title: A short-type peptidoglycan recognition protein from the silkworm: expression, characterization and involvement in the prophenoloxidase activation pathway.
abstract: Recognition of invading microbes as non-self is the first step of immune responses. In insects, peptidoglycan recognition proteins (PGRPs) detect peptidoglycans (PGs) of bacterial cell wall, leading to the activation of defense responses. Twelve PGRPs have been identified in the silkworm, Bombyx mori, through bioinformatics analysis. However, their biochemical functions are mostly uncharacterized. In this study, we found PGRP-S5 transcript levels were up-regulated in fat body and midgut after bacterial infection. Using recombinant protein isolated from Escherichia coli, we showed that PGRP-S5 binds to PGs from certain bacterial strains and induces bacteria agglutination. Enzyme activity assay confirmed PGRP-S5 is an amidase; we also showed it is an antibacterial protein effective against both Gram-positive and -negative bacteria. Additionally, we demonstrated that specific recognition of PGs by PGRP-S5 is involved in the prophenoloxidase activation pathway. Together, these data suggest the silkworm PGRP-S5 functions as a pattern recognition receptor for the prophenoloxidase pathway initiation and as an effecter to inhibit bacterial growth as well. We finally discussed possible roles of PGRP-S5 as a receptor for antimicrobial peptide gene induction and as an immune modulator in the midgut.
authors: Department of Entomology, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors: Kangkang
authors: K
authors: Chen
authors: Department of Entomology, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors: Chen
authors: C
authors: Liu
authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
authors: Yan
authors: Y
authors: He
authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
authors: Haobo
authors: H
authors: Jiang
authors: Department of Entomology, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China; Key Laboratory of Plant Protection Resources and Pest Management, Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: zhiqiang.lu@nwsuaf.edu.cn.
authors: Zhiqiang
authors: Z
authors: Lu
mesh_terms: D000371:Agglutination; D000581:Amidohydrolases / Q000737:chemistry / Q000494:pharmacology / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D012831:Bombyx / Q000201:enzymology* / Q000276:immunology; D004156:Catechol Oxidase / Q000378:metabolism*; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D005216:Fat Body / Q000201:enzymology / Q000276:immunology; D054884:Host-Pathogen Interactions; D006868:Hydrolysis; D019476:Insect Proteins / Q000737:chemistry / Q000494:pharmacology / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000737:chemistry; D010802:Phylogeny; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000502:physiology; D051192:Receptors, Pattern Recognition / Q000737:chemistry / Q000502:physiology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000502:physiology; D015854:Up-Regulation
chemical_list: D000900:Anti-Bacterial Agents; D004792:Enzyme Precursors; D019476:Insect Proteins; D010457:Peptidoglycan; D051192:Receptors, Pattern Recognition; C038451:pro-phenoloxidase; D004156:Catechol Oxidase; D000581:Amidohydrolases; C019665:amidase
keywords: Bombyx mori; Insect immunity; Melanization; Pattern recognition