Su1777 GIP Activation of Signaling Pathways Traffick PepT1 Proteins to the Apical Membrane of Intestinal Epithelial Cells

Ezrin connects the apical F-actin scaffold to membrane proteins in the apical brush border of intestinal epithelial cells. Yet, the mechanisms that recruit ezrin to the apical domain remain obscure. Using stable CACO-2 transfectants expressing keratin 8 (K8) antisense RNA under a tetracycline-responsive element, we showed that the actin-ezrin scaffold cannot assemble in the absence of intermediate filaments (IFs). Overexpression of ezrin partially rescued this phenotype. Overexpression of K8 in mice also disrupted the assembly of the brush border, but ezrin distributed away from the apical membrane in spots along supernumerary IFs. In cytochalasin D-treated cells ezrin localized to a subapical compartment and coimmunoprecipitated with IFs. Overexpression of ezrin in undifferentiated cells showed a Triton-insoluble ezrin compartment negative for phospho-T567 (dormant) ezrin visualized as spots along IFs. Pulse-chase analysis showed that Triton-insoluble, newly synthesized ezrin transiently coimmunoprecipitates with IFs during the first 30 min of the chase. Dormant, but not active (p-T567), ezrin bound in vitro to isolated denatured keratins in Far-Western analysis and to native IFs in pull-down assays. We conclude that a transient association to IFs is an early step in the polarized assembly of apical ezrin in intestinal epithelial cells.

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Trafficking of Shigella Lipopolysaccharide in Polarized Intestinal Epithelial Cells

The Journal of Cell Biology ◽

10.1083/jcb.145.4.689 ◽

1999 ◽

Vol 145 (4) ◽

pp. 689-698 ◽

Cited By ~ 42

Author(s):

Wandy L. Beatty ◽

Stéphane Méresse ◽

Pierre Gounon ◽

Jean Davoust ◽

Joëlle Mounier ◽

...

Keyword(s):

Epithelial Cells ◽

Tight Junctions ◽

Apical Membrane ◽

Intestinal Epithelial Cells ◽

Fluid Phase ◽

Apical Surface ◽

Intestinal Epithelial ◽

Electron Microscopic ◽

Basolateral Side ◽

Endocytic Compartments

Bacterial lipopolysaccharide (LPS) at the apical surface of polarized intestinal epithelial cells was previously shown to be transported from the apical to the basolateral pole of the epithelium (Beatty, W.L., and P.J. Sansonetti. 1997. Infect. Immun. 65:4395–4404). The present study was designed to elucidate the transcytotic pathway of LPS and to characterize the endocytic compartments involved in this process. Confocal and electron microscopic analyses revealed that LPS internalized at the apical surface became rapidly distributed within endosomal compartments accessible to basolaterally internalized transferrin. This compartment largely excluded fluid-phase markers added at either pole. Access to the basolateral side of the epithelium subsequent to trafficking to basolateral endosomes occurred via exocytosis into the paracellular space beneath the intercellular tight junctions. LPS appeared to exploit other endocytic routes with much of the internalized LPS recycled to the original apical membrane. In addition, analysis of LPS in association with markers of the endocytic network revealed that some LPS was sent to late endosomal and lysosomal compartments.

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Mycobacterium avium enters intestinal epithelial cells through the apical membrane, but not by the basolateral surface, activates small GTPase Rho and, once within epithelial cells, expresses an invasive phenotype

Cellular Microbiology ◽

10.1046/j.1462-5822.2000.00080.x ◽

2000 ◽

Vol 2 (6) ◽

pp. 561-568 ◽

Cited By ~ 36

Author(s):

Felix J. Sangari ◽

Joseph Goodman ◽

Luiz E. Bermudez

Keyword(s):

Epithelial Cells ◽

Mycobacterium Avium ◽

Apical Membrane ◽

Intestinal Epithelial Cells ◽

Small Gtpase ◽

Intestinal Epithelial ◽

Invasive Phenotype

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Caenorhabditis elegans chaperonin CCT/TRiC is required for actin and tubulin biogenesis and microvillus formation in intestinal epithelial cells

Molecular Biology of the Cell ◽

10.1091/mbc.e13-09-0530 ◽

2014 ◽

Vol 25 (20) ◽

pp. 3095-3104 ◽

Cited By ~ 24

Author(s):

Keiko Saegusa ◽

Miyuki Sato ◽

Katsuya Sato ◽

Junko Nakajima-Shimada ◽

Akihiro Harada ◽

...

Keyword(s):

Caenorhabditis Elegans ◽

Epithelial Cells ◽

Apical Membrane ◽

Intestinal Epithelial Cells ◽

Intestinal Cells ◽

Intermediate Filament Protein ◽

Apical Surface ◽

Intestinal Epithelial ◽

Microtubule Network

Intestinal epithelial cells have unique apical membrane structures, known as microvilli, that contain bundles of actin microfilaments. In this study, we report that Caenorhabditis elegans cytosolic chaperonin containing TCP-1 (CCT) is essential for proper formation of microvilli in intestinal cells. In intestinal cells of cct-5(RNAi) animals, a substantial amount of actin is lost from the apical area, forming large aggregates in the cytoplasm, and the apical membrane is deformed into abnormal, bubble-like structures. The length of the intestinal microvilli is decreased in these animals. However, the overall actin protein levels remain relatively unchanged when CCT is depleted. We also found that CCT depletion causes a reduction in the tubulin levels and disorganization of the microtubule network. In contrast, the stability and localization of intermediate filament protein IFB-2, which forms a dense filamentous network underneath the apical surface, appears to be superficially normal in CCT-deficient cells, suggesting substrate specificity of CCT in the folding of filamentous cytoskeletons in vivo. Our findings demonstrate physiological functions of CCT in epithelial cell morphogenesis using whole animals.

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