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.

Tissue damage control in disease tolerance

“…Hypoxia triggers an evolutionarily conserved stress-response regulated by the transcription factor hypoxia-inducible factor 1 alpha (HIF-1α)( forming toxins, given that these can disrupt cellular osmolarity 50 .…”

PSM Peptides of Staphylococcus aureus Activate the p38–CREB Pathway in Dendritic Cells, Thereby Modulating Cytokine Production and T Cell Priming

“…This conclusion is supported by Bebien et al (18) showing that the virulence factor b hemolysin/cytolysin of group B streptococcus induces IL-10 secretion via p38 MAPK activation. PFTs activate MAPK signaling pathways in different eukaryotic cells; whether this is beneficial or detrimental for the pathogen is species dependent (29)(30)(31)(32)(33)(34)(35)(36).…”

Biophysical and biochemical strategies to understand membrane binding and pore formation by sticholysins, pore-forming proteins from a sea anemone

“…These changes in cytoplasmic ionic composition trigger what are known as side effects that result in the activation of various signaling pathways of mitogen-activated protein (MAP) kinases (Huffman et al 2004;Gurcel et al 2006;Bischof et al 2008), which are considered to be essential for survival following toxinmediated membrane disruption. Such activation results in the transcriptional regulation of a broad range of physiological activities involved in the recovery of plasma membrane integrity, cell survival and adaptation (Kao et al 2011;Wald et al 2014).…”