Biomedical subjects

D E Barnett Foster

Publications and source records attributed to D E Barnett Foster.

6 recordsLinked to original sources

PubMed2004

Enteropathogenic Escherichia coli infection triggers host phospholipid metabolism perturbations.

Enteropathogenic Escherichia coli (EPEC) specifically recognizes phosphatidylethanolamine (PE) on the outer leaflet of host epithelial cells. EPEC also induces apoptosis in epithelial cells, which results in increased levels of outer leaflet PE and increased bacterial binding. Consequently, it is of interest to investigate whether EPEC infection perturbs host cell phospholipid metabolism and whether the changes play a role in the apoptotic signaling. Our findings indicate that EPEC infection results in a significant increase in the epithelial cell PE level and a corresponding decrease in the phosphatidylcholine (PC) level. PE synthesis via both the de novo pathway and the serine decarboxylation pathway was enhanced, and de novo synthesis of phosphatidylcholine via CDP-choline was reduced. The changes were transitory, and the maximum change was noted after 4 to 5 h of infection. Addition of exogenous PC or CDP-choline to epithelial cells prior to infection abrogated EPEC-induced apoptosis, suggesting that EPEC infection inhibits the CTP-phosphocholine cytidylyltransferase step in PC synthesis, which is reportedly inhibited during nonmicrobially induced apoptosis. On the other hand, incorporation of exogenous PE by the host cells enhanced EPEC-induced apoptosis and necrosis without increasing bacterial adhesion. This is the first report that pathogen-induced apoptosis is associated with significant changes in PE and PC metabolism, and the results suggest that EPEC adhesion to a host membrane phospholipid plays a role in disruption of host phospholipid metabolism.

Apoptosis↗

PubMed2001

Enteropathogenic Escherichia coli virulence factor bundle-forming pilus has a binding specificity for phosphatidylethanolamine.

The bundle-forming pilus (BFP) of enteropathogenic Escherichia coli (EPEC), an established virulence factor encoded on the EPEC adherence factor (EAF) plasmid, has been implicated in the formation of bacterial autoaggregates and in the localized adherence of EPEC to cultured epithelial cells. While understanding of the pathogenic mechanism of this organism is rapidly improving, a receptor ligand for BFP has not yet been identified. We now report, using both solid-phase and liposome binding assays, that BFP expression correlates with phosphatidylethanolamine (PE) binding. In a thin-layer chromatogram overlay assay, specific recognition of PE was documented for BFP-expressing strains, including E2348/69, a wild-type EPEC clinical isolate, as well as a laboratory strain, HB101, transformed with a bfp-carrying plasmid. Strains which did not express BFP did not bind PE, including a bfpA disruptional mutant of E2348/69, EAF plasmid-cured E2348/69, and HB101. E2348/69 also aggregated PE-containing liposomes but not phosphatidylcholine- or phosphatidylserine-containing liposomes, while BFP-negative strains did not produce aggregates with any tested liposomes. Purified BFP preparations bound commercial PE standards as well as a PE-containing band within lipid extracts from human epithelial cells and from E2348/69. Our results therefore indicate a specific interaction between BFP and PE and suggest that PE may serve as a BFP receptor for bacterial autoaggregation and may promote localized adherence to host cells, both of which contribute to bacterial pathogenesis.

Bacterial Outer Membrane Proteins↗

PubMed1999

A comparison of the effects of verocytotoxin-1 on primary human renal cell cultures.

Infection with verocytotoxin-producing Escherichia coli causes haemolytic uraemic syndrome (HUS). Verocytotoxin-1 (VT1) is cytopathic to renal microvascular endothelial cells in culture, supporting the hypothesis that the vasculopathy of HUS is caused directly by the toxic action of VT1 on cells. We provide evidence that VT1 inhibits protein synthesis in primary cultures of glomerular epithelial cells (GE), cortical tubular epithelial cells (CTE) and mesangial cells (MC). Using 100 pg/ml of VT1 we saw a decrease in protein synthesis to 14.3+/-1.9% in vero cells (a primate cell line), 1.7+/-0.3% in GE, 0.9+/-0.4% in CTE and 74.8+/-1.3% in MC at 24 h. The human renal epithelial cells are at least as sensitive as vero cells to the protein synthesis inhibitory effects of VT1 if not more so. Cell viability decreased in all cultures as measured by MTT reduction, neutral red incorporation and lactate dehydrogenase release and followed the same pattern of susceptibility as for protein synthesis inhibition. However, unlike vero cells, death occurred without DNA fragmentation. Cell sensitivity was greatest in cells which bound more VT1.

Animals↗

PubMed1982

The effect of fragment B of staphylococcal protein A on the binding of rabbit IgG to human granulocytes and monocytes.

The effect of fragment B of staphylococcal protein A on the binding of rabbit IgG to human granulocytes has been examined. When rabbit IgG sensitized sheep erythrocytes (EA) were preincubated with increasing amounts of fragment B, a dose dependent inhibition of rosette formation between the human granulocytes and the treated EA was observed. In contrast, rosette formation between human monocytes and fragment B treated EA was not impaired. These results confirm previous findings which revealed differences in the specificities of the human Fc receptors of these cells. Rabbit IgG was used in place of human IgG for the preparation of the sensitized erythrocytes since human IgG coated human erythrocytes were agglutinated by fragment B, indicating the possibility of a secondary binding site for human IgG in this fragment.

Animals↗

PubMed1980

Structure and function of immunoglobulin domains. VIII. An analysis of the structural requirements in human IgG1 for binding to the Fc receptor of human monocytes.

A human mononuclear cell population, enriched with monocytes by adhering them to microexudate on Petri dishes previously used for fibroblast cultures was used in a homologous human system to form EA rosettes. IgG1, Fc, and subfragments of Fc representing the C gamma 2 and C gamma 3 domains were tested for their ability to inhibit rosette formation. Although Fc and IgG were equally effective in inhibiting rosette formation over the concentration range 10(-6) to 10(-5) M, all subfragments were inactive at these concentrations. At 10-fold higher concentrations the C gamma 2 fragment was still inactive; however, both the C gamma 3 fragments, pFc' and at C gamma 3, did show significant activity at this higher level. Reduction and alkylation diminished the inhibitory capacity of IgG 10-fold but had a lesser effect on Fc. In a parallel series of experiments the ability of IgG and Fc to inhibit granulocyte rosettes was found to be markedly diminished by reduction and alkylation in both cases. These experiments reveal differences between Fc receptors in different cells, confirm a role for the C gamma 3 homology region in monocyte Fc receptor recognition, but do suggest a requirement, either direct or indirect, for the C gamma 2 domain.

Alkylation↗

PubMed1978

Structure and function of immunoglobulin domains. VII. Studies on the structural requirements of human immunoglobulin G for granulocyte binding.

The ability of various fragments of human myeloma IgG1 to inhibit rosette formation between human anti-D-coated human red blood cells and human polymorphonuclear leukocytes has been investigated. Although IgG and Fc showed a dose-dependent inhibition of rosettes and Fc showed a dose-dependent inhibition of rosettes at equimolar concentrations, neither of the fragments corresponding to the Cgamma2 and Cgamma3 homology regions obtained by acid-tryptic cleavage of Fc was able to inhibit rosette formation. The pepsin fragment of Fc, pFc', which represents the complete Cgamma3 domain, was also unable to prevent rosette formation. Reduction and alkylation of IgG or Fc markedly diminished cytophilic activity as measured by this system. These data indicate that the site in human IgG1 bound by granulocytes is dependent on the full quaternary structure of Fc, a requirement in marked contrast to that noted for binding by macrophages and monocytes.

Binding Sites, Antibody↗