title: Molecular cloning and characterization of a short peptidoglycan recognition protein (PGRP-S) with antibacterial activity from the bumblebee Bombus ignitus.
abstract: Peptidoglycan recognition proteins (PGRPs) are pattern recognition molecules of the innate immune system that recognize peptidoglycan, a unique bacterial cell wall component. Here we cloned and characterized PGRP-S from the bumblebee Bombus ignitus (BiPGRP-S). The BiPGRP-S gene consists of four exons that encode 194 amino acid residues. Comparative analysis indicates that the predicted amino acid sequence of BiPGRP-S shares a high identity with enzymatically active PGRP-S proteins and contains the amino acids required for amidase activity. BiPGRP-S in B. ignitus worker bees is constitutively expressed in both the fat body and epidermis, and it is secreted into the hemolymph. Quantitative real-time PCR assays revealed that the BiPGRP-S gene is highly induced in both the fat body and the epidermis after an injection of Bacillus thuringiensis. In addition, recombinant BiPGRP-S expressed as a 19-kDa protein in baculovirus-infected insect cells can bind to Bacillus megaterium and B. thuringiensis but not to Staphylococcus aureus, Escherichia coli or Beauveria bassiana. Consistent with these data, BiPGRP-S shows antibacterial activity against B. megaterium and B. thuringiensis. After B. thuringiensis injection, the expression profiles of four antibacterial peptide genes in the fat body of RNA interference (RNAi)-mediated BiPGRP-S-knock-down B. ignitus worker bees was similar to that of control worker bees, indicating that BiPGRP-S does not affect the activation of antibacterial peptide gene expression. These results indicate that BiPGRP-S is an inducible protein that may function as an amidase-type PGRP-S during the immune response against Bacillus bacteria.
authors.affiliation: Department of Plant Protection, Huazhong Agricultural University, Wuhan 430070, PR China.
authors.forename: Hong
authors.initials: H
authors.lastname: You
authors.forename: Hu
authors.initials: H
authors.lastname: Wan
authors.forename: Jianhong
authors.initials: J
authors.lastname: Li
authors.forename: Byung Rae
authors.initials: BR
authors.lastname: Jin
mesh_terms: D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001413:Bacillus thuringiensis / Q000276:immunology* / Q000472:pathogenicity; D001516:Bees / Q000276:immunology* / Q000382:microbiology; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004817:Epidermis / Q000276:immunology / Q000378:metabolism; D005216:Fat Body / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D016908:Gram-Positive Bacterial Infections / Q000235:genetics / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D006458:Hemolymph / Q000276:immunology / Q000378:metabolism; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D034741:RNA, Small Interfering; C118897:peptidoglycan recognition protein; D000581:Amidohydrolases; C019665:amidase