scholarly journals JUNCTIONAL COMPLEXES IN VARIOUS EPITHELIA

1963 ◽  
Vol 17 (2) ◽  
pp. 375-412 ◽  
Author(s):  
Marilyn G. Farquhar ◽  
George E. Palade
Keyword(s):  
Tight Junction ◽  
Intercellular Space ◽  
Cell Membranes ◽  
Amorphous Material ◽  
Dense Material ◽  
Junctional Complex ◽  
Cytoplasmic Matrix ◽  
Pancreatic Acini ◽  
Zonula Occludens ◽  
Adjoining Cell

The epithelia of a number of glands and cavitary organs of the rat and guinea pig have been surveyed, and in all cases investigated, a characteristic tripartite junctional complex has been found between adjacent cells. Although the complex differs in precise arrangement from one organ to another, it has been regularly encountered in the mucosal epithelia of the stomach, intestine, gall bladder, uterus, and oviduct; in the glandular epithelia of the liver, pancreas, parotid, stomach, and thyroid; in the epithelia of pancreatic, hepatic, and salivary ducts; and finally, between the epithelial cells of the nephron (proximal and distal convolution, collecting ducts). The elements of the complex, identified as zonula occludens (tight junction), zonula adhaerens (intermediary junction), and macula adhaerens (desmosome), occupy a juxtaluminal position and succeed each other in the order given in an apical-basal direction. The zonula occludens (tight junction) is characterized by fusion of the adjacent cell membranes resulting in obliteration of the intercellular space over variable distances. Within the obliterated zone, the dense outer leaflets of the adjoining cell membranes converge to form a single intermediate line. A diffuse band of dense cytoplasmic material is often associated with this junction, but its development varies from one epithelium to another. The zonula adhaerens (intermediate junction) is characterized by the presence of an intercellular space (∼200 A) occupied by homogeneous, apparently amorphous material of low density; by strict parallelism of the adjoining cell membranes over distances of 0.2 to 0.5 µ; and by conspicuous bands of dense material located in the subjacent cytoplasmic matrix. The desmosome or macula adhaerens is also characterized by the presence of an intercellular space (∼240 A) which, in this case, contains a central disc of dense material; by discrete cytoplasmic plaques disposed parallel to the inner leaflet of each cell membrane; and by the presence of bundles of cytoplasmic fibrils converging on the plaques. The zonula occludens appears to form a continuous belt-like attachment, whereas the desmosome is a discontinuous, button-like structure. The zomula adhaerens is continuous in most epithelia but discontinuous in some. Observations made during experimental hemoglobinuria in rats showed that the hemoglobin, which undergoes enough concentration in the nephron lumina to act as an electron-opaque mass tracer, does not penetrate the intercellular spaces beyond the zonula occludens. Similar observations were made in pancreatic acini and ducts where discharged zymogen served as a mass tracer. Hence the tight junction is impervious to concentrated protein solutions and appears to function as a diffusion barrier or "seal." The desmosome and probably also the zonula adhaerens may represent intercellular attachment devices.

Cell relationships in Hymenolepis diminuta

Parasitology ◽  
1970 ◽  
Vol 60 (2) ◽  
pp. 181-184 ◽  
Author(s):  
L. T. Threadgold ◽  
C. P. Read
Keyword(s):  
Electron Microscope ◽  
Tight Junction ◽  
Hymenolepis Diminuta ◽  
Excretory System ◽  
Junctional Complex ◽  
Dense Granules ◽  
Zonula Occludens ◽  
Rice University ◽  
Intercellular Region ◽  
Zoology Department

SUMMARYThe intimate cell relationships of Hymenolepis diminuta are described and occur between cells of the parenchyma, excretory system, muscle and tegument. The cell relationships are of three types: (a) a tight junction or zonula occludens; (b) a desmosome-like structure without tonofibrils or intercellular dense line; (c) a junctional complex with modified unit membranes and an intercellular region of dense granules and fibres.This research was begun while one of us (L.T.T.) was a Visiting Lecturer in the Biology Department, Rice University, and completed in the Zoology Department, Queen's University, Belfast. We should like to thank Dr C. W. Philpott for allowing us the full use of the facilities of his electron-microscope unit and Mr W. Ferguson for photographic assistance.

scholarly journals THE STRUCTURE OF THE ZONULA OCCLUDENS

1974 ◽  
Vol 60 (1) ◽  
pp. 168-180 ◽  
Author(s):  
James B. Wade ◽  
Morris J. Karnovsky
Keyword(s):  
Urinary Bladder ◽  
Tight Junction ◽  
Cell Membranes ◽  
Adjacent Cell ◽  
Toad Urinary Bladder ◽  
Zonula Occludens ◽  
Single Set

Replicas of freeze-fractured toad urinary bladder and gallbladder were analysed in an attempt to determine the fracturing properties and structure of the zonula occludens (tight junction). Chalcroft and Bullivant have proposed that the junction has a double set of fibrils with one set associated with each of the adjacent cell membranes. However, the fracturing pattern that is observed might also result from only a single set of fibrils which is shared by the adjacent membranes if fracturing occurred around either side of the fibrils. These two models predict quite different structures at regions of the junction where tranl sitions are made between face A and face B. The relative heights of face A and face B and the shape of the transition from face A to face B do not agree with that expected according to the two fibril model but agree exactly with that expected if only a single set of fibrils existed. Further evidence for the single fibril model is derived from fractures of the mucosa membrane which cross the junction to the membrane of the adjacent cell without deflection. Such fractures reveal a single ridge which appears to be identical to the juxtaluminal fibril of the junction. In addition, small ridges are occasionally found in place of the grooves on face B which, although not consistent with the double fibril model, is expected if the single fibril model were correct. Although alternative explanations might account for these observations, we believe that the simplest and most consistent explanation is that the zonula occludens fractures as would be expected of a single set of fibrils shared by adjacent cells.

Tight-junction protein zonula occludens 2 is a target of phosphorylation by protein kinase C

2001 ◽  
Vol 360 (2) ◽  
pp. 295-304 ◽  
Author(s):  
Antonia AVILA-FLORES ◽  
Erika RENDÓN-HUERTA ◽  
Jacqueline MORENO ◽  
Socorro ISLAS ◽  
Abigail BETANZOS ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tight Junction ◽  
Junctional Complex ◽  
Dependent Protein Kinase ◽  
Kinase C ◽  
Zonula Occludens ◽  
Phosphorylation Level ◽  
Junction Protein ◽  
Dependent Protein

Zonula occludens 2 (ZO-2) protein is a tight-junction phos phorylated protein that belongs to the membrane-associated guanylate kinase (‘MAGUK’) family. Here we study the interaction between ZO-2 and protein kinase C (PKC). We have constructed two ZO-2 fusion proteins of the middle (3PSG) and C-terminal (AP) regions of the molecule and demonstrate that they are phosphorylated by PKC isoenzymes β, ∊, λ and ∊. To understand the physiological significance of the interaction between ZO-2 and PKC, we analysed the phosphorylation state of ZO-2 immunoprecipitated from monolayers with mature tight junctions or from cells that either lack them or have them disassembled through Ca2+ chelation. We found that in the latter condition the phosphorylation level of ZO-2 is significantly higher and is due to the action of both PKC and cAMP-dependent protein kinase. These results therefore suggest that the phosphorylated state of ZO-2 restrains its capacity to operate at the junctional complex.

The Structure of Tight Junctions

1978 ◽  
Vol 36 (3) ◽  
pp. 659-672 ◽  
Author(s):  
S. Bullivant
Keyword(s):  
Tight Junction ◽  
Intercellular Space ◽  
Membrane Structure ◽  
Paracellular Permeability ◽  
Apical Region ◽  
Unit Membrane ◽  
Thin Sections ◽  
Freeze Fracturing ◽  
Outer Leaflet ◽  
Zonula Occludens

The tight junction, or zonula occludens, is generally found as a continuous belt, joining adjacent cells in the apical region of the border between them. It forms a seal across the intercellular space and hence regulates paracellular permeability. Farquhar and Palade (1963), recognised the belt-like sealing character, and showed that in thin sections the junction was seen as either punctate or linear fusions of the two membranes, often with the loss of the outer leaflet of the unit membrane at the fusion. With thin sections it can only be inferred that the junction forms a continuous belt, but with freeze-fracturing it can be seen directly. Moreover, in the junctional region the membrane structure is modified by a series of interconnected fibrils approximately parallel to the line of the belt (Kreutziger, 1968; Staehelin et al, 1969; Goodenough and Revel, 1970), and within the interior of the membrane Tchalcroft and Bullivant, 1970). The fibrils are at the lines of membrane fusion.

scholarly journals DIFFERENTIATION OF THE JUNCTIONAL COMPLEX OF SURFACE CELLS IN THE DEVELOPING FUNDULUS BLASTODERM

1971 ◽  
Vol 48 (3) ◽  
pp. 455-472 ◽  
Author(s):  
Thomas L. Lentz ◽  
J. P. Trinkaus
Keyword(s):  
Gap Junction ◽  
Teleost Fish ◽  
Intercellular Space ◽  
Fundulus Heteroclitus ◽  
Early Embryo ◽  
Intermediate Zone ◽  
Junctional Complex ◽  
Apical Region ◽  
Basic Organization ◽  
Zonula Occludens

The structure of the junctional complex between surface cells was investigated in blastula, mid gastrula, late gastrula, and early embryo of the teleost fish Fundulus heteroclitus. In blastulae, the intercellular complex is simple and consists of an apical region where the adjacent membranes are closely apposed (40–60 A) and in places touch, an intermediate zone with a wider intercellular space (> 100 A), and incipient desmosomes. In gastrulae, there are frequent points of fusion of membranes along the apical zone of the complex. Dilatations and an increased number of desmosomes in different stages of development are found along the intermediate zone. In mid gastrula, a close or gap junction with an intercellular space of 20 A occurs below the level of the desmosomes. In late gastrula, the gap junction is reduced in extent and desmosomes are better developed. In the early embryo, the basic organization of the complex is the same, although the deeply situated close junctions are no longer apparent and desmosomes and their associated system of filaments are well developed. At this time, the junctional complex is comparable to that of many epithelia and consists of an apical zonula occludens, a short zonula adherens, and deeply situated maculae adherentes.

Intercellular Junctions in the Organ of Corti

1978 ◽  
Vol 87 (1) ◽  
pp. 70-80 ◽  
Author(s):  
Joseph B. Nadol
Keyword(s):  
Tight Junctions ◽  
Intercellular Space ◽  
Basilar Membrane ◽  
Membrane Surface ◽  
Morphological Characteristics ◽  
Organ Of Corti ◽  
Intercellular Junctions ◽  
Junctional Complex ◽  
Supporting Cells ◽  
Zonula Occludens

The intercellular junctions between adjacent supporting cells and between apposed hair and supporting cells in the organ of Corti of cat and human were studied. At the endolymphatic surface, the intercellular space was closed by a series of tight junctions (zonula occludens), whereas there were no tight junctions at the basilar membrane surface of the neuro-epithelium. Beneath the adlumenal zonula occludens between adjacent supporting cells, a zonula adherens (intermediate junction, “desmosome”) was found. Many gap junctions joined apposed supporting cells both within and below the endolymphatic junctional complex. Below the zonula occludens between apposed hair and supporting cells, membrane specialization sharing the morphological characteristics of both the macula adherens and zonula adherens was found. Between areas of tight junctional specialization in the junctional complex between hair and supporting cells, there were short areas of parallel limiting membranes separated by a 20A intercellular space. These areas were suggestive but not characteristic of gap junctional specialization. The functional significance of the junctional specialization between cells in the organ of Corti was discussed.

GENETIC SUSCEPTIBILITY TO IBD OPERATES VIA CONTROL OF APICAL JUNCTIONAL COMPLEXES

2021 ◽  
Vol 27 (Supplement_1) ◽  
pp. S30-S30
Author(s):  
Isabelle Hébert-Milette ◽  
Chloé Lévesque ◽  
Guy Charron ◽  
John Rioux
Keyword(s):  
Tight Junction ◽  
Tight Junctions ◽  
Intestinal Inflammation ◽  
Protein Localization ◽  
Junctional Complex ◽  
Epithelial Permeability ◽  
3D Cultures ◽  
Apical Junctional Complex ◽  
Junction Protein ◽  
The Impact

Abstract Introduction Intestinal permeability is increased in unaffected 1st degree relatives of patients with inflammatory bowel disease (IBD), and is considered a risk factor for the development of IBD, likely increasing the interactions between intestinal microorganisms and the immune system. We recently reported that C1orf106, a gene located within a genomic region associated with IBD, regulates epithelial permeability. We further demonstrated that a rare coding variant within C1orf106 (p.Y333F) decreases protein stability and that lower levels of C1orf106 protein leads altered stability of adherens junctions (AJ) and to an increase in epithelial permeability. Hypothesis In addition to altering AJ, we believe that C1orf106 is also involved in the regulation of tight junction (TJ) formation, which also impacts epithelial permeability. Objectives The objectives of the project are to (a) validate the impact of C1orf106 on tight junctions and (b) verify the impact of C1orf106 IBD-associated variants on intestinal barrier integrity. Results We observed that knocking down the expression of C1orf106 in Caco-2 cells leads to a number of phenotypes in human epithelial monolayer (2D) and spheroid (3D) cultures that are associated with alterations in TJs. Specifically, when studying the dynamic reformation of TJ in 2D cultures after transient withdrawal of calcium, which is required for TJ stability, we observed that lower levels of C1orf106 resulted in (1) decreased recovery of barrier function as measured by transepithelial electrical resistance (TEER); (2) an alteration of tight junction protein localization; and (3) thickening of the circumferential actin belt. Moreover, in 3D cultures, we observed an altered spheroid formation associated with impaired epithelial polarization. In addition, our preliminary studies of human induced pluripotent stem cell (hiPSC)-derived epithelial cultures support that Y333F heterozygotes also have altered structure and function of their tight junctions. Conclusion Our observations indicate an important role of C1orf106 in apical junctional complex (AJC) formation likely mediated by a regulation of the circumferential actin belt. This can affect other functions of AJC, like the establishment of cell polarity. AJC formation is important for epithelial repair after an injury and its dysregulation impairs the formation of an impermeable epithelial barrier, which likely facilitates the passage of microorganisms and the induction and maintenance of intestinal inflammation.

Nonmitogenic morphoregulatory action of pp60v-src on multicellular epithelial structures

1987 ◽  
Vol 7 (4) ◽  
pp. 1326-1337
Author(s):  
S L Warren ◽  
W J Nelson
Keyword(s):  
Tyrosine Kinases ◽  
Mdck Cells ◽  
Growth Potential ◽  
Junctional Complex ◽  
Madin Darby Canine Kidney ◽  
Epithelial Monolayers ◽  
Zonula Occludens ◽  
Darby Canine Kidney ◽  
Canine Kidney

Madin-Darby canine kidney (MDCK) cells form polarized, multicellular epithelial structures in vitro. Low-level expression of pp60v-src in MDCK cells elicits plasticity in these multicellular structures. Plasticity was revealed by the displacement of cells from mechanically stressed regions of the epithelial monolayers; however, the two-dimensional relationship between the cells in the remainder of the monolayer was maintained. Electron microscopy of multicellular structures revealed abnormal separation of the lateral membranes of adjacent cells and selective uncoupling of the junctional complex; the zonula adherens was disrupted, but the zonula occludens and desmosomes were retained. Significantly, this result was not accompanied by transformation of the cells, as judged by the absence of anchorage-independent growth potential. These results demonstrate a nonmitogenic biological activity of pp60v-src which is experimentally dissociable from transformation. This morphoregulatory action on higher-order epithelial structures may reflect a function of related cellular tyrosine kinases.

scholarly journals Decreased ZO1 expression causes loss of time-dependent tight junction function in the liver of ob/ob mice

2021 ◽  
Author(s):  
Yuya Tsurudome ◽  
Nao Morita ◽  
Michiko Horiguchi ◽  
Kentaro Ushijima
Keyword(s):  
Tight Junction ◽  
Dark Period ◽  
Vital Role ◽  
Time Dependent ◽  
Signal Transduction System ◽  
Binding Ability ◽  
Protein Levels ◽  
Multiple Organs ◽  
Zonula Occludens ◽  
Zonula Occludens 1

Abstract Diabetes patients are at a high risk of developing complications related to angiopathy and disruption of the signal transduction system. The liver is one of the multiple organs damaged during diabetes. Few studies have evaluated the morphological effects of adhesion factors in diabetic liver. The influence of diurnal variation has been observed in the expression and functioning of adhesion molecules to maintain tissue homeostasis associated with nutrient uptake. The present study demonstrated that the rhythm-influenced functioning of tight junction was impaired in the liver of ob/ob mice. The tight junctions of hepatocytes were loosened during the dark period in normal mice compared to those in ob/ob mice, where the hepatocyte gaps remained open throughout the day. The time-dependent expression of zonula occludens 1 (ZO1) in the liver plays a vital role in the functioning of the tight junction. The time-dependent expression of ZO1 was nullified and its expression was attenuated in the liver of ob/ob mice. ZO1 expression was inhibited at the mRNA and protein levels. The expression rhythm of ZO1 was found to be regulated by heat shock factor (HSF)1/2, the expression of which was reduced in the liver of ob/ob mice. The DNA-binding ability of HSF1/2 was decreased in the liver of ob/ob mice compared to that in normal mice. These findings suggest the involvement of impaired expression and functioning of adhesion factors in diabetic liver complications.

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