Disease relevance of cnf1

• One milliliter of a culture of Escherichia coli (with five uro-pathogenic virulence factors as identified by PCR: pap, sfa, hlyA, cnf1 and fim) was inoculated intra-vaginally daily throughout the simulated estrus (Group 2) [1].
• The prevalence of sfa, hly and cnf1 was higher in prostatitis isolates than in pyelonephritis and cystitis isolates, and the pap+sfa+hly+cnf1+ genotype was dominant among prostatitis isolates (48.8%) [2].
• The N-terminal half of CNF2 showed striking homology (27% identity and 80% conserved residues) to the N-terminal portion of Pasteurella multocida toxin [3].
• Preincubation of cells with CNF1 impairs the cytotoxic effects of Clostridium difficile toxin B, which inactivates Rho but not those of Clostridium sordellii LT toxin, which inhibits Ras and Rac [4].
• Recently, a novel cytotoxic necrotizing factor termed CNFY was identified in Yersinia pseudotuberculosis strains (Lockman, H. A., Gillespie, R. A., Baker, B. D., and Shakhnovich, E. (2002) Infect. Immun. 70, 2708-2714) [5].

High impact information on cnf1

• Here, we show that the modulation of cerebral RhoA and Rac1 activity induced by CNF1 in mice leads to (i) rearrangement of cerebral actin cytoskeleton, (ii) enhanced neurotransmission and synaptic plasticity, and (iii) improved learning and memory in various behavioral tasks [6].
• The effects persist for weeks and are not observed in mice treated with a recombinant CNF1, in which the enzymatic activity was abolished by substituting serine to cysteine at position 866 [6].
• Here we show that the catalytic region of CNF1 exhibits a novel protein fold as determined by its 1.83 A resolution crystal structure [7].
• We cloned the CNF2 gene from a large plasmid carried by an Escherichia coli strain isolated from a lamb with septicemia [3].
• Although it is clear that the CNF toxins can affect a wide variety of adherent nonhematopoietic cell lines, we propose that the response to CNF, in terms of reorganizing actin structure and increase in DNA content in hematologic suspension cells, correlates with the capability of these target cells to differentiate along the megakaryocytic lineage [8].

Chemical compound and disease context of cnf1

• The cytotoxic necrotizing factor 1 (CNF1) from Escherichia coli activates members of the Rho family by deamidation of glutamine 61/63 [9].
• The Rho-deamidating cytotoxic necrotizing factor 1 from Escherichia coli possesses transglutaminase activity. Cysteine 866 and histidine 881 are essential for enzyme activity [10].
• Microinjection of Clostridium botulinum C3 exoenzyme which ADP-ribosylates and inactivates p21(rho) function, prevented tyrosine phosphorylation of focal adhesion proteins in response to either CNF1 or DNT [11].
• CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria such as Listeria innocua, which were taken as a model system [12].
• Cytotoxic necrotizing factor 2 (CNF2) is an exotoxin identified from virulent clinical isolates of Escherichia coli [13].

Biological context of cnf1

• Expression of cnf1 by Escherichia coli J96 involves a large upstream DNA region including the hlyCABD operon, and is regulated by the RfaH protein [14].
• Nevertheless, in this model, the CNF1 toxin does not appear to be a major factor for pathogenicity or cytokine response, as demonstrated by the use of an isogenic cnf1 mutant [15].
• Rho-dependent cell spreading activated by E.coli cytotoxic necrotizing factor 1 hinders apoptosis in epithelial cells [16].
• In addition to the promotion of cell spreading, CNF1 protects cells from the experimentally-induced rounding up and detachment and improves the ability of cells to adhere to each other and to the extracellular matrix by modulating the expression of proteins related to cell adhesion [16].
• We also studied the effects of CNF1 on phagocytosis [17].

Anatomical context of cnf1

• Seven of the cnf1-positive isolates were tested and shown to have a cytopathic effect on HeLa cell monolayers [18].
• The cnf1 sequences from the mink and bovine isolates of E. coli were compared to each other and to cnf1 sequences of E. coli from urinary tract and diarrhoea-associated infections of humans [19].
• CNF1 belongs to a unique group of large cytotoxins that cause constitutive activation of Rho guanosine triphosphatases (GTPases), which are key regulators of the actin cytoskeleton [7].
• We have examined the effect of CNF toxin on one of the few cell types that naturally increase nuclear DNA content, megakaryocytes [8].
• In addition, CNF1-enhanced E. coli invasion of brain endothelial cells and stress fiber formation were independent of focal adhesion kinase and phosphatidylinositol 3-kinase activation [20].

Associations of cnf1 with chemical compounds

• Some strains possessed toxin genes cdt-IIIB and cnf1/2 (both 14.3%), the invasion gene tia (23.8%), and the serine protease encoding gene espP (23.8%) [21].
• The data indicate that CNF1 shares a catalytic dyad of cysteine and histidine residues with eukaryotic transglutaminases and cysteine proteases [10].
• When immobilized onto polystyrene beads, CNF1 was sufficient to induce internalization of coupled beads into HBMEC through interaction with 67LR [22].
• In addition, we identified histidine 881 to be essential for the enzyme activity of CNF1 [10].
• Cytochalasin D and high concentrations of platelet-derived growth factor disrupted the actin cytoskeleton and completely inhibited CNF1 and DNT induced tyrosine phosphorylation [11].

Analytical, diagnostic and therapeutic context of cnf1

• CONCLUSIONS: A small proportion of patients with BPH undergoing TURP are positive for E. coli 16S RNA and cnf1 gene in the prostate tissue [23].
• CNF1 is acting in the cytosol since microinjection of the toxin into HEp-2 cells mimics the effects of the externally applied CNF1 [4].
• Rat pheochromocytoma PC12 cells microinjected with Ras55Rho developed formation of neurite-like structures after treatment with the CNF1 holotoxin indicating activation of the Ha-Ras chimera and Ras-like effects in intact cells [24].
• In addition, we show that cytotoxic necrotizing factor-1 (CNF1) contributes to E. coli K1 invasion of brain endothelial cells in vitro and traversal of the blood-brain barrier in the experimental hematogenous meningitis animal model [20].
• To delineate further the functional domains of CNF1, we generated 16 monoclonal antibodies (MAbs) against the toxin and used them for epitope mapping studies [25].

References