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At least 325 records · Page 18Linked to original sources
PubMed1984

The antibacterial effect of attacins from the silk moth Hyalophora cecropia is directed against the outer membrane of Escherichia coli.

The attacins are antibacterial proteins which accumulate in the hemolymph of the giant silk moth, Hyalophora cecropia, in response to a bacterial infection. Here we show that the permeability barrier function of the outer membrane is affected shortly after addition of attacin to growing cultures of Escherichia coli. Specifically, the penetration through the outer membrane of beta-lactam antibiotics, chicken egg white lysozyme and the detergent Triton X-100 was found to be facilitated. The sensitivity of E. coli to cecropin B, another antibacterial protein present in the hemolymph of H. cecropia, was also found to be increased after treatment with attacin. The results suggest that the target of the attacins in E. coli is the outer membrane. Other effects of the attacins which have been observed are likely to be indirect consequences of the alteration in the properties of the outer membrane. These effects include changes in the cell shape, irregular patterns of cell division and lysis. The minimal concentration at which the attacins affected the growth of E. coli was 1 and 0.5 microM for the neutral (pI 7) and basic (pI 9) attacins, respectively, which corresponds to less than 2% of the concentration of the attacins in the hemolymph of infected pupae.

Animals↗
PubMed1989

The Drosophila hairy protein acts in both segmentation and bristle patterning and shows homology to N-myc.

The Drosophila segmentation gene, hairy (h), acts to regulate embryonic segmentation and bristle pattern. We present the DNA sequence of the h gene and of h cDNAs, thereby deducing the organization of the h transcripts. The h gene encodes a 337 amino acid protein that acts in both embryonic segmentation and adult bristle patterning. The h protein includes a domain that shows extensive similarity to a domain of the proto-oncogene N-myc that may be involved in DNA binding and/or protein dimerization. We discuss mechanisms of h action as a transcriptional regulator.

Amino Acid Sequence↗
PubMed1990

Insect immunity: expression of the two major inducible antibacterial peptides, defensin and diptericin, in Phormia terranovae.

Injections of low doses of bacteria into larvae of Phormia terranovae induce the appearance of potent bactericidal peptides in the blood, among which predominate the anti-Gram positive insect defensins and the anti-Gram negative diptericins. Insect defensins show significant homologies to mammalian (including human) microbicidal peptides present in polymorphonuclear leukocytes and macrophages. We report the molecular cloning of cDNAs and primer extension studies which indicate that insect defensin is produced as a prepro-peptide yielding mature defensin A (40 residues) after cleavage of a putative signal peptide (23 residues) and a prosequence (34 residues). Previous studies have established that diptericin (82 residues) is matured from a pre-peptide by cleavage of a putative signal peptide (19 residues) and C-terminal amidation. Using oligonucleotide probes complementary to the sequences of the mRNAs for defensin and diptericin, we show by in situ hybridization that both antibacterial peptides are concomitantly synthesized by the same cells: thrombocytoids, a specialized blood cell type, and adipocytes. Transcriptional studies based on hybridization of RNAs to cDNAs of defensin and diptericin indicate that the transcription of both genes is induced regardless of the nature of the stimulus (injection of Gram positive or Gram negative bacteria, lipopolysaccharides). Even a sterile injury applied to axenically raised larvae is efficient in inducing the transcription of both genes suggesting that the local disruption of the integument aspecifically initiates a signalling mechanism which the thrombocytoids and the adipocytes are able to interpret. The transcription of immune genes is relatively short lived and a second challenge yields a response similar to that of the first stimulus, indicating that the experimental insects do not keep a 'memory' of their first injection.

Amino Acid Sequence↗
PubMed1990

The immune response in Drosophila: pattern of cecropin expression and biological activity.

Cecropins are antibacterial peptides, induced in Drosophila as part of the humoral immune response to a bacterial invasion. We have used the cloned Drosophila cecropin genes CecA1, A2 and B as probes to study the developmental and tissue specific regulation of this response. The genes are strongly expressed in fat body and hemocytes after injection of bacteria, the CecA genes being much more active than CecB in the fat body. All parts of the fat body and 5-10% of the hemocytes are involved in this response. CecA1 and A2 are most active in larvae and adults; CecB is preferentially active in early pupae. A small peak of constitutive cecropin expression in early pupae appears to be caused by bacteria in the food. Cecropin A, the common product of the CecA1 and A2 genes, was identified in the hemolymph of immunized flies at a concentration of 25-50 microM, enough to kill all tested bacteria except Serratia, a Drosophila pathogen. A useful in vitro system to study the immune response has been found in Schneider's line 2 cells which respond to lipopolysaccharide and laminarin by cecropin expression.

Animals↗
PubMed1990

The cecropin locus in Drosophila; a compact gene cluster involved in the response to infection.

Cecropins are antibacterial peptides that are synthesized in insects as a response to infection. As a first step towards a molecular study of the induction of this response, we have isolated genomic clones that cover the cecropin locus in Drosophila melanogaster. This locus was found to be unique, and it was mapped cytologically to the chromosomal location 99E. Sequence analysis showed it to be unusually compact, with three expressed genes and two pseudogenes within less than 4 kb of DNA, and with another homologous region less than 4 kb away. Two of the genes, A1 and A2, encode a product that is identical to the major cecropin from Sarcophaga peregrina, while the cecropin encoded by the B gene differs in five positions. Cecropin transcripts appear within an hour after bacteria have been injected into the hemocoel, reach a maximum after 2-6 h, and have almost disappeared again after 24 h. The B gene is induced in parallel with the A genes, but on a lower level. The cecropin genes were also induced when the flies were kept on food with the Drosophila pathogenic bacterium Serratia marcescens Db10 or its non-pathogenic derivative Db1140.

Animals↗
PubMed1991

A microsomal protein is involved in ATP-dependent transport of presecretory proteins into mammalian microsomes.

Ribonucleoparticle (i.e. ribosome and SRP)-independent transport of proteins into mammalian microsomes is stimulated by a cytosolic ATPase which involves proteins belonging to the hsp70 family. Here we addressed the question of whether there are additional nucleoside triphosphate requirements involved in this transport mechanism. We employed a purified presecretory protein which upon solubilization in dimethyl sulfoxide and subsequent dilution into an aqueous buffer was processed by and transported into mammalian microsomes in the absence of the cytosolic ATPase. Membrane insertion of this precursor protein was found to depend on the hydrolysis of ATP and to involve a microsomal protein which can be photoaffinity inactivated with azido-ATP. Furthermore, a microsomal protein with a similar sensitivity towards photoaffinity modification with azido-ATP was observed to be involved in ribonucleoparticle-dependent transport. We suggest that a novel microsomal protein which depends on ATP hydrolysis is involved in membrane insertion of both ribonucleoparticle-dependent and -independent precursor proteins.

Adenosine Triphosphatases↗
PubMed1991

The andropin gene and its product, a male-specific antibacterial peptide in Drosophila melanogaster.

In our study of the cecropin locus in Drosophila we have found a gene for a new peptide, andropin, with antibacterial properties. Transcripts from this gene, Anp, could be detected in newly eclosed males and reached steady-state levels after 1 day. Transcription was strongly induced in response to mating and is strictly confined to the ejaculatory duct of adult males. The deduced peptide sequence reveals a hydrophobic amino terminus with striking similarity to the signal peptide of the cecropins. The sequence of the predicted mature andropin shows no direct homology with the cecropins, but the two peptides may have similar secondary structures. We have synthesized the predicted gene product and shown it to be antibacterial. Crude extracts from male genital tracts show a potent bactericidal activity, and electrophoretic separation revealed at least three antibacterial components, one with the same mobility as the synthetic peptide. It appears that insects have evolved a mechanism for the protection of the seminal fluid and the male reproductive tract against microbial infections.

Amino Acid Sequence↗
PubMed1992

Insect immunity: developmental and inducible activity of the Drosophila diptericin promoter.

Diptericins are 9 kDa inducible antibacterial peptides initially isolated from immune haemolymph of Phormia (Diptera). Following the isolation of a Drosophila cDNA encoding a diptericin homologue, we have now cloned a genomic fragment containing the Drosophila diptericin gene. To dissect the regulation of this gene, we have transformed flies with a fusion gene in which the reporter beta-galactosidase gene is under the control of 2.2 kb upstream sequences of the diptericin gene. We show that such a fusion gene is inducible by injection of live bacteria or complete Freund's adjuvant and respects the tissue specific expression pattern of the resident diptericin gene. Our analysis reveals at least four distinct phases in the regulation of this gene: young larvae, late third instar larvae, pupae and adults. This complexity may be related to the presence in the upstream sequences of multiple copies of response elements previously characterized in genes encoding acute phase response proteins in mammals (e.g. NK-kappa B, NF-kappa B related, NF-IL6 response elements).

Acute-Phase Proteins↗
PubMed1993

Insect immunity. Two 17 bp repeats nesting a kappa B-related sequence confer inducibility to the diptericin gene and bind a polypeptide in bacteria-challenged Drosophila.

The Drosophila diptericin gene codes for a 9 kDa antibacterial peptide and is rapidly and transiently expressed in larvae and adults after bacterial challenge. It is also induced in a tumorous Drosophila blood cell line by the addition of lipopolysaccharide (LPS). The promoter of this gene contains two 17 bp repeats located closely upstream of the TATA-box and harbouring a decameric kappa B-related sequence. This study reports that the replacement of the two 17 bp repeats by random sequences abolishes bacteria inducibility in transgenic fly lines. In transfected tumorous blood cells, the replacement of both or either of the 17 bp motifs reduces dramatically LPS inducibility, whereas multiple copies significantly increase the level of transcriptional activation by LPS challenge. A specific DNA-protein binding activity is evidenced in cytoplasmic and nuclear extracts of induced blood cells and fat body. It is absent in controls. It is proposed that induction of the diptericin gene mediated by the two 17 bp repeats occurs via a mechanism similar to that of mammalian NF-kappa B.

Animals↗
PubMed1993

Kettin, a large modular protein in the Z-disc of insect muscles.

Z-discs of insect flight muscle contain a large protein of 500-700 kDa. Monoclonal antibodies label an epitope in the molecule at the Z-disc in Drosophila and Lethocerus (waterbug). A partial cDNA of 1.6 kb from the Drosophila gene has been cloned and sequenced. The corresponding amino acid sequence has a modular structure composed of four conserved repeats of 95 amino acids homologous to immunoglobulin C2 domains (called class II domains in muscle proteins), separated by less conserved linker sequences of 35 amino acids. An expressed class II domain with flanking linker sequences binds to actin and alpha-actinin but not to myosin. Single molecules of the protein would be large enough to span the Z-disc. We suggest that the protein acts as scaffolding in the Z-disc and we call the protein kettin. The Ca2+ activated protease, calpain, disrupts the Z-disc of striated muscle, releasing alpha-actinin intact. Calpain digests kettin to a series of peptides of between 30 and 170 kDa which are released from the myofibril. Digestion of kettin may cause disintegration of the Z-disc and alpha-actinin release which lead to disassembly of the myofibril.

Amino Acid Sequence↗
PubMed1994

Insect immunity. A transgenic analysis in Drosophila defines several functional domains in the diptericin promoter.

Diptericins are antibacterial polypeptides which are strongly induced in the fat body and blood cells of dipteran insects in response to septic injury. The promoter of the single-copy, intronless diptericin gene of Drosophila contains several nucleotide sequences homologous to mammalian cis-regulatory motifs involved in the control of acute phase response genes. Extending our previous studies on the expression of the diptericin gene, we now report a quantitative analysis of the contribution of various putative regulatory elements to the bacterial inducibility of this gene, based on the generation of 60 transgenic fly lines carrying different elements fused to a reporter gene. Our data definitively identify two Kappa B-related motifs in the proximal promoter as the sites conferring inducibility and tissue-specific expression to the diptericin gene. These motifs alone, however, mediate only minimal levels of expression. Additional proximal regulatory elements are necessary to attain some 20% of the full response and we suspect a role for sequences homologous to mammalian IL6 response elements and interferon-gamma responsive sites in this up-regulation. The transgenic experiments also reveal the existence of a distal regulatory element located upstream of -0.6 kb which increases the level of expression by a factor of five.

Animals↗
PubMed1995

Two heads are better than one: crystal structure of the insect derived double domain Kazal inhibitor rhodniin in complex with thrombin.

Rhodniin is a highly specific inhibitor of thrombin isolated from the assassin bug Rhodnius prolixus. The 2.6 Angstrum crystal structure of the non-covalent complex between recombinant rhodniin and bovine alpha-thrombin reveals that the two Kazal-type domains of rhodniin bind to different sites of thrombin. The amino-terminal domain binds in a substrate-like manner to the narrow active-site cleft of thrombin; the imidazole group of the P1 His residue extends into the S1 pocket to form favourable hydrogen/ionic bonds with Asp189 at its bottom, and additionally with Glu192 at its entrance. The carboxy-terminal domain, whose distorted reactive-site loop cannot adopt the canonical conformation, docks to the fibrinogen recognition exosite via extensive electrostatic interactions. The rather acidic polypeptide linking the two domains is displaced from the thrombin surface, with none of its residues involved in direct salt bridges with thrombin. The tight (Ki = 2 x 10(-13) M) binding of rhodniin to thrombin is the result of the sum of steric and charge complementarity of the amino-terminal domain towards the active-site cleft, and of the electrostatic interactions between the carboxy-terminal domain and the exosite.

Amino Acid Sequence↗
PubMed1995

Functional analysis and regulation of nuclear import of dorsal during the immune response in Drosophila.

In addition to its function in embryonic development, the NF-kappa B/rel-related gene dorsal (dl) of Drosophila is expressed in larval and adult fat body where its RNA expression is enhanced upon injury. Injury also leads to a rapid nuclear translocation of dl from the cytoplasm in fat body cells. Here we present data which strongly suggest that the nuclear localization of dl during the immune response is controlled by the Toll signaling pathway, comprising gene products that participate in the intracellular part of the embryonic dorsoventral pathway. We also report that in mutants such as Toll or cactus, which exhibit melanotic tumor phenotypes, dl is constitutively nuclear. Together, these results point to a potential link between the Toll signaling pathway and melanotic tumor induction. Although dl has been shown previously to bind to kappa B-related motifs within the promoter of the antibacterial peptide coding gene diptericin, we find that injury-induced expression of diptericin can occur in the absence of dl. Furthermore, the melanotic tumor phenotype of Toll and cactus is not dl dependent. These data underline the complexity of the Drosophila immune response. Finally, we observed that like other rel proteins, dl can control the level of its own transcription.

Animals↗
PubMed1992

Experimental morphology of insect olfaction: tracer studies, X-ray microanalysis, autoradiography, and immunocytochemistry with silkmoth antennae.

The general morphology and methodological peculiarities of insect sensilla are briefly reviewed. The stimulus conducting pore-tubule systems of pheromone-sensitive sensilla of the silkmoths Bombyx mori and Antheraea polyphemus are described. Lipophilic tracers readily enter the hair lumen, while hydrophilic tracers do so only after prolonged extraction with lipid solvents and/or pronase. X-ray microanalysis demonstrates a high potassium content of the sensillum lymph; calcium was only found in the haemolymph above detection limit. Auxiliary cells rapidly take up radioactive leucine administered via the haemolymph. Antibodies against pheromone-binding protein of Antheraea polyphemus label the sensillum lymph of sensilla trichodea, but not of sensilla basiconica in A. polyphemus as well as in B. mori. The cytoplasm of auxiliary cells of the sensilla trichodea is also labelled. The results are discussed in context with present hypotheses on the role of sensillum lymph in stimulus transport and inactivation.

Animals↗
PubMed1992

Enhanced in vitro growth of murine fibroblast cells and preimplantation embryos cultured in medium supplemented with an amphipathic peptide.

Preliminary studies on the proliferative effects of lytic peptides were carried out using NIH 3T3 murine fibroblast cells and human lymphocytes. Cells were cultured in various concentrations of three different amphipathic peptides (SB-37, Shiva-1, and Vishnu), and enhanced proliferation was determined by uptake of 3H-thymidine with treated cells compared with control cultures. Enhanced proliferation of 3T3 cells was observed in cultures containing 50 microM or less SB-37. The primary study consisted of 263 four-cell- to eight-cell-stage mouse embryos from naturally bred mice and incubated in Whitten's medium containing 0.2, 1, or 10 microM of the amino terminus of an amphipathic cecropin B analog (Vishnu) or in Whitten's medium alone. Embryos were cultured to the hatched blastocyst stage, and effect of treatment was determined by the rate of growth to that stage of development. Statistical analysis revealed that culture in all three levels of Vishnu significantly accelerated in vitro growth of these stages of preimplantation embryos compared with controls. These results indicate that Vishnu promotes increased cleavage rates of embryos in vitro. A growth factor receptor clustering mechanism of action is proposed. This peptide may have some potential as an embryo culture medium additive to enhance in vitro growth rate.

3T3 Cells↗
PubMed2002

Remodeling of an identified motoneuron during metamorphosis: central and peripheral actions of ecdysteroids during regression of dendrites and motor terminals.

During metamorphosis of the moth Manduca sexta, an identified leg motoneuron, the femoral depressor motoneuron (FeDe MN), undergoes reorganization of its central and peripheral processes. This remodeling is under the control of two insect hormones: the ecdysteroids and juvenile hormone (JH). Here, we asked whether peripheral or central actions of the ecdysteroids influenced specific regressive aspects of MN remodeling. We used stable hormonal mimics to manipulate the hormonal environment of either the FeDe muscle or the FeDe MN soma. Our results demonstrate that motor-terminal retraction and dendritic regression can be experimentally uncoupled, indicating that central actions of ecdysteroids trigger dendritic regression whereas peripheral actions trigger terminal retraction. Our results further demonstrate that discrete aspects of motor-terminal retraction can also be experimentally uncoupled, suggesting that they also are regulated differently.

Animals↗
PubMed2001

Pigment-dispersing factor in the locust abdominal ganglia may have roles as circulating neurohormone and central neuromodulator.

Pigment-dispersing factor (PDF) is a neuropeptide that has been indicated as a likely output signal from the circadian clock neurons in the brain of Drosophila. In addition to these brain neurons, there are PDF-immunoreactive (PDFI) neurons in the abdominal ganglia of Drosophila and other insects; the function of these neurons is not known. We have analyzed PDFI neurons in the abdominal ganglia of the locust Locusta migratoria. These PDFI neurons can first be detected at about 45% embryonic development and have an adult appearance at about 80%. In each of the abdominal ganglia (A3-A7) there is one pair of lateral PDFI neurons and in each of the A5-A7 ganglia there is additionally a pair of median neurons. The lateral neurons supply varicose branches to neurohemal areas of the lateral heart nerves and perisympathetic organs, whereas the median cells form processes in the terminal abdominal ganglion and supply terminals on the hindgut. Because PDF does not influence hindgut contractility, it is possible that also these median neurons release PDF into the circulation. Release from one or both the PDFI neuron types was confirmed by measurements of PDF-immunoreactivity in hemolymph by enzyme immunoassay. PDF applied to the terminal abdominal ganglion triggers firing of action potentials in motoneurons with axons in the genital nerves of males and the 8th ventral nerve of females. Because this action is blocked in calcium-free saline, it is likely that PDF acts via interneurons. Thus, PDF seems to have a modulatory role in central neuronal circuits of the terminal abdominal ganglion that control muscles of genital organs.

Abdomen↗
PubMed1993

Bacterial expression and photoaffinity labeling of a pheromone binding protein.

The first high-level production of a binding-active odorant binding protein is described. The expression cassette polymerase chain reaction was used to generate a DNA fragment encoding the pheromone binding protein (PBP) of the male moth Antheraea polyphemus. Transformation of Escherichia coli cells with a vector containing this construct generated clones which, when induced with isopropyl beta-D-thiogalactopyranoside, produced the 14-kDa PBP in both the soluble fraction and in inclusion bodies. Purification of the soluble recombinant PBP by preparative isoelectric focusing and gel filtration gave > 95% homogeneous protein, which was immunoreactive with an anti-PBP antiserum and exhibited specific, pheromone-displaceable covalent modification by the photoaffinity label [3H]6E,11Z-hexadecadienyl diazoacetate. Recombinant PBP was indistinguishable from the insect-derived PBP, as determined by both native and denaturing gel electrophoresis, immunoreactivity, and photoaffinity labeling properties. Moreover, the insoluble inclusion body protein could be solubilized, refolded, and purified by the same procedures to give a recombinant PBP indistinguishable from the soluble PBP. Proton NMR spectra of the soluble and refolded protein provide further evidence that they possess the same folded structure.

Affinity Labels↗