Phospholipase A2 activity-dependent stimulation of Ca2+ entry by human parvovirus B19 capsid protein VP1

Recent reports demonstrated an association of human parvovirus B19 with inflammatory cardiomyopathy (iCMP), which is accompanied by endothelial dysfunction. As intracellular Ca(2+) activity is a key regulator of cell function and participates in mechanisms leading to endothelial dysfunction, the present experiments explored the effects of the B19 capsid proteins VP1 and VP2. A secreted phospholipase A2 (PLA2)-like activity has been located in the VP1 unique region of the B19 minor capsid protein. As PLA2 has recently been shown to activate the store-operated or capacitative Ca(2+) channel I(CRAC), we analyzed the impact of the viral PLA2 motif on Ca(2+) entry. We cloned the VP1 and VP2 genes isolated from a patient suffering from fatal B19 iCMP into eukaryotic expression vectors. We also generated a B19 replication-competent plasmid to demonstrate PLA2 activity under the control of the complete B19 genome. After the transfection of human endothelial cells (HMEC-1), cytosolic Ca(2+) activity was determined by utilizing Fura-2 fluorescence. VP1 and VP2 expression did not significantly modify basal cytosolic Ca(2+) activity or the decline of cytosolic Ca(2+) activity following the removal of extracellular Ca(2+). However, expression of VP1 and of the full-length B19 clone, but not of VP2, significantly accelerated the increase of cytosolic Ca(2+) activity following the readdition of extracellular Ca(2+) in the presence of thapsigargin, indicating an activation of I(CRAC.) The effect of VP1 was mimicked by the PLA2 product lysophosphatidylcholine and abolished by an inactivating mutation of the PLA2-encoding region of the VP1 gene. Our observations point to the activation of Ca(2+) entry by VP1 PLA2 activity, an effect likely participating in the pathophysiology of B19 infection.     

The neural cell adhesion molecule binds to fibroblast growth factor receptor 2

The neural cell adhesion molecule (NCAM) can bind to and activate fibroblast growth factor receptor 1 (FGFR1). However, there are four major FGFR isoforms (FGFR1-FGFR4), and it is not known whether NCAM also interacts directly with the other three FGFR isoforms. In this study, we show by surface plasmon resonance analysis that NCAM can bind to FGFR2 with an affinity similar to that for the NCAM-FGFR1 interaction. However, the kinetic parameters for the NCAM-FGFR2 binding are different from those of the NCAM-FGFR1 binding. Both receptors were shown to cycle relatively fast between the NCAM bound and unbound states, although FGFR2 cycling was clearly faster (13 times) than the FGFR1 cycling. Moreover, ATP was more effective in inhibiting the binding of NCAM to FGFR1 than to FGFR2, indicating that the binding sites in NCAM for the two receptors are similar, but not identical.     

Olive fruit fly (Diptera: Tephritidae) populations in relation to region, trap type, season, and availability of fruit

Olive fruit fly, Bactrocera oleae (Gmelin), was monitored with adult captures by season and trap type, and was related to fruit volume and nonharvested fruit to elucidate the occurrence of the newly introduced pest in California. The highest numbers of adults captured in ChamP traps in olive trees, Olea europaea, were in October in an inland valley location, and in September in a coastal location. Comparisons of trap types showed that the number of olive fruit fly adults captured in Pherocon AM traps in a commercial orchard was significantly greater than in ChamP traps. A significantly greater number of females were captured in Pherocon AM traps with bait packets and pheromone lures than traps with pheromone lures alone, while a significantly greater number of adults and males were captured in traps with pheromone lures alone. Significantly more adults were captured in ChamP traps with bait packets and pheromone lures versus traps with bait packets alone. Fruit volume increased by four times from mid-June to mid-November. Olive fruit fly was found to oviposit on small olive fruit <1 cm3 shortly after fruit set, the maximum number of ovipositional sites per fruit occurred in October, and the greatest number of pupae and adults were reared from fruit collected in September and October. The highest numbers of pupae were collected from nonharvested fruit in March when high numbers of adults were captured in the same orchard.     

Role of pyruvate dehydrogenase kinase isoenzyme 4 (PDHK4) in glucose homoeostasis during starvation

The PDC (pyruvate dehydrogenase complex) is strongly inhibited by phosphorylation during starvation to conserve substrates for gluconeogenesis. The role of PDHK4 (pyruvate dehydrogenase kinase isoenzyme 4) in regulation of PDC by this mechanism was investigated with PDHK4-/- mice (homozygous PDHK4 knockout mice). Starvation lowers blood glucose more in mice lacking PDHK4 than in wild-type mice. The activity state of PDC (percentage dephosphorylated and active) is greater in kidney, gastrocnemius muscle, diaphragm and heart but not in the liver of starved PDHK4-/- mice. Intermediates of the gluconeogenic pathway are lower in concentration in the liver of starved PDHK4-/- mice, consistent with a lower rate of gluconeogenesis due to a substrate supply limitation. The concentration of gluconeogenic substrates is lower in the blood of starved PDHK4-/- mice, consistent with reduced formation in peripheral tissues. Isolated diaphragms from starved PDHK4-/- mice accumulate less lactate and pyruvate because of a faster rate of pyruvate oxidation and a reduced rate of glycolysis. BCAAs (branched chain amino acids) are higher in the blood in starved PDHK4-/- mice, consistent with lower blood alanine levels and the importance of BCAAs as a source of amino groups for alanine formation. Non-esterified fatty acids are also elevated more in the blood of starved PDHK4-/- mice, consistent with lower rates of fatty acid oxidation due to increased rates of glucose and pyruvate oxidation due to greater PDC activity. Up-regulation of PDHK4 in tissues other than the liver is clearly important during starvation for regulation of PDC activity and glucose homoeostasis.     

Mouse emi1 has an essential function in mitotic progression during early embryogenesis

For successful mitotic entry and spindle assembly, mitosis-promoting factors are activated at the G(2)/M transition stage, followed by stimulation of the anaphase-promoting complex (APC), an E3 ubiquitin ligase, to direct the ordered destruction of several critical mitotic regulators. Given that inhibition of APC activity is important for preventing premature or improper ubiquitination and destruction of substrates, several modulators and their regulation mechanisms have been studied. Emi1, an early mitotic inhibitor, is one of these regulatory factors. Here we show, by analyzing Emi1-deficient embryos, that Emi1 is essential for precise mitotic progression during early embryogenesis. Emi1(-/-) embryos were found to be lethal due to a defect in preimplantation development. Cell proliferation appeared to be normal, but mitotic progression was severely defective during embryonic cleavage. Moreover, multipolar spindles and misaligned chromosomes were frequently observed in Emi1 mutant cells, possibly due to premature APC activation. Our results collectively suggest that the late prophase checkpoint function of Emi1 is essential for accurate mitotic progression and embryonic viability.     

Estimation and prediction in a multi-state model for breast cancer

An important aim in clinical studies in oncology is to study how treatment and prognostic factors influence the course of disease of a patient. Typically in these trials, besides overall survival, also other endpoints such as locoregional recurrence or distant metastasis are of interest. Most commonly in these situations, Cox regression models are applied for each of these endpoints separately or to composite endpoints such as disease-free survival. These approaches however fail to give insight into what happens to a patient after a first event. We re-analyzed data of 2795 patients from a breast cancer trial (EORTC 10854) by applying a multi-state model, with local recurrence, distant metastasis, and both local recurrence and distant metastasis as transient states and death as absorbing state. We used an approach where the clock is reset on entry of a new state. The influence of prognostic factors on each of the transition rates is studied, as well as the influence of the time at which intermediate events occur. The estimated transition rates between the states in the model are used to obtain predictions for patients with a given history. Formulas are developed and illustrated for these prediction probabilities for the clock reset approach.     

Generation and characterization of a humanized bradykinin B1 receptor mouse

Antagonists of the B1 bradykinin receptor (B1R), encoded by the BDKRB1 gene, offer the promise of novel therapeutic agents for inflammatory and neuropathic pain. However, the in vivo characterization of the pharmacodynamics of B1R antagonists is hindered by the low level of B1R expression in healthy tissue and the profound species selectivity exhibited by many compounds for the B1R. To circumvent these issues we generated two genetically engineered rodent models. The first is a transgenic rat over-expressing the human B1R under the control of the neuronal-specific enolase promoter; we previously reported the utility of this model in assessing human B1R receptor occupancy in the central nervous system of the rat. The second model, reported here, utilized gene-targeting by homologous recombination to replace the genomic coding sequence for the endogenous mouse B1R with that of the human B1R. The mRNA expression profile of the humanized Bdkrb1 (hBkdrb1) allele is similar to that of the mouse Bdkrb1 (mBkdrb1) in the wild-type animal. Furthermore, in vitro assays indicate that tissues isolated from the humanized mouse possess pharmacological properties characteristic of the human B1R. Therefore, we have generated a humanized B1R mouse model that is suitable for testing the efficacy of human B1R-selective compounds.