CD38 controls ADP-ribosyltransferase-2-catalyzed ADP-ribosylation of T cell surface proteins

ADP-ribosyltransferase-2 (ART2), a GPI-anchored, toxin-related ADP-ribosylating ectoenzyme, is prominently expressed by murine T cells but not by B cells. Upon exposure of T cells to NAD, the substrate for ADP-ribosylation, ART2 catalyzes ADP-ribosylation of the P2X7 purinoceptor and other functionally important cell surface proteins. This in turn activates P2X7 and induces exposure of phosphatidylserine and shedding of CD62L. CD38, a potent ecto-NAD-glycohydrolase, is strongly expressed by most B cells but only weakly by T cells. Following incubation with NAD, CD38-deficient splenocytes exhibited lower NAD-glycohydrolase activity and stronger ADP-ribosylation of cell surface proteins than their wild-type counterparts. Depletion of CD38(high) cells from wild-type splenocytes resulted in stronger ADP-ribosylation on the remaining cells. Similarly, treatment of total splenocytes with the CD38 inhibitor nicotinamide 2'-deoxy-2'-fluoroarabinoside adenine dinucleotide increased the level of cell surface ADP-ribosylation. Furthermore, the majority of T cells isolated from CD38-deficient mice "spontaneously" exposed phosphatidylserine and lacked CD62L, most likely reflecting previous encounter with ecto-NAD. Our findings support the notion that ecto-NAD functions as a signaling molecule following its release from cells by lytic or nonlytic mechanisms. ART2 can sense and translate the local concentration of ecto-NAD into corresponding levels of ADP-ribosylated cell surface proteins, whereas CD38 controls the level of cell surface protein ADP-ribosylation by limiting the substrate availability for ART2.     

Inhibition of cell aggregation by specific carbohydrates.

One approach to investigating the potential role of surface carbohydrates in mediating intercellular adhesion is to study cell reaggregation in the presence of defined concentrations of specific saccharides. Fifteen different exogenously added saccharides were tested for their effect on the reaggregation of 24 h sea urchin embryo cells (Strongylocentrotus purpuratus) dissociated by removal of divalent cations. Aliquots (0.2 ml) of cell suspension were rotated at 68 rpm, 17 °C, pH 8.0, with varying concentrations (0.5 × 1^?1?0.5 × 10^?5 M) of the sugars. Relative percents of cell aggregation were determined using an electronic particle counter assay. In all experiments cell viability using trypan blue was over 95.8%. Among the sugars tested, in 15 separate experiments, d-galactose and N-acetyl-d-galactosamine consistently inhibited aggregation to the greatest extent at early time points. d-Galactose, at all concentrations tested, at 10, 20, 30, 40, and 60 min rotation, showed mean decreases of aggregation over control values in the absence of sugar of 59.3, 53.6, 43.2, 35.0 and 36.4%, respectively. N-Acetyl-d-galactosamine also caused mean decreases in aggregation of 73.5, 54.5, 40.8, 42.2 and 45.6%, respectively. Each difference over the control is significant to the p value of less than 0.01. In three experiments, β-galactosidase substantially inhibited reaggregation of these cells. These results suggest that galactopyranosyl-like groups may be implicated in mediating adhesion of 24 h sea urchin embryo cells to each other.     

Pyridine coenzyme analogues. Synthesis and characterization of alpha- and beta-nicotinamide arabinoside adenine dinucleotides

The synthesis and characterization of a new pyridine coenzyme analogue containing a nicotinamide arabinonucleotide moiety are reported. The redox potentials are -339 mV for beta-oxidized nicotinamide arabinoside adenine dinucleotide and -319 mV for alpha-oxidized nicotinamide adenine dinucleotide, and the lambda max is 346 and 338 nm for beta- and alpha-reduced nicotinamide arabinoside adenine dinucleotides (araNADH), respectively. Anomerization of the reduced analogues leads to a 5:1 ratio of alpha-araNADH to beta-araNADH at 90 degrees C. These results establish that the relative configuration of the 2'-hydroxyl to the base is the primary determinant for the configuration-dependent changes in lambda max, the redox potential of the pyridine nucleotides, and the preferred anomeric configuration of the reduced coenzymes. Comparison of the 1H and 31P NMR spectral data of the analogues with those for the ribo coenzymes is reported and the conformational analysis discussed. The coenzyme properties of the arabino analogues have been evaluated with yeast and horse liver alcohol dehydrogenases. Both the alpha- and beta-anomers are found to serve as coenzymes, and the stereochemistry of hydride transfer is identical for both anomers.     

Novel pyrrolo[2,1-f][1,2,4]triazin-4-amines: Dual inhibitors of EGFR and HER2 protein tyrosine kinases

A novel series of 5-((4-aminopiperidin-1-yl)methyl)-pyrrolo[2,1-f][1,2,4]triazin-4-amines with small aniline substituents at the C4 position were optimized for dual EGFR and HER2 protein tyrosine kinase inhibition. Compound 8l exhibited promising oral efficacy in both EGFR and HER2-driven human tumor xenograft models.     

Survey says? A primer on web-based survey design and distribution

The Internet has changed the way in which we gather and interpret information. Although books were once the exclusive bearers of data, knowledge is now only a keystroke away. The Internet has also facilitated the synthesis of new knowledge. Specifically, it has become a tool through which medical research is conducted. A review of the literature reveals that in the past year, over 100 medical publications have been based on Web-based survey data alone. Because of emerging Internet technologies, Web-based surveys can now be launched with little computer knowledge. They may also be self-administered, eliminating personnel requirements. Ultimately, an investigator may build, implement, and analyze survey results with speed and efficiency, obviating the need for mass mailings and data processing. All of these qualities have rendered telephone and mail-based surveys virtually obsolete. Despite these capabilities, Web-based survey techniques are not without their limitations, namely, recall and response biases. When used properly, however, Web-based surveys can greatly simplify the research process. This article discusses the implications of Web-based surveys and provides guidelines for their effective design and distribution.     

Facultative response to a kleptoparasite by the cooperatively breeding pied babbler

In many cases of interspecific kleptoparasitism, hosts developdefensive behaviors to minimize the impact of kleptoparasites.Because vigilance and defensive behaviors are often costly,selection should favor hosts that adjust the amount of investmentneeded to minimize losses to kleptoparasitism. However, examplesof such facultative responses are rare. Here, we investigatethe response of cooperatively breeding pied babblers (Turdoidesbicolor) to the drongo (Dicrurus adsimilis), an avian kleptoparasitethat regularly follows pied babbler groups, often giving alarmcalls to alert the group to predators but also occasionallygiving false alarm calls in order to steal food items. We showthat pied babbler response to drongos varies markedly accordingto babbler group size. In small groups, where there are fewindividuals available to act as sentinels, babblers sentinelless when a drongo is present and respond strongly to drongoalarm calls. However, in large groups, where there are manyindividuals available to participate in predator vigilance,babblers sentinel more often when a drongo is present, rarelyrespond to drongo alarm calls, and aggressively displace drongos,with a consequent decline in the number of successful kleptoparasitismevents. This behavior represent a facultative response to akleptoparasite according to the costs versus benefits of toleratingtheir presence.     

Why Do Sleeping Nematodes Adopt a Hockey-Stick-Like Posture?

A characteristic posture is considered one of the behavioral hallmarks of sleep, and typically includes functional features such as support for the limbs and shielding of sensory organs. The nematode C. elegans exhibits a sleep-like state during a stage termed lethargus, which precedes ecdysis at the transition between larval stages. A hockey-stick-like posture is commonly observed during lethargus. What might its function be? It was previously noted that during lethargus, C. elegans nematodes abruptly rotate about their longitudinal axis. Plausibly, these “flips” facilitate ecdysis by assisting the disassociation of the old cuticle from the new one. We found that body-posture during lethargus was established using a stereotypical motor program and that body bends during lethargus quiescence were actively maintained. Moreover, flips occurred almost exclusively when the animals exhibited a single body bend, preferentially in the anterior or mid section of the body. We describe a simple biomechanical model that imposes the observed lengths of the longitudinally directed body-wall muscles on an otherwise passive elastic rod. We show that this minimal model is sufficient for generating a rotation about the anterior-posterior body axis. Our analysis suggests that posture during lethargus quiescence may serve a developmental role in facilitating flips and that the control of body wall muscles in anterior and posterior body regions are distinct.