scholarly journals Differential regulation of junctional complex assembly in renal epithelial cell lines

2003 ◽  
Vol 285 (1) ◽  
pp. C102-C111 ◽  
Author(s):  
Shobha Gopalakrishnan ◽  
Mark A. Hallett ◽  
Simon J. Atkinson ◽  
James. A. Marrs
Keyword(s):  
Epithelial Cells ◽  
Tight Junction ◽  
Rho Gtpase ◽  
Mdck Cells ◽  
Adherens Junction ◽  
Stress Fiber ◽  
Cell Junctions ◽  
Junctional Complex ◽  
Complex Assembly ◽  
E Cadherin

Several signaling pathways that regulate tight junction and adherens junction assembly are being characterized. Calpeptin activates stress fiber assembly in fibroblasts by inhibiting SH2-containing phosphatase-2 (SHP-2), thereby activating Rho-GTPase signaling. Here, we have examined the effects of calpeptin on stress fiber and junctional complex assembly in Madin-Darby canine kidney (MDCK) and LLC-PK epithelial cells. Calpeptin induced disassembly of stress fibers and inhibition of Rho GTPase activity in MDCK cells. Interestingly, calpeptin augmented stress fiber formation in LLC-PK epithelial cells. Calpeptin treatment of MDCK cells resulted in a displacement of zonula occludens-1 (ZO-1) and occludin from cell-cell junctions and a loss of phosphotyrosine on ZO-1 and ZO-2, without any detectable effect on tight junction permeability. Surprisingly, calpeptin increased paracellular permeability in LLC-PK cells even though it did not affect tight junction assembly. Calpeptin also modulated adherens junction assembly in MDCK cells but not in LLC-PK cells. Calpeptin treatment of MDCK cells induced redistribution of E-cadherin and β-catenin from intercellular junctions and reduced the association of p120ctn with the E-cadherin/catenin complex. Together, our studies demonstrate that calpeptin differentially regulates stress fiber and junctional complex assembly in MDCK and LLC-PK epithelial cells, indicating that these pathways may be regulated in a cell line-specific manner.

scholarly journals Polycystin-1 and Gα12 regulate the cleavage of E-cadherin in kidney epithelial cells

2015 ◽  
Vol 47 (2) ◽  
pp. 24-32 ◽  
Author(s):  
Jen X. Xu ◽  
Tzong-Shi Lu ◽  
Suyan Li ◽  
Yong Wu ◽  
Lai Ding ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Signaling Pathway ◽  
Cell Polarity ◽  
Mdck Cells ◽  
Adherens Junction ◽  
Renal Epithelial Cells ◽  
Extracellular Milieu ◽  
Kidney Epithelial Cells ◽  
Autosomal Dominant Polycystic Kidney ◽  
E Cadherin

Interaction of polycystin-1 (PC1) and Gα12 is important for development of kidney cysts in autosomal dominant polycystic kidney disease (ADPKD). The integrity of cell polarity and cell-cell adhesions (mainly E-cadherin-mediated adherens junction) is altered in the renal epithelial cells of ADPKD. However, the key signaling pathway for this alteration is not fully understood. Madin-Darby canine kidney (MDCK) cells maintain the normal integrity of epithelial cell polarity and adherens junctions. Here, we found that deletion of Pkd1 increased activation of Gα12, which then promoted the cystogenesis of MDCK cells. The morphology of these cells was altered after the activation of Gα12. By using liquid chromatography-mass spectrometry, we found several proteins that could be related this change in the extracellular milieu. E-cadherin was one of the most abundant peptides after active Gα12 was induced. Gα12 activation or Pkd1 deletion increased the shedding of E-cadherin, which was mediated via increased ADAM10 activity. The increased shedding of E-cadherin was blocked by knockdown of ADAM10 or specific ADAM10 inhibitor GI254023X. Pkd1 deletion or Gα12 activation also changed the distribution of E-cadherin in kidney epithelial cells and caused β-catenin to shift from cell membrane to nucleus. Finally, ADAM10 inhibitor, GI254023 X, blocked the cystogenesis induced by PC1 knockdown or Gα12 activation in renal epithelial cells. Our results demonstrate that the E-cadherin/β-catenin signaling pathway is regulated by PC1 and Gα12 via ADAM10. Specific inhibition of this pathway, especially ADAM10 activity, could be a novel therapeutic regimen for ADPKD.

Abstract 19664: Molecular Mechanisms of Gα12 Regulated E-cadherin Shedding in Epithelial Cells

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Jen Xu ◽  
Yong Wu ◽  
Suyang Li ◽  
Kenneth Lim ◽  
Tianqing Kong ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Molecular Mechanisms ◽  
Mdck Cells ◽  
Active Form ◽  
Cell Junctions ◽  
Mice Model ◽  
Polycystic Kidneys ◽  
Cystic Fluid ◽  
Kidney Cysts ◽  
E Cadherin

Introduction and hypothesis: E-cadherin plays an important role in maintaining the integrity of cell polarity and cell junctions. It is one of the major proteins that forms part of the polycystin-1 (PC1) complex in renal epithelial cells. We previously showed that deletion of the PC1-regulated protein, Gα12, protected kidneys from development of kidney cysts induced by Pkd1 inactivation and activation of Gα12 increased the shedding of E-cadherin in autosomal dominant polycystic kidney disease (ADPKD). The objective of this study was to determine the molecular mechanisms by which Gα12 regulates E-cadherin shedding. Methods: We analyzed polycystic kidneys from human and from Pkd1 knock-out mice. Using Madin-Darby canine kidney (MDCK) cells, we developed a Pkd1 deletion in vitro model using Pkd1 siRNA. Results: Our data shows that Pkd1 deletion caused accumulation of cleaved E-cadherin fragment in renal cystic fluid in both human polycystic kidneys and in our mice model. In addition, we found that activation of Gα12 increased the active form of ADAM10, the cleavage protein for E-cadherin in both human and mice polycystic kidneys, in vivo. In our MDCK cellular three-dimensional culture system, Gα12 activation promoted cyst formation and this phenomenon was inhibited by ADAM10 knockdown. Furthermore, knockdown of ADAM10 abolished the shedding of E-cadherin caused by Gα12 activation. These data indicate that ADAM10 is the major sheddase for cleavage of E-cadherin caused by Gα12 activation. Conclusion: Our results demonstrate that Gα12 activation increases ADAM10 activity and promotes the ectodomain shedding of E-cadherin, which is an important mechanism in the development of kidney cysts induced by Pkd1 deletion in ADPKD.

Selective degradation of E-cadherin and dissolution of E-cadherin-catenin complexes in epithelial ischemia

2000 ◽  
Vol 278 (5) ◽  
pp. F847-F852 ◽  
Author(s):  
Kevin T. Bush ◽  
Tatsuo Tsukamoto ◽  
Sanjay K. Nigam
Keyword(s):  
Epithelial Cells ◽  
Mdck Cells ◽  
Transmembrane Protein ◽  
Adherens Junction ◽  
Intercellular Junctions ◽  
Atp Depletion ◽  
Cell Phenotype ◽  
Western Blots ◽  
Selective Degradation ◽  
E Cadherin

Ischemic epithelial cells are characterized by disruption of intercellular junctions and loss of apical-basolateral protein polarity, which are normally dependent on the integrity of the adherens junction (AJ). Biochemical analysis of both whole ischemic kidneys and ATP-depleted Madin-Darby canine kidney (MDCK) cells demonstrated a striking loss of E-cadherin (the transmembrane protein of the AJ) with the appearance and accumulation of an ∼80-kDa fragment reactive with anti-E-cadherin antibodies on Western blots of ATP-depleted MDCK cells. This apparent ischemia-induced degradation of E-cadherin was not blocked by either inhibitors of the major proteolytic pathways (i.e., proteasome, lysosome, or calpain), or by chelation of intracellular calcium, suggesting the involvement of a protease capable of functioning at low ATP and low calcium levels. Immunocytochemistry revealed the movement of several proteins normally comprising the AJ, including E-cadherin and β-catenin, away from lateral portions of the plasma membrane to intracellular sites. Moreover, rate-zonal centrifugation and immunoprecipitation with anti-E-cadherin and anti-β-catenin antibodies indicated that ATP depletion disrupted normal E-cadherin-catenin interactions, resulting in the dissociation of α- and γ-catenin from E-cadherin and β-catenin-containing complexes. Because the generation and maintenance of polarized epithelial cells are dependent upon E-cadherin-mediated cell-cell adhesion and normal AJ function, we propose that the rapid degradation of E-cadherin and dissolution of the AJ is a key step in the development of the ischemic epithelial cell phenotype. Furthermore, we hypothesize that the reassembly of the AJ after ischemia/ATP depletion may require a novel bioassembly mechanism involving recombination of newly synthesized and sorted E-cadherin with preexisting pools of catenins that have (temporally) redistributed intracellularly.

Gα12 regulates epithelial cell junctions through Src tyrosine kinases

2003 ◽  
Vol 285 (5) ◽  
pp. C1281-C1293 ◽  
Author(s):  
Tobias N. Meyer ◽  
Jennifer Hunt ◽  
Catherine Schwesinger ◽  
Bradley M. Denker
Keyword(s):  
Epithelial Cell ◽  
Tyrosine Kinase ◽  
Mdck Cells ◽  
Adherens Junction ◽  
Paracellular Permeability ◽  
Cell Junctions ◽  
Scaffolding Protein ◽  
Junctional Complex ◽  
Adherens Junction Proteins ◽  
Junction Proteins

Regulation and assembly of the epithelial cell junctional complex involve multiple signaling mechanisms, including heterotrimeric G proteins. Recently, we demonstrated that Gα12 binds to the tight junction scaffolding protein ZO-1 through the SH3 domain and that activated Gα12 increases paracellular permeability in Madin-Darby canine kidney (MDCK) cells (Meyer et al. J Biol Chem 277: 24855-24858, 2002). In the present studies, we explore the effects of Gα12 expression on tight and adherens junction proteins and examine downstream signaling pathways. By confocal microscopy, we detect disrupted tight and adherens junction proteins with increased actin stress fibers in constitutively active Gα12 (QLα12)-expressing MDCK cells. The normal distribution of ZO-1 and Na-K-ATPase was altered in QLα12-expressing MDCK cells, consistent with loss of polarity. We found that the tyrosine kinase inhibitor genistein and the Src-specific inhibitor PP-2 reversibly abrogated the QLα12 phenotype on the junctional complex. Junctional protein localization was preserved in PP-2- or genistein-treated QLα12-expressing cells, and the increase in paracellular permeability as measured by transepithelial resistance and [3H]mannitol flux was prevented by the inhibitors. Src activity was increased in QLα12-expressing MDCK cells as assessed by Src autophosphorylation, and β-catenin tyrosine phosphorylation was also increased, although there was no detectable increase in Rho activity. Taken together, these results indicate that Gα12 regulates MDCK cell junctions, in part through Src tyrosine kinase pathways.

Inhibiting cadherin function by dominant mutant E-cadherin expression increases the extent of tight junction assembly

2000 ◽  
Vol 113 (6) ◽  
pp. 985-996 ◽  
Author(s):  
M.L. Troxell ◽  
S. Gopalakrishnan ◽  
J. McCormack ◽  
B.A. Poteat ◽  
J. Pennington ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Tight Junction ◽  
Mdck Cells ◽  
Freeze Fracture ◽  
Junctional Complex ◽  
Negative Effects ◽  
Tight Junction Formation ◽  
Freeze Fracture Electron Microscopy ◽  
E Cadherin ◽  
Cell Cell

Previous studies have shown that induction of cadherin-mediated cell-cell adhesion leads to tight junction formation, and that blocking cadherin-mediated cell-cell adhesion inhibits tight junction assembly. Here we report analysis of tight junction assembly in MDCK cells overexpressing a mutant E-cadherin protein that lacks an adhesive extracellular domain (T151 cells). Mutant E-cadherin overexpression caused a dramatic reduction in endogenous cadherin levels. Despite this, tight junction assembly was extensive. The number of tight junction strands observed by freeze-fracture electron microscopy significantly increased in T151 cells compared to that in control cells. Our data indicate that the hierarchical regulation of junctional complex assembly is not absolute, and that inhibition of cadherin function has both positive and negative effects on tight junction assembly.

scholarly journals Exogenous Expression of the Amino-Terminal Half of the Tight Junction Protein Zo-3 Perturbs Junctional Complex Assembly

2000 ◽  
Vol 151 (4) ◽  
pp. 825-836 ◽  
Author(s):  
Erika S. Wittchen ◽  
Julie Haskins ◽  
Bruce R. Stevenson
Keyword(s):  
Tight Junction ◽  
Actin Cytoskeleton ◽  
Mdck Cells ◽  
Dominant Negative ◽  
Tight Junction Protein ◽  
Junctional Complex ◽  
Amino Terminal ◽  
Junction Protein ◽  
Exogenous Expression ◽  
E Cadherin

The functional characteristics of the tight junction protein ZO-3 were explored through exogenous expression of mutant protein constructs in MDCK cells. Expression of the amino-terminal, PSD95/dlg/ZO-1 domain-containing half of the molecule (NZO-3) delayed the assembly of both tight and adherens junctions induced by calcium switch treatment or brief exposure to the actin-disrupting drug cytochalasin D. Junction formation was monitored by transepithelial resistance measurements and localization of junction-specific proteins by immunofluorescence. The tight junction components ZO-1, ZO-2, endogenous ZO-3, and occludin were mislocalized during the early stages of tight junction assembly. Similarly, the adherens junction proteins E-cadherin and β-catenin were also delayed in their recruitment to the cell membrane, and NZO-3 expression had striking effects on actin cytoskeleton dynamics. NZO-3 expression did not alter expression levels of ZO-1, ZO-2, endogenous ZO-3, occludin, or E-cadherin; however, the amount of Triton X-100–soluble, signaling-active β-catenin was increased in NZO-3–expressing cells during junction assembly. In vitro binding experiments showed that ZO-1 and actin preferentially bind to NZO-3, whereas both NZO-3 and the carboxy-terminal half of the molecule (CZO-3) contain binding sites for occludin and cingulin. We hypothesize that NZO-3 exerts its dominant-negative effects via a mechanism involving the actin cytoskeleton, ZO-1, and/or β-catenin.

scholarly journals Integrin regulation of cell-cell adhesion during epithelial tubule formation

2001 ◽  
Vol 114 (5) ◽  
pp. 941-952 ◽  
Author(s):  
G.K. Ojakian ◽  
D.R. Ratcliffe ◽  
R. Schwimmer
Keyword(s):  
Extracellular Matrix ◽  
Adherens Junction ◽  
Cell Junctions ◽  
Junctional Complex ◽  
Tubule Formation ◽  
Epithelial Remodeling ◽  
Adherens Junction Proteins ◽  
Junction Proteins ◽  
E Cadherin ◽  
Cell Cell

The extracellular matrix plays an important role in regulation of epithelial development and organization. To determine more precisely the function of extracellular matrix in this process, the initial steps in collagen-mediated formation of epithelial tubules were studied using a model cell culture system. Previous studies have demonstrated that incubation of Madin-Darby canine kidney (MDCK) epithelial cells with a collagen gel overlay induces (beta)1 integrin-regulated epithelial remodeling accompanied by extensive cell rearrangements and formation of epithelial tubules. During epithelial remodeling there was extensive disruption of the epithelial junctional complex. Progressive opening of tight junctions was observed over 8 hours using transepithelial resistance measurements and immunofluorescence microscopy demonstrated that tight and adherens junction proteins were dispersed throughout the apical and basolateral membranes. Junction complex disruption allowed the formation of apical cell extensions and subsequent migration of selected cell sheets from the epithelial monolayer. Confocal microscopy demonstrated the presence of adherens junction (E-cadherin, (alpha)-catenin, (beta)-catenin, plakoglobin) and desmosomal (desmoplakin-1/2, plakoglobin) proteins on, and within, cell extensions demonstrating that cell junctions had undergone considerable disassembly. However, groups of cell extensions appeared to be associated by E-cadherin/catenin-mediated interactions. Association of E-cadherin/catenin complexes with the epithelial cytoskeleton was analyzed by differential detergent extraction. SDS-PAGE and immunoblot analysis demonstrated that adherens junction proteins were primarily cytoskeleton-associated in control cells. During integrin-regulated remodeling, there was a progressive reduction in the interaction of adherens junction proteins with the cytoskeleton suggesting that they play an important role in the maintenance of epithelial integrity. Since loss of transepithelial electrical resistance and disruption of junctional complexes were inhibited by an antifunctional integrin antibody, we propose that activation of integrin signaling pathways regulate junctional complex stability, cell-cell interactions and cell migration. These observations provide evidence that integrin-regulated MDCK epithelial tubule formation can serve as a model system for studying rearrangements of epithelial sheets which occur during development.

Rho GTPase signaling regulates tight junction assembly and protects tight junctions during ATP depletion

1998 ◽  
Vol 275 (3) ◽  
pp. C798-C809 ◽  
Author(s):  
Shobha Gopalakrishnan ◽  
Narayan Raman ◽  
Simon J. Atkinson ◽  
James A. Marrs
Keyword(s):  
Tight Junction ◽  
Tight Junctions ◽  
Rho Gtpase ◽  
Mdck Cells ◽  
Atp Depletion ◽  
Cell Junctions ◽  
Mutant Proteins ◽  
Vitro Model ◽  
The Relationship

Tight junctions control paracellular permeability and cell polarity. Rho GTPase regulates tight junction assembly, and ATP depletion of Madin-Darby canine kidney (MDCK) cells (an in vitro model of renal ischemia) disrupts tight junctions. The relationship between Rho GTPase signaling and ATP depletion was examined. Rho inhibition resulted in decreased localization of zonula occludens-1 (ZO-1) and occludin at cell junctions; conversely, constitutive Rho signaling caused an accumulation of ZO-1 and occludin at cell junctions. Inhibiting Rho before ATP depletion resulted in more extensive loss of junctional components between transfected cells than control junctions, whereas cells expressing activated Rho better maintained junctions during ATP depletion than control cells. ATP depletion and Rho signaling altered phosphorylation signaling mechanisms. ZO-1 and occludin exhibited rapid decreases in phosphoamino acid content following ATP depletion, which was restored on recovery. Expression of Rho mutant proteins in MDCK cells also altered levels of occludin serine/threonine phosphorylation, indicating that occludin is a target for Rho signaling. We conclude that Rho GTPase signaling induces posttranslational effects on tight junction components. Our data also demonstrate that activating Rho signaling protects tight junctions from damage during ATP depletion.

Cadherin function in junctional complex rearrangement and posttranslational control of cadherin expression

1999 ◽  
Vol 276 (2) ◽  
pp. C404-C418 ◽  
Author(s):  
Megan L. Troxell ◽  
Yih-Tai Chen ◽  
Nicole Cobb ◽  
W. James Nelson ◽  
James A. Marrs
Keyword(s):  
Tight Junction ◽  
Adherens Junction ◽  
Junctional Complex ◽  
Adhesion Protein ◽  
Cell Monolayers ◽  
Calcium Dependent ◽  
Protein Levels ◽  
Epithelial Junctions ◽  
Junctional Complexes ◽  
E Cadherin

The role of E-cadherin, a calcium-dependent adhesion protein, in organizing and maintaining epithelial junctions was examined in detail by expressing a fusion protein (GP2-Cad1) composed of the extracellular domain of a nonadherent glycoprotein (GP2) and the transmembrane and cytoplasmic domains of E-cadherin. All studies shown were also replicated using an analogous cell line that expresses a mutant cadherin construct (T151) under the control of tet repressor. Mutant cadherin was expressed at ∼10% of the endogenous E-cadherin level and had no apparent effect on tight junction function or on distributions of adherens junction, tight junction, or desmosomal marker proteins in established Madin-Darby canine kidney cell monolayers. However, GP2-Cad1 accelerated the disassembly of epithelial junctional complexes and delayed their reassembly in calcium switch experiments. Inducing expression of GP2-Cad1 to levels approximately threefold greater than endogenous E-cadherin expression levels in control cells resulted in a decrease in endogenous E-cadherin levels. This was due in part to increased protein turnover, indicating a cellular mechanism for sensing and controlling E-cadherin levels. Cadherin association with catenins is necessary for strong cadherin-mediated cell-cell adhesion. In cells expressing low levels of GP2-Cad1, protein levels and stoichiometry of the endogenous cadherin-catenin complex were unaffected. Thus effects of GP2-Cad1 on epithelial junctional complex assembly and stability were not due to competition with endogenous E-cadherin for catenin binding. Rather, we suggest that GP2-Cad1 interferes with the packing of endogenous cadherin-catenin complexes into higher-order structures in junctional complexes that results in junction destabilization.

scholarly journals Depletion of E-Cadherin Disrupts Establishment but Not Maintenance of Cell Junctions in Madin-Darby Canine Kidney Epithelial Cells

2007 ◽  
Vol 18 (1) ◽  
pp. 189-200 ◽  
Author(s):  
Christopher T. Capaldo ◽  
Ian G. Macara
Keyword(s):  
Epithelial Cells ◽  
Mdck Cells ◽  
Morphological Changes ◽  
Cell Junctions ◽  
Cell Cortex ◽  
Apical Surface ◽  
Madin Darby Canine Kidney ◽  
Darby Canine Kidney ◽  
Canine Kidney ◽  
E Cadherin

E-cadherin forms calcium-dependent homophilic intercellular adhesions between epithelial cells. These contacts regulate multiple aspects of cell behavior, including the organization of intercellular tight junctions (TJs). To distinguish between the roles of E-cadherin in formation versus maintenance of junctions, Madin-Darby canine kidney (MDCK) cells were depleted of E-cadherin by RNA interference. Surprisingly, reducing E-cadherin expression had little effect on the protein levels or localization of adherens junction (AJ) or TJ markers. The cells underwent morphological changes, as the normally flat apical surface swelled into a dome. However, apical–basal polarity was not compromised, transmembrane resistance was normal, and zonula occludin protein 1 dynamics at the TJs were unchanged. Additionally, an E-cadherin/Cadherin-6 double knockdown also failed to disrupt established TJs, although β-catenin was lost from the cell cortex. Nevertheless, cells depleted of E-cadherin failed to properly reestablish cell polarity after junction disassembly. Recovery of cell–cell adhesion, transepithelial resistance, and the localization of TJ and AJ markers were all delayed. In contrast, depletion of α-catenin caused long-term disruption of junctions. These results indicate that E-cadherin and Cadherin-6 function as a scaffold for the construction of polarized structures, and they become largely dispensable in mature junctions, whereas α-catenin is essential for the maintenance of functional junctions.

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