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D Hultmark

Publications and source records attributed to D Hultmark.

At least 37 records · Page 2Linked to original sources
PubMed1995

FKBP39, a Drosophila member of a family of proteins that bind the immunosuppressive drug FK506.

A cDNA, coding for the first Drosophila melanogaster homolog of a family of proteins (FK506-binding proteins, FKBPs) which bind to the immunosuppressive drug FK506, was isolated. The deduced aa sequence corresponds to a 39-kDa product (FKBP39) which, besides a domain with similarity to FKBPs, has a highly charged domain with two strongly acidic stretches. The transcript could be detected in all developmental stages, with the highest expression in the embryo. In adult flies, the strongest signal was detected in the ovaries. Although the FKBP39 gene is expressed in the immunocompetent D. melanogaster blood cell line, mbn-2, the antibacterial defense reaction of these cells is unaffected by FK506.

Amino Acid Sequence↗
PubMed1995

Signals from the IL-1 receptor homolog, Toll, can activate an immune response in a Drosophila hemocyte cell line.

The Toll gene encodes an interleukin 1 receptor-like protein that mediates dorsoventral polarity in the Drosophila embryo. The possible involvement of Toll or Toll-like proteins also in the Drosophila immune response was investigated by overexpressing Toll10B, a constitutively active mutant protein, in the Drosophila blood cell line mbn-2. Induction of the Cecropin A1 (CecA1) gene, coding for a bactericidal peptide, was used as an indicator for the immune response. Toll10B was found to increase CecA1 transcription, as detected with a cotransfected CecA1-lacZ reporter gene construct. This effect depends on the presence of a kappa B-like site in the CecA1 promoter. The endogenous Toll gene is expressed in mbn-2 cells, indicating that this gene may normally play a role in Drosophila blood cells.

Animals↗
PubMed1995

Identification of early genes in the Drosophila immune response by PCR-based differential display: the Attacin A gene and the evolution of attacin-like proteins.

We are using the PCR-based differential display technique to isolate genes which are induced during the immune response in Drosophila. In this way, a cDNA clone for a member of the attacin family of antibacterial proteins was isolated. The corresponding Attacin A (Att A) gene is localized at 51A-B on the second chromosome, and it is closely linked to at least one more cross-hybridizing gene. Injection of bacteria induces a 0.8 kb transcript, with expression kinetics similar to that of cecropin. Drosophila attacin is most closely related to sarcotoxin II of Sarcophaga peregrina, but it lacks the extra domains that are unique to this protein, and the overall domain structure of the Att A gene product is identical to that of the attacins from Hyalophora cecropia.

Amino Acid Sequence↗
PubMed1995

CalpA, a Drosophila calpain homolog specifically expressed in a small set of nerve, midgut, and blood cells.

Calpains are calcium-dependent proteases believed to participate in calcium-regulated signal pathways in cells. Ubiquitous calpains as well as tissue-specific calpains have been found in vertebrates. We isolated cDNA clones for a highly tissue-specific calpain gene from Drosophila melanogaster, CalpA, at 56C-D on the second chromosome. The expression of the CalpA gene product was monitored by using a specific antiserum directed against the product expressed by one cDNA clone. The encoded protein is found in a few neurons in the central nervous system, in scattered endocrine cells in the midgut, and in blood cells. In the blood cell line mbn-2, calpain is associated with a granular component in the cytoplasm. The expression of this protein is more restricted than that of the corresponding transcripts, which are widely distributed in the central nervous system, digestive tract, and other tissues. The sequence of CalpA is closely related to that of vertebrate calpains, but an additional segment is inserted in the calmodulin-like carboxy-terminal domain. This insert contains a hydrophobic region that may be involved in membrane attachment of the enzyme. Differential splicing also gives rise to a minor transcript that lacks the calmodulin-like domain.

Amino Acid Sequence↗
PubMed1994

Macrophage differentiation marker MyD88 is a member of the Toll/IL-1 receptor family.

The interleukin-1 receptor in mammals and the product of the Toll gene in Drosophila are related transmembrane receptors, involved in the activation of transcription factors of the rel family. Whereas the interleukin-1 receptor mediates the effects of interleukin-1 in the immune system, Toll is part of the system that determines dorsoventral polarity in the Drosophila embryo, although Toll may also have a function in the immune response in the fly. Here, I demonstrate that the open reading frame of MyD88, a gene induced in myeloid differentiation, is related to the cytoplasmic domains of the interleukin-1 receptor and the Toll gene product. The three related proteins define a family of signal transmitters, the original function of which may be to mediate responses in the immune system.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Drosophila as a model system for antibacterial peptides.

As a defence against bacteria, infected insects synthesize cecropins and a large number of other bactericidal proteins and peptides. To understand this response and its possible relationship with similar systems in mammals, we need to characterize the induced components and how they act, as well as how this antibacterial response is initiated. To study the molecular basis for this response we cloned the genes for cecropins and other bactericidal peptides from Drosophila, 14 genes in total. The cecropin genes were selected as convenient markers for the immune response because they are strongly induced by different microbial substances. In contrast the lysozyme gene family is constitutively expressed in the digestive tract. We have developed an inducible blood cell line from Drosophila for studying the immune response in vitro. Using this system we are now investigating the function of membrane proteins and signal pathways in the transcriptional activation of immune genes in Drosophila.

Animals↗
PubMed1994

The lysozyme locus in Drosophila melanogaster: an expanded gene family adapted for expression in the digestive tract.

Lysozyme has been studied in insects as part of the system of inducible antibacterial defence in the haemolymph. We recently found two Drosophila lysozyme genes that are constitutively expressed in the digestive tract, and are probably involved in the digestion of bacteria in the food. To obtain an overview of the lysozyme genes in this species and their possible roles in immunity and digestion, we have now characterized all six lysozyme genes in the cloned part of the lysozyme locus at 61F, and a seventh gene that maps to the same chromosomal location. The expression of the genes follows four different patterns: firstly, four closely related genes, LysB, C, D and E, are all strongly expressed in the midgut of larvae and adults; secondly, LysP is expressed in the adult salivary gland; thirdly, LysS is expressed mainly in the gastric caecae of larvae; and finally, LysX is primarily expressed in the metamorphosing midgut of late larvae and early pupae. The LysD-like genes and LysS are strongly repressed in artificially infected animals, possibly reflecting a malaise reaction in the digestive tract. None of the genes is expressed in the fat body or haemocytes. Thus rather than being a component of the haemolymph, the Drosophila lysozymes are found mainly in the digestive tract where they are expressed at a high level. Furthermore all genes, except LysP, encode acidic proteins, in contrast to the strongly basic "typical" lysozymes. This is highly reminiscent of the situation in ruminants, where the lysozymes have been recruited for the digestion of symbiotic bacteria in the stomach.

Adaptation, Physiological↗
PubMed1993

kappa B-like motifs regulate the induction of immune genes in Drosophila.

The mammalian transcription factor NF-kappa B regulates a number of genes involved in immune and acute phase responses, by interacting with a nucleotide sequence element, the kappa B-motif. In this work we demonstrate the participation of similar motifs in the immune response of insects as well: kappa B-like motifs have a regulatory role in the synthesis of cecropins, a set of anti-bacterial peptides, triggered by the presence of bacterial cell wall components in the insect blood. We show that the upstream region of the Cecropin gene CecA1 contains elements responsible for inducible and tissue-specific expression. Furthermore, a trimer of kappa B-like motif confers high levels of inducible expression from the reporter gene, after transfection in a Drosophila blood cell line. As in the moth Hyalophora cecropia, stimulation with bacterial lipopolysaccharide induces a nuclear factor that specifically binds to the kappa B-like motif. Our data suggest a functional and evolutionary relationship between these insect immune response factors and the mammalian NF-kappa B.

Animals↗
PubMed1993

Immune reactions in Drosophila and other insects: a model for innate immunity.

All insects defend themselves against bacteria and parasites, using cellular and humoral systems that are rapidly activated in infected animals. Among the induced effector molecules are antibacterial proteins and peptides such as cecropins, attacins, lysozymes and insect defensins, the genes for many of which have now been cloned. The induction of this system, which lacks clonally selected receptors like those of vertebrate B and T cells, may provide a model for innate immune reactions in other animals, including vertebrates.

Amino Acid Sequence↗
PubMed1992

In vitro induction of cecropin genes--an immune response in a Drosophila blood cell line.

The Drosophila melanogaster cell line mbn-2 was explored as a model system to study insect immune responses in vitro. This cell line is of blood cell origin, derived from larval hemocytes of the mutant lethal (2) malignant blood neoplasm (1(2)mbn). The mbn-2 cells respond to microbial substances by the activation of cecropin genes, coding for bactericidal peptides. The response is stronger than that previously described for SL2 cells, and four other tested Drosophila cell lines were totally unresponsive. Bacterial lipopolysaccharide, algal laminarin (a beta-1,3-glucan), and bacterial flagellin were strong inducers, bacterial peptidoglycan fragments gave a weaker response, whereas a formyl-methionine-containing peptide had no effect. Experiments with different drugs indicate that the response may be mediated by a G protein, but not by protein kinase C or eicosanoids, and that it requires a protein factor with a high rate of turnover.

Animals↗
PubMed1992

CecC, a cecropin gene expressed during metamorphosis in Drosophila pupae.

Cecropins are antibacterial peptides, induced in insects in response to bacterial infections. In Drosophila, three cecropin genes have previously been characterized, CecA1, CecA2, and CecB, in a dense cluster at 99E on the third chromosome. From the same locus, we now describe a fourth member of the cecropin gene family, CecC, which is mainly expressed at the early pupal stage. In situ hybridization to immunized pupae show that CecC is induced in the anterior end of the larval hindgut and in other larval tissues that are undergoing histolysis. Within these other tissues it is often expressed in distinct foci that may correspond to hemocytes. A similar pattern of expression in the metamorphosing pupa is also observed for the CecA and CecB genes. Comparing the DNA sequences of the cecropin genes, a conserved region is observed about 30 bp upstream of the TATA box. It consists of three shorter motifs, two of which are reminiscent of a putative promoter element in immune protein genes from the cecropia moth.

Amino Acid Sequence↗
PubMed1992

The lysozyme locus in Drosophila melanogaster: different genes are expressed in midgut and salivary glands.

As part of a study of the genes involved in antibacterial defense in Drosophila melanogaster, we have isolated genomic clones harboring a family of chicken-type lysozyme genes, using a lepidopteran lysozyme cDNA as probe. The locus was mapped to the cytological location 61F1-4 on the third chromosome and two of the genes at this locus, LysD and LysP, were analyzed in detail. In contrast to the bacteria-induced lysozymes in the hemolymph of many insects, the transcription levels of both Drosophila genes decrease after bacterial injections into the hemocoel. Apparently, these gene products, like the specifically adapted lysozymes in mammalian foregut fermenters, have been recruited for the digestion of bacteria present in fermenting food. The LysD gene is expressed in an anterior section of the midgut during all feeding stages of development in both larvae and adults. The LysP gene is only active in the adult where it is expressed in the salivary glands. The transcription units for both genes are very compact and they lack introns. Lysozyme D is unusual in that it is predicted to have an acidic isoelectric point whereas lysozyme P appears to be a typical basic lysozyme.

Amino Acid Sequence↗
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↗
PubMed1990

Insect immunity. Characterization of a Drosophila cDNA encoding a novel member of the diptericin family of immune peptides.

Drosophila shows an immune response when challenged by injection of low doses of bacteria. To date, the molecules involved in this immune reaction have remained elusive, with the exception of cecropins (4-kDa antibacterial peptides initially isolated from the moth Hyalophora cecropia) for which three closely related genes have been characterized recently. We report the molecular cloning and sequencing of a cDNA from a library of immune Drosophila which encodes a novel member of the family of diptericins (9-kDa antibacterial peptides initially isolated from the fly Phormia terranovae). Transcripts for the Drosophila diptericin are detected 2 h after injection of bacteria. They are apparently derived from a single gene mapping at position 56 A on the right arm of the second chromosome. We discuss the existence of a distant relationship between the diptericins and two other groups of anti-bacterial insect proteins, the attacins, and the sarcotoxins II.

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↗