scholarly journals Tropomyosin distinguishes between the two actin-binding sites of villin and affects actin-binding properties of other brush border proteins.

1987 ◽  
Vol 104 (1) ◽  
pp. 29-40 ◽  
Author(s):  
D R Burgess ◽  
K O Broschat ◽  
J M Hayden
Keyword(s):  
Epithelial Cell ◽  
Protein Interactions ◽  
Brush Border ◽  
Binding Sites ◽  
Intestinal Epithelial Cell ◽  
Actin Binding ◽  
Intestinal Epithelial ◽  
Binding Properties ◽  
Order Of Magnitude ◽  
Protein Components

The intestinal epithelial cell brush border exhibits distinct localizations of the actin-binding protein components of its cytoskeleton. The protein interactions that dictate this subcellular organization are as yet unknown. We report here that tropomyosin, which is found in the rootlet but not in the microvillus core, can bind to and saturate the actin of isolated cores, and can cause the dissociation of up to 30% of the villin and fimbrin from the cores but does not affect actin binding by 110-kD calmodulin. Low speed sedimentation assays and ultrastructural analysis show that the tropomyosin-containing cores remain bundled, and that 110-kD calmodulin remains attached to the core filaments. The effects of tropomyosin on the binding and bundling activities of villin were subsequently determined by sedimentation assays. Villin binds to F-actin with an apparent Ka of 7 X 10(5) M-1 at approximate physiological ionic strength, which is an order of magnitude lower than that of intestinal epithelial cell tropomyosin. Binding of villin to F-actin presaturated with tropomyosin is inhibited relative to that to pure F-actin, although full saturation can be obtained by increasing the villin concentration. Villin also inhibits the binding of tropomyosin to F-actin, although not to the same extent. However, tropomyosin strongly inhibits bundling of F-actin by villin, and bundling is not recovered even at a saturating villin concentration. Since villin has two actin-binding sites, both of which are required for bundling, the fact that tropomyosin inhibits bundling of F-actin under conditions where actin is fully saturated with villin strongly suggests that tropomyosin's and one of villin's F-actin-binding sites overlap. These results indicate that villin and tropomyosin could compete for actin filaments in the intestinal epithelial cell, and that tropomyosin may play a major role in the regulation of microfilament structure in these and other cells.

scholarly journals Reactivation of intestinal epithelial cell brush border motility: ATP-dependent contraction via a terminal web contractile ring.

1982 ◽  
Vol 95 (3) ◽  
pp. 853-863 ◽  
Author(s):  
D R Burgess
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cell ◽  
Brush Border ◽  
Intestinal Epithelial Cell ◽  
Intercellular Junctions ◽  
Intestinal Epithelial ◽  
Differential Interference Contrast Microscopy ◽  
Contractile Ring ◽  
Terminal Web ◽  
Brush Borders

Various models have been put forward suggesting ways in which brush borders from intestinal epithelial cells may be motile. Experiments documenting putative brush border motility have been performed on isolated brush borders and have generated models suggesting microvillar retraction or microvillar rootlet interactions. The reported Ca++ ATP-induced retraction of microvilli has been shown, instead, to be microvillar dissolution in response to Ca++ and not active brush border motility. I report here studies on the reactivation of motility in intact sheets of isolated intestinal epithelium. Whole epithelial sheets were glycerinated, which leaves the brush border and intercellular junctions intact, and then treated with ATP, PPi, ITP, ADP, GTP, or delta S-ATP. Analysis by video enhanced differential interference-contrast microscopy and thin-section transmission electron microscopy reveals contractions in the terminal web region causing microvilli to be fanned apart in response to ATP and delta S-ATP but not in response to ADP, PPi, ITP, or GTP. Electron microscopy reveals that the contractions occur at the level of the intermediate junction in a circumferential constriction which can pull cells completely apart. This constriction occurs in a location occupied by an actin-containing circumferential band of filaments, as demonstrated by S-1 binding, which completely encircles the terminal web at the level of the intermediate junction. Upon contraction, this band becomes denser and thicker. Since myosin, alpha-actinin and tropomyosin, in addition to actin, have been localized to this region of the terminal web, it is proposed that the intestinal epithelial cell can be motile via a circumferential terminal web contractile ring analogous to the contractile ring of dividing cells.

scholarly journals Stimulation of constitutive nitric oxide uniquely and compensatorily regulates intestinal epithelial cell brush border membrane Na absorption

2019 ◽  
Vol 7 (9) ◽  
pp. e14086
Author(s):  
Balasubramanian Palaniappan ◽  
Palanikumar Manoharan ◽  
Subha Arthur ◽  
Soudamani Singh ◽  
Usha Murughiyan ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Epithelial Cell ◽  
Brush Border ◽  
Intestinal Epithelial Cell ◽  
Brush Border Membrane ◽  
Intestinal Epithelial ◽  
Stimulation Of

scholarly journals FOXA2 regulates a network of genes involved in critical functions of human intestinal epithelial cells

2015 ◽  
Vol 47 (7) ◽  
pp. 290-297 ◽  
Author(s):  
Nehal Gosalia ◽  
Rui Yang ◽  
Jenny L. Kerschner ◽  
Ann Harris
Keyword(s):  
Transcription Factors ◽  
Epithelial Cell ◽  
Binding Sites ◽  
Intestinal Epithelial Cell ◽  
Cell Function ◽  
Mrna Levels ◽  
Intestinal Epithelial ◽  
Membrane Function ◽  
Protein Levels ◽  
Genome Wide

The forkhead box A (FOXA) family of pioneer transcription factors is critical for the development of many endoderm-derived tissues. Their importance in regulating biological processes in the lung and liver is extensively characterized, though much less is known about their role in intestine. Here we investigate the contribution of FOXA2 to coordinating intestinal epithelial cell function using postconfluent Caco2 cells, differentiated into an enterocyte-like model. FOXA2 binding sites genome-wide were determined by ChIP-seq and direct targets of the factor were validated by ChIP-qPCR and siRNA-mediated depletion of FOXA1/2 followed by RT-qPCR. Peaks of FOXA2 occupancy were frequent at loci contributing to gene ontology pathways of regulation of cell migration, cell motion, and plasma membrane function. Depletion of both FOXA1 and FOXA2 led to a significant reduction in the expression of multiple transmembrane proteins including ion channels and transporters, which form a network that is essential for maintaining normal ion and solute transport. One of the targets was the adenosine A2B receptor, and reduced receptor mRNA levels were associated with a functional decrease in intracellular cyclic AMP. We also observed that 30% of FOXA2 binding sites contained a GATA motif and that FOXA1/A2 depletion reduced GATA-4, but not GATA-6 protein levels. These data show that FOXA2 plays a pivotal role in regulating intestinal epithelial cell function. Moreover, that the FOXA and GATA families of transcription factors may work cooperatively to regulate gene expression genome-wide in the intestinal epithelium.

scholarly journals Cellular titin localization in stress fibers and interaction with myosin II filaments in vitro.

1994 ◽  
Vol 126 (5) ◽  
pp. 1201-1210 ◽  
Author(s):  
K J Eilertsen ◽  
S T Kazmierski ◽  
T C Keller
Keyword(s):  
Epithelial Cell ◽  
Brush Border ◽  
Intestinal Epithelial Cell ◽  
Myosin Ii ◽  
Gel Filtration ◽  
Stress Fibers ◽  
Myosin Isoforms ◽  
Intestinal Epithelial ◽  
Muscle Myosin

We previously discovered a cellular isoform of titin (originally named T-protein) colocalized with myosin II in the terminal web domain of the chicken intestinal epithelial cell brush border cytoskeleton (Eilertsen, K.J., and T.C.S. Keller. 1992. J. Cell Biol. 119:549-557). Here, we demonstrate that cellular titin also colocalizes with myosin II filaments in stress fibers and organizes a similar array of myosin II filaments in vitro. To investigate interactions between cellular titin and myosin in vitro, we purified both proteins from isolated intestinal epithelial cell brush borders by a combination of gel filtration and hydroxyapatite column chromatography. Electron microscopy of brush border myosin bipolar filaments assembled in the presence and absence of cellular titin revealed a cellular titin-dependent side-by-side and end-to-end alignment of the filaments into highly ordered arrays. Immunogold labeling confirmed cellular titin association with the filament arrays. Under similar assembly conditions, purified chicken pectoralis muscle titin formed much less regular aggregates of muscle myosin bipolar filaments. Sucrose density gradient analyses of both cellular and muscle titin-myosin supramolecular arrays demonstrated that the cellular titin and myosin isoforms coassembled with a myosin/titin ratio of approximately 25:1, whereas the muscle isoforms coassembled with a myosin:titin ratio of approximately 38:1. No coassembly aggregates were found when cellular myosin was assembled in the presence of muscle titin or when muscle myosin was assembled in the presence of cellular titin. Our results demonstrate that cellular titin can organize an isoform-specific association of myosin II bipolar filaments and support the possibility that cellular titin is a key organizing component of the brush border and other myosin II-containing cytoskeletal structures including stress fibers.

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