Targeted deletion of CD44v7 exon leads to decreased endothelial cell injury but not tumor cell killing mediated by interleukin-2-activated cytolytic lymphocytes

In the current study, we investigated the nature and role of CD44 variant isoforms involved in endothelial cell (EC) injury and tumor cell cytotoxicity mediated by IL-2-activated killer (LAK) cells. Treatment of CD44 wild-type lymphocytes with IL-2 led to increased gene expression of CD44 v6 and v7 variant isoforms and to significant induction of vascular leak syndrome (VLS). CD44v6-v7 knockout (KO) and CD44v7 KO mice showed markedly reduced levels of IL-2-induced VLS. The decreased VLS in CD44v6-v7 KO and CD44v7 KO mice did not result from differential activation and expansion of CD8+ T cells, NK, and NK-T cells or from altered degree of perivascular lymphocytic infiltration in the lungs. LAK cells from CD44v7 KO mice showed a significant decrease in their ability to adhere to and mediate lysis of EC but not lysis of P815 tumor cells in vitro. CD44v7-mediated lysis of EC by LAK cells was dependent on the activity of phosphatidylinositol 3-kinase and tyrosine kinases. Interestingly, IL-2-activated LAK cells expressing CD44hi but not CD44lo were responsible for EC lysis. Furthermore, lysis of EC targets could be blocked by addition of soluble or enzymatic cleavage of CD44v6-v7-binding glycosaminoglycans. Finally, anti-CD44v7 mAbs caused a significant reduction in the adherence to and killing of EC and led to suppression of IL-2-induced VLS. Together, this study suggests that the expression of CD44v7 on LAK cells plays a specific role in EC injury and that it may be possible to reduce EC injury but not tumor cell killing by specifically targeting CD44v7.     

Rice HMGB1 protein recognizes DNA structures and bends DNA efficiently

We analyzed the DNA-binding and DNA-bending properties of recombinant HMGB1 proteins based on a rice HMGB1 cDNA. Electrophoretic mobility shift assay demonstrated that rice HMGB1 can bind synthetic four-way junction (4H) DNA and DNA minicircles efficiently but the binding to 4H can be completed out by HMGA and histone H1. Conformational changes were detected by circular dichroism analysis with 4H DNA bound to various concentrations of HMGB1 or its truncated forms. T4 ligase-mediated circularization assays with short DNA fragments of 123 bp showed that the protein is capable of increasing DNA flexibility. The 123-bp DNA formed closed circular monomers efficiently in its presence, similar to that in an earlier study on maize HMG. Additionally, our results show for the first time that the basic N-terminal domain enhances the affinity of the plant HMGB1 protein for 4H DNA, while the acidic C-terminal domain has the converse effects.     

Past exposure to densely ionizing radiation leaves a unique permanent signature in the genome

Speculation has long surrounded the question of whether past exposure to ionizing radiation leaves a unique permanent signature in the genome. Intrachromosomal rearrangements or deletions are produced much more efficiently by densely ionizing radiation than by chemical mutagens, x-rays, or endogenous aging processes. Until recently, such stable intrachromosomal aberrations have been very hard to detect, but a new chromosome band painting technique has made their detection practical. We report the detection and quantification of stable intrachromosomal aberrations in lymphocytes of healthy former nuclear-weapons workers who were exposed to plutonium many years ago. Even many years after occupational exposure, more than half the blood cells of the healthy plutonium workers contain large (>6 Mb) intrachromosomal rearrangements. The yield of these aberrations was highly correlated with plutonium dose to the bone marrow. The control groups contained very few such intrachromosomal aberrations. Quantification of this large-scale chromosomal damage in human populations exposed many years earlier will lead to new insights into the mechanisms and risks of cytogenetic damage.     

Two new polyhydroxysteroids from the gorgonian Isis hippuris

Two new polyhydroxysteroids isihippurols A (1) and B (2) were isolated from the MeOH extract of the gorgonian Isis hippuris in addition to nine known steroids namely gorgosterol, 3alpha-acetoxy-24-methyl 11beta,18; 18,20beta; 22,25-triepoxy-5alpha-furostane, hippurin-1, 22-epi-hippuristanol, 22-epi-hippurin-1, 3-acetyl-2-deacetyl-22-epi-hippurin-1, 2-deacetylhippurin-1, 3beta, 7alpha, 11alpha-trihydroxygorgost-5-ene-12beta-acetate and 2-deacetyl-22-epi-hippurin-1. The structures of 1 and 2 have been determined as 1alpha, 3beta, 5alpha, 6beta, 11alpha-pentahydroxygorgosta-12beta-monoacetate and 1alpha, 3beta, 11alpha-trihydroxygorgosta-5alpha, 6alpha-epoxy-12beta-monoacetate respectively by spectral analysis and chemical correlation.     

Cardiac myocyte adenosine A2a receptor activation fails to alter cAMP or contractility: role of receptor localization

Adenosine A2a receptors are found in coronary vascular tissue although, their presence in myocardium is subject to investigation. Although there have been numerous studies on adenosine A2a receptor agonist effects on contractility and cAMP levels in ventricular myocytes, these have yielded conflicting results. Negative pharmacological studies have even led to the conclusion that A2a receptors are not present in cardiac myocytes. The purpose of this study was to determine whether A2a receptors are expressed in rat ventricular myocytes and what physiological effects are mediated via activation of these receptors. Western blot analysis with a polyclonal antibody raised against a peptide sequence specific to the carboxy terminus of the A2a receptor revealed the presence of a band at approximately 45 kDa. However, the immunoreactivity was located in the nonmembrane fraction of the cell lysate. The membrane fraction only exhibited an immunoreactive band > or = 50 kDa. Treatment of isolated myocytes with the adenosine A2a agonist 2-[4-[(2-carboxyethyl)-phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine (CGS-21680) exerted no effects on cAMP levels or myocyte twitch amplitude. These results indicate that although rat ventricular myocytes appear to express adenosine A2a receptors, stimulation with an A2a agonist exerts no functional effects, possibly because of the subcellular localization of the A2a receptor.     

Concurrent translocation of multiple polypeptide chains through the proteasomal degradation channel

The proteasome can actively unfold proteins by sequentially unraveling their substrates from the attachment point of the degradation signal. To investigate the steric constraints imposed on substrate proteins during their degradation by the proteasome, we constructed a model protein in which specific parts of the polypeptide chain were covalently connected through disulfide bridges. The cross-linked model proteins were fully degraded by the proteasome, but two or more cross-links retarded the degradation slightly. These results suggest that the pore of the proteasome allows the concurrent passage of at least three stretches of a polypeptide chain. A degradation channel that can tolerate some steric bulk may reconcile the two opposing needs for degradation that is compartmentalized to avoid aberrant proteolysis yet able to handle a range of substrates of various sizes.     

Yeast Rev1 protein is a G template-specific DNA polymerase

Rev1 protein of Saccharomyces cerevisiae functions with DNA polymerase zeta in mutagenic trans-lesion synthesis. Because of the reported preferential incorporation of a C residue opposite an abasic site, Rev1 has been referred to as a deoxycytidyltransferase. Here, we use steady-state kinetics to examine nucleotide incorporation by Rev1 opposite undamaged and damaged template residues. We show that Rev1 specifically inserts a C residue opposite template G, and it is approximately 25-, 40-, and 400-fold less efficient at inserting a C residue opposite an abasic site, an O(6)-methylguanine, and an 8-oxoguanine lesion, respectively. Rev1 misincorporates G, A, and T residues opposite template G with a frequency of approximately 10(-3) to 10(-4). Consistent with this finding, Rev1 replicates DNA containing a string of Gs in a template-specific manner, but it has a low processivity incorporating 1.6 nucleotides per DNA binding event on the average. From these observations, we infer that Rev1 is a G template-specific DNA polymerase.     

Bioassay of three sulphur containing compounds as rat attractant admixed in cereal-based bait against Rattus rattus Linn

Three sulphur containing compounds, carbon disulphide, dimethyl disulphide and dimethyl sulphide were bioassayed for preference after admixing them in cereal base as ready bait block for use against commensal rat, R. rattus (wild type) in four way choice chamber system. Rat preference for different baits was also studied with automatic recording animal activity meter. Rats exhibited attractancy to the baits at 0.005% concentration of all the three compounds while at 0.01% concentration they have showed repellency. Dimethyl sulphide at 0.005% concentration showed better attractancy towards both sexes of rat.