Signaling function of PSGL-1 in neutrophil: tyrosine-phosphorylation-dependent and c-Abl-involved alteration in the F-actin-based cytoskeleton

P-selectin glycoprotein ligand-1 (PSGL-1) is the best-characterized selectin ligand that has been demonstrated to mediate leukocytes rolling on endothelium and leukocytes recruitment into inflamed tissue in vivo. In addition to its direct role in leukocyte capturing, PSGL-1 also functions as a signal-transducing receptor. The present work showed that after cross-linking of PSGL-1 with KPL1, an anti-PSGL-1 monoclonal antibody, PSGL-1 linked to the cytoskeleton and became a detergent-insoluble component in activated neutrophils. The antibody cross-linking led to the polymerization and redistribution of F-actin-based cytoskeleton, and this alteration of cytoskeleton was spatiotemporally related to the polarization of PSGL-1. PSGL-1's polarization was cytoskeleton-dependent because it was eliminated by cytochalasin B. Furthermore, the polymerization and redistribution of F-actin filaments were tyrosine-phosphorylation-dependent since the alteration of F-actin-based cytoskeleton was severely blocked by genistein, a universal tyrosine kinase inhibitor. STI571, a small molecule inhibitor for cytoplasmic tyrosine kinase c-Abl, also inhibited the alteration of F-actin-based cytoskeleton, and c-Abl was redistributed to where F-actin concentrated in the activated neutrophils. The results suggested that cross-linking of PSGL-1 induces the phosphorylation-dependent and c-Abl-involved alteration of F-actin-based cytoskeleton in neutrophils.     

A nitrosated arginine derivative, a powerful mutagen

An arginine derivative, benzoyl-L-arginineamide, when nitrosated, showed a powerful mutagenic action on $\text{E. coli}$ and $\text{Salmonella typhimurium}$. The active principle was identified to be 4-benzoylamido-4-carboxamidon(N-nitroso)butylcyanamide. The mutagenic activity of the new compound was more than 30 times higher than that of N-methyl-N′-nitro-N-nitrosoguanidine at neutral pH.     

Characterization of trimethylpsoralen as a mutagen for mouse embryonic stem cells

Given a large number of genes with unknown functions in model organisms, collections of mutants are valuable resources for studying gene function. For the mouse, embryonic stem cell technology offers the possibility to manipulate the genome and select for mutations in vitro. Mutant mice can then be generated from clones of interest to study the phenotype of these animals. We manipulate the genome of mouse embryonic stem (ES) cells chemically using the mutagen trimethylpsoralen (TMP). TMP predominantly causes deletions in the genome of Caenorhabditis elegans and Escherichia coli, but has not been established as a mutagen in mammalian systems yet. We have characterized TMP as a mutagen for mouse ES cells regarding death rates, mutation frequencies, and mutation spectrum. Allowing for 12.5% of cell survival, the mutation frequency at the mouse hypoxanthine-guanine phosphoribosyltransferase (Hprt) locus was 3.5 x 10(-5) on average. The characterization of a non-redundant set of 17 Hprt-deficient ES clones revealed that only 12% of clones contained genomic deletions and almost 50% were point mutations. Base substitutions were mostly transversions and all affected AT base pairs. We conclude that the mutation spectrum of TMP in mouse ES cells is different from that observed in C. elegans and E. coli.     

Nedd4, a human ubiquitin ligase, affects actin cytoskeleton in yeast cells

Human Nedd4 ubiquitin ligase is involved in protein trafficking, signal transduction and oncogenesis. Nedd4 with an inactive WW4 domain is toxic to yeast cells. We report here that actin cytoskeleton is abnormal in yeast cells expressing the NEDD4 or NEDD4w4 gene and these cells are more sensitive to Latrunculin A, an actin-depolymerizing drug. These phenotypes are less pronounced when a mutation inactivating the catalytic domain of the ligase has been introduced. In contrast, overexpression of the LAS17 gene, encoding an activator of the Arp2/3 actin nucleating complex, is detrimental to NEDD4w4-expressing cells. The level of Las17p is increased in cells overproducing Nedd4w4 and this depends partially on its catalytic domain. Expression of genes encoding Nedd4 variants, like overexpression of LAS17, suppresses the growth defect of the arp2-1 strain. Our results suggest that human Nedd4 ligase inhibits yeast cell growth by disturbing the actin cytoskeleton, in part by increasing Las17p level, and that Nedd4 ubiquitination targets may include actin cytoskeleton-associated proteins conserved in evolution.     

Nitrite converts 2-amino-alpha-carboline, an indirect mutagen, into 2-hydroxy-alpha-carboline, a non-mutagen, and 2-hydroxy-3-nitroso-alpha-carboline, a direct mutagen

2-Amino-alpha-carboline [26148-68-5] which was isolated from a pyrolysate of soybean globulin and which was mutagenic to Salmonella typhimurium in the presence of a rat-liver microsomal fraction (S9 mix), was converted into non-mutagenic 2-hydroxy-alpha-carboline by treatment with nitrite in acidic conditions. However, on prolonged treatment with nitrite and acid, 2-hydroxy-alpha-carboline was further converted into a new mutagen which did not require S9 mix for exhibition of the mutagenicity. This direct-acting mutagen was found to be 2-hydroxy-3-nitroso-alpha-carboline by mass and proton magnetic resonance spectroscopies.     

Hycanthone as a specific frameshift mutagen in Saccharomyces cerevisiae

Reversion of mutations of different molecular nature was studied after treatment with hycanthone in mild conditions (0.05–0.4 mM, 4 h in the dark, pH 7.2). The mutagen had a very low reversion activity on 3 missense and 4 nonsense mutations (2 UAA and 2 UAG), although it was very active on 3 frameshift mutations. Our data on intragenic reversion and frameshift suppressors indicate that hycanthone can induce both insertions and deletions.     

Reorganization of cytoskeleton as a basis of morphogenesis

A brief review of the cytoskeleton dynamic structure in cells of two types: fibroblasts and epitheliocytes. Differences have been described between the functions of γ-actin filaments and β-actomyosin bundles. Tubulogenesis and angiogenesis have been considered as consequences of partial epitheliomesenchymal transformation and neoplastic transformation as a consequence of γ-actomyosin bundles disturbance.     

Natulan,a bacterial mutagen requiring complex mammalian metabolic activation

Following administration of Natulan^R and Escherichia coli to mice a dose-dependent increase in the frequency of induced bacterial mutations was observed. This mutation response was dependent on the route of Natulan administration and, following short exposures, was limited by the rate of metabolic activation of the compound.     

Identification of methylglyoxal as a major mutagen in wood and bamboo pyroligneous acids

To identify the major mutagen in pyroligneous acid (PA), 10 wood and 10 bamboo pyroligneous acids were examined using the Ames test in Salmonella typhimurium strains TA100 and TA98. Subsequently, the mutagenic dicarbonyl compounds (DCs), glyoxal, methylglyoxal (MG), and diacetyl in PA were quantified using high-performance liquid chromatography, and the mutagenic contribution ratios for each DC were calculated relative to the mutagenicity of PA. Eighteen samples were positive for mutagens and showed the strongest mutagenicity in TA100 in the absence of S9 mix. MG had the highest mutagenic contribution ratio, and its presence was strongly correlated with the specific mutagenicity of PA. These data indicate that MG is the major mutagen in PA.