title: Global functional analyses of cellular responses to pore-forming toxins.
abstract: Here we present the first global functional analysis of cellular responses to pore-forming toxins (PFTs). PFTs are uniquely important bacterial virulence factors, comprising the single largest class of bacterial protein toxins and being important for the pathogenesis in humans of many Gram positive and Gram negative bacteria. Their mode of action is deceptively simple, poking holes in the plasma membrane of cells. The scattered studies to date of PFT-host cell interactions indicate a handful of genes are involved in cellular defenses to PFTs. How many genes are involved in cellular defenses against PFTs and how cellular defenses are coordinated are unknown. To address these questions, we performed the first genome-wide RNA interference (RNAi) screen for genes that, when knocked down, result in hypersensitivity to a PFT. This screen identifies 106 genes (∼0.5% of genome) in seven functional groups that protect Caenorhabditis elegans from PFT attack. Interactome analyses of these 106 genes suggest that two previously identified mitogen-activated protein kinase (MAPK) pathways, one (p38) studied in detail and the other (JNK) not, form a core PFT defense network. Additional microarray, real-time PCR, and functional studies reveal that the JNK MAPK pathway, but not the p38 MAPK pathway, is a key central regulator of PFT-induced transcriptional and functional responses. We find C. elegans activator protein 1 (AP-1; c-jun, c-fos) is a downstream target of the JNK-mediated PFT protection pathway, protects C. elegans against both small-pore and large-pore PFTs and protects human cells against a large-pore PFT. This in vivo RNAi genomic study of PFT responses proves that cellular commitment to PFT defenses is enormous, demonstrates the JNK MAPK pathway as a key regulator of transcriptionally-induced PFT defenses, and identifies AP-1 as the first cellular component broadly important for defense against large- and small-pore PFTs.
authors.affiliation: Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, California, United States of America.
authors.forename: Cheng-Yuan
authors.initials: CY
authors.lastname: Kao
authors.forename: Ferdinand C O
authors.initials: FC
authors.lastname: Los
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Huffman
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Wachi
authors.forename: Nicole
authors.initials: N
authors.lastname: Kloft
authors.forename: Matthias
authors.initials: M
authors.lastname: Husmann
authors.forename: Valbona
authors.initials: V
authors.lastname: Karabrahimi
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Schwartz
authors.forename: Audrey
authors.initials: A
authors.lastname: Bellier
authors.forename: Christine
authors.initials: C
authors.lastname: Ha
authors.forename: Youn
authors.initials: Y
authors.lastname: Sagong
authors.forename: Hui
authors.initials: H
authors.lastname: Fan
authors.forename: Partho
authors.initials: P
authors.lastname: Ghosh
authors.forename: Mindy
authors.initials: M
authors.lastname: Hsieh
authors.forename: Chih-Shen
authors.initials: CS
authors.lastname: Hsu
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Raffi V
authors.initials: RV
authors.lastname: Aroian
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000633:toxicity*; D001427:Bacterial Toxins / Q000633:toxicity*; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism / Q000472:pathogenicity; D017238:Genes, Helminth; D049751:Genome, Helminth; D006801:Humans; D020935:MAP Kinase Signaling System; D020411:Oligonucleotide Array Sequence Analysis; D052899:Pore Forming Cytotoxic Proteins / Q000633:toxicity*; D034622:RNA Interference; D018510:RNA, Helminth / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D029742:Caenorhabditis elegans Proteins; D052899:Pore Forming Cytotoxic Proteins; D018510:RNA, Helminth; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D037521:Virulence Factors