Cellular Scaffolding Research Articles

Cellular scaffolding: Crowdsourcing cellular responses in health and disease

Cellular scaffolding: Crowdsourcing cellular responses in health and disease In this article, Dr Alan Herbert discusses how different types of cellular scaffolds interact and impact the risk of diseases, citing the example of Z-RNAs pushing cells to inflammatory states in tumors and autoimmune conditions, setting the stage for new therapeutics. The cell is full of so many proteins and RNA versions that it is a challenge to see how anything works at all. There is so much crowding it is like trying to get to your train through the mass of people on the station platform during rush hour. All the different biomolecules involved can be modified by the addition of phosphates, sugars, and lipids in so many different ways and at so many alternative sites that it seems impossible to track the one that matters. Yet, somehow, cells work in a highly efficient manner.

Programmable soft DNA hydrogels stimulate cellular endocytic pathways and proliferation

Hydrogels are pivotal in tissue engineering, regenerative medicine, and drug delivery applications. Existing hydrogel platforms are not easily customizable and often lack precise programmability, making them less suited for 3D tissue culture and programming of cells. DNA molecules stand out among other promising biomaterials due to their unparalleled precision, programmability, and customization. In this study, we introduced a palette of novel cellular scaffolding platforms made of pure DNA-based hydrogel systems while improving the shortcomings of the existing platforms. We showed a quick and easy one step synthesis of DNA hydrogels using thermal annealing based on sequence specific hybridization strategy. We also demonstrated the formation of multi-armed branched supramolecular scaffolds with custom mechanical stiffness, porosity, and network density by increasing or decreasing the number of branching arms. These mechanically tuneable DNA hydrogels proved to be a suitable suitable platform for modulating the physiological processes of retinal pigment epithelial cells (RPE1). In-vitro studies showed dynamic changes at multiple levels, ranging from a change in morphology to protein expression patterns, enhanced membrane traffic, and proliferation. The soft DNA hydrogels explored here are mechanically compliant and pliable, thus excellently suited for applications in cellular programming and reprogramming. This research lays the groundwork for developing a DNA hydrogel system with a higher dynamic range of stiffness, which will open exciting avenues for tissue engineering and beyond.

Peptide hydrogel based electrochemical biosensor for simultaneous monitoring ofH2O2 and NO released from three-dimensional cultured breast cancer cells.

Anantifouling peptide hydrogel-based electrochemical biosensor was developedfor real-time monitoring of hydrogen peroxide (H2O2) and nitric oxide (NO) released by 3D cultured breast cancer cells upon drug stimulation. Platinum nanoparticles (Pt NPs) were electrodeposited on titanium mesh (Pt NPs/TM) to enhance sensitivity and shown topossess excellent electrocatalytic ability toward H2O2 and NO. The composite hydrogel formed by co-assembling of N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) and a fluorine methoxycarbonyl group-functionalized Lys-(Fmoc)-Asp was coated on Pt NPs/TM electrode surface to provide cellular scaffolding. Their favorable biocompatibility promoted cell adhesion and growth, while good hydrophilicity endowed the sensor with greatly enhanced antifouling capability in complex cell culture environments. The biosensor successfully determined H2O2 and NO secretion from both non-metastatic and metastatic breast cancer cells in real time. Our results demonstrated robust associations between reactive oxygen species (ROS) and reactive nitrogen species (RNS) production and cell malignancy, with the main difference in oxidative stress between the two subtypes of cells being NO release, particularly emphasizing RNS's critical leading in driving cancer metastasis and invasion progression. This sensor holds great potential for cell-release research under the in vivo-like microenvironment and could reveal RNS as an attractive therapeutic target for treating breast cancer.

A rosette approach for the determination of the compliance matrix

The computation of the Young's moduli and Poisson's ratio using finite element analysis is comparatively straight forward in the case of systems with non-orthogonal lattice vectors. However, the corresponding calculation of the shear coupling coefficients and the shear modulus is more demanding and less readily attainable. Yet these are needed in order to determine the compliance matrix, which is essential in order to obtain a complete description of the mechanical properties of a structure in any direction. Based on these considerations, this work aims at providing a general methodology for the computation of the complete compliance matrix for systems with non-orthogonal lattice vectors from measurements of the Young's modulus and Poisson's ratio obtained using a suitable rosette of unit cells. The theoretical framework will be outlined and then applied on an accordion-like honeycomb that does not possess a rectangular unit cell and has potential applications in cellular scaffolding, particularly of heart muscle tissue. For the computation, the values of the Young's moduli and Poisson's ratio from three differently-orientated non-rectangular unit cells were obtained using finite element simulations allowing the determination of the complete compliance matrix. The results were validated by comparison with numerical simulations carried out on another unit cell having a different orientation from the other three.

The magic of MAGI-1: A scaffolding protein with multi signalosomes and functional plasticity.

MAGI-1 is a critical cellular scaffolding protein with over 110 different cellular and microbial protein interactors. Since the discovery of MAGI-1 in 1997, MAGI-1 has been implicated in diverse cellular functions such as polarity, cell-cell communication, neurological processes, kidney function, and a host of diseases including cancer and microbial infection. Additionally, MAGI-1 has undergone nomenclature changes in response to the discovery of an additional PDZ domain, leading to lack of continuity in the literature. We address the nomenclature of MAGI-1 as well as summarize many of the critical functions of the known interactions. Given the importance of many of the interactors, such as human papillomavirus E6, the Coxsackievirus and adenovirus receptor (CAR), and PTEN, the enhancement or disruption of MAGI-based interactions has the potential to affect cellular functions that can potentially be harnessed as a therapeutic strategy for a variety of diseases.

Preliminary Results of a Reverse Thermal Gel Patch for Fetal Ovine Myelomeningocele Repair

BackgroundPrenatal surgical closure of Myelomeningocele (MMC) is considered part of the current age armamentarium. Clinical data has demonstrated the need for innovative patches to maximize the benefits and decrease the risks of this approach. Our team has developed a minimally invasive reverse thermal gel (RTG) patch with cellular scaffolding properties. Here, we demonstrate the initial gross and microscopic histological effects of this RTG patch in the fetal ovine model of MMC. Materials and MethodsA fetal ovine MMC defect was created at 68-75 days gestation, RTG patch application or untreated at 100-103 days, and harvest at 135-140 days. The RTG was applied to the defect and secured in place with an overlay sealant. Defect areas underwent gross and microscopic analysis for inflammation and skin development. Brains were analyzed for hindbrain herniation and hydrocephalus. ResultsThe untreated fetus (n = 1) demonstrated an open defect lacking tissue coverage, evidence of spinal cord injury, increased caspase-3, Iba1 and GFAP in spinal cord tissues, and hindbrain herniation and ventricular dilation. RTG treated fetuses (n = 3) demonstrated defect healing with well-organized dermal and epidermal layers throughout the entire healed tissue area overlaying the defect with minimal inflammation, reduced caspase-3, Iba1 and GFAP in spinal cord tissues, and no hindbrain herniation or ventricular dilation. ConclusionAn RTG patch applied to MMC defects in fetal sheep promoted skin coverage over the defect, was associated with minimal inflammation of the spinal cord tissues and prevented brain abnormalities. The present findings provide exciting results for future comprehensive radiological, functional, and mechanistic evaluation of the RTG.

Multifunctional Fructose 1,6-Bisphosphate Aldolase as a Therapeutic Target.

Fructose 1,6-bisphosphate aldolase is a ubiquitous cytosolic enzyme that catalyzes the fourth step of glycolysis. Aldolases are classified into three groups: Class-I, Class-IA, and Class-II; all classes share similar structural features but low amino acid identity. Apart from their conserved role in carbohydrate metabolism, aldolases have been reported to perform numerous non-enzymatic functions. Here we review the myriad “moonlighting” functions of this classical enzyme, many of which are centered on its ability to bind to an array of partner proteins that impact cellular scaffolding, signaling, transcription, and motility. In addition to the cytosolic location, aldolase has been found the extracellular surface of several pathogenic bacteria, fungi, protozoans, and metazoans. In the extracellular space, the enzyme has been reported to perform virulence-enhancing moonlighting functions e.g., plasminogen binding, host cell adhesion, and immunomodulation. Aldolase’s importance has made it both a drug target and vaccine candidate. In this review, we note the several inhibitors that have been synthesized with high specificity for the aldolases of pathogens and cancer cells and have been shown to inhibit classical enzyme activity and moonlighting functions. We also review the many trials in which recombinant aldolases have been used as vaccine targets against a wide variety of pathogenic organisms including bacteria, fungi, and metazoan parasites. Most of such trials generated significant protection from challenge infection, correlated with antigen-specific cellular and humoral immune responses. We argue that refinement of aldolase antigen preparations and expansion of immunization trials should be encouraged to promote the advancement of promising, protective aldolase vaccines.

Heterozygous variants in SPTBN1 cause intellectual disability and autism.

Spectrins are common components of cytoskeletons, binding to cytoskeletal elements and the plasma membrane, allowing proper localization of essential membrane proteins, signal transduction, and cellular scaffolding. Spectrins are assembled from α and β subunits, encoded by SPTA1 and SPTAN1 (α) and SPTB, SPTBN1, SPTBN2, SPTBN4, and SPTBN5 (β). Pathogenic variants in various spectrin genes are associated with erythroid cell disorders (SPTA1, SPTB) and neurologic disorders (SPTAN1, SPTBN2, and SPTBN4), but no phenotypes have been definitively associated with variants in SPTBN1 or SPTBN5. Through exome sequencing and case matching, we identified seven unrelated individuals with heterozygous SPTBN1 variants: two with de novo missense variants and five with predicted loss-of-function variants (found to be de novo in two, while one was inherited from a mother with a history of learning disabilities). Common features include global developmental delays, intellectual disability, and behavioral disturbances. Autistic features (4/6) and epilepsy (2/7) or abnormal electroencephalogram without overt seizures (1/7) were present in a subset. Identification of loss-of-function variants suggests a haploinsufficiency mechanism, but additional functional studies are required to fully elucidate disease pathogenesis. Our findings support the essential roles of SPTBN1 in human neurodevelopment and expand the knowledge of human spectrinopathy disorders.

Chemically‐Induced Cross‐Linking of Peptidic Fibrils for Scaffolding Polymeric Particles and Macrophages

EAK16-II (EAK) is a self-assembling peptide (SAP) that forms β-sheets and β-fibrils through ionic-complementary interactions at physiological ionic strengths. The soft materials can be injected in vivo, creating depots of drugs and cells for rendering pharmacological and biological actions. The scope of the applications of EAK is sought to extend to tissues through which the flow of extracellular fluid tends to be limited. In such anatomical locales the rate and extent of the fibrilization are limited insofar as drug delivery and cellular scaffolding would be impeded. A method is generated utilizing a carbodiimide cross-linker by which EAK fibrils are pre-assembled yet remain injectable soft materials. It is hypothesized that the resulting de novo covalent linkages enhance the stacking of the β-sheet bilayers, thereby increasing the lengths of the fibrils and the extent of their cross-linking, as evidenced in Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, scanning electron microscopy, and atomic force microscopy analyses. The cross-linked EAK (clEAK) retains polymeric microspheres with an average diameter of 1µm. Macrophages admixed with clEAK remain viable and do not produce the inflammatory mediator interleukin-1β. These results indicate that clEAK should be investigated further as a platform for delivering particles and cells in vivo.

Improved Coverage of Mouse Myelomeningocele With a Mussel Inspired Reverse Thermal Gel

BackgroundMyelomeningocele (MMC) is an open neural tube defect of the spinal column. Our laboratory previously introduced a reverse thermal gel (RTG) as the first in situ forming patch for in utero MMC application. To overcome the challenges of anchoring the RTG in the wet amniotic environment to improve MMC coverage, we modified the RTG to mimic the underwater adhesive properties of mussels. We have separated this study into three separate hypotheses-based components:1Based on mussel inspired chemistry, modification of the RTG with dopamine will increase the underwater adhesive properties to improve RTG anchoring ability in a wet environment. Methods: The dopamine-modified RTG (DRTG) was synthesized using carbonyldiimidazole chemistry and characterized with proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. Rheology and underwater adhesive tests measured mechanical properties. Results: DRTG synthesis was confirmed with proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy. Rheology demonstrated increased elasticity. Underwater adhesion testing revealed DRTG has similar wet adhesive strength to Tisseel fibrin sealant.2The DRTG will support in vitro skin cell growth and will be safe for injection in a mouse animal model. Methods: Biocompatibility testing included 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, DRTG-fibroblast and keratinocyte cultures, and subcutaneous injections to quantify macrophages stained with immunohistochemistry. Results: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and DRTG cell cultures revealed no cytotoxicity and demonstrated the growth of fibroblasts and keratinocytes. Subcutaneous injections cause a macrophage response that decreases after 4 wk.3In utero injection of novel DRTG into a mouse MMC model will be effective with improved patch coverage of the MMC defect. Methods: MMC coverage by DRTG was assessed using in utero mouse injections in the Grainy head-like 3 (Grhl3) mouse model. Results: In utero Grhl3 mouse injections demonstrate statistically significant (P = 0.012) improved MMC coverage of DRTG compared with previous RTG coverage with no significant macrophage response. ConclusionsThe DRTG demonstrates increased elasticity, cellular scaffolding properties, and improved MMC coverage in the Grhl3 mouse model. Future studies will be translated to the preclinical ovine model to evaluate this novel gel.

Long non-coding RNA TIRY promotes tumor metastasis by enhancing epithelial-to-mesenchymal transition in oral cancer.

Long non-coding RNAs (lncRNAs) modulate a variety of cancerous biological processes, including the promotion of tumorigenicity in tumor parenchymal cells. However, there is a lack of studies assessing the regulation of lncRNAs in cancer-associated fibroblasts. In the present study, a novel lncRNA, TIRY, was found to act as a miRNA sponge and to downregulate miR-14 expression in oral squamous cell carcinoma (OSCC). Fluorescence in situ hybridization assay was used to evaluate TIRY expression in OSCC tissues. Survival analysis in a prospective cohort revealed a correlation between high TIRY expression and short progression-free survival. Subsequently, TIRY expression in cancer-associated fibroblasts and primary fibroblasts from adjacent normal (para-carcinoma) tissues was assessed using quantitative reverse transcription polymerase chain reaction. TIRY overexpression in cancer-associated fibroblasts isolated from OSCC tissues was induced by overexpressing the TIRY plasmid, and candidate microRNA expressions were assessed using quantitative real-time polymerase chain reaction. Moreover, the expression of proteins related to epithelial-to-mesenchymal transition (EMT) was determined; the proliferation, metastasis, and invasion of cancer cells co-cultured with TIRY-overexpressing cancer-associated fibroblasts were determined. We found significantly decreased miR-14 expression in cancer-associated fibroblast-derived exosomes and increased expression of EMT markers including transcription factors (Snail and FOXC2) and cellular scaffolding proteins (α-SMA, β-catenin, and FSP1). TIRY overexpression in cancer-associated fibroblasts activated the Wnt/β-catenin signaling pathway and promoted the invasion and metastasis of OSCC cells through miR-14 sponging based on cancer-associated exosome secretion. Our findings provide a novel molecular mechanism underlying the role of TIRY in cancer-associated fibroblasts in tumor biology; moreover, TIRY is a potential therapeutic target in OSCC. Impact statement This study demonstrated the novel lncRNA, TIRY, enhances epithelial-to-mesenchymal transition in cancer-associated fibroblasts and promotes the metastasis of tumor via miR-14 sponging in oral squamous cell carcinoma, and thus provide a novel molecular mechanism underlying the role of TIRY in CAFs in tumor biology and a potential target in OSCC. Further, the data showed that TIRY expression was negatively correlated with miR-14 transcription levels and was associated with poor prognosis in OSCC specimens. Therefore, TIRY may be a potential prognostic biomarker of overall survival and progression-free survival in OSCC. Moreover, TIRY adds to the understanding of regulatory mechanisms involved in CAFs and epithelial cancer cells in OSCC and may provide novel insights for further understanding tumor biology.

The Nature of Actin-Family Proteins in Chromatin-Modifying Complexes.

Actin is not only one of the most abundant proteins in eukaryotic cells, but also one of the most versatile. In addition to its familiar involvement in enabling contraction and establishing cellular motility and scaffolding in the cytosol, actin has well-documented roles in a variety of processes within the confines of the nucleus, such as transcriptional regulation and DNA repair. Interestingly, monomeric actin as well as actin-related proteins (Arps) are found as stoichiometric subunits of a variety of chromatin remodeling complexes and histone acetyltransferases, raising the question of precisely what roles they serve in these contexts. Actin and Arps are present in unique combinations in chromatin modifiers, helping to establish structural integrity of the complex and enabling a wide range of functions, such as recruiting the complex to nucleosomes to facilitate chromatin remodeling and promoting ATPase activity of the catalytic subunit. Actin and Arps are also thought to help modulate chromatin dynamics and maintain higher-order chromatin structure. Moreover, the presence of actin and Arps in several chromatin modifiers is necessary for promoting genomic integrity and an effective DNA damage response. In this review, we discuss the involvement of actin and Arps in these nuclear complexes that control chromatin remodeling and histone modifications, while also considering avenues for future study to further shed light on their functional importance.

Pro-angiogenic near infrared-responsive hydrogels for deliberate transgene expression

CuS nanoparticles (CuSNP) are degradable, readily prepared, inexpensive to produce and efficiently cleared from the body. In this work, we explored the feasibility of CuSNP to function as degradable near infrared (NIR) nanotransducers within fibrin-based cellular scaffolds. To prepare NIR-responsive CuSNP hydrogels, fibrinogen was dissolved in cell culture medium and supplemented with aqueous dispersions of CuSNP. Fibrinogen polymerization was catalyzed by the addition of thrombin. In some experiments, HUVEC, C3H/10T1/2 or C3H/10T1/2-fLuc cells, that harbor a heat-activated and rapamycin-dependent gene switch for regulating the expression of firefly luciferase transgene, were incorporated to the sol phase of the hydrogel. For in vivo experiments, hydrogels were injected subcutaneously in the back of adult C3H/HeN mice. Upon NIR irradiation, CuSNP hydrogels allowed heat-inducible and rapamycin-dependent transgene expression in cells contained therein, in vitro and in vivo. C3H/10T1/2 cells cultured in CuSNP hydrogels increased metabolic activity, survival rate and fibrinolytic activity, which correlated with changes at the transcriptome level. Media conditioned by CuSNP hydrogels increased viability of HUVEC which formed pseudocapillary structures and remodeled protein matrix when entrapped within these hydrogels. After long-term implantation, the skin patches that covered the CuSNP hydrogels showed increased capillary density which was not detected in mice implanted with matrices lacking CuSNP. In summary, NIR-responsive scaffolds harboring CuSNP offer compelling features in the tissue engineering field, as degradable implants with enhanced integration capacity in host tissues that can provide remote controlled deployment of therapeutic gene products. Statement of SignificanceHydrogels composed of fibrin embedding copper sulfide nanoparticles (CuSNP) efficiently convert incident near infrared (NIR) energy into heat and can function as cellular scaffolding. NIR laser irradiation of CuSNP hydrogels can be employed to remotely induce spatiotemporal patterns of transgene expression in genetically engineered multipotent stem cells. CuSNP incorporation in hydrogel architecture accelerates the cell-mediated degradation of the fibrin matrix and induces pro-angiogenic responses that may facilitate the integration of these NIR-responsive scaffolds in host tissues. CuSNP hydrogels that harbor cells capable of controlled expression of therapeutic gene products may be well suited for tissue engineering as they are biodegradable, enhance implant vascularization and can be used to deploy growth factors in a desired spatiotemporal fashion.

Engineering new cellular scaffolding

Most cells have a network of protein filaments that help give the cells shape and organize their contents, among other important functions. These cytoskeletons vary in size and complexity: The scaffolds in bacteria are not as extensive as the ones found in cells from higher organisms. Researchers have now engineered bacteria with a more extensive scaffold that extends throughout the cells. The scientists used the scaffold to bring proteins closer together to increase the output of a synthetic enzyme cascade. Such an approach could aid the development of bacteria engineered for biomanufacturing of chemicals and materials. The team, led by Martin J. Warren of the University of Kent and Derek N. Woolfson and Paul Verkade at the University of Bristol, engineered Escherichia coli to produce scaffolds made of a bacterial protein linked to designer coiled-coil peptides (Nat. Chem. Biol. 2017, DOI: 10.1038/nchembio.2535). The protein, PduA, naturally forms hexamers that assemble

176. Novel Molecules That Enhance Adenovirus Transduction of the Airway Epithelium: Reinvigorating Adenovirus-Mediated Gene Therapy

Adenovirus remains the most common vector system used in gene therapy clinical trials worldwide and several adenoviral vectors show promise in phase III clinical trials. One major limitation to the efficacy of adenovirus-mediated gene therapy is low transduction due to the limited primary receptor availability in most tissues. Interventions able to boost adenovirus transduction would have significant implications for both improving transduction and lowering the viral dose below the immunogenic threshold. Most human and several key animal adenoviruses share a common receptor with group B coxsackieviruses named the coxsackievirus and adenovirus receptor (CAR). CAR has several alternatively spliced isoforms. We have recently discovered that the eight-exon isoform (CAREx8) can specifically localize to the apical membrane of polarized primary human airway epithelia where it can mediate apical adenovirus infection. Moreover, we have discovered that CAREx8 is both positively and negatively regulated by the cellular scaffolding protein MAGI-1. We hypothesized that cell permeable decoy peptides targeting the interaction between MAGI-1 and CAREx8 would increase CAREx8 protein levels and increase AdV transduction. Tat-conjugated peptide entry into polarized epithelia was confirmed by mass spectrometry and fluorescence microscopy. Relative to control, peptides increased the levels of CAREx8 at the apical surface of polarized epithelia and significantly increased AdV entry and transduction, as measured by apical surface biotinylation, qPCR, and AdV5-β-Gal transduction. Moreover, AdV5 transduction was increased by 300-500% after intranasal peptide administration in mice demonstrating in vivo activity. To determine the mechanism of action, we followed the synthesis and co-localization of CAREx8 with key molecules in the cellular ER-Golgi-vesicular trafficking pathways. We found that CAREx8 was in compartments distinct from MAGI-1 and spread throughout the apical trafficking pathway and at the apical surface of the epithelium. Removal of the peptides reversed both the amount and localization of CAREx8 and returned the susceptibility of the epithelium to baseline. Taken together, these data indicate that decoy peptides able to block the MAGI-1-CAREx8 interaction transiently increase adenovirus-mediated gene transfer and offer the potential to increase the efficacy of adenovirus-mediated gene therapy.

Ligand binding to the PDZ domains of postsynaptic density protein 95.

Cellular scaffolding and signalling is generally governed by multidomain proteins, where each domain has a particular function. Postsynaptic density protein 95 (PSD-95) is involved in synapse formation and is a typical example of such a multidomain protein. Protein-protein interactions of PSD-95 are well studied and include the following three protein ligands: (i)N-methyl-d-aspartate-type ionotropic glutamate receptor subunit GluN2B, (ii) neuronal nitric oxide synthase and (iii) cysteine-rich protein (CRIPT), all of which bind to one or more of the three PDZ domains in PSD-95. While interactions for individual PDZ domains of PSD-95 have been well studied, less is known about the influence of neighbouring domains on the function of the respective individual domain. We therefore performed a systematic study on the ligand-binding kinetics of PSD-95 using constructs of different size for PSD-95 and its ligands. Regarding the canonical peptide-binding pocket and relatively short peptides (up to 15-mer), the PDZ domains in PSD-95 by and large work as individual binding modules. However, in agreement with previous studies, residues outside of the canonical binding pocket modulate the affinity of the ligands. In particular, the dissociation of the 101 amino acid CRIPT from PSD-95 is slowed down at least 10-fold for full-length PSD-95 when compared with the individual PDZ3 domain.

The PDZ3 domain of the cellular scaffolding protein MAGI-1 interacts with the Coxsackievirus and adenovirus receptor (CAR)

The Coxsackievirus and adenovirus receptor (CAR) is an essential cellular protein that is involved in cell–cell adhesion, protein trafficking, and viral infection. The major isoform of CAR is selectively sorted to the basolateral membrane of polarized epithelial cells where it co-localizes with the cellular scaffolding protein membrane-associated guanylate kinase with inverted domain structure-1 (MAGI-1). Previously, we demonstrated CAR interacts with MAGI-1 through a PDZ–domain dependent interaction. Here, we show that the PDZ3 domain of MAGI-1 is exclusively responsible for the high affinity interaction between the seven exon isoform of CAR and MAGI-1 using yeast-two-hybrid analysis and confirming this interaction biochemically and in cellular lysates by in vitro pull down assay and co-immunoprecipitation. The high affinity interaction between the PDZ3 domain and CAR C-terminus was measured by fluorescence resonance energy transfer. Further, we investigated the biological relevance of this high affinity interaction between CAR and the PDZ3 domain of MAGI-1 and found that it does not alter CAR-mediated adenovirus infection. By contrast, interruption of this high affinity interaction altered the localization of MAGI-1 indicating that CAR is able to traffic MAGI-1 to cell junctions. These data deepen the molecular understanding of the interaction between CAR and MAGI-1 and indicate that although CAR plays a role in trafficking PDZ-based scaffolding proteins to cellular junctions, association with a high affinity intracellular binding partner does not significantly alter adenovirus binding and entry via CAR.

Targeted disruption of β-arrestin 2-mediated signaling pathways by aptamer chimeras leads to inhibition of leukemic cell growth.

β-arrestins, ubiquitous cellular scaffolding proteins that act as signaling mediators of numerous critical cellular pathways, are attractive therapeutic targets because they promote tumorigenesis in several tumor models. However, targeting scaffolding proteins with traditional small molecule drugs has been challenging. Inhibition of β-arrestin 2 with a novel aptamer impedes multiple oncogenic signaling pathways simultaneously. Additionally, delivery of the β-arrestin 2-targeting aptamer into leukemia cells through coupling to a recently described cancer cell-specific delivery aptamer, inhibits multiple β-arrestin-mediated signaling pathways known to be required for chronic myelogenous leukemia (CML) disease progression, and impairs tumorigenic growth in CML patient samples. The ability to target scaffolding proteins such as β-arrestin 2 with RNA aptamers may prove beneficial as a therapeutic strategy.HighlightsAn RNA aptamer inhibits β-arrestin 2 activity.Inhibiting β-arrestin 2 impedes multiple tumorigenic pathways simultaneously.The therapeutic aptamer is delivered to cancer cells using a cell-specific DNA aptamer.Targeting β-arrestin 2 inhibits tumor progression in CML models and patient samples.

A new era

To describe basic principles of tissue engineering with emphasis on the potential role of gastrointestinal endoscopy in regenerative medicine. Stricturing associated with endoscopic submucosal resection and circumferential endoscopic mucosal resection can be prevented through transplantation of autologous epidermal cell sheets or seeded decellularized biological scaffolds. Lower esophageal sphincter augmentation through injection of muscle-derived cells is a novel potential treatment for gastroesophageal reflux disease. Stem cell derived tissue has been used to repair injured colon in a mouse model of colitis. A bioengineered internal anal sphincter has been successfully implanted in mice and showed preserved functionality. The immediate foreseeable application of tissue engineering in gastrointestinal endoscopy is in the field of mucosal repair after acute injury. Tissue regeneration can be achieved through expansion of autologous somatic cells or by induction of multipotent or pluripotent stem cells. Advances in cellular scaffolding have made bioengineering of complex tissues a reality. Tissue engineering in endoscopy is also being pioneered by studies looking at enteral sphincter augmentation and regeneration. The availability of engineered tissue for endoscopic application will increase with advances in cell-culturing techniques.

The Coxsackievirus and adenovirus receptor interacts with PDZ3 of the cellular scaffolding protein MAGI‐1

The Coxsackievirus and Adenovirus receptor (CAR) is an essential protein that is involved in cell‐cell adhesion, protein trafficking, and viral infection. The major isoform of CAR is selectively sorted to the basolateral membrane of polarized epithelial cells where it co‐localizes with the cellular scaffolding protein membrane‐associated guanylate kinase with inverted domain structure‐1 (MAGI‐1). We hypothesized that CAR directly interacts with MAGI‐1 via a PDZ‐based interaction and these two proteins interact in polarized epithelial cells. Each MAGI‐1 PDZ domain and the C‐terminus of CAR were subcloned into expression vectors and direct interactions were investigated by yeast‐2‐hybrid (Y2H) analysis and fluorescence resonance energy transfer (FRET). Interaction was investigated in polarized Madin‐Darby canine kidney (MDCK) epithelial cells. Y2H showed that CAR interacts with the third PDZ domain of MAGI‐1 (PDZ3) and FRET showed a Kd of 2.0 ± 0.9 nM. MAGI‐1 and CAR co‐immunoprecipate from polarized MDCK cells. These results show that CAR and MAGI‐1 interacts directly and this interaction occurs in polarized cells. Future work will investigate potential therapeutic interventions that may disrupt or enhance CAR‐MAGI‐1 interactions and alter epithelial susceptibility viral infection.This work was supported by NIH grants R15AI090625 (KE), DK77573 (HH) and R25 GM086257.