title: INVOLVEMENT OF PEPTIDOGLYCAN RECOGNITION PROTEIN L6 IN ACTIVATION OF IMMUNE DEFICIENCY PATHWAY IN THE IMMUNE RESPONSIVE SILKWORM CELLS.
abstract: The immune deficiency (Imd) signaling pathway is activated by Gram-negative bacteria for producing antimicrobial peptides (AMPs). In Drosophila melanogaster, the activation of this pathway is initiated by the recognition of Gram-negative bacteria by peptidoglycan (PGN) recognition proteins (PGRPs), PGRP-LC and PGRP-LE. In this study, we found that the Imd pathway is involved in enhancing the promoter activity of AMP gene in response to Gram-negative bacteria or diaminopimelic (DAP) type PGNs derived from Gram-negative bacteria in an immune responsive silkworm cell line, Bm-NIAS-aff3. Using gene knockdown experiments, we further demonstrated that silkworm PGRP L6 (BmPGRP-L6) is involved in the activation of E. coli or E. coli-PGN mediated AMP promoter activation. Domain analysis revealed that BmPGRP-L6 contained a conserved PGRP domain, transmembrane domain, and RIP homotypic interaction motif like motif but lacked signal peptide sequences. BmPGRP-L6 overexpression enhances AMP promoter activity through the Imd pathway. BmPGRP-L6 binds to DAP-type PGNs, although it also binds to lysine-type PGNs that activate another immune signal pathway, the Toll pathway in Drosophila. These results indicate that BmPGRP-L6 is a key PGRP for activating the Imd pathway in immune responsive silkworm cells.
authors.affiliation: Insect-Microbe Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Insect-Microbe Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
authors.forename: Aki
authors.initials: A
authors.lastname: Sagisaka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics* / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D019476:Insect Proteins; D012333:RNA, Messenger; C118897:peptidoglycan recognition protein
keywords: antimicrobial peptides; gene expression; insect immunity; peptidoglycan recognition protein; silkworm