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A mammalian peptidoglycan recognition protein with N-acetylmuramoyl-L-alanine amidase activity
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
Stockholm University, Faculty of Science, Department of Genetics, Microbiology and Toxicology.
2003 (English)In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, Vol. 306, no 4, 988-994 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
2003. Vol. 306, no 4, 988-994 p.
URN: urn:nbn:se:su:diva-20035DOI: 10.1016/S0006-291X(03)01096-9PubMedID: 12821140OAI: diva2:186560
Available from: 2007-11-21 Created: 2007-11-21 Last updated: 2010-01-11Bibliographically approved
In thesis
1. Peptidoglycan regulation of Drosophila immunity
Open this publication in new window or tab >>Peptidoglycan regulation of Drosophila immunity
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Innate immunity is an ancient defense system that distinguishes between self and non self and is present in both vertebrates and invertebrates. Peptidoglycan (PGN), a cell wall component shared by both gram-negative and gram-positive bacteria, is the major recognition molecule for the detection of bacteria in Drosophila. Peptidoglycan Recognition Proteins (PGRPs) are conserved from insect to mammals and bind PGN with high affinity. In Drosophila, distinct PGRPs provide essential signals upstream of the Toll and Imd pathways. This thesis concerns the recognition of PGN by PGRPs and the expression of antibacterial peptides from the Imd pathway.

The PGRP-LC locus encodes three splice forms, a, x, and y. PGRP-LCx and PGRP-LCa form heterodimers in the presence of monomeric PGN. We propose a model for activation of Imd where PGRP-LCx binds to monomeric PGN leading to dimerization with PGRP-LCa and activation of the Imd pathway. With polymeric PGN, PGRP-LCx dimers activate the Imd pathway.

Drosophila PGRP-SC1B has amidase activity and cleaves the PGN lactamyl bond between the glycan strand and the peptide. The digested material is less immunogenic than intact PGN or PGN digested by egg white lysozyme. We suggest PGRP-SC1B to be a scavenger of immunogenic PGN. Amino acid sequence homology predicts six of the Drosophila PGRPs as well as two vertebrate PGRPs to be amidases. Murine PGRP-L is expressed in the liver and was shown to have PGN degrading activity. We found that an earlier purified human serum amidase is in fact identical to PGRP-L.

Although PGN is a potential trigger of the insect immune system, the actual detection of PGN in vivo poses problems. In gram-negative bacteria, PGN is covered by an outer membrane. Using a cell line approach we demonstrate that bacteria can be recognized by the Imd pathway without the need of phagocytosis or contact between bacteria and cells. Instead growing bacteria release immune eliciting fragments of PGN nature.

Place, publisher, year, edition, pages
Stockholm: Department of Genetics, Microbiology and Toxicology, Stockholm University, 2009. 50 p.
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Genetics
urn:nbn:se:su:diva-29828 (URN)978-91-7155-938-8 (ISBN)
Public defence
2009-10-23, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted.Available from: 2009-10-01 Created: 2009-09-15 Last updated: 2009-09-17Bibliographically approved

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Persson, CarinaKarlsson, JennySteiner, Håkan
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