scholarly journals Domain-swapped Dimerization of the Second PDZ Domain of ZO2 May Provide a Structural Basis for the Polymerization of Claudins

2007 ◽  
Vol 282 (49) ◽  
pp. 35988-35999 ◽  
Author(s):  
Jiawen Wu ◽  
Yinshan Yang ◽  
Jiahai Zhang ◽  
Peng Ji ◽  
Wenjing Du ◽  
...  
Keyword(s):  
Solution Structure ◽  
Pdz Domain ◽  
Three Dimensional ◽  
Structural Basis ◽  
Pdz Domains ◽  
Zonula Occludens ◽  
Associated Proteins ◽  
High Conservation

Zonula occludens proteins (ZOs), including ZO1/2/3, are tight junction-associated proteins. Each of them contains three PDZ domains. It has been demonstrated that ZO1 can form either homodimers or heterodimers with ZO2 or ZO3 through the second PDZ domain. However, the underlying structural basis is not well understood. In this study, the solution structure of the second PDZ domain of ZO2 (ZO2-PDZ2) was determined using NMR spectroscopy. The results revealed a novel dimerization mode for PDZ domains via three-dimensional domain swapping, which can be generalized to homodimers of ZO1-PDZ2 or ZO3-PDZ2 and heterodimers of ZO1-PDZ2/ZO2-PDZ2 or ZO1-PDZ2/ZO3-PDZ2 due to high conservation between PDZ2 domains in ZO proteins. Furthermore, GST pulldown experiments and immunoprecipitation studies demonstrated that interactions between ZO1-PDZ2 and ZO2-PDZ2 and their self-associations indeed exist both in vitro and in vivo. Chemical cross-linking and dynamic laser light scattering experiments revealed that both ZO1-PDZ2 and ZO2-PDZ2 can form oligomers in solution. This PDZ domain-mediated oligomerization of ZOs may provide a structural basis for the polymerization of claudins, namely the formation of tight junctions.

scholarly journals A Regulated Complex of the Scaffolding Proteins PDZK1 and EBP50 with Ezrin Contribute to Microvillar Organization

2010 ◽  
Vol 21 (9) ◽  
pp. 1519-1529 ◽  
Author(s):  
David P. LaLonde ◽  
Damien Garbett ◽  
Anthony Bretscher
Keyword(s):  
Epithelial Cells ◽  
Complex Formation ◽  
Ternary Complex ◽  
Apical Membrane ◽  
Pdz Domain ◽  
Scaffolding Proteins ◽  
Pdz Domains ◽  
Zona Occludens

PDZK1 and ezrin, radixin, moesin binding phosphoprotein 50 kDa (EBP50) are postsynaptic density 95/disc-large/zona occludens (PDZ)-domain–containing scaffolding proteins found in the apical microvilli of polarized epithelial cells. Binary interactions have been shown between the tail of PDZK1 and the PDZ domains of EBP50, as well as between EBP50 and the membrane–cytoskeletal linking protein ezrin. Here, we show that these molecules form a regulated ternary complex in vitro and in vivo. Complex formation is cooperative because ezrin positively influences the PDZK1/EBP50 interaction. Moreover, the interaction of PDZK1 with EBP50 is enhanced by the occupancy of EBP50's adjacent PDZ domain. The complex is further regulated by location, because PDZK1 shuttles from the nucleus in low confluence cells to microvilli in high confluence cells, and this regulates the formation of the PDZK1/EBP50/ezrin complex in vivo. Knockdown of EBP50 decreases the presence of microvilli, a phenotype that can be rescued by EBP50 re-expression or expression of a PDZK1 chimera that is directly targeted to ezrin. Thus, when appropriately located, PDZK1 can provide a function necessary for microvilli formation normally provided by EBP50. By entering into the ternary complex, PDZK1 can both enhance the scaffolding at the apical membrane as well as augment EBP50's role in microvilli formation.

scholarly journals Particulate Matter Decreases Intestinal Barrier-Associated Proteins Levels in 3D Human Intestinal Model

2020 ◽  
Vol 17 (9) ◽  
pp. 3234
Author(s):  
Brittany Woodby ◽  
Maria Lucia Schiavone ◽  
Erika Pambianchi ◽  
Angela Mastaloudis ◽  
Shelly N. Hester ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Particulate Matter ◽  
Redox Homeostasis ◽  
Three Dimensional ◽  
Intestinal Barrier ◽  
Gi Tract ◽  
Inflammatory Conditions ◽  
Associated Proteins

(1) Background: The gastrointestinal tract (GI) tract is one of the main organs exposed to particulate matter (PM) directly through ingestion of contaminated food or indirectly through inhalation. Previous studies have investigated the effects of chronic PM exposure on intestinal epithelia in vitro using Caco−2 cells and in vivo using mice. In this study, we hypothesized that chronic PM exposure would increase epithelial permeability and decrease barrier function due to altered redox homeostasis, which alters levels and/or localization of barrier-associated proteins in human three-dimensional (3D) intestinal tissues. (2) Methods: Transepithelial electrical resistance (TEER) in tissues exposed to 50, 100, 150, 250, and 500 µg/cm2 of PM for 1 week and 2 weeks was analyzed. Levels and localization of tight junction proteins zonula occludens protein 1 (ZO−1) and claudin−1 and desmosome-associated desmocollin were analyzed using immunofluorescence. As a marker of oxidative stress, levels of 4-hydroxy-nonenal (4HNE) adducts were measured. (3) Results: No differences in TEER measurements were observed between exposed and un-exposed tissues. However, increased levels of 4HNE adducts in exposed tissues were observed. Additionally, decreased levels of ZO−1, claudin−1, and desmocollin were demonstrated. (4) Conclusion: These data suggest that chronic PM exposure results in an increase of oxidative stress; modified levels of barrier-associated proteins could possibly link to GI tract inflammatory conditions.

Understanding the highly efficient catalysis of prokaryotic peptide deformylases by shedding light on the determinants specifying the low activity of the human counterpart

2014 ◽  
Vol 70 (2) ◽  
pp. 242-252 ◽  
Author(s):  
Sonia Fieulaine ◽  
Michel Desmadril ◽  
Thierry Meinnel ◽  
Carmela Giglione
Keyword(s):  
Sequence Similarity ◽  
Three Dimensional ◽  
Binding Pocket ◽  
Dimensional Structure ◽  
Structural Basis ◽  
Human Counterpart ◽  
Low Activity

Peptide deformylases (PDFs), which are essential and ubiquitous enzymes involved in the removal of theN-formyl group from nascent chains, are classified into four subtypes based on the structural and sequence similarity of specific conserved domains. All PDFs share a similar three-dimensional structure, are functionally interchangeablein vivoand display similar propertiesin vitro, indicating that their molecular mechanism has been conserved during evolution. The human mitochondrial PDF is the only exception as despite its conserved fold it reveals a unique substrate-binding pocket together with an unusual kinetic behaviour. Unlike human PDF, the closely related mitochondrial PDF1As from plants have catalytic efficiencies and enzymatic parameters that are similar to those of other classes of PDFs. Here, the aim was to identify the structural basis underlying the properties of human PDF compared with all other PDFs by focusing on plant mitochondrial PDF1A. The construction of a chimaera composed of plant PDF1A with the nonrandom substitutions found in a conserved motif of its human homologue converted it into an enzyme with properties similar to the human enzyme, indicating the crucial role of these positions. The crystal structure of this human-like plant PDF revealed that substitution of two residues leads to a reduction in the volume of the ligand-binding site together with the introduction of negative charges, unravelling the origin of the weak affinity of human PDF for its substrate. In addition, the substitution of the two residues of human PDF modifies the transition state of the reaction through alteration of the network of interactions between the catalytic residues and the substrate, leading to an overall reduced reaction rate.

scholarly journals The function and dynamics of the apical scaffolding protein E3KARP are regulated by cell-cycle phosphorylation

2015 ◽  
Vol 26 (20) ◽  
pp. 3615-3627 ◽  
Author(s):  
Cécile Sauvanet ◽  
Damien Garbett ◽  
Anthony Bretscher
Keyword(s):  
Pdz Domain ◽  
Duplication Event ◽  
Scaffolding Protein ◽  
Gene Duplication Event ◽  
Pdz Domains ◽  
Tail Region ◽  
Dynamics And Function ◽  
And Function

We examine the dynamics and function of the apical scaffolding protein E3KARP/NHERF2, which consists of two PDZ domains and a tail containing an ezrin-binding domain. The exchange rate of E3KARP is greatly enhanced during mitosis due to phosphorylation at Ser-303 in its tail region. Whereas E3KARP can substitute for the function of the closely related scaffolding protein EBP50/NHERF1 in the formation of interphase microvilli, E3KARP S303D cannot. Moreover, the S303D mutation enhances the in vivo dynamics of the E3KARP tail alone, whereas in vitro the interaction of E3KARP with active ezrin is unaffected by S303D, implicating another factor regulating dynamics in vivo. A-Raf is found to be required for S303 phosphorylation in mitotic cells. Regulation of the dynamics of EBP50 is known to be dependent on its tail region but modulated by PDZ domain occupancy, which is not the case for E3KARP. Of interest, in both cases, the mechanisms regulating dynamics involve the tails, which are the most diverged region of the paralogues and probably evolved independently after a gene duplication event that occurred early in vertebrate evolution.

scholarly journals NHERF1/EBP50 Head-to-Tail Intramolecular Interaction Masks Association with PDZ Domain Ligands

2007 ◽  
Vol 27 (7) ◽  
pp. 2527-2537 ◽  
Author(s):  
Fabiana C. Morales ◽  
Yoko Takahashi ◽  
Safan Momin ◽  
Henry Adams ◽  
Xiaomin Chen ◽  
...  
Keyword(s):  
Intramolecular Interaction ◽  
Pdz Domain ◽  
Epithelial Tissue ◽  
Binding Motif ◽  
Pdz Domains ◽  
Erm Proteins ◽  
Epithelial Cancers ◽  
Associated Proteins ◽  
Α Helix

ABSTRACT Loss of cell polarity is one of the initial alterations in the development of human epithelial cancers. Na+/H+ exchanger regulatory factor (NHERF) homologous adaptors 1 and 2 are membrane-associated proteins composed of two amino (N)-terminal PDZ domains and an ezrin-radixin-moesin (ERM)-binding (EB) carboxyl (C)-terminal region. We describe here an intramolecular conformation of NHERF1/EBP50 (ERM-binding phosphoprotein 50) in which the C-terminal EB region binds to the PDZ2 domain. This novel head-to-tail conformation masked the interaction of both PDZ domains with PDZ domain-specific ligands, such as PTEN and β-catenin. An EB region composite structure comprising an α-helix ending in a PDZ-binding motif imparted opposite effects to NHERF1 associations, mediating binding to ERM proteins and inhibiting binding of PDZ domain ligands. The PDZ domain inhibition was released by prior association of ezrin with the EB region, a condition that occurs in vivo and likely disrupts NHERF1 head-to-tail interaction. In contrast, NHERF2 did not present a regulatory mechanism for protein complex formation. Functionally, NHERF1 is required to organize complexes at the apical membranes of polarized epithelial cells. The regulation of NHERF1 interactions at the apical membrane thus appears to be a dynamic process that is important for maintaining epithelial-tissue integrity.

scholarly journals PDZ interactions regulate rapid turnover of the scaffolding protein EBP50 in microvilli

2012 ◽  
Vol 198 (2) ◽  
pp. 195-203 ◽  
Author(s):  
Damien Garbett ◽  
Anthony Bretscher
Keyword(s):  
Cell Extract ◽  
Scaffolding Protein ◽  
Scaffolding Proteins ◽  
Pdz Domains ◽  
Kinase C ◽  
Zonula Occludens ◽  
Discs Large ◽  
Specific Proteins

Scaffolding proteins containing PDZ (postsynaptic density 95/discs large/zonula occludens-1) domains are believed to provide relatively stable linkages between components of macromolecular complexes and in some cases to bridge to the actin cytoskeleton. The microvillar scaffolding protein EBP50 (ERM-binding phosphoprotein of 50 kD), consisting of two PDZ domains and an ezrin-binding site, retains specific proteins in microvilli and is necessary for microvillar biogenesis. Our analysis of the dynamics of microvillar proteins in vivo indicated that ezrin and microvillar membrane proteins had dynamics consistent with actin treadmilling and microvillar lifetimes. However, EBP50 was highly dynamic, turning over within seconds. EBP50 turnover was reduced by mutations that inactivate its PDZ domains and was enhanced by protein kinase C phosphorylation. Using a novel in vitro photoactivation fluorescence assay, the EBP50–ezrin interaction was shown to have a slow off-rate that was dramatically enhanced in a PDZ-regulated manner by addition of cell extract to near in vivo levels. Thus, the linking of relatively stable microvillar components can be mediated by surprisingly dynamic EBP50, a finding that may have important ramifications for other scaffolding proteins.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

Epithelial Organotypic Cultures: A Viable Model to Address Mechanisms of Carcinogenesis by Epitheliotropic Viruses

2018 ◽  
Vol 18 (4) ◽  
pp. 246-255 ◽  
Author(s):  
Lara Termini ◽  
Enrique Boccardo
Keyword(s):  
Three Dimensional ◽  
Cell Types ◽  
Experimental Models ◽  
Biological Research ◽  
Specific Gene ◽  
Specific Cell ◽  
Organotypic Cultures ◽  
Skin Physiology

In vitro culture of primary or established cell lines is one of the leading techniques in many areas of basic biological research. The use of pure or highly enriched cultures of specific cell types obtained from different tissues and genetics backgrounds has greatly contributed to our current understanding of normal and pathological cellular processes. Cells in culture are easily propagated generating an almost endless source of material for experimentation. Besides, they can be manipulated to achieve gene silencing, gene overexpression and genome editing turning possible the dissection of specific gene functions and signaling pathways. However, monolayer and suspension cultures of cells do not reproduce the cell type diversity, cell-cell contacts, cell-matrix interactions and differentiation pathways typical of the three-dimensional environment of tissues and organs from where they were originated. Therefore, different experimental animal models have been developed and applied to address these and other complex issues in vivo. However, these systems are costly and time consuming. Most importantly the use of animals in scientific research poses moral and ethical concerns facing a steadily increasing opposition from different sectors of the society. Therefore, there is an urgent need for the development of alternative in vitro experimental models that accurately reproduce the events observed in vivo to reduce the use of animals. Organotypic cultures combine the flexibility of traditional culture systems with the possibility of culturing different cell types in a 3D environment that reproduces both the structure and the physiology of the parental organ. Here we present a summarized description of the use of epithelial organotypic for the study of skin physiology, human papillomavirus biology and associated tumorigenesis.

scholarly journals Stu2p binds tubulin and undergoes an open-to-closed conformational change

2006 ◽  
Vol 172 (7) ◽  
pp. 1009-1022 ◽  
Author(s):  
Jawdat Al-Bassam ◽  
Mark van Breugel ◽  
Stephen C. Harrison ◽  
Anthony Hyman
Keyword(s):  
Conformational Change ◽  
Conformational Transition ◽  
Budding Yeast ◽  
Microtubule Dynamics ◽  
Open Structure ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
The Common

Stu2p from budding yeast belongs to the conserved Dis1/XMAP215 family of microtubule-associated proteins (MAPs). The common feature of proteins in this family is the presence of HEAT repeat–containing TOG domains near the NH2 terminus. We have investigated the functions of the two TOG domains of Stu2p in vivo and in vitro. Our data suggest that Stu2p regulates microtubule dynamics through two separate activities. First, Stu2p binds to a single free tubulin heterodimer through its first TOG domain. A large conformational transition in homodimeric Stu2p from an open structure to a closed one accompanies the capture of a single free tubulin heterodimer. Second, Stu2p has the capacity to associate directly with microtubule ends, at least in part, through its second TOG domain. These two properties lead to the stabilization of microtubules in vivo, perhaps by the loading of tubulin dimers at microtubule ends. We suggest that this mechanism of microtubule regulation is a conserved feature of the Dis1/XMAP215 family of MAPs.

scholarly journals The Revolutionary Roads to Study Cell–Cell Interactions in 3D In Vitro Pancreatic Cancer Models

Cancers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 930
Author(s):  
Donatella Delle Cave ◽  
Riccardo Rizzo ◽  
Bruno Sainz ◽  
Giuseppe Gigli ◽  
Loretta L. del Mercato ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Therapeutic Response ◽  
Three Dimensional ◽  
Cellular Models ◽  
Common Cancer ◽  
Cancer Models ◽  
Anti Cancer ◽  
Tumor Environment

Pancreatic cancer, the fourth most common cancer worldwide, shows a highly unsuccessful therapeutic response. In the last 10 years, neither important advancements nor new therapeutic strategies have significantly impacted patient survival, highlighting the need to pursue new avenues for drug development discovery and design. Advanced cellular models, resembling as much as possible the original in vivo tumor environment, may be more successful in predicting the efficacy of future anti-cancer candidates in clinical trials. In this review, we discuss novel bioengineered platforms for anticancer drug discovery in pancreatic cancer, from traditional two-dimensional models to innovative three-dimensional ones.

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