Adenoviral Bid overexpression induces caspase-dependent cleavage of truncated Bid and p53-independent apoptosis in human non-small cell lung cancers

Proapoptotic gene transfer to promote death or to augment killing by DNA-damaging agents represents a promising strategy for cancer therapy. We have constructed an adenoviral Tet-Off trade mark vector with tightly controlled expression of Bid (Ad-Bid) (Clontech, Palo Alto, CA). Using the non-small cell lung cancer cell lines H460, H358, and A549, low dose Ad-Bid was shown to induce high levels of full-length Bid as well as caspase-3 and -9 activity. Although only a small fraction of Bid was processed to truncated Bid (a step inhibited by benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone), Ad-Bid gene transfer resulted in mitochondrial changes consistent with apoptosis (mitochondrial depolarization, cytochrome c release), DNA fragmentation, and a dramatic loss of cell viability. The proapoptotic effects of Ad-Bid were independent of p53 status and were augmented markedly by caspase-8 activators such as the DNA-damaging agent cisplatin. When Ad-Bid and cisplatin were used together, chemosensitivity was restored in p53-null H358 cells, increasing death from 35% following treatment with cisplatin and Ad-LacZ to >90% death with Ad-Bid and cisplatin (Ad-Bid alone induced 50% cell death under these conditions). Ad-Bid can induce apoptosis in malignant cells and enhance chemosensitivity in the absence of p53, suggesting this approach as a potential cancer therapy.     

Cloning and characterization of a novel RING-B-box-coiled-coil protein with apoptotic function

We have identified a novel RING-B-box-coiled-coil (RBCC) protein (MAIR for macrophage-derived apoptosis-inducing RBCC protein) that consists of an N-terminal RING finger, followed by a B-box zinc finger, a coiled-coil domain, and a B30.2 domain. MAIR mRNA was expressed widely in mouse tissues and was induced by macrophage colony-stimulating factor in murine peritoneal and bone marrow macrophages. MAIR protein initially showed a granular distribution predominantly in the cytoplasm. The addition of zinc to transfectants containing MAIR cDNA as part of a heavy metal-inducible vector caused apoptosis of the cells characterized by cell fragmentation; a reduction in mitochondrial membrane potential; activation of caspase-7, -8, and -9, but not caspase-3; and DNA degradation. We also found that the RING finger and coiled-coil domains were required for MAIR activity by analysis with deletion mutants.     

A novel hematopoietic adaptor protein,Chat-H,positively regulates T cell receptor-mediated interleukin-2 production by Jurkat cells

Chat (Cas/HEF1-associated signal transducer) is a novel adaptor protein with an N-terminal Src homology-2 domain and C-terminal Cas/HEF1 association domain. We report here the molecular cloning of Chat-H, the hematopoietic isoform of Chat. Chat-H has an extended N-terminal domain besides the known Chat domain structures, suggesting a unique function of Chat-H in hematopoietic cells. Jurkat transfectants overexpressing Chat-H show a marked increase in interleukin-2 production after costimulation of T cell receptor and CD28. The degree of JNK activation is enhanced substantially in the Chat-H transfectants upon costimulation. The Src homology-2 domain mutant of Chat-H loses this signal modulating activity. Expression of the Cas/HEF1 association domain mutant exhibits a dominant negative effect on both JNK activation and interleukin-2 production. We further found that Chat-H forms a complex with Pyk2H and enhances its tyrosine 402 phosphorylation, an up-regulator of the JNK pathway. These results suggest that Chat-H positively controls T cell function via integrating the costimulatory signals.     

SigB, SigC, and SigE from Myxococcus xanthus homologous to sigma32 are not required for heat shock response but for multicellular differentiation

Myxococcus xanthus has been known to have multiple sigma factors which are considered to play important roles in regulation of gene expression in development. A new gene encoding a putative sigma factor, sigE, was cloned by using a degenerate oligonucleotide corresponding to the conserved region 2.2 of M. xanthus SigA. In the 2.0-kb nucleotide sequence, an open reading frame consisting of 280 amino acid residues was identified. The amino acid sequence of SigE shows high similarity to heat shock sigma factors in bacteria. However, the sigE gene is not induced by heat shock and deletion of sigE does not affect production of heat shock proteins. SigE is expressed during both vegetative growth and fruiting body development. In the deletion mutant of the sigE gene fruiting body formation is initiated earlier and fewer spores are produced than in the parent strain. Interestingly, the deltasigE mutant shows defects in fruiting body formation at 37 degrees C. In addition to SigE, SigB and SigC show high sequence similarity to heat shock sigma factors. However, even if all three sigma factor genes are disrupted, heat shock proteins are still normally induced. A deltasigBdeltasigCdeltasigE triple deletion strain forms fruiting bodies earlier, but sporulats later than the parent strain. Spores from the triple deletion mutant are aberrant and their viability is less than 0.001% compared with that of the parent strain, suggesting that these sigma factors may have redundant functions in multicellular differentiation of M. xanthus.     

A molecular marker diagnostic of a specific isolate of an arbuscular mycorrhizal fungus,Gigaspora margarita

To investigate the auto-ecology of a strain of Gigaspora margarita in a commercial inoculum, we found a pair of PCR primers amplifying a sequence of 235 bp diagnostic of the isolate. We designed an oligonucleotide probe based on the DNA sequence. The combination of PCR and the probing successfully detected the diagnostic sequence from both DNA preparations of single spores and colonized roots. This protocol enabled us to distinguish the isolate among several isolates from Japan, Nepal and the USA.     

Phosphorylation of neuroglycan C, a brain-specific transmembrane chondroitin sulfate proteoglycan, and its localization in the lipid rafts

Neuroglycan C (NGC) is a brain-specific transmembrane chondroitin sulfate proteoglycan. In the present study, we examined whether NGC could be phosphorylated in neural cells. On metabolic labeling of cultured cerebral cortical cells from the rat fetus with (32)P(i), serine residues in NGC were radiolabeled. Some NGC became detectable in the raft fraction from the rat cerebrum, a signaling microdomain of the plasma membrane, with cerebral development. NGC from the non-raft fraction, not the raft fraction, could be phosphorylated by an in vitro kinase reaction. The phosphorylation of NGC was inhibited by adding to the reaction mixture a recombinant peptide representing the ectodomain of NGC, but not by adding a peptide representing its cytoplasmic domain. NGC could be labeled by an in vitro kinase reaction using [gamma-(32)P]GTP as well as [gamma-(32)P]ATP, and this kinase activity was partially inhibited by 5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole, a selective inhibitor of casein kinase II. In addition to the intracellular phosphorylation, NGC was also phosphorylated at the cell surface by an ectoprotein kinase. This is the first report to demonstrate that NGC can be phosphorylated both intracellularly and pericellularly, and our findings suggest that a kinase with a specificity similar to that of casein kinase II is responsible for the NGC ectodomain phosphorylation.     

Sulfite induces adherence of polymorphonuclear neutrophils to immobilized fibrinogen through activation of Mac-1 beta2-integrin (CD11b/CD18)

Sulfite is a major air pollutant which can cause respiratory tract inflammation characterized by an influx of polymorphonuclear neutrophils (PMN). We have previously shown that human PMN can produce sulfite either spontaneously or in response to stimulation with lipopolysaccharide. We now demonstrate that sulfite activates PMN to adhere to immobilized fibrinogen via the beta2-integrin Mac-1 (CD11b/CD18). Mac-1 expression is not altered by treatment with this agent. Although unaffected by pertussis toxin, sulfite-triggered PMN adhesion was abrogated by pretreating cells with the membrane-impermeant sulfhydryl reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), a modifier of thiol groups on the cell surface. These results suggest that sulfite-induced PMN adhesion is dependent on a modification of thiols at the cell surface. Given its potent antioxidant and antimicrobial activities, sulfite may act as an endogenous mediator in host defense and/or inflammation.