4.5 and 9 mM) directly inhibited respiration in conjunction with an unusual cleavage anomaly (blastomere refusion) in embryos of the frog, Rana pipiens. Lower doses (2.1-3 mM) did not affect respiration or cleavage and, when added later, did not directly affect respiration or development at any tested stage. Continuous incubation in the latter doses, however, did eventually, by day 6 or 7, produce a parallel retardation of embryonic development and of respiratory development relative to controls, suggestive of impaired mitochondrial biogenesis. A lower continuous dose (0.9 mM) affected neither respiration nor development at any stage.