Alteration of epithelial cell transferrin-iron homeostasis by Neisseria meningitidis and Neisseria gonorrhoeae

Abstract

Iron is an essential element for nearly all organisms. In mammals, iron is transported to body tissues by the serum glycoprotein transferrin. Transferrin‐iron is internalized by binding to specific receptors followed by endocytosis. In vitro, Neisseria meningitidis and Neisseria gonorrhoeae can use iron from a variety of iron‐containing compounds, including human transferrin. In vivo, transferrin is an important source of iron for N. gonorrhoeae: a mutant that is unable to bind and use transferrin‐iron is unable to colonize the urethra of men or initiate disease at this site. As pathogenic Neisseria and its human host derive much of their iron from transferrin, we reasoned that a competition may exist between microbe and host epithelial cells for transferrin‐iron at certain stages of infection. We therefore tested the hypothesis that N. meningitidis and N. gonorrhoeae may actively interfere with host transferrin‐iron metabolism. We report that Neisseria‐infected human epithelial cells have reduced levels of transferrin receptor messenger RNA and cycling transferrin receptors. The ability of infected cells to internalize transferrin receptor is also reduced. Finally, the relative distribution of surface and cycling transferrin receptors is altered in an infected cell. We conclude that Neisseria infection alters epithelial cell transferrin‐iron homeostasis at multiple levels.

Global Gene Expression and the Role of Sigma Factors in Neisseria gonorrhoeae in Interactions with Epithelial Cells

“…For the experiments described in this work, A431 cells (20), an epithelial cell line derived from the endocervix (56), were used. Gonococci have been shown to adhere to and invade A431 cells at a high frequency (3,30,43,48,76), and there have been several reports investigating the response of these cells to gonococcal adherence at the molecular level (4,5,7,43).…”

Expression of the Gonococcal Global Regulatory Protein Fur and Genes Encompassing the Fur and Iron Regulon during In Vitro and In Vivo Infection in Women

“…Bonnah et al (4,5) have shown previously that human epithelial cells infected with N. gonorrhoeae or N. meningitidis have reduced levels of transferrin receptor mRNA and cycling transferrin receptors. Using DNA microarray analysis, these investigators reported altered expression levels of a number of host genes during Neisseria infection of epithelial cells, and these researchers suggested that bacterial growth in epithelial cells represents growth in an iron-limited environment.…”

“…Oligonucleotides were synthesized on an ABI 3900 DNA synthesizer (Applied Biosystems, Foster City, CA) on a 200-nmol scale using standard phorphoramidite chemistry and 5Ј-DMT-mdC (TEG-FMOC) columns (Biosearch Technologies, Novato, CA). After synthesis, oligonucleotides were cleaved from the support and deprotected by using concentrated NH 4 OH at 65°C for 5 h. Oligonucleotides were purified on Varian TOP columns (Varian Instruments, Walnut Creek, CA) according to the manufacturer's protocol and then quantitated by using an Oligreen ssDNA quantitation kit (Molecular Probes, Eugene, OR). Oligonucleotides (50 M in 150 mM sodium phosphate [pH 8.5]) were spotted in duplicate onto Codelink slides (Amersham Biosciences; Piscataway, NJ) at 25°C (55% relative humidity) from 384-well chilled spotting plates (15°C) using a QArraymini spotter (Genetix, Boston, MA) using Stealth SMP4 pins (Telechem, Sunnyvale, CA).…”

Neisseria gonorrhoeae Porin P1.B Induces Endosome Exocytosis and a Redistribution of Lamp1 to the Plasma Membrane

“…Cultures were incubated with purified protein, live bacteria, or membrane preparations derived from these bacteria for various times and quickly chilled to 4°C by adding ice-cold DMEM and placing the microtiter plates on an ice bath. Surface Lamp1 was quantitated with biotinylated MAb H4A3 for Lamp1 (2), and TfR levels were quantitated with HRP-transferrin (6).…”