scholarly journals FACTORS CONTROLLING THE REASSEMBLY OF THE MICROVILLOUS BORDER OF THE SMALL INTESTINE OF THE SALAMANDER

1970 ◽  
Vol 47 (2) ◽  
pp. 408-422 ◽  
Author(s):  
Lewis G. Tilney ◽  
Robert R. Cardell

Hydrostatic pressure, when applied to segments of the small intestine of the salamander, causes a tremendous reduction in number of microvilli and a loss of the terminal web. The intestinal epithelium strips off from its deeper layers at the level of the basement membrane. When the pressure is released and this epithelial sheet is allowed to recover, the microvilli and its terminal web reappear. Stages in the reformation of microvilli are described. In the earliest stages, foci of dense material seem to associate with the cytoplasmic surface of the apical plasma membrane. From this material, filaments appear and their regrowth is correlated with the extension of the microvilli. We suggest that the dense material nucleates the assembly of the filaments which, in turn, appear instrumental in the redevelopment of microvilli. This concept is supported by the existing literature. Further, since neither the microvilli nor the terminal web reappear on any surface but the apical surface, even though the apical and basal surfaces are bathed with the same medium, we suggest that information in the membrane itself or directly associated with the membrane dictates the distribution of the dense material which leads to the formation of the microvilli and ultimately to the polarity of the cell.

2010 ◽  
Vol 22 (9) ◽  
pp. 112
Author(s):  
S. N. Dowland ◽  
L. A. Lindsay ◽  
C. R. Murphy

Prominin-1 is a recently discovered pentaspan membrane protein present in characteristic cholesterol-based vesicles and associated with microvilli. These vesicles are used to deliver prominin-1 to the apical plasma membrane in a number of cell types. Previous work on uterine epithelial cells has demonstrated a loss of microvilli and the presence of large, cholesterol-based vesicles at the time of implantation. Thus this study aims to determine a role for prominin-1 in rat uterine epithelial cells during early pregnancy. Immunofluorescence microscopy reveals punctate and diffuse prominin-1 staining below the apical plasma membrane on day 1 of pregnancy. At the time of blastocyst implantation (day 6) however, prominin-1 appears concentrated at the apical surface of the cell. Western blotting of isolated uterine epithelial cell lysate revealed a change in prominin-1 glycosylation during early pregnancy. Prominin-1 was determined to be glycosylated on day 1 of pregnancy, but these carbohydrate side chains were lost by the time of attachment. Results seen in the present study indicate that prominin-containing vesicles may be prevented from reaching the apical plasma membrane by the terminal web on day 1 of pregnancy. On day 6, the loss of the terminal web may allow the vesicles to approach and incorporate into the apical plasma membrane, as seen with other uterine vesicles. The deglycosylation of prominin-1 at this time is suggested to allow the protein to bind its ligand and activate downstream signalling pathways that permit implantation. This study constitutes the first reported observation of prominin in endometrial lumenal epithelial cells. These preliminary results, in consideration with previous reports of prominin expression in trophoblast cells, suggest an important role for this protein in early pregnancy.


1996 ◽  
Vol 109 (6) ◽  
pp. 1215-1227 ◽  
Author(s):  
I. Hemery ◽  
A.M. Durand-Schneider ◽  
G. Feldmann ◽  
J.P. Vaerman ◽  
M. Maurice

In hepatocytes, newly synthesized apical plasma membrane proteins are first delivered to the basolateral surface and are supposed to reach the apical surface by transcytosis. The transcytotic pathway of apical membrane proteins and its relationship with other endosomal pathways has not been demonstrated morphologically. We compared the intracellular route of an apical plasma membrane protein, B10, with that of polymeric IgA (pIgA), which is transcytosed, transferrin (Tf) which is recycled, and asialoorosomucoid (ASOR) which is delivered to lysosomes. Ligands and anti-B10 monoclonal IgG were linked to fluorochromes or with peroxidase. The fate of each ligand was followed by confocal and electron microscopy in polarized primary monolayers of rat hepatocytes. When fluorescent anti-B10 IgG and fluorescent pIgA were simultaneously endocytosed for 15–30 minutes, they both uniformly labelled a juxtanuclear compartment. By 30–60 minutes, they reached the bile canaliculi. Tf and ASOR were also routed to the juxtanuclear area, but their fluorescence patterns were more punctate. Microtubule disruption prevented all ligands from reaching the juxtanuclear area. This area corresponded, at least partially, to the localization of the mannose 6-phosphate receptor, an endosomal marker. By electron microscopy, the juxtanuclear compartment was made up of anastomosing tubules connected to vacuoles, and was organized around the centrioles. B10 and pIgA were mainly found in the tubules, whereas ASOR was segregated inside the vacuolar elements and Tf within thinner, recycling tubules. In conclusion, transcytosis of the apical membrane protein B10 occurs inside tubules similar to those carrying pIgA, and involves passage via the pericentriolar area. In the pericentriolar area, the transcytotic tubules appear to maintain connections with other endosomal elements where sorting between recycled and degraded ligands occurs.


1987 ◽  
Vol 105 (4) ◽  
pp. 1623-1635 ◽  
Author(s):  
G van Meer ◽  
E H Stelzer ◽  
R W Wijnaendts-van-Resandt ◽  
K Simons

To study the intracellular transport of newly synthesized sphingolipids in epithelial cells we have used a fluorescent ceramide analog, N-6[7-nitro-2,1,3-benzoxadiazol-4-yl] aminocaproyl sphingosine (C6-NBD-ceramide; Lipsky, N. G., and R. E. Pagano, 1983, Proc. Natl. Acad. Sci. USA, 80:2608-2612) as a probe. This ceramide was readily taken up by filter-grown Madin-Darby canine kidney (MDCK) cells from liposomes at 0 degrees C. After penetration into the cell, the fluorescent probe accumulated in the Golgi area at temperatures between 0 and 20 degrees C. Chemical analysis showed that C6-NBD-ceramide was being converted into C6-NBD-sphingomyelin and C6-NBD-glucosyl-ceramide. An analysis of the fluorescence pattern after 1 h at 20 degrees C by means of a confocal scanning laser fluorescence microscope revealed that the fluorescent marker most likely concentrated in the Golgi complex itself. Little fluorescence was observed at the plasma membrane. Raising the temperature to 37 degrees C for 1 h resulted in intense plasma membrane staining and a loss of fluorescence from the Golgi complex. Addition of BSA to the apical medium cleared the fluorescence from the apical but not from the basolateral plasma membrane domain. The basolateral fluorescence could be depleted only by adding BSA to the basal side of a monolayer of MDCK cells grown on polycarbonate filters. We conclude that the fluorescent sphingomyelin and glucosylceramide were delivered from the Golgi complex to the plasma membrane where they accumulated in the external leaflet of the membrane bilayer. The results also demonstrated that the fatty acyl labeled lipids were unable to pass the tight junctions in either direction. Quantitation of the amount of NBD-lipids delivered to the apical and the basolateral plasma membranes during incubation for 1 h at 37 degrees C showed that the C6-NBD-glucosylceramide was two- to fourfold enriched on the apical as compared to the basolateral side, while C6-NBD-sphingomyelin was about equally distributed. Since the surface area of the apical plasma membrane is much smaller than that of the basolateral membrane, both lipids achieved a higher concentration on the apical surface. Altogether, our results suggest that the NBD-lipids are sorted in MDCK cells in a way similar to their natural counterparts.


2016 ◽  
Vol 212 (3) ◽  
pp. 297-306 ◽  
Author(s):  
Atsuhiro Nakajo ◽  
Shin-ichiro Yoshimura ◽  
Hiroko Togawa ◽  
Masataka Kunii ◽  
Tomohiko Iwano ◽  
...  

The highly conserved Rab guanosine triphosphatase (GTPase) Rab8 plays a role in exocytosis toward the polarized plasma membrane in eukaryotic cells. In murine Rab8-deficient small intestine cells, apical proteins are missorted into lysosomes. In this study, we identified a novel Rab8-interacting protein complex containing an EH domain–binding protein 1–like 1 (EHBP1L1), Bin1/amphiphysin II, and dynamin. Biochemical analyses showed that EHBP1L1 directly bound to GTP-loaded Rab8 and Bin1. The spatial dependency of these complexes at the endocytic recycling compartment (ERC) was demonstrated through overexpression and knockdown experiments. EHBP1L1- or Bin1-depleted or dynamin-inhibited small intestine organoids significantly accumulated apical membrane proteins but not basolateral membrane proteins in lysosomes. Furthermore, in EHBP1L1-deficient mice, small intestine cells displayed truncated and sparse microvilli, suggesting that EHBP1L1 maintains the apical plasma membrane by regulating apical transport. In summary, our data demonstrate that EHBP1L1 links Rab8 and the Bin1–dynamin complex, which generates membrane curvature and excises the vesicle at the ERC for apical transport.


2000 ◽  
Vol 149 (7) ◽  
pp. 1473-1484 ◽  
Author(s):  
Pamela J. Plant ◽  
Frank Lafont ◽  
Sandra Lecat ◽  
Paul Verkade ◽  
Kai Simons ◽  
...  

Nedd4 is a ubiquitin protein ligase (E3) containing a C2 domain, three or four WW domains, and a ubiquitin ligase HECT domain. We have shown previously that the C2 domain of Nedd4 is responsible for its Ca2+-dependent targeting to the plasma membrane, particularly the apical region of epithelial MDCK cells. To investigate this apical preference, we searched for Nedd4-C2 domain-interacting proteins that might be involved in targeting Nedd4 to the apical surface. Using immobilized Nedd4-C2 domain to trap interacting proteins from MDCK cell lysate, we isolated, in the presence of Ca2+, a ∼35–40-kD protein that we identified as annexin XIII using mass spectrometry. Annexin XIII has two known isoforms, a and b, that are apically localized, although XIIIa is also found in the basolateral compartment. In vitro binding and coprecipitation experiments showed that the Nedd4-C2 domain interacts with both annexin XIIIa and b in the presence of Ca2+, and the interaction is direct and optimal at 1 μM Ca2+. Immunofluorescence and immunogold electron microscopy revealed colocalization of Nedd4 and annexin XIIIb in apical carriers and at the apical plasma membrane. Moreover, we show that Nedd4 associates with raft lipid microdomains in a Ca2+-dependent manner, as determined by detergent extraction and floatation assays. These results suggest that the apical membrane localization of Nedd4 is mediated by an association of its C2 domain with the apically targeted annexin XIIIb.


1990 ◽  
Vol 259 (6) ◽  
pp. G991-G997 ◽  
Author(s):  
M. G. Oliver ◽  
R. D. Specian

Although microtubules appear necessary to maintain mucin granule transport in intestinal goblet cells, the role of microfilaments in mucus secretion is unknown. To determine the functional significance of microfilaments in goblet cell secretion, fluorescent cytochemistry of microfilaments and autoradiographic studies on granule movement were performed on rabbit intestinal goblet cells, with and without the actin depolymerizing agents, cytochalasin D (cyto D), and dihydro-cytochalasin B (dihydro B). In normal goblet cells, cytochemical localization of F-actin with NBD-phallacidin demonstrated their restriction to the apical surface of the goblet cell. Visualization of the goblet cell apical surface by electron microscopy revealed the presence of a thin layer of cytoplasm overlying the granule mass. Treatment with cyto D and dihydro B eliminated NBD-phallacidin staining of the apical cell surface. Quantitative analysis of baseline granule translocation demonstrated that treatment with cyto D and dihydro B resulted in dramatic acceleration of granule movement through goblet cells. This cellular response results from an increase in baseline secretion and facilitation of secretion of newly synthesized mucins, not stimulation of an accelerated secretory event. These data imply that actin filaments fulfill a barrier function in baseline secretion by hindering granule access to the plasma membrane; once the granule contacts the plasma membrane, exocytosis occurs. Secretion is balanced by the translocation of subjacent granules. In contrast, an accelerated secretory event is not triggered by plasma membrane access alone; this event requires a regulatory signal. We hypothesize that, unlike accelerated secretion, baseline secretion is constitutive, with exocytosis limited solely by the physical constraint of secretory granule access to the apical plasma membrane.


2002 ◽  
Vol 76 (7) ◽  
pp. 3544-3553 ◽  
Author(s):  
Rosalia Mora ◽  
Enrique Rodriguez-Boulan ◽  
Peter Palese ◽  
Adolfo García-Sastre

ABSTRACT Influenza virions bud preferentially from the apical plasma membrane of infected epithelial cells, by enveloping viral nucleocapsids located in the cytosol with its viral integral membrane proteins, i.e., hemagglutinin (HA), neuraminidase (NA), and M2 proteins, located at the plasma membrane. Because individually expressed HA, NA, and M2 proteins are targeted to the apical surface of the cell, guided by apical sorting signals in their transmembrane or cytoplasmic domains, it has been proposed that the polarized budding of influenza virions depends on the interaction of nucleocapsids and matrix proteins with the cytoplasmic domains of HA, NA, and/or M2 proteins. Since HA is the major protein component of the viral envelope, its polarized surface delivery may be a major force that drives polarized viral budding. We investigated this hypothesis by infecting MDCK cells with a transfectant influenza virus carrying a mutant form of HA (C560Y) with a basolateral sorting signal in its cytoplasmic domain. C560Y HA was expressed nonpolarly on the surface of infected MDCK cells. Interestingly, viral budding remained apical in C560Y virus-infected cells, and so did the location of NP and M1 proteins at late times of infection. These results are consistent with a model in which apical viral budding is a shared function of various viral components rather than a role of the major viral envelope glycoprotein HA.


2006 ◽  
Vol 17 (8) ◽  
pp. 3638-3650 ◽  
Author(s):  
Kacper A. Wojtal ◽  
Erik de Vries ◽  
Dick Hoekstra ◽  
Sven C.D. van IJzendoorn

In hepatocytes, cAMP/PKA activity stimulates the exocytic insertion of apical proteins and lipids and the biogenesis of bile canalicular plasma membranes. Here, we show that the displacement of PKA-RIIα from the Golgi apparatus severely delays the trafficking of the bile canalicular protein MDR1 (P-glycoprotein), but not that of MRP2 (cMOAT), DPP IV and 5′NT, to newly formed apical surfaces. In addition, the direct trafficking of de novo synthesized glycosphingolipid analogues from the Golgi apparatus to the apical surface is inhibited. Instead, newly synthesized glucosylceramide analogues are rerouted to the basolateral surface via a vesicular pathway, from where they are subsequently endocytosed and delivered to the apical surface via transcytosis. Treatment of HepG2 cells with the glucosylceramide synthase inhibitor PDMP delays the appearance of MDR1, but not MRP2, DPP IV, and 5′NT at newly formed apical surfaces, implicating glucosylceramide synthesis as an important parameter for the efficient Golgi-to-apical surface transport of MDR1. Neither PKA-RIIα displacement nor PDMP inhibited (cAMP-stimulated) apical plasma membrane biogenesis per se, suggesting that other cAMP effectors may play a role in canalicular development. Taken together, our data implicate the involvement of PKA-RIIα anchoring in the efficient direct apical targeting of distinct proteins and glycosphingolipids to newly formed apical plasma membrane domains and suggest that rerouting of Golgi-derived glycosphingolipids may underlie the delayed Golgi-to-apical surface transport of MDR1.


1983 ◽  
Vol 97 (3) ◽  
pp. 638-643 ◽  
Author(s):  
M Pesonen ◽  
K Simons

The envelope of vesicular stomatitis virus was fused with the apical plasma membrane of Madin-Darby canine kidney cells by low pH treatment. The fate of the implanted G protein was then followed using a protein A-binding assay, which was designed to quantitate the amount of G protein in the apical and the basolateral membranes. The implanted G protein was rapidly internalized at 31 degrees C, whereas at 10 degrees C no uptake was observed. Already after 15 min at 31 degrees C, a fraction of the G protein could be detected at the basolateral membrane. After 60 min 25-48% of the G protein was basolateral as measured by the protein A-binding assay. At the same time, 25-33% of the implanted G protein was detected at the apical membrane. Internalization of G protein was not affected by 20 mM ammonium chloride or by 10 microM monensin. However, the endocytosed G protein accumulated in intracellular vacuoles and redistribution back to the plasma membrane was inhibited. We conclude that the implanted G protein was rapidly internalized from the apical surface of Madin-Darby canine kidney cells and a major fraction was routed to the basolateral domain.


1988 ◽  
Vol 107 (5) ◽  
pp. 1717-1728 ◽  
Author(s):  
D E Vega-Salas ◽  
P J Salas ◽  
E Rodriguez-Boulan

The vacuolar apical compartment (VAC) is an organelle found in Madin-Darby canine kidney (MDCK) cells with incomplete intercellular contacts by incubation in 5 microM Ca++ and in cells without contacts (single cells in subconfluent culture); characteristically, it displays apical biochemical markers and microvilli and excludes basolateral markers (Vega-Salas, D. E., P. J. I. Salas, and E. Rodriguez-Boulan. 1987. J. Cell Biol. 104:1249-1259). The apical surface of cells kept under these culture conditions is immature, with reduced numbers of microvilli and decreased levels of an apical biochemical marker (184 kD), which is, however, still highly polarized (Vega-Salas, D. E., P. J. I. Salas, D. Gundersen, and E. Rodriguez-Boulan. 1987. J. Cell Biol. 104:905-916). We describe here the morphological stages of VAC exocytosis which ultimately lead to the establishment of a differentiated apical domain. Addition of 1.8 mM Ca++ to monolayers developed in 5 microM Ca++ causes the rapid (20-40 min) fusion of VACs with the plasma membrane and their accessibility to external antibodies, as demonstrated by immunofluorescence, immunoperoxidase EM, and RIA with antibodies against the 184-kD apical plasma membrane marker. Exocytosis occurs towards areas of cell-cell contact in the developing lateral surface where they form intercellular pockets; fusion images are always observed immediately adjacent to the incomplete junctional bands detected by the ZO-1 antibody (Stevenson, B. R., J. D. Siliciano, M. S. Mooseker, and D. A. Goodenough. 1986. J. Cell Biol. 103:755-766). Blocks of newly incorporated VAC microvilli and 184-kD protein progressively move from intercellular ("primitive" lateral) spaces towards the microvilli-poor free cell surface. The definitive lateral domain is sealed behind these blocks by the growing tight junctional fence. These results demonstrate a fundamental role of cell-cell contact-mediated VAC exocytosis in the establishment of epithelial surface polarity. Because isolated stages (intercellular pockets) of the stereotyped sequence of events triggered by the establishment of intercellular contacts in MDCK cells have been reported during normal differentiation of intestine epithelium (Colony, P. C., and M. R. Neutra. 1983. Dev. Biol. 97:349-363), we speculate that the mechanism we describe here plays an important role in the establishment of epithelial cell polarity in vivo.


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