Cloning, Expression, and Affinity Purification of RecombinantShigella flexneriInvasion Plasmid Antigens IpaB and IpaC

Shigella flexneriand related enteropathogenic bacteria are important agents of bacillary dysentery, a potentially life-threatening illness for children in underdeveloped regions of the world. Onset of shigellosis stems fromS. flexneriinvasion of colonic epithelial cells, leading to localized cell death and inflammation. Invasion plasmid antigens (Ipa) B, C, and D are three secreted proteins encoded by the large virulence plasmid ofS. flexnerithat have been implicated as essential effectors of this cell invasion process. These proteins are expressed as part of theipaoperon and are among the major targets of the host immune response to shigellosis. Biochemical characterization of the Ipa invasins has been complicated by the fact they have not been purified in the quantities needed for detailedin vitroanalysis. Here we describe the first cloning, expression, and extensive purification of IpaB and IpaC fusion proteins fromEscherichia colifor use in dissecting of the protein biochemistry ofS. flexneripathogenesis. A variety of approaches were used to prepare significant quantities of these proteins in their soluble forms, including the use of different host cell lines, modification of bacterial growth conditions, and the use of alternative plasmid expression vectors. Now that these Ipa proteins are available in a highly pure form, it will be possible to initiate studies on their important biological and immunological properties as well as their recruitment into high-molecular-weight protein complexes. Together with IpaD (purified as part of a previous study), these purified proteins will be useful for: (a) exploring properties of the host immune response toS. flexneriinvasion, (b) elucidating the specific biochemical properties that lead to pathogen internalization, (c) analyzing the importance of specific Ipa protein complexes in host cell invasion, and (d) monitoring, or perhaps even augmenting, the efficacy of live oral vaccines in human trials.     

Effect of platelet-derived growth factor on DNA synthesis and gene expression in bone marrow stromal cells derived from adult and old rats

The effects of platelet-derived growth factor (PDGF) on DNA synthesis and mRNA expression of osteoblast markers in marrow stromal cells derived from adult (6 months) and old (24 months) rats were examined. Treatment of stromal cells from adult rats with dexamethasone induced the appearance of osteoblast-like cells. PDGF partially also inhibited the differentiation of stromal cells induced by dexamethasone. In cultures of serum-starved stromal cells, PDGF stimulated [³H]-thymidine incorporation into DNA in a dose-dependent manner with a maximum stimulation of 15-fold at 500 ng/ml. By comparison, insulin-like growth factor (IGF-I) has a small effect on [³H] -thymidine incorporation. The effect of PDGF and IGF-I on DNA synthesis was additive. Treatment of the confluent stromal cells from adult rats with PDGF increased the mRNA level of osteopontin fourfold without any significant effect on alkaline phosphatase and type I collagen mRNAs. In contrast, dexamethasone stimulated the mRNA expression of alkaline phosphatase, type I collagen, and osteopontin 2.1-, 2.3-, and 14-fold, respectively. Addition of PDGF to dexamethasone-treated cells failed to induce any further increase in osteopontin expression whereas the expression of alkaline phosphatase and type I collagen was partially reduced. The expression of osteocalcin mRNA was negligible in stromal cells but stimulated several fold by dexamethasone and 1,25(OH)₂D₃. PDGF inhibited drastically the elevation of osteocalcin mRNA. In contrast, IGF-I stimulated type I collagen expression 100% without any appreciable effect on the expression of osteopontin and alkaline phosphatase. The stimulatory effect of PDGF on osteopontin expression was augmented by IGF-I. Furthermore, PDGF attenuated the stimulatory effect of IGF-I on type I collagen expression. The responses of cultured cells from old rats to growth factors were also examined. PDGF or PDGF plus IGF-I increased [³H]-thymidine incorporation in stromal cells from old rats but to a lesser extent. However, PDGF was equally effective in stimulating osteopontin expression in cells from both adult and old rats. We concluded that PDGF is a potent mitogen but that the response of stromal cells from old rats is impaired. In addition, PDGF stimulates osteopontin expression in stromal cells and this effect is not age dependent. © 1995 Wiley-Liss, Inc.     

Protracted release of the LHRH agonist avorelin (MF 6001) from two depot formulations in dogs and men

Avorelin is a new superagonist of naturalluteinizing-hormone-releasing-hormone. Avorelin hasbeen formulated in high molecular weight polylactic glycolic acid to afford protracted andcontinuous release of the peptide from subcutaneousimplants. Two different formulations (10 and 15 mg)were tested first in dogs and then in men during aclinical phase II trial. Chemical castration wasmaintained for at least 6 months in dogs withboth formulations. A similar duration of activity(approximately 6 months) was observed in men.     

The application of robotics and mass spectrometry to the characterisation of the Drosophila melanogaster indirect flight muscle proteome

The rapid accumulation of sequence data generated by the various genome sequencingprojects and the generation of expressed sequence tag databases has resulted in the need forthe development of fast and sensitive methods for the identification and characterisation oflarge numbers of gel electrophoretically separated proteins to translate the sequence data intobiological function. To achieve this goal it has been necessary to devise new approaches toprotein analysis: matrix-assisted laser desorption and electrospray mass spectrometry havebecome important protein analytical tools which are both fast and sensitive. When combinedwith a robotic system for the in-gel digestion of electrophoretically separated proteins, itbecomes possible to rapidly identify many proteins by searching databases with MS data. Thepower of this combination of techniques is demonstrated by an analysis of the proteins presentin the myofibrillar lattice of the indirect flight muscle of Drosophila melanogaster. Theproteins were separated by SDS-PAGE and in-gel proteolysis was performed bothautomatically and manually. All 16 major proteins could quickly be identified by massspectrometry. Although most of the protein components were known to be present in theflight muscle, two new components were also identified. The combination of methodsdescribed offers a means for the rapid identification of large numbers of gel separatedproteins.     

Characterization of midgut proteinase activities of white grubs: Lepidiota noxia,Lepidiota negatoria,and Antitrogus consanguineus (scarabaeidae,melolonthini)

The proteinases in the midguts of three scarab white grub species, Lepidiota noxia, L. negatoria, and Antitrogus consanguineus, were investigated to classify the proteinases present and to determine the most effective proteinase inhibitor for potential use as an insect control agent. pH activity profiles indicated the presence of serine proteinases and the absence of cysteine proteinases. This was confirmed by the lack of inhibition by specific cysteine proteinase inhibitors. Trypsin, chymotrypsin, elastase, and leucine aminopeptidase activities were detected by using specific synthetic substrates. A screen of 32 proteinase inhibitors produced 9 inhibitors of trypsin, chymotrypsin, and elastase which reduced proteolytic activity by greater than 75%. © 1995 Wiley-Liss, Inc.     

Crystallization and X-ray analysis of a single fab binding domain from protein L of Peptostreptococcus magnus

Protein L is a multi domain cell wall constituent of certain strains of Peptostreptococcus magnus which binds to the variable domain of immunoglobulin κ-light chains. A single immunoglobulin-binding domain of M_r = 9000 from this protein has been isolated and crystallized. The crystals are of space group P4₂2₁2, with cell dimensions a = b = 66.9 Å, c = 68.3 Å, and diffract to at least 2.2 Å resolution. The asymmetric unit of the crystal contains two molecules of the protein L domain, related by a noncrystallographic 2-fold axis, as revealed by a self-rotation function calculated with native diffraction data. © 1995 Wiley-Liss, Inc.     

Homology between the ribosomal DNA of Escherichia coli and mitochondrial DNA preparations of maize is principally to sequences other than mitochondrial rRNA genes

E. coli ribosomal DNA has been used to probe maize mitochondrial DNA. It hybridizes primarily with chloroplast ribosomal DNA sequences and with fungal and bacterial sequences which may contaminate the mtDNA preparations. It also hybridizes to the chloroplast 16S ribosomal RNA gene sequence present in the mitochondrial genome (1) as well as to the mitochondrial 18S ribosomal RNA gene sequence. Weak sequence homology was detected between E. coli rDNA and the mitochondrial 26S ribosomal RNA gene.