title: Inhibition of intracellular bacterial replication in fibroblasts is dependent on the perforin-like protein (perforin-2) encoded by macrophage-expressed gene 1.
abstract: Fibroblasts are known to eliminate intracellular bacteria, but the lethal hit of the bactericidal mechanism has not been defined. We show that primary embryonic and established fibroblasts can be induced by interferons or by intracellular bacterial infection to express a perforin-like mRNA previously described as macrophage-expressed gene 1 (Mpeg1). The presence and level of the perforin-like mRNA correlate with the ability of primary mouse embryonic fibroblasts (MEF) to eliminate intracellular bacteria. In addition, siRNA knockdown of the perforin-like molecule abolishes bactericidal activity and allows intracellular bacterial replication. Complementation of MEF in which the endogenous perforin-like molecule has been knocked down with a red fluorescent protein-tagged version restores bactericidal activity. The perforin-like molecule has broad bactericidal specificity for pathogenic and non-pathogenic bacteria, including Gram-positive and -negative, and acid fast bacteria. The perforin-like molecule renders previously lysozyme-resistant bacteria sensitive to lysis by lysozyme suggesting physical damage of the outer cell wall by the perforin-like protein. MEF damage cell walls of intracellular bacteria by insertion, polymerization, and pore formation of the perforin-like protein, analogous to pore formers of complement and perforin-1 of cytolytic lymphocytes. We propose the name perforin-2.
authors.affiliation: Department of Microbiology and Immunology, University of Miami, Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: McCormack
authors.forename: Lesley R
authors.initials: LR
authors.lastname: de Armas
authors.forename: Motoaki
authors.initials: M
authors.lastname: Shiratsuchi
authors.forename: Jahir E
authors.initials: JE
authors.lastname: Ramos
authors.forename: Eckhard R
authors.initials: ER
authors.lastname: Podack
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001424:Bacterial Infections / Q000276:immunology*; D002460:Cell Line; D004269:DNA, Bacterial / Q000096:biosynthesis; D005347:Fibroblasts / Q000276:immunology* / Q000382:microbiology; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics; D042541:Intracellular Space / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D052899:Pore Forming Cytotoxic Proteins / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D034741:RNA, Small Interfering / Q000235:genetics; D016415:Sequence Alignment; D019076:Transgenes / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D008565:Membrane Proteins; C483884:Mpeg1 protein, mouse; D052899:Pore Forming Cytotoxic Proteins; D034741:RNA, Small Interfering; C510469:perforin 2