Mechanisms underlying TGF-beta1-induced expression of VEGF and Flk-1 in mouse macrophages and their implications for angiogenesis.

TGF-beta induces vascular endothelial growth factor (VEGF), a potent angiogenic factor, at the transcriptional and protein levels in mouse macrophages. VEGF secretion in response to TGF-beta1 is enhanced by hypoxia and by overexpression of Smad3/4 and hypoxia-inducible factor-1alpha/beta (HIF-1alpha/beta). To examine the transcriptional regulation of VEGF by TGF-beta1, we constructed mouse reporters driven by the VEGF promoter. Overexpression of HIF-1alpha/beta or Smad3/4 caused a slight increase of VEGF promoter activity in the presence of TGF-beta1, whereas cotransfection of HIF-1alpha/beta and Smad3/4 had a marked effect. Smad2 was without effect on this promoter activity, whereas Smad7 markedly reduced it. Analysis of mutant promoters revealed that the one putative HIF-1 and two Smad-binding elements were critical for TGF-beta1-induced VEGF promoter activity. The relevance of these elements was confirmed by chromatin immunoprecipitation assay. p300, which has histone acetyltransferase activity, augmented transcriptional activity in response to HIF-1alpha/beta and Smad3/4, and E1A, an inhibitor of p300, inhibited it. TGF-beta1 also increased the expression of fetal liver kinase-1 (Flk-1), a major VEGF receptor, and TGF-beta1 and VEGF stimulated pro-matrix metalloproteinase 9 (MMP-9) and active-MMP-9 expression, respectively. The results from the present study indicate that TGF-beta1 can activate mouse macrophages to express angiogenic mediators such as VEGF, MMP-9, and Flk-1.

Alternative production of avermectin components in Streptomyces avermitilis by gene replacement.

The avermectins are composed of eight compounds, which exhibit structural differences at three positions. A family of four closely-related major components, A1a, A2a, B1a and B2a, has been identified. Of these components, B1a exhibits the most potent antihelminthic activity. The coexistence of the "1" components and "2" components has been accounted for by the defective dehydratase of aveAI module 2, which appears to be responsible for C22-23 dehydration. Therefore, we have attempted to replace the dehydratase of aveAI module 2 with the functional dehydratase from the erythromycin eryAII module 4, via homologous recombination. Erythromycin polyketide synthetase should contain the sole dehydratase domain, thus generating a saturated chain at the C6-7 of erythromycin. We constructed replacement plasmids with PCR products, by using primers which had been derived from the sequences of avermectin aveAI and the erythromycin eryAII biosynthetic gene cluster. If the original dehydratase of Streptomyces avermitilis were exchanged with the corresponding erythromycin gene located on the replacement plasmid, it would be expected to result in the formation of precursors which contain alkene at C22-23, formed by the dehydratase of erythromycin module 4, and further processed by avermectin polyketide synthase. Consequently, the resulting recombinant strain JW3105, which harbors the dehydratase gene derived from erythromycin, was shown to produce only C22,23-unsaturated avermectin compounds. Our research indicates that the desired compound may be produced via polyketide gene replacement.

Affinity adsorbent based on combinatorial phage display peptides that bind alpha-cobratoxin.

Combinatorial phage display was used to discover peptides that selectively bind to the alpha-cobratoxin (neurotoxin) component of the multi-component venom of the Thai cobra, Naja kaouthia. Peptide sequences determined in this way were synthesized chemically and were covalently attached to agarose through the alpha-amino terminus. Such affinity chromatography supports selectively bound the alpha-cobratoxin component from crude venom, while passage of the crude venom over the support selectively depleted the venom of this component. The selective binding of alpha-cobratoxin to peptide-based solid-phase supports suggests that a limitless variety of peptides similarly obtained by combinatorial phage display can be used to craft specific analytical and preparative tools.

Induction of growth phase-specific autolysis in Bacillus subtilis 168 by growth inhibitors.

Growth phase-specific autolysis of Bacillus subtilis by inhibitors of membrane permeability, inhibitors of macromolecule biosynthesis, inhibitors of cell wall biosynthesis and detergents were tested and characterized in glucose limited liquid medium. The minimum autolysin induction concentration (MAIC) of test compounds, which was at least 1/20th lower than the conventional autolysis induction concentration, induced autolysis only for cells at the glucose exhaustion point (diauxic point) of the growth phase, while it was not induced for cells at pre- and post-diauxic points. Inhibitors of macromolecule synthesis that are not known for inducing autolysis, such as chloramphenicol, rifampicin, nalidixic acid, and detergents, also induced specific autolysis. Two types of autolysis corresponding to the concentrations of compounds are distinguished: concentration-sensitive and concentration-insensitive types.

IL-4-induced AID expression and its relevance to IgA class switch recombination.

Activation-induced cytidine deaminase (AID) is an inducible gene that plays a critical role in Ig class switch recombination and somatic hypermutation in B cells. We explored the mechanisms by which IL-4 induces AID expression in mouse B cells. IL-4 increased AID expression and over-expression of Stat6 further augmented IL-4-induced promoter activity. The involvement of Stat6 in the promoter activity was confirmed using ChIP assays and site-directed mutagenesis. Treatment with H89, a PKA inhibitor, markedly decreased IL-4-induced AID expression, and over-expression of CREB enhanced it. These results indicate that Stat6 and PKA/CREB are involved in IL-4-induced AID expression. The relevance of these signal transducing molecules was verified using the TGFbeta1-induced IgA isotype switching model. Our results indicate that IL-4, through Stat6 and PKA/CREB, induces AID expression leading to Ig isotype switching event.