Intestinal Transport and Processing of Immunoglobulin G in the Neonatal and Adult Rat

Benlounes, Nadia; Chedid, Rima; Thuillier, F.; Desjeux, J. F.; Rousselet, F; Heyman, Martine

doi:10.1159/000244173

Cited by 33 publications

(30 citation statements)

References 17 publications

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“…It is interesting to note that the literature already has a number of studies that demonstrate transcytosis of intact proteins across intestinal epithelial cells (36 -40), and in some cases the studies report rates of transcytosis (29,(41)(42)(43). The rate of transcytosis of BoNT/A determined in the present study is within the range of that reported for other proteins, but it is at the low end of the range.…”

Section: Discussionsupporting

confidence: 78%

Binding and Transcytosis of Botulinum Neurotoxin by Polarized Human Colon Carcinoma Cells

Maksymowych

Simpson

1998

Journal of Biological Chemistry

114

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-84 cells, nor were they efficiently transcytosed (8 -10% of serotype A). MDCK cells did not bind or efficiently transcytose (0.32 fmol/h/cm2 ) botulinum toxin. Further characterization demonstrated that the rate of transcytosis for serotype A in T-84 cells was increased 66% when vesicle sorting was disrupted by 5 M brefeldin A, decreased 42% when microtubules were disrupted by 10 M nocodazole, and decreased 74% at 18°C. Drugs that antagonize toxin action at the nerve terminal, such as bafilomycin A 1 (which prevents acidification of endosomes) and methylamine HCl (which neutralizes acidification of endosomes), produced only a modest inhibitory effect on the rate of transcytosis (17-22%). These results may provide an explanation for the mechanism by which botulinum toxin escapes the human gastrointestinal tract, and they may also explain why specific serotypes cause human disease and others do not.

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Section: Discussionsupporting

confidence: 78%

Binding and Transcytosis of Botulinum Neurotoxin by Polarized Human Colon Carcinoma Cells

Maksymowych

Simpson

1998

Journal of Biological Chemistry

114

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“…In contrast to the rat and mouse neonatal intestine, where maternal IgG binds FcRn at the apical cell surface (47), FcRn expressed in the rat yolk sac appears to bind IgG only within apical compartments after fluidphase uptake (48). Also, Benlounes et al (49) have observed transepithelial IgG transport across isolated neonatal rat intestine in which both the serosal and mucosal solutions were clamped at neutral pH and thus inhibitory for IgG binding to FcRn at the cell surface.…”

Section: Discussionmentioning

confidence: 99%

Bidirectional FcRn-dependent IgG transport in a polarized human intestinal epithelial cell line

Dickinson¹,

Badizadegan²,

Wu³

et al. 1999

J. Clin. Invest.

399

361

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IntroductionSteady-state levels of IgG in the blood of adult mice, and likely all mammals, depend on IgG catabolism mediated in part by the MHC class I-related Fc receptor, FcRn (1). FcRn also mediates vectorial transport of IgG across certain epithelial barriers. In suckling mice and rats, intestinal absorption of maternal IgG from breast milk into the systemic circulation depends on FcRn (2). In humans, maternofetal transfer of IgG across the placenta also likely depends on FcRn (3). Thus, FcRn plays critical and well-documented roles in the regulation of IgG metabolism in adults and in the acquisition of humoral immunity in early life. These effects on the physiology of IgG in vivo result from the action of FcRn as an intracellular trafficking receptor (4).FcRn has been cloned from the rat, mouse, and human. The molecule is expressed as a heterodimer composed of a glycosylated heavy (α) chain (51 kDa in rodents and 40-45 kDa in humans) associated noncovalently with β2-microglobulin (β2M) (5). Binding of IgG to FcRn requires contact between solvent-exposed peptide sequences in the CH2 and CH3 domains of IgG and the α1 and α2 domains of FcRn, together with a single contact site in β2M (6-11). A hallmark of FcRn interaction with IgG is its pH dependence, showing high-affinity binding at acidic pH (pH ≤ 6.5) and weak or no binding at neutral pH (pH ≥ 7.0) (12, 13). FcRn is the only Fcγ receptor that exhibits MHC class I structure, and the only Fcγ receptor to exhibit pH dependency in ligand binding.The function of FcRn in the intestine of suckling mice and rats has been well documented (14). In neonatal mice and rats, FcRn is expressed at high levels by intestinal epithelial cells and mediates absorption of IgG by receptor-mediated transcytosis. FcRn expression in the neonatal rodent is developmentally downregulated, resulting in nearly complete loss of intestinal FcRn at the time of weaning (15)(16)(17) The MHC class I-related Fc receptor, FcRn, mediates the intestinal absorption of maternal IgG in neonatal rodents and the transplacental transport of maternal IgG in humans by receptor-mediated transcytosis. In mice and rats, expression of FcRn in intestinal epithelial cells is limited to the suckling period. We have recently observed, however, clear expression of FcRn in the adult human intestine, suggesting a function for FcRn in intestinal IgG transport beyond neonatal life in humans. We tested this hypothesis using the polarized human intestinal T84 cell line as a model epithelium. Immunocytochemical data show that FcRn is present in T84 cells in a punctate apical pattern similar to that found in human small intestinal enterocytes. Solute flux studies show that FcRn transports IgG across T84 monolayers by receptor-mediated transcytosis. Transport is bidirectional, specific for FcRn, and dependent upon endosomal acidification. These data define a novel bidirectional mechanism of IgG transport across epithelial barriers that predicts an important effect of FcRn on IgG function in immune surveillance and host de...

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“…These experiments were done using intestinal samples from neonatal rats that had been fed Au-Fc. The concentration of Au-Fc that was fed to neonatal rats was 2-3 μM, approximately equal to the IgG concentration in rat milk, because higher concentrations saturate FcRn, resulting in degradation of excess IgG (Benlounes et al, 1995). In this system for Au-Fc uptake, we had two controls for the specificity of uptake and gold enhancement: first, the presence or absence of ingested Au-Fc, and second, the requirement that enhanced gold particles should appear in physiologically-relevant locations in cells; e.g., in locations corresponding to FcRn expression (apical cell surface, coated vesicles and tubulovesicular compartments) in samples from the proximal small intestine, and inside degradative compartments (e.g., giant lysosomes) in samples from the neonatal distal small intestine (ileum), which does not express FcRn (Rodewald, 1973).…”

Section: Specific Enhancement Of Endocytosed 14 Nm Au-fc In Chemicalmentioning

confidence: 99%

A freeze substitution fixation-based gold enlarging technique for EM studies of endocytosed Nanogold-labeled molecules

Kivork

Machinani

et al. 2007

Journal of Structural Biology

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We have developed methods to locate individual ligands that can be used for electron microscopy studies of dynamic events during endocytosis and subsequent intracellular trafficking. The methods are based on enlargement of 1.4 nm Nanogold attached to an endocytosed ligand. Nanogold, a small label that does not induce misdirection of ligand-receptor complexes, is ideal for labeling ligands endocytosed by live cells, but is too small to be routinely located in cells by electron microscopy. Traditional pre-embedding enhancement protocols to enlarge Nanogold are not compatible with high pressure freezing/freeze substitution fixation (HPF/FSF), the most accurate method to preserve ultrastructure and dynamic events during trafficking. We have developed an improved enhancement procedure for chemically-fixed samples that reduced autonucleation, and a new pre-embedding goldenlarging technique for HPF/FSF samples that preserved contrast and ultrastructure and can be used for high-resolution tomography. We evaluated our methods using labeled Fc as a ligand for the neonatal Fc receptor. Attachment of Nanogold to Fc did not interfere with receptor binding or uptake, and gold-labeled Fc could be specifically enlarged to allow identification in 2D projections and in tomograms. These methods should be broadly applicable to many endocytosis and transcytosis studies.

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Intestinal Transport and Processing of Immunoglobulin G in the Neonatal and Adult Rat

Cited by 33 publications

References 17 publications

Binding and Transcytosis of Botulinum Neurotoxin by Polarized Human Colon Carcinoma Cells

Binding and Transcytosis of Botulinum Neurotoxin by Polarized Human Colon Carcinoma Cells

Bidirectional FcRn-dependent IgG transport in a polarized human intestinal epithelial cell line

A freeze substitution fixation-based gold enlarging technique for EM studies of endocytosed Nanogold-labeled molecules

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