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  • 1. Coteur, Geoffroy
    et al.
    Mellroth, Peter
    De Lefortery, Coline
    Gillan, David
    Dubois, Philippe
    Communi, David
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Peptidoglycan recognition proteins with amidase activity in early deuterostomes (Echinodermata).2007In: Dev Comp Immunol, ISSN 0145-305X, Vol. 31, no 8, p. 790-804Article in journal (Refereed)
  • 2. Dziarski, Roman
    et al.
    Platt, Kenneth A
    Gelius, Eva
    Steiner, Håkan
    Stockholm University.
    Gupta, Dipika
    Defect in neutrophil killing and increased susceptibility to infection with nonpathogenic gram-positive bacteria in peptidoglycan recognition protein-S (PGRP-S)-deficient mice.2003In: Blood, ISSN 0006-4971, Vol. 102, no 2, p. 689-97Article in journal (Refereed)
  • 3. Gelius, Eva
    et al.
    Persson, Carina
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Karlsson, Jenny
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    A mammalian peptidoglycan recognition protein with N-acetylmuramoyl-L-alanine amidase activity2003In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 306, no 4, p. 988-994Article in journal (Refereed)
    Abstract [en]

    The family of peptidoglycan recognition proteins (PGRPs) is conserved from insects to mammals. Recently, Drosophila PGRP-SC1B was demonstrated to be an N-acetylmuramoyl- -alanine amidase (NAMLAA), an enzyme that cleaves the lactylamide bond between muramic acid and the peptide chain in peptidoglycan (PGN). We now show an M.mPGRP-L mRNA to be expressed in the liver. The recombinant M.mPGRP-L protein has NAMLAA activity and degrades PGN from both Escherichia coli and Staphylococcus aureus; however, the Gram-positive PGN was a better substrate after lysozyme treatment. The activity of M.mPGRP-L was further analysed using Bordetella pertussis tracheal toxin as a substrate. Cleavage products were separated on HPLC and identified using mass spectrometry. From these results we conclude that M.mPGRP-L has activity and other properties identifying it as the NAMLAA protein present in mammalian sera.

  • 4. Kaneko, Takashi
    et al.
    Goldman, William E
    Mellroth, Peter
    Steiner, Håkan
    Stockholm University.
    Fukase, Koichi
    Kusumoto, Shoichi
    Harley, William
    Fox, Alvin
    Golenbock, Douglas
    Silverman, Neal
    Monomeric and polymeric gram-negative peptidoglycan but not purified LPS stimulate the Drosophila IMD pathway.2004In: Immunity, ISSN 1074-7613, Vol. 20, no 5, p. 637-49Article in journal (Refereed)
  • 5.
    Karlsson, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Oldenvi, Sandra
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Daenthanasanmak, Anusara
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Growing bacteria shed elicitors of Drosophila humoral immunityArticle in journal (Refereed)
    Abstract [en]

    Peptidoglycan (PGN) is a well-characterized cell wall component from bacteria that is recognized by Peptidoglycan Recognition Receptors (PGRPs) in the Drosophila immune system. It has long been a forum of debate how the immune system is able to recognize this elicitor since the PGN is hidden by the outer membrane in gram-negative bacteria and by teichoic acids in gram-positive bacteria. We show here that bacteria separated from Drosophila S2 cells by a semi permeable membrane are able to up-regulate the Imd pathway. Studies with supernatants from exponentially growning bacterial cultures show that bacteria shed elicitors in sufficient amounts to potentially induce the Imd pathway. However, when employing supernatants from bacteria in stationary phase, no stimulatory effect of the Imd pathway was detected. The elicitor effect was much reduced when the supernatans was treated with the N-acetylmuramoyl-Lalanine amidase M.mPGRP-L, which is a known scavenger of PGN. Our studies therefore indicate that bacteria in growth phase shed elicitors of PGN nature that can induce a humoral immune response in Drosophila S2 cells.

  • 6.
    Karlsson, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Oldenvi, Sandra
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Fahlander, Carina
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Daenthanasanmak, Anusara
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Growing bacteria shed elicitors of Drosophila humoral immunity.2012In: Journal of innate immunity, ISSN 1662-8128, Vol. 4, no 1, p. 111-116Article in journal (Refereed)
    Abstract [en]

    It has been much debated how the Drosophila immune system can recognize bacterial peptidoglycan that is often hidden. We show that bacteria separated from Drosophila S2 cells by a semipermeable membrane can upregulate the Imd pathway. Supernatants from exponentially growing but not from stationary-phase bacterial cultures induce antimicrobial peptides. It is also made likely that the shed elicitors are of peptidoglycan nature.

  • 7.
    Lindberg, Bo G.
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Oldenvi, Sandra
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Medium from gamma-irradiated Escherichia coli bacteria stimulates a unique immune response in Drosophila cells2014In: Developmental and Comparative Immunology, ISSN 0145-305X, E-ISSN 1879-0089, Vol. 46, no 2, p. 392-400Article in journal (Refereed)
    Abstract [en]

    It is well known that gamma-irradiated, non-dividing bacteria can elicit potent immune responses in mammals. Compared to traditional heat or chemical inactivation of microbes, gamma -irradiation likely preserves metabolic activity and antigenic features to a larger extent. We have previously shown that antimicrobial peptides are induced in Drosophila by peptidoglycan fragments secreted into the medium of exponentially growing bacterial cultures. In this study, we gamma-irradiated Escherichia coil cells at a dose that halted cell division. The temporal synthesis and release of peptidoglycan fragments were followed as well as the potential of bacterial supernatants to induce immune responses in Drosophila S2 cells. We demonstrate that peptidoglycan synthesis continues for several days post irradiation and that monomeric peptidoglycan is shed into the medium. Whole transcriptome analysis revealed a strong immune response against the bacterial medium. The response to medium taken directly post irradiation shows a large overlap to that of peptidoglycan. Medium from prolonged bacterial incubation does, however, stimulate a selective set of immune genes. A shift towards a stress response was instead observed with a striking induction of several heat shock proteins. Our findings suggest that gamma-irradiated bacteria release elicitors that stimulate a novel response in Drosophila.

  • 8. Mellroth, Peter
    et al.
    Karlsson, Jenny
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Håkansson, Janet
    Schultz, Niklas
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Goldman, William E
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Ligand-induced dimerization of Drosophila peptidoglycan recognition proteins in vitro2005In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 102, no 18, p. 6455-6460Article in journal (Refereed)
    Abstract [en]

    Drosophila knockout mutants have placed peptidoglycan recognition proteins (PGRPs) in the two major pathways controlling immune gene expression. We now examine PGRP affinities for peptidoglycan. PGRP-SA and PGRP-LCx are bona fide pattern recognition receptors, and PGRP-SA, the peptidoglycan receptor of the Toll/Dif pathway, has selective affinity for different peptidoglycans. PGRP-LCx, the default peptidoglycan receptor of the Imd/Relish pathway, has strong affinity for all polymeric peptidoglycans tested and for monomeric peptidoglycan. PGRP-LCa does not have affinity for polymeric or monomeric peptidoglycan. Instead, PGRP-LCa can form heterodimers with LCx when the latter is bound to monomeric peptidoglycan. Hence, PGRP-LCa can be said to function as an adaptor, thus adding a new function to a member of the PGRP family.

  • 9. Mellroth, Peter
    et al.
    Karlsson, Jenny
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Steiner, Hakan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    A scavenger function for a Drosophila peptidoglycan recognition protein2003In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 278, no 9, p. 7059-7064Article in journal (Refereed)
    Abstract [en]

    Recent studies of peptidoglycan recognition protein (PGRP) have shown that 2 of the 13 Drosophila PGRP genes encode proteins that function as receptors mediating immune responses to bacteria. We show here that another member, PGRP-SC1B, has a totally different function because it has enzymatic activity and thereby can degrade peptidoglycan. A mass spectrometric analysis of the cleavage products demonstrates that the enzyme hydrolyzes the lactylamide bond between the glycan strand and the cross-linking peptides. This result assigns the protein as anN-acetylmuramoyl-l-alanine amidase (EC3.5.1.28), and the corresponding gene is thus the first of this class to be described from a eukaryotic organism. Mutant forms of PGRP-SC1B lacking a potential zinc ligand are enzymatically inactive but retain their peptidoglycan affinity. The immunostimulatory properties of PGRP-SC1B-degraded peptidoglycan are much reduced. This is in striking contrast to lysozyme-digested peptidoglycan, which retains most of its elicitor activity. This points toward a scavenger function for PGRP-SC1B. Furthermore, a sequence homology comparison with phage T7 lysozyme, also an N-acetylmuramoyl-l-alanine amidase, shows that as many as six of the Drosophila PGRPs could belong to this class of proteins.

  • 10. Mellroth, Peter
    et al.
    Steiner, Håkan
    Stockholm University.
    PGRP-SB1: an N-acetylmuramoyl L-alanine amidase with antibacterial activity.2006In: Biochem Biophys Res Commun, ISSN 0006-291X, Vol. 350, no 4, p. 994-9Article in journal (Refereed)
  • 11. Persson, Carina
    et al.
    Oldenvi, Sandra
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Peptidoglycan recognition protein LF, A negative regulator of Drosophila immunity.2007In: Insect Biochem Mol Biol, ISSN 0965-1748, Vol. 37, no 12, p. 1309-16Article in journal (Refereed)
  • 12.
    Steiner, Håkan
    Stockholm University.
    Peptidoglycan recognition proteins: on and off switches for innate immunity.2004In: Immunol Rev, ISSN 0105-2896, Vol. 198, p. 83-96Article in journal (Refereed)
  • 13. Zaidman-Remy, Anna
    et al.
    Poidevin, Mickael
    Herve, Mireille
    Welchman, David P.
    Paredes, Juan C.
    Fahlander, Carina
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Steiner, Håkan
    Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
    Mengin-Lecreulx, Dominique
    Lemaitre, Bruno
    Drosophila Immunity: Analysis of PGRP-SB1 Expression, Enzymatic Activity and Function2011In: PLOS ONE, E-ISSN 1932-6203, Vol. 6, no 2, p. e17231-Article in journal (Refereed)
    Abstract [en]

    Peptidoglycan is an essential and specific component of the bacterial cell wall and therefore is an ideal recognition signature for the immune system. Peptidoglycan recognition proteins (PGRPs) are conserved from insects to mammals and able to bind PGN (non-catalytic PGRPs) and, in some cases, to efficiently degrade it (catalytic PGRPs). In Drosophila, several non-catalytic PGRPs function as selective peptidoglycan receptors upstream of the Toll and Imd pathways, the two major signalling cascades regulating the systemic production of antimicrobial peptides. Recognition PGRPs specifically activate the Toll pathway in response to Lys-type peptidoglycan found in most Gram-positive bacteria and the Imd pathway in response to DAP-type peptidoglycan encountered in Gram-positive bacilli-type bacteria and in Gram-negative bacteria. Catalytic PGRPs on the other hand can potentially reduce the level of immune activation by scavenging peptidoglycan. In accordance with this, PGRP-LB and PGRP-SC1A/B/2 have been shown to act as negative regulators of the Imd pathway. In this study, we report a biochemical and genetic analysis of PGRP-SB1, a catalytic PGRP. Our data show that PGRP-SB1 is abundantly secreted into the hemolymph following Imd pathway activation in the fat body, and exhibits an enzymatic activity towards DAP-type polymeric peptidoglycan. We have generated a PGRP-SB1/2 null mutant by homologous recombination, but its thorough phenotypic analysis did not reveal any immune function, suggesting a subtle role or redundancy of PGRP-SB1/2 with other molecules. Possible immune functions of PGRP-SB1 are discussed.

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