scholarly journals An alternative mode of epithelial polarity in the Drosophila midgut

2018 ◽  
Author(s):  
Jia Chen ◽  
Aram-Christopher Sayadian ◽  
Nick Lowe ◽  
Holly E. Lovegrove ◽  
Daniel St Johnston
Keyword(s):  
Epithelial Cells ◽  
Adherens Junctions ◽  
Epithelial Polarity ◽  
Alternative Mode ◽  
Epithelial Tissues ◽  
Occluding Junctions ◽  
Discs Large ◽  
And Function ◽  
Adhesion Complex

AbstractApical-basal polarity is essential for the formation and function of epithelial tissues, whereas loss of polarity is a hallmark of tumours. Studies in Drosophila have identified conserved polarity factors that define the apical (Crumbs, Stardust, Par-6, aPKC), junctional (Baz/Par-3) and basolateral (Scribbled, Discs large, Lgl) domains of epithelial cells (1, 2). Because these conserved factors mark equivalent domains in diverse vertebrate and invertebrate epithelial types, it is generally assumed that this system organises polarity in all epithelia. Here we show that this is not the case, as none of these canonical factors are required for the polarisation of the endodermal epithelium of the Drosophila adult midgut. Furthermore, unlike other Drosophila epithelia, the midgut forms occluding junctions above adherens junctions, as in vertebrates, and requires the integrin adhesion complex for polarity (3, 4). Thus, Drosophila contains two types of epithelia that polarise by different mechanisms. Since knock-outs of canonical polarity factors often have little effect on the polarity of vertebrate epithelia, this diversity of polarity mechanisms is likely to be conserved in other animals (5-8).

scholarly journals E–N-cadherin heterodimers define novel adherens junctions connecting endoderm-derived cells

2011 ◽  
Vol 195 (5) ◽  
pp. 873-887 ◽  
Author(s):  
Beate K. Straub ◽  
Steffen Rickelt ◽  
Ralf Zimbelmann ◽  
Christine Grund ◽  
Caecilia Kuhn ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Adherens Junctions ◽  
Tumor Biology ◽  
Intercellular Junctions ◽  
Pivotal Role ◽  
Major Portion ◽  
Tissue Development ◽  
Cadherin Switch ◽  
And Function ◽  
E Cadherin

Intercellular junctions play a pivotal role in tissue development and function and also in tumorigenesis. In epithelial cells, decrease or loss of E-cadherin, the hallmark molecule of adherens junctions (AJs), and increase of N-cadherin are widely thought to promote carcinoma progression and metastasis. In this paper, we show that this “cadherin switch” hypothesis does not hold for diverse endoderm-derived cells and cells of tumors derived from them. We show that the cadherins in a major portion of AJs in these cells can be chemically cross-linked in E–N heterodimers. We also show that cells possessing E–N heterodimer AJs can form semistable hemihomotypic AJs with purely N-cadherin–based AJs of mesenchymally derived cells, including stroma cells. We conclude that these heterodimers are the major AJ constituents of several endoderm-derived tissues and tumors and that the prevailing concept of antagonistic roles of these two cadherins in developmental and tumor biology has to be reconsidered.

scholarly journals Distinct activities of Scrib module proteins organize epithelial polarity

2020 ◽  
Vol 117 (21) ◽  
pp. 11531-11540 ◽  
Author(s):  
Mark J. Khoury ◽  
David Bilder
Keyword(s):  
Protein Interactions ◽  
Molecular Mechanisms ◽  
Epithelial Polarity ◽  
Protein Protein Interactions ◽  
Kinase C ◽  
Mutual Antagonism ◽  
Discs Large ◽  
Lethal Giant Larvae ◽  
Epithelial Structure ◽  
And Function

A polarized architecture is central to both epithelial structure and function. In many cells, polarity involves mutual antagonism between the Par complex and the Scribble (Scrib) module. While molecular mechanisms underlying Par-mediated apical determination are well-understood, how Scrib module proteins specify the basolateral domain remains unknown. Here, we demonstrate dependent and independent activities of Scrib, Discs-large (Dlg), and Lethal giant larvae (Lgl) using theDrosophilafollicle epithelium. Our data support a linear hierarchy for localization, but rule out previously proposed protein–protein interactions as essential for polarization. Cortical recruitment of Scrib does not require palmitoylation or polar phospholipid binding but instead an independent cortically stabilizing activity of Dlg. Scrib and Dlg do not directly antagonize atypical protein kinase C (aPKC), but may instead restrict aPKC localization by enabling the aPKC-inhibiting activity of Lgl. Importantly, while Scrib, Dlg, and Lgl are each required, all three together are not sufficient to antagonize the Par complex. Our data demonstrate previously unappreciated diversity of function within the Scrib module and begin to define the elusive molecular functions of Scrib and Dlg.

scholarly journals Na,K-ATPase Activity Is Required for Formation of Tight Junctions, Desmosomes, and Induction of Polarity in Epithelial Cells

2001 ◽  
Vol 12 (12) ◽  
pp. 3717-3732 ◽  
Author(s):  
Sigrid A. Rajasekaran ◽  
Lawrence G. Palmer ◽  
Sun Y. Moon ◽  
Alejandro Peralta Soler ◽  
Gerard L. Apodaca ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Atpase Activity ◽  
Tight Junctions ◽  
Stress Fibers ◽  
Epithelial Polarity ◽  
Rhoa Gtpase ◽  
Key Enzyme ◽  
And Function ◽  
Atpase Inhibition ◽  
Darby Canine Kidney

Na,K-ATPase is a key enzyme that regulates a variety of transport functions in epithelial cells. In this study, we demonstrate a role for Na,K-ATPase in the formation of tight junctions, desmosomes, and epithelial polarity with the use of the calcium switch model in Madin-Darby canine kidney cells. Inhibition of Na,K-ATPase either by ouabain or potassium depletion prevented the formation of tight junctions and desmosomes and the cells remained nonpolarized. The formation of bundled stress fibers that appeared transiently in control cells was largely inhibited in ouabain-treated or potassium-depleted cells. Failure to form stress fibers correlated with a large reduction of RhoA GTPase activity in Na,K-ATPase-inhibited cells. In cells overexpressing wild-type RhoA GTPase, Na,K-ATPase inhibition did not affect the formation of stress fibers, tight junctions, or desmosomes, and epithelial polarity developed normally, suggesting that RhoA GTPase is an essential component downstream of Na,K-ATPase-mediated regulation of these junctions. The effects of Na,K-ATPase inhibition were mimicked by treatment with the sodium ionophore gramicidin and were correlated with the increased intracellular sodium levels. Furthermore, ouabain treatment under sodium-free condition did not affect the formation of junctions and epithelial polarity, suggesting that the intracellular Na+ homeostasis plays a crucial role in generation of the polarized phenotype of epithelial cells. These results thus demonstrate that the Na,K-ATPase activity plays an important role in regulating both the structure and function of polarized epithelial cells.

scholarly journals A heterologous in-cell assay for investigating intermicrovillar adhesion complex interactions and function

2020 ◽  
Author(s):  
Meredith L. Weck ◽  
Scott W. Crawley ◽  
Matthew J. Tyska
Keyword(s):  
Epithelial Cells ◽  
Apical Surface ◽  
Tail Domain ◽  
Complex Interactions ◽  
Brush Borders ◽  
Specific Complex ◽  
Dynamic Length ◽  
And Function ◽  
Adhesion Complex ◽  
Dependent Mechanism

ABSTRACTSolute transporting epithelial cells build arrays of microvilli on their apical surface to increase membrane scaffolding capacity and enhance function potential. In epithelial tissues such as the kidney and gut, microvilli are length-matched and assembled into tightly packed ‘brush borders’, which are organized by ∼50 nm thread-like links that form between the distal tips of adjacent protrusions. Composed of protocadherins CDHR2 and CDHR5, adhesion links are stabilized at the tips by a cytoplasmic tripartite module containing the scaffolds USH1C and ANKS4B, and the actin-based motor, MYO7B. As several questions about the formation and function of this ‘intermicrovillar adhesion complex’ remain open, we devised a system that allows one to study individual binary interactions between specific complex components and MYO7B. Our approach employs a chimeric myosin consisting of the motor domain of MYO10 fused to the cargo-binding tail domain of MYO7B. When expressed in HeLa cells, which do not normally produce adhesion complex proteins, this motor exhibited robust trafficking to the tips of filopodia and was also able to transport individual components to these sites. Unexpectedly, the MYO10/MYO7B chimera was able to deliver CDHR2 and CDHR5 to distal tips in the absence USH1C or ANKS4B. Cells engineered to localize high levels of CDHR2 at filopodial tips acquired inter-filopodial adhesion and exhibited a striking dynamic length matching activity that aligned distal tips over time. These observations reveal a robust adhesion-dependent mechanism for matching the lengths of adjacent surface protrusions, and may offer insight on how epithelial cells minimize microvillar length variability.

A Polarizing Issue: Diversity in the Mechanisms Underlying Apico-Basolateral Polarization In Vivo

2019 ◽  
Vol 35 (1) ◽  
pp. 285-308 ◽  
Author(s):  
Melissa A. Pickett ◽  
Victor F. Naturale ◽  
Jessica L. Feldman
Keyword(s):  
Epithelial Cells ◽  
Symmetry Breaking ◽  
Recent Work ◽  
Epithelial Polarity ◽  
Epithelial Tissues ◽  
Polarity Establishment ◽  
Context Dependent ◽  
Different Tissues

Polarization along an apico-basolateral axis is a hallmark of epithelial cells and is essential for their selective barrier and transporter functions, as well as for their ability to provide mechanical resiliency to organs. Loss of polarity along this axis perturbs development and is associated with a wide number of diseases. We describe three steps involved in polarization: symmetry breaking, polarity establishment, and polarity maintenance. While the proteins involved in these processes are highly conserved among epithelial tissues and species, the execution of these steps varies widely and is context dependent. We review both theoretical principles underlying these steps and recent work demonstrating how apico-basolateral polarity is established in vivo in different tissues, highlighting how developmental and physiological contexts play major roles in the execution of the epithelial polarity program.

scholarly journals Tricellular junctions: how to build junctions at the TRICkiest points of epithelial cells

2017 ◽  
Vol 28 (15) ◽  
pp. 2023-2034 ◽  
Author(s):  
Tomohito Higashi ◽  
Ann L. Miller
Keyword(s):  
Epithelial Cells ◽  
Tight Junctions ◽  
Barrier Function ◽  
Hot Spots ◽  
Adherens Junctions ◽  
New Model ◽  
Open Questions ◽  
And Function ◽  
Molecular Components

Tricellular contacts are the places where three cells meet. In vertebrate epithelial cells, specialized structures called tricellular tight junctions (tTJs) and tricellular adherens junctions (tAJs) have been identified. tTJs are important for the maintenance of barrier function, and disruption of tTJ proteins contributes to familial deafness. tAJs have recently been attracting the attention of mechanobiologists because these sites are hot spots of epithelial tension. Although the molecular components, regulation, and function of tTJs and tAJs, as well as of invertebrate tricellular junctions, are beginning to be characterized, many questions remain. Here we broadly cover what is known about tricellular junctions, propose a new model for tension transmission at tAJs, and discuss key open questions.

scholarly journals A heterologous in-cell assay for investigating intermicrovillar adhesion complex interactions reveals a novel protrusion length-matching mechanism

2020 ◽  
Vol 295 (48) ◽  
pp. 16191-16206
Author(s):  
Meredith L. Weck ◽  
Scott W. Crawley ◽  
Matthew J. Tyska
Keyword(s):  
Epithelial Cells ◽  
Apical Surface ◽  
Tail Domain ◽  
Complex Interactions ◽  
Specific Complex ◽  
Matching Mechanism ◽  
Dynamic Length ◽  
And Function ◽  
Adhesion Complex ◽  
Complex Components

Solute transporting epithelial cells build arrays of microvilli on their apical surface to increase membrane scaffolding capacity and enhance function potential. In epithelial tissues such as the kidney and gut, microvilli are length-matched and assembled into tightly packed “brush borders,” which are organized by ∼50-nm thread-like links that form between the distal tips of adjacent protrusions. Composed of protocadherins CDHR2 and CDHR5, adhesion links are stabilized at the tips by a cytoplasmic tripartite module containing the scaffolds USH1C and ANKS4B and the actin-based motor MYO7B. Because several questions about the formation and function of this “intermicrovillar adhesion complex” remain open, we devised a system that allows one to study individual binary interactions between specific complex components and MYO7B. Our approach employs a chimeric myosin consisting of the MYO10 motor domain fused to the MYO7B cargo-binding tail domain. When expressed in HeLa cells, which do not normally produce adhesion complex proteins, this chimera trafficked to the tips of filopodia and was also able to transport individual complex components to these sites. Unexpectedly, the MYO10–MYO7B chimera was able to deliver CDHR2 and CDHR5 to distal tips in the absence of USH1C or ANKS4B. Cells engineered to localize high levels of CDHR2 at filopodial tips acquired interfilopodial adhesion and exhibited a striking dynamic length-matching activity that aligned distal tips over time. These findings deepen our understanding of mechanisms that promote the distal tip accumulation of intermicrovillar adhesion complex components and also offer insight on how epithelial cells minimize microvillar length variability.

scholarly journals 2041 The cell-cell adhesion component PLEKHA7 regulates the pro-tumorigenic MIR17HG long non-coding RNA in colon epithelial cells

2018 ◽  
Vol 2 (S1) ◽  
pp. 30-30
Author(s):  
Mary C. Bridges ◽  
Joyce Nair-Menon ◽  
Antonis Kourtidis
Keyword(s):  
Colon Cancer ◽  
Epithelial Cells ◽  
Cell Transformation ◽  
Adherens Junctions ◽  
Mature Mirnas ◽  
Epithelial Tissue ◽  
Mrna Levels ◽  
Rna Seq ◽  
Non Coding Rna ◽  
And Function

OBJECTIVES/SPECIFIC AIMS: The goal of this study is to test the hypothesis that the adherens junctions of colon epithelial cells regulate lncRNAs levels and function via the microprocessor and RISC complexes to suppress expression of pro-tumorigenic markers and aberrant cell behavior. METHODS/STUDY POPULATION: To test this hypothesis, we used colon epithelial cancer cell lines. We performed RNA-seq following knockdown of PLEKHA7, a key component of the adherens junctions, to identify changes in lncRNA expression and downstream mRNA levels. We confirmed junctional localization of affected lncRNAs from the RNA-seq and those that we found in our preliminary study by using in situ hybridization (ISH). RESULTS/ANTICIPATED RESULTS: RNA-seq identified junction-associated lncRNAs whose expression levels are regulated by PLEKHA7. The top upregulated lncRNA upon PLEKHA7 depletion was MIR17HG, an oncogenic host transcript of a cluster of miRNAs. These mature miRNAs also co-precipitate with PLEKHA7. PLEKHA7 knockdown results in increased levels of MIR17HG, but only a subset of its hosted miRNAs (miR-19a,b). Notably, miR-19a and mir-19b are highly upregulated in colon cancer. Our data suggest that 2 PLEKHA7-associated miRNAs, miR-203a and miR-372, mediate suppression MIR17HG. Re-expression of PLEKHA7 in aggressive colon cancer cells that lack PLEKHA7 suppressed expression of MIR17HG, as well as anchorage independent growth of these cells. DISCUSSION/SIGNIFICANCE OF IMPACT: Our data point towards a novel mechanism of lncRNA regulation that tethers epithelial tissue integrity with pro-tumorigenic cell transformation. Reducing elevated MIR17HG levels, is a potential therapeutic approach to suppress the tumorigenic behavior of cells that have lost their junctional integrity and homeostasis. identify a network of miRNA-mRNA-lncRNA interactions that could be exploited for further mechanistic studies, as well as for diagnostic and therapeutic purposes in the future.

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