Inhibition of RhoA by p120 catenin

Double-sided niche regulation in skin stem cell and cancer: mechanisms and clinical applications

The niche microenvironment plays a crucial role in regulating the fate of normal skin stem cells (SSCs) and cancer stem cells (CSCs). Therapeutically targeting the CSC niche holds promise as an effective strategy; however, the dual effects of shared SSC niche signaling in CSCs have contributed to the aggressive characteristics of tumors and poor survival rates in skin cancer patients. The lack of a clear underlying mechanism has significantly hindered drug development for effective treatment. This article explores recent advances in understanding how niche factors regulate cell fate determination between skin stem cells and skin CSCs, along with their clinical implications. The dual roles of key components of the adhesive niche, including the dermo-epidermal junction and adherens junction, various cell types-especially immune cells and fibroblasts-as well as major signaling pathways such as Sonic hedgehog (Shh), Wingless-related integration site (Wnt)/β-catenin, YAP (Yes-associated protein)/TAZ (transcriptional coactivator with PDZ-binding motif), and Notch, are highlighted. Additionally, recent advances in clinical trials and drug development targeting these pathways are discussed. Overall, this review provides valuable insights into the complex interactions between skin cancer stem cells and their microenvironment, laying the groundwork for future research and clinical strategies.

Cadherin dynamics and cortical tension in remodeling cell-cell adhesion during EMT

Epithelial-to-mesenchymal transition (EMT), a key process in cancer metastasis and fibrosis, disrupts cellular adhesion by replacing epithelial E-cadherin with mesenchymal N-cadherin. While, how the shift from E-cadherin to N-cadherin impacts molecular-scale adhesion mechanics and cluster dynamics-and how these changes weaken adhesion under varying mechanical and environmental conditions-remains poorly understood, limiting our ability to target EMT-driven pathological adhesion dynamics. Here, we developed a unified lattice-clutch model to investigate cadherin clustering, cortical tension, and adhesion strength during EMT. Using atomic force microscopy experiments, we measured the mechanical properties of single cadherin trans-bonds and cadherin-mediated cell-cell and cell-matrix adhesions across varying conditions. Our results demonstrate that N-cadherin trans-bonds are mechanically weaker than E-cadherin trans-bonds, leading to reduced adhesion strength during EMT. Computational modeling and experimental validation further revealed that EMT impairs cadherin clustering and cortical tension regulation, which collectively weaken both cell-cell and cell-matrix adhesions, particularly on stiff substrates. These findings highlight how EMT disrupts adhesion strength at multiple scales-from individual cadherin bonds to collective cluster dynamics. Our study elucidates how EMT-driven changes in cadherin type weaken adhesion strength and mechanotransduction, providing insights into cellular adhesion mechanics and potential therapeutic strategies for targeting EMT-associated diseases such as cancer metastasis and tissue remodeling.

Collective mechanics of small migrating cell groups

Migration of adhesive cell groups is a fundamental part of wound healing, development and carcinogenesis. Intense research has been conducted on mechanisms of collective migration of adhesive groups of cells. Here we focus on mechanical and mechanistic lessons from small migrating cell groups. We review forces and locomotory dynamics of two- and three-cell clusters, rotation of cell doublets, self-organization of one-dimensional cell trains, nascent efforts to understand three-dimensional collective migration and border cell clusters in Drosophila embryo.

Model supports asymmetric regulation across the intercellular junction for collective cell polarization

Symmetry breaking, which is ubiquitous in biological cells, functionally enables directed cell movement and organized embryogenesis. Prior to movement, cells break symmetry to form a well-defined cell front and rear in a process called polarization. In developing and regenerating tissues, collective cell movement requires the coordination of the polarity of the migration machineries of neighboring cells. Though several works shed light on the molecular basis of polarity, fewer studies have focused on the regulation across the cell-cell junction required for collective polarization, thus limiting our ability to connect tissue-level dynamics to subcellular interactions. Here, we investigated how polarity signals are communicated from one cell to its neighbor to ensure coordinated front-to-rear symmetry breaking with the same orientation across the group. In a theoretical setting, we systematically searched a variety of intercellular interactions and identified that co-alignment arrangement of the polarity axes in groups of two and four cells can only be achieved with strong asymmetric regulation of Rho GTPases or enhanced assembly of complementary F-actin structures across the junction. Our results held if we further assumed the presence of an external stimulus, intrinsic cell-to-cell variability, or larger groups. The results underline the potential of using quantitative models to probe the molecular interactions required for macroscopic biological phenomena. Lastly, we posit that asymmetric regulation is achieved through junction proteins and predict that in the absence of cytoplasmic tails of such linker proteins, the likeliness of doublet co-polarity is greatly diminished.

Plakophilin 4 controls the spatio-temporal activity of RhoA at adherens junctions to promote cortical actin ring formation and tissue tension

Plakophilin 4 (PKP4) is a component of cell-cell junctions that regulates intercellular adhesion and Rho-signaling during cytokinesis with an unknown function during epidermal differentiation. Here we show that keratinocytes lacking PKP4 fail to develop a cortical actin ring, preventing adherens junction maturation and generation of tissue tension. Instead, PKP4-depleted cells display increased stress fibers. PKP4-dependent RhoA localization at AJs was required to activate a RhoA-ROCK2-MLCK-MLC2 axis and organize actin into a cortical ring. AJ-associated PKP4 provided a scaffold for the Rho activator ARHGEF2 and the RhoA effectors MLCK and MLC2, facilitating the spatio-temporal activation of RhoA signaling at cell junctions to allow cortical ring formation and actomyosin contraction. In contrast, association of PKP4 with the Rho suppressor ARHGAP23 reduced ARHGAP23 binding to RhoA which prevented RhoA activation in the cytoplasm and stress fiber formation. These data identify PKP4 as an AJ component that transduces mechanical signals into cytoskeletal organization.

A novel strategy to facilitate uniform epithelial cell maturation using liquid-liquid interfaces

Epithelial tissue forms and maintains a critical barrier function in the body. A novel culture design aimed at promoting uniform maturation of epithelial cells using liquid materials is described. Culturing Madin-Darby canine kidney (MDCK) cells at the liquid-liquid interface yielded reduced migration and stimulated active cell growth. Similar to solid-liquid interfaces, cells cultured on a fibronectin-coated liquid-liquid interface exhibited active migration and growth, ultimately reaching a confluent state. These cells exhibited reduced stress fiber formation and adopted a cobblestone-like shape, which led to their even distribution in the culture vessel. To inhibit stress fiber formation and apoptosis, the exposure of cells on liquid-liquid interfaces to Y27632, a specific inhibitor of the Rho-associated protein kinase (ROCK), facilitated tight junction formation (frequency of ZO-2-positive cells, FZ = 0.73). In Y27632-exposed cells on the liquid-liquid interface, the value obtained by subtracting the standard deviation of the ratio of nucleus densities in each region that compartmentalized a culture vessel from 1, denoted as HLN, was 0.93 ± 0.01, indicated even cell distribution in the culture vessel at t = 72 h. The behavior of epithelial cells on liquid-liquid interfaces contributes to the promotion of their uniform maturation.

N-Cadherin Targeted Melanin Nanoparticles Reverse the Endothelial-Mesenchymal Transition in Vascular Endothelial Cells to Potentially Slow the Progression of Atherosclerosis and Cancer

Endothelial-mesenchymal transition (EndoMT) of vascular endothelial cells has recently been considered as a key player in the early progression of a variety of vascular and nonvascular diseases, including atherosclerosis, cancer, and organ fibrosis. However, current strategies attempting to identify pharmacological inhibitors to block the regulatory pathways of EndoMT suffer from poor selectivity, unwanted side effects, and a heterogeneous response from endothelial cells with different origins. Furthermore, EndoMT inhibitors focus on preventing EndoMT, leaving the endothelial cells that have already undergone EndoMT unresolved. Here, we report the design of a simple but powerful nanoparticle system (i.e., N-cadherin targeted melanin nanoparticles) to convert cytokine-activated, mesenchymal-like endothelial cells back to their original endothelial phenotype. We term this process "Reversed EndoMT" (R-EndoMT). R-EndoMT allows the impaired endothelial barriers to recover their quiescence and intactness, with significantly reduced leukocyte and cancer cell adhesion and transmigration, which could potentially stop atheromatous plaque formation and cancer metastasis in the early stages. R-EndoMT is achieved on different endothelial cell types originating from arteries, veins, and capillaries, independent of activating cytokines. We reveal that N-cadherin targeted melanin nanoparticles reverse EndoMT by downregulating an N-cadherin dependent RhoA activation pathway. Overall, this approach offers a different prospect to treat multiple EndoMT-associated diseases by designing nanoparticles to reverse the phenotypical transition of endothelial cells.

Genome-wide meta-analysis, functional genomics and integrative analyses implicate new risk genes and therapeutic targets for anxiety disorders

Anxiety disorders are the most prevalent mental disorders. However, the genetic etiology of anxiety disorders remains largely unknown. Here we conducted a genome-wide meta-analysis on anxiety disorders by including 74,973 (28,392 proxy) cases and 400,243 (146,771 proxy) controls. We identified 14 risk loci, including 10 new associations near CNTNAP5, MAP2, RAB9BP1, BTN1A1, PRR16, PCLO, PTPRD, FARP1, CDH2 and RAB27B. Functional genomics and fine-mapping pinpointed the potential causal variants, and expression quantitative trait loci analysis revealed the potential target genes regulated by the risk variants. Integrative analyses, including transcriptome-wide association study, proteome-wide association study and colocalization analyses, prioritized potential causal genes (including CTNND1 and RAB27B). Evidence from multiple analyses revealed possibly causal genes, including RAB27B, BTN3A2, PCLO and CTNND1. Finally, we showed that Ctnnd1 knockdown affected dendritic spine density and resulted in anxiety-like behaviours in mice, revealing the potential role of CTNND1 in anxiety disorders. Our study identified new risk loci, potential causal variants and genes for anxiety disorders, providing insights into the genetic architecture of anxiety disorders and potential therapeutic targets.

Adhesion-induced cortical flows pattern E-cadherin-mediated cell contacts

Metazoan development relies on the formation and remodeling of cell-cell contacts. Dynamic reorganization of adhesion receptors and the actomyosin cell cortex in space and time plays a central role in cell-cell contact formation and maturation. Nevertheless, how this process is mechanistically achieved when new contacts are formed remains unclear. Here, by building a biomimetic assay composed of progenitor cells adhering to supported lipid bilayers functionalized with E-cadherin ectodomains, we show that cortical F-actin flows, driven by the depletion of myosin-2 at the cell contact center, mediate the dynamic reorganization of adhesion receptors and cell cortex at the contact. E-cadherin-dependent downregulation of the small GTPase RhoA at the forming contact leads to both a depletion of myosin-2 and a decrease of F-actin at the contact center. At the contact rim, in contrast, myosin-2 becomes enriched by the retraction of bleb-like protrusions, resulting in a cortical tension gradient from the contact rim to its center. This tension gradient, in turn, triggers centrifugal F-actin flows, leading to further accumulation of F-actin at the contact rim and the progressive redistribution of E-cadherin from the contact center to the rim. Eventually, this combination of actomyosin downregulation and flows at the contact determines the characteristic molecular organization, with E-cadherin and F-actin accumulating at the contact rim, where they are needed to mechanically link the contractile cortices of the adhering cells.

Extracellular Matrix Protein-1 as a Mediator of Inflammation-Induced Fibrosis After Myocardial Infarction

Irreversible fibrosis is a hallmark of myocardial infarction (MI) and heart failure. Extracellular matrix protein-1 (ECM-1) is up-regulated in these hearts, localized to fibrotic, inflammatory, and perivascular areas. ECM-1 originates predominantly from fibroblasts, macrophages, and pericytes/vascular cells in uninjured human and mouse hearts, and from M1 and M2 macrophages and myofibroblasts after MI. ECM-1 stimulates fibroblast-to-myofibroblast transition, up-regulates key fibrotic and inflammatory pathways, and inhibits cardiac fibroblast migration. ECM-1 binds HuCFb cell surface receptor LRP1, and LRP1 inhibition blocks ECM-1 from stimulating fibroblast-to-myofibroblast transition, confirming a novel ECM-1-LRP1 fibrotic signaling axis. ECM-1 may represent a novel mechanism facilitating inflammation-fibrosis crosstalk.

Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome

Familial Exudative Vitreoretinopathy (FEVR), Norrie disease, and persistent fetal vascular syndrome (PFVS) are extremely rare retinopathies that are clinically distinct but are unified by abnormal retinal endothelial cell function, and subsequent irregular retinal vascular development and/or aberrant inner blood-retinal-barrier (iBRB) function. The early angiogenesis of the retina and its iBRB is a delicate process that is mediated by the canonical Norrin Wnt-signaling pathway in retinal endothelial cells. Pathogenic variants in genes that play key roles within this pathway, such as NDP, FZD4, TSPAN12, and LRP5, have been associated with the incidence of these retinal diseases. Recent efforts to further elucidate the etiology of these conditions have not only highlighted their multigenic nature but have also resulted in the discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway. Recent discoveries of FEVR-linked variants in two other Catenin genes (CTNND1, CTNNA1) and the Endoplasmic Reticulum Membrane Complex Subunit-1 gene (EMC1) suggest that we will continue to find additional genes that impact the neural retinal vasculature, especially in multi-syndromic conditions. The goal of this review is to briefly highlight the current understanding of the roles of their encoded proteins in retinal endothelial cells to understand the essential functional mechanisms that can be altered to cause these very rare pediatric retinal vascular diseases.

Tissue Morphogenesis Through Dynamic Cell and Matrix Interactions

Multicellular organisms generate tissues of diverse shapes and functions from cells and extracellular matrices. Their adhesion molecules mediate cell-cell and cell-matrix interactions, which not only play crucial roles in maintaining tissue integrity but also serve as key regulators of tissue morphogenesis. Cells constantly probe their environment to make decisions: They integrate chemical and mechanical information from the environment via diffusible ligand- or adhesion-based signaling to decide whether to release specific signaling molecules or enzymes, to divide or differentiate, to move away or stay, or even whether to live or die. These decisions in turn modify their environment, including the chemical nature and mechanical properties of the extracellular matrix. Tissue morphology is the physical manifestation of the remodeling of cells and matrices by their historical biochemical and biophysical landscapes. We review our understanding of matrix and adhesion molecules in tissue morphogenesis, with an emphasis on key physical interactions that drive morphogenesis.

3D cell segregation geometry and dynamics are governed by tissue surface tension regulation

Tissue morphogenesis and patterning during development involve the segregation of cell types. Segregation is driven by differential tissue surface tensions generated by cell types through controlling cell-cell contact formation by regulating adhesion and actomyosin contractility-based cellular cortical tensions. We use vertebrate tissue cell types and zebrafish germ layer progenitors as in vitro models of 3-dimensional heterotypic segregation and developed a quantitative analysis of their dynamics based on 3D time-lapse microscopy. We show that general inhibition of actomyosin contractility by the Rho kinase inhibitor Y27632 delays segregation. Cell type-specific inhibition of non-muscle myosin2 activity by overexpression of myosin assembly inhibitor S100A4 reduces tissue surface tension, manifested in decreased compaction during aggregation and inverted geometry observed during segregation. The same is observed when we express a constitutively active Rho kinase isoform to ubiquitously keep actomyosin contractility high at cell-cell and cell-medium interfaces and thus overriding the interface-specific regulation of cortical tensions. Tissue surface tension regulation can become an effective tool in tissue engineering.

Cadherins and catenins in cancer: connecting cancer pathways and tumor microenvironment

Cadherin-catenin complexes are integral components of the adherens junctions crucial for cell-cell adhesion and tissue homeostasis. Dysregulation of these complexes is linked to cancer development via alteration of cell-autonomous oncogenic signaling pathways and extrinsic tumor microenvironment. Advances in multiomics have uncovered key signaling events in multiple cancer types, creating a need for a better understanding of the crosstalk between cadherin-catenin complexes and oncogenic pathways. In this review, we focus on the biological functions of classical cadherins and associated catenins, describe how their dysregulation influences major cancer pathways, and discuss feedback regulation mechanisms between cadherin complexes and cellular signaling. We discuss evidence of cross regulation in the following contexts: Hippo-Yap/Taz and receptor tyrosine kinase signaling, key pathways involved in cell proliferation and growth; Wnt, Notch, and hedgehog signaling, key developmental pathways involved in human cancer; as well as TGFβ and the epithelial-to-mesenchymal transition program, an important process for cancer cell plasticity. Moreover, we briefly explore the role of cadherins and catenins in mechanotransduction and the immune tumor microenvironment.

p120-catenin subfamily members have distinct as well as shared effects on dendrite morphology during neuron development in vitro

Dendritic arborization is essential for proper neuronal connectivity and function. Conversely, abnormal dendrite morphology is associated with several neurological pathologies like Alzheimer's disease and schizophrenia. Among major intrinsic mechanisms that determine the extent of the dendritic arbor is cytoskeletal remodeling. Here, we characterize and compare the impact of the four proteins involved in cytoskeletal remodeling-vertebrate members of the p120-catenin subfamily-on neuronal dendrite morphology. In relation to each of their own distributions, we find that p120-catenin and delta-catenin are expressed at relatively higher proportions in growth cones compared to ARVCF-catenin and p0071-catenin; ARVCF-catenin is expressed at relatively high proportions in the nucleus; and all catenins are expressed in dendritic processes and the soma. Through altering the expression of each p120-subfamily catenin in neurons, we find that exogenous expression of either p120-catenin or delta-catenin correlates with increased dendritic length and branching, whereas their respective depletion decreases dendritic length and branching. While increasing ARVCF-catenin expression also increases dendritic length and branching, decreasing expression has no grossly observable morphological effect. Finally, increasing p0071-catenin expression increases dendritic branching, but not length, while decreasing expression decreases dendritic length and branching. These distinct localization patterns and morphological effects during neuron development suggest that these catenins have both shared and distinct roles in the context of dendrite morphogenesis.

Critical roles of adherens junctions in diseases of the oral mucosa

The oral cavity is directly exposed to a variety of environmental stimuli and contains a diverse microbiome that continuously interacts with the oral epithelium. Therefore, establishment and maintenance of the barrier function of the oral mucosa is of paramount importance for its function and for the body's overall health. The adherens junction is a cell-cell adhesion complex that is essential for epithelial barrier function. Although a considerable body of work has associated barrier disruption with oral diseases, the molecular underpinnings of these associations have not been equally investigated. This is critical, since adherens junction components also possess significant signaling roles in the cell, in addition to their architectural ones. Here, we summarize current knowledge involving adherens junction components in oral pathologies, such as cancer and oral pathogen-related diseases, while we also discuss gaps in the knowledge and opportunities for future investigation of the relationship between adherens junctions and oral diseases.

CAR links hypoxia signaling to improved survival after myocardial infarction

The coxsackievirus and adenovirus receptor (CAR) mediates homo- and heterotopic interactions between neighboring cardiomyocytes at the intercalated disc. CAR is upregulated in the hypoxic areas surrounding myocardial infarction (MI). To elucidate whether CAR contributes to hypoxia signaling and MI pathology, we used a gain- and loss-of-function approach in transfected HEK293 cells, H9c2 cardiomyocytes and CAR knockout mice. CAR overexpression increased RhoA activity, HIF-1α expression and cell death in response to chemical and physical hypoxia. In vivo, we subjected cardiomyocyte-specific CAR knockout (KO) and wild-type mice (WT) to coronary artery ligation. Survival was drastically improved in KO mice with largely preserved cardiac function as determined by echocardiography. Histological analysis revealed a less fibrotic, more compact lesion. Thirty days after MI, there was no compensatory hypertrophy or reduced cardiac output in hearts from CAR KO mice, in contrast to control mice with increased heart weight and reduced ejection fraction as signs of the underlying pathology. Based on these findings, we suggest CAR as a therapeutic target for the improved future treatment or prevention of myocardial infarction.

Understanding the Role of CDH4 in Multiple System Atrophy Brain

BACKGROUND

Multiple system atrophy (MSA) is a rapidly progressive neurodegenerative disease clinically characterized by parkinsonism, cerebellar ataxia, and autonomic dysfunction. A major pathological feature of MSA is the presence of α-synuclein aggregates in oligodendrocytes, the myelinating cells of the central nervous system. A genome-wide association study revealed that the CDH4 gene is associated with MSA. However, virtually nothing is known about the role of CDH4 in the context of MSA.

OBJECTIVE

Our aim was to compare the expression of CDH4 between MSA and control brains, and to investigate its relationship with α-synuclein in oligodendrocytes.

METHODS

RNA and protein were prepared from putamen, motor cortex white matter, cerebellum, and superior occipital cortex tissues collected from MSA (N = 11) and control (N = 13) brains. The expression of CDH4 was measured at mRNA and protein levels by qPCR and western blotting. Oligodendrocyte cells were cultured on plates and transfected with CDH4 cDNA and its impact on α-synuclein was analyzed.

RESULTS

Firstly, we found that CDH4 in MSA brain was significantly elevated in the disease-affected motor cortex white matter in MSA (N = 11) compared to controls (N = 13) and unaltered in the disease-unaffected superior occipital cortex. Secondly, we determined that increases in CDH4 expression caused changes in the cellular levels of α-synuclein in oligodendrocytes.

CONCLUSIONS

When put together, these results provide evidence that support the GWAS association of CDH4 with MSA.

Therapeutic silencing of p120 in fascia fibroblasts ameliorate tissue repair

Deep skin wounds rapidly heal by mobilizing extracellular matrix and cells from the fascia, deep beneath the dermal layer of the skin, to form scars. Despite wounds being an extensively studied area and an unmet clinical need, the biochemistry driving this patch-like repair remains obscure. Lacking also are efficacious therapeutic means to modulate scar formation in vivo. In this study, we identify a central role for p120 in mediating fascia mobilization and wound repair. Injury triggers p120 expression, largely within engrailed-1 lineage-positive fibroblasts of the fascia that exhibit a supracellular organization. Using adeno-associated virus‒mediated gene silencing, we show that p120 establishes the supracellular organization of fascia engrailed-1 lineage-positive fibroblasts, without which fascia mobilization is impaired. Gene silencing of p120 in fascia fibroblasts disentangles their supracellular organization, reducing the transfer of fascial cells and extracellular matrix into wounds and augmenting wound healing. Our findings place p120 as essential for fascia mobilization, opening, to our knowledge, a previously unreported therapeutic avenue for targeted intervention in the treatment of a variety of skin scar conditions.

Identification of potential regulatory long non-coding RNA-associated competing endogenous RNA axes in periplaque regions in multiple sclerosis

Slow-burning inflammation at the lesion rim is connected to the expansion of chronic multiple sclerosis (MS) lesions. However, the underlying processes causing expansion are not clearly realized. In this context, the current study used a bioinformatics approach to identify the expression profiles and related lncRNA-associated ceRNA regulatory axes in the periplaque region in MS patients. Expression data (GSE52139) from periplaque regions in the secondary progressive MS spinal cord and controls were downloaded from the Gene Expression Omnibus database (GEO), which has details on mRNAs and lncRNAs. Using the R software's limma package, the differentially expressed lncRNAs (DElncRNAs) and mRNAs (DEmRNAs) were found. The RNA interactions were also found using the DIANA-LncBase, miRTarBase, and HMDD databases. The Pearson correlation coefficient was used to determine whether there were any positive correlations between DEmRNAs and DElncRNAs in the ceRNA network. Finally, lncRNA-associated ceRNA axes were created based on co-expression and connections between DElncRNA, miRNA, and DEmRNA. We used the Enrichr tool to enrich the biological process, molecular function, and pathways for DEmRNAs and DElncRNAs. A network of DEmRNAs' protein-protein interactions was developed, and the top five hub genes were found using Cytoscape and STRING. The current study indicates that 15 DEmRNAs, including FOS, GJA1, NTRK2, CTNND1, and SP3, are connected to the MS ceRNA network. Additionally, four DElncRNAs (such as TUG1, ASB16-AS1, and LINC01094) that regulated the aforementioned mRNAs by sponging 14 MS-related miRNAs (e.g., hsa-miR-145-5p, hsa-miR-200a-3p, hsa-miR-20a-5p, hsa-miR-22-3p, hsa-miR-23a-3p, hsa-miR-27a-3p, hsa-miR-29b-3p, hsa-miR-29c-3p, hsa-miR-34a-5p) were found. In addition, the analysis of pathway enrichment revealed that DEmRNAs were enriched in the pathways for the "MAPK signaling pathway", "Kaposi sarcoma-associated herpesvirus infection", "Human immunodeficiency virus one infection", "Lipid and atherosclerosis", and "Amphetamine addiction". Even though the function of these ceRNA axes needs to be investigated further, this study provides research targets for studying ceRNA-mediated molecular mechanisms related to periplaque demyelination in MS.

Adhesion-Based Self-Organization in Tissue Patterning

Since the proposal of the differential adhesion hypothesis, scientists have been fascinated by how cell adhesion mediates cellular self-organization to form spatial patterns during development. The search for molecular tool kits with homophilic binding specificity resulted in a diverse repertoire of adhesion molecules. Recent understanding of the dominant role of cortical tension over adhesion binding redirects the focus of differential adhesion studies to the signaling function of adhesion proteins to regulate actomyosin contractility. The broader framework of differential interfacial tension encompasses both adhesion and nonadhesion molecules, sharing the common function of modulating interfacial tension during cell sorting to generate diverse tissue patterns. Robust adhesion-based patterning requires close coordination between morphogen signaling, cell fate decisions, and changes in adhesion. Current advances in bridging theoretical and experimental approaches present exciting opportunities to understand molecular, cellular, and tissue dynamics during adhesion-based tissue patterning across multiple time and length scales.

β-cells retain a pool of insulin-containing secretory vesicles regulated by adherens junctions and the cadherin binding protein p120 catenin

The β-cells of the islets of Langerhans are the sole producers of insulin in the human body. In response to rising glucose levels, insulin-containing vesicles inside β-cells fuse with the plasma membrane and release their cargo. However, the mechanisms regulating this process are only partly understood. Previous evidence indicated reductions in α-catenin elevate insulin release, while reductions in β-catenin decrease insulin release. α- and β-catenin contribute to cellular regulation in a range of ways but one is as members of the adherens junction complex and these contribute to the development of cell polarity in b-cells. Therefore, we investigated the effects of adherens junctions on insulin release. We show in INS-1E β-cells knockdown of either E- or N-cadherin had only small effects on insulin secretion, but simultaneous knockout of both cadherins resulted in a significant increase in basal insulin release to the same level as glucose-stimulated release. This double knockdown also significantly attenuated levels of p120 catenin, a cadherin binding partner involved in regulating cadherin turnover. Conversely, reducing p120 catenin levels with siRNA destabilized both E- and N-cadherin, and this was also associated with an increase in levels of insulin secreted from INS-1E cells. Furthermore, there were also changes in these cells consistent with higher insulin release, namely reductions in levels of F-actin and increased intracellular free Ca²⁺ levels in response to KCl-induced membrane depolarization. Taken together, these data provide evidence that adherens junctions play important roles in retaining a pool of insulin secretory vesicles within the cell and establish a role for p120 catenin in regulating this process.

Reconstitution of the full transmembrane cadherin-catenin complex

The dynamic regulation of epithelial adherens junctions relies on all components of the E-cadherin-catenin complex. Previously, the complexes have been partially reconstituted and composed only of α-catenin, β-catenin, and the E-cadherin cytoplasmic domain. However, p120-catenin and the full-length E-cadherin including the extracellular, transmembrane, and intra-cellular domains are vital to the understanding of the relationship between extracellular adhesion and intracellular signaling. Here, we reconstitute the complete and full-length cadherin-catenin complex, including full-length E-cadherin, α-catenin, β-catenin, and p120-catenin, into nanodiscs. We are able to observe the cadherin in nanodiscs by cryo-EM. We also reconstitute α-catenin, β-catenin, and p120-catenin with the E-cadherin cytoplasmic tail alone in order to analyze the affinities of their binding interactions. We find that p120-catenin does not associate strongly with α- or β-catenin and binds much more transiently to the cadherin cytoplasmic tail than does β-catenin. Overall, this work creates many new possibilities for biochemical studies understanding transmembrane signaling of cadherins and the role of p120-catenin in adhesion activation.

Tension-dependent stabilization of E-cadherin limits cell-cell contact expansion in zebrafish germ-layer progenitor cells

Cell–cell contact formation is a key step in the evolution of multicellularity. While the molecular and cellular processes underlying cell–cell adhesion and contact formation have been extensively studied, comparably little is known about the physical principles guiding these processes. Actomyosin cortex tension differentially applied at the cell–cell and cell–medium interfaces was shown to promote expansion of the cell–cell contacts. Here, we uncover a nonlinear relationship between cortex tension and cell–cell contact size; in a low-tension regime, cell–cell contact size positively scales with cortex tension, while the high-tension regime promotes small contacts. This change in behavior is due to tension decreasing the turnover of adhesion molecules at the cell–cell contact, limiting contact expansion.

Tension of the actomyosin cell cortex plays a key role in determining cell–cell contact growth and size. The level of cortical tension outside of the cell–cell contact, when pulling at the contact edge, scales with the total size to which a cell–cell contact can grow [J.-L. Maître et al., Science 338, 253–256 (2012)]. Here, we show in zebrafish primary germ-layer progenitor cells that this monotonic relationship only applies to a narrow range of cortical tension increase and that above a critical threshold, contact size inversely scales with cortical tension. This switch from cortical tension increasing to decreasing progenitor cell–cell contact size is caused by cortical tension promoting E-cadherin anchoring to the actomyosin cytoskeleton, thereby increasing clustering and stability of E-cadherin at the contact. After tension-mediated E-cadherin stabilization at the contact exceeds a critical threshold level, the rate by which the contact expands in response to pulling forces from the cortex sharply drops, leading to smaller contacts at physiologically relevant timescales of contact formation. Thus, the activity of cortical tension in expanding cell–cell contact size is limited by tension-stabilizing E-cadherin–actin complexes at the contact.

Effect of Cadherin-11 Expression on the Prognosis of a Newly Diagnosed Primary Glioblastoma

Background

Cadherin-11, a cell-to-cell adhesion molecule, is associated with higher tumor grade and decreased patient survival. The purpose of this study was to investigate the clinical significance of cadherin-11 expression in the progression and prognosis of a newly diagnosed primary glioblastoma (GBL).

Methods

Between 2007 and 2016, 52 out of 178 patients diagnosed with a GBL and satisfied the following criteria: 1) a new primary GBL, 2) gross-total resection, 3) immunohistochemically-available tissue, and 4) standardized adjuvant treatment.

Results

In terms of staining intensity, the low-intensity cadherin-11 group showed longer progression-free survival (PFS) than the high-intensity cadherin-11 group (median PFS, 12.0 months [95% CI, 11.1–12.9] vs. median PFS, 6.0 months [95% CI, 3.7–8.3]; p<0.001). The low-intensity cadherin-11 group revealed longer overall survival (OS) than the high-intensity cadherin-11 group (median OS, 20.0 months [95% CI, 11.8–16.6] vs. median OS, 15.0 months [95% CI, 11.8–18.2]; p=0.003). The staining intensity of cadherin-11 was a statistically significant factor in PFS and OS in terms of univariate and multivariate analyses (univariate analysis: p<0.001 and p=0.005; multivariate analysis: p<0.001 and p=0.005).

Conclusion

Our clinical study demonstrates high cadherin-11 expression may be associated with poor PFS and OS for a newly diagnosed primary GBL.

Comprehensive Atlas of the Myelin Basic Protein Interaction Landscape

Intrinsically disordered myelin basic protein (MBP) is one of the key autoantigens in autoimmune neurodegeneration and multiple sclerosis particularly. MBP is highly positively charged and lacks distinct structure in solution and therefore its intracellular partners are still mostly enigmatic. Here we used combination of formaldehyde-induced cross-linking followed by immunoprecipitation and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to elucidate the interaction network of MBP in mammalian cells and provide the list of potential MBP interacting proteins. Our data suggest that the largest group of MBP-interacting proteins belongs to cellular proteins involved in the protein translation machinery, as well as in the spatial and temporal regulation of translation. MBP interacts with core ribosomal proteins, RNA helicase Ddx28 and RNA-binding proteins STAU1, TDP-43, ADAR-1 and hnRNP A0, which are involved in various stages of RNA biogenesis and processing, including specific maintaining MBP-coding mRNA. Among MBP partners we identified CTNND1, which has previously been shown to be necessary for myelinating Schwann cells for cell-cell interactions and the formation of a normal myelin sheath. MBP binds proteins MAGEB2/D2 associated with neurotrophin receptor p75NTR, involved in pathways that promote neuronal survival and neuronal death. Finally, we observed that MBP interacts with RNF40-a component of heterotetrameric Rnf40/Rnf20 E3 ligase complex, recruited by Egr2, which is the central transcriptional regulator of peripheral myelination. Concluding, our data suggest that MBP may be more actively involved in myelination not only as a main building block but also as a self-regulating element.

Genetic Code Expansion Tools to Study Lysine Acylation

Lysine acylation is a ubiquitous protein modification that controls various aspects of protein function, such as the activity, localization, and stability of enzymes. Mass spectrometric identification of lysine acylations has witnessed tremendous improvements in sensitivity over the last decade, facilitating the discovery of thousands of lysine acylation sites in proteins involved in all essential cellular functions across organisms of all domains of life. However, the vast majority of currently known acylation sites are of unknown function. Semi-synthetic methods for installing lysine derivatives are ideally suited for in vitro experiments, while genetic code expansion (GCE) allows the installation and study of such lysine modifications, especially their dynamic properties, in vivo. An overview of the current state of the art is provided, and its potential is illustrated with case studies from recent literature. These include the application of engineered enzymes and GCE to install lysine modifications or photoactivatable crosslinker amino acids. Their use in the context of central metabolism, bacterial and viral pathogenicity, the cytoskeleton and chromatin dynamics, is investigated.

Novel truncating mutations in CTNND1 cause a dominant craniofacial and cardiac syndrome

CTNND1 encodes the p120-catenin (p120) protein, which has a wide range of functions, including the maintenance of cell–cell junctions, regulation of the epithelial-mesenchymal transition and transcriptional signalling. Due to advances in next-generation sequencing, CTNND1 has been implicated in human diseases including cleft palate and blepharocheilodontic (BCD) syndrome albeit only recently. In this study, we identify eight novel protein-truncating variants, six de novo, in 13 participants from nine families presenting with craniofacial dysmorphisms including cleft palate and hypodontia, as well as congenital cardiac anomalies, limb dysmorphologies and neurodevelopmental disorders. Using conditional deletions in mice as well as CRISPR/Cas9 approaches to target CTNND1 in Xenopus, we identified a subset of phenotypes that can be linked to p120-catenin in epithelial integrity and turnover, and additional phenotypes that suggest mesenchymal roles of CTNND1. We propose that CTNND1 variants have a wider developmental role than previously described and that variations in this gene underlie not only cleft palate and BCD but may be expanded to a broader velocardiofacial-like syndrome.

Neuronal Cytoskeleton in Intellectual Disability: From Systems Biology and Modeling to Therapeutic Opportunities

Intellectual disability (ID) is a pathological condition characterized by limited intellectual functioning and adaptive behaviors. It affects 1–3% of the worldwide population, and no pharmacological therapies are currently available. More than 1000 genes have been found mutated in ID patients pointing out that, despite the common phenotype, the genetic bases are highly heterogeneous and apparently unrelated. Bibliomic analysis reveals that ID genes converge onto a few biological modules, including cytoskeleton dynamics, whose regulation depends on Rho GTPases transduction. Genetic variants exert their effects at different levels in a hierarchical arrangement, starting from the molecular level and moving toward higher levels of organization, i.e., cell compartment and functions, circuits, cognition, and behavior. Thus, cytoskeleton alterations that have an impact on cell processes such as neuronal migration, neuritogenesis, and synaptic plasticity rebound on the overall establishment of an effective network and consequently on the cognitive phenotype. Systems biology (SB) approaches are more focused on the overall interconnected network rather than on individual genes, thus encouraging the design of therapies that aim to correct common dysregulated biological processes. This review summarizes current knowledge about cytoskeleton control in neurons and its relevance for the ID pathogenesis, exploiting in silico modeling and translating the implications of those findings into biomedical research.

A catenin of the plakophilin-subfamily, Pkp3, responds to canonical-Wnt pathway components and signals

Vertebrate beta-catenin plays a key role as a transducer of canonical-Wnt signals. We earlier reported that, similar to beta-catenin, the cytoplasmic signaling pool of p120-catenin-isoform1 is stabilized in response to canonical-Wnt signals. To obtain a yet broader view of the Wnt-pathway's impact upon catenin proteins, we focused upon plakophilin3 (plakophilin-3; Pkp3) as a representative of the plakophilin-catenin subfamily. Promoting tissue integrity, the plakophilins assist in linking desmosomal cadherins to intermediate filaments at desmosome junctions, and in common with other catenins they perform additional functions including in the nucleus. In this report, we test whether canonical-Wnt pathway components modulate Pkp3 protein levels. We find that in common with beta-catenin and p120-catenin-isoform1, Pkp3 is stabilized in the presence of a Wnt-ligand or a dominant-active form of the LRP6 receptor. Pkp3's levels are conversely lowered upon expressing destruction-complex components such as GSK3β and Axin, and in further likeness to beta-catenin and p120-isoform1, Pkp3 associates with GSK3beta and Axin. Finally, we note that Pkp3-catenin trans-localizes into the nucleus in response to Wnt-ligand and its exogenous expression stimulates an accepted Wnt reporter. These findings fit an expanded model where context-dependent Wnt-signals or pathway components modulate Pkp3-catenin levels. Future studies will be needed to assess potential gene regulatory, cell adhesive, or cytoskeletal effects.

Effects of advanced glycation end products on neutrophil migration and aggregation in diabetic wounds

Increased accumulation of advanced glycation end products (AGEs) in diabetic skin is closely related to delayed wound healing. Studies have shown that the concentration of AGEs is elevated in the skin tissues and not subcutaneous tissues in refractory diabetic wounds, which suggests there may be a causal relationship between the two. In the present study, in vitro experiments revealed that AGEs activated neutrophils, and the migratory and adhesive functions of neutrophils decreased once AGE levels reached a certain threshold. Different levels of AGE expression differentially affected the function of neutrophils. Messenger RNA (mRNA) sequencing analysis combined with real-time polymerase chain reaction (PCR) showed that poliovirus receptor (PVR/CD155) and CTNND1, which play a role in migration- and adhesion-related signaling pathways, were decreased following AGE stimulation. Consequently, neutrophils cannot effectively stimulate the formation of the inflammatory belt needed to remove necrotic tissues and defend against foreign microorganisms within diabetic chronic wounds. In addition, this phenomenon may be related to the differential accumulation of AGEs in different layers of the skin.

VE-cadherin endocytosis controls vascular integrity and patterning during development

Tissue morphogenesis requires dynamic intercellular contacts that are subsequently stabilized as tissues mature. The mechanisms governing these competing adhesive properties are not fully understood. Using gain- and loss-of-function approaches, we tested the role of p120-catenin (p120) and VE-cadherin (VE-cad) endocytosis in vascular development using mouse mutants that exhibit increased (VE-cad^GGG/GGG) or decreased (VE-cad^DEE/DEE) internalization. VE-cad^GGG/GGG mutant mice exhibited reduced VE-cad-p120 binding, reduced VE-cad levels, microvascular hemorrhaging, and decreased survival. By contrast, VE-cad^DEE/DEE mutants exhibited normal vascular permeability but displayed microvascular patterning defects. Interestingly, VE-cad^DEE/DEE mutant mice did not require endothelial p120, demonstrating that p120 is dispensable in the context of a stabilized cadherin. In vitro, VE-cadDEE mutant cells displayed defects in polarization and cell migration that were rescued by uncoupling VE-cadDEE from actin. These results indicate that cadherin endocytosis coordinates cell polarity and migration cues through actin remodeling. Collectively, our results indicate that regulated cadherin endocytosis is essential for both dynamic cell movements and establishment of stable tissue architecture.

Pancreas morphogenesis: Branching in and then out

The pancreas of adult mammals displays a branched structure which transports digestive enzymes produced in the distal acini through a tree-like network of ducts into the duodenum. In contrast to several other branched organs, its branching patterns are not stereotypic. Moreover, the branches do not grow from dichotomic splitting of an initial stem but rather from the formation of microlumen in a mass of cells. These lumen progressively assemble into a hyperconnected network that refines into a tree by the time of birth. We review the cell remodeling events and the molecular mechanisms governing pancreas branching, as well as the role of the surrounding tissues in this process. Furthermore, we draw parallels with other branched organs such as the salivary and mammary gland.

APC regulation of ESRP1 and p120-catenin isoforms in colorectal cancer cells

The adenomatous polyposis coli (APC) tumor suppressor protein is associated with the regulation of Wnt signaling; however, APC also controls other cellular processes including the regulation of cell adhesion and migration. The expression of full-length APC in SW480 colorectal cancer cells (SW480+APC) not only reduces Wnt signaling, but increases membrane E-cadherin and restores cell–cell adhesion. This report describes the effects of full-length, wild-type APC (fl-APC) on cell–cell adhesion genes and p120-catenin isoform switching in SW480 colon cancer cells: fl-APC increased the expression of genes implicated in cell–cell adhesion, whereas the expression of negative regulators of E-cadherin was decreased. Analysis of cell–cell adhesion-related proteins in SW480+APC cells revealed an increase in p120-catenin isoform 3A; similarly, depletion of APC altered the p120-catenin protein isoform profile. Expression of ESRP1 (epithelial splice regulatory protein 1) is increased in SW480+APC cells, and its depletion results in reversion to the p120-catenin isoform 1A phenotype and reduced cell–cell adhesion. The ESRP1 transcript is reduced in primary colorectal cancer, and its expression correlates with the level of APC. Pyrvinium pamoate, which inhibits Wnt signaling, promotes ESRP1 expression. We conclude that re-expression of APC restores the cell–cell adhesion gene and posttranscriptional regulatory programs leading to p120-catenin isoform switching and associated changes in cell–cell adhesion.

Coordination between Cell Motility and Cell Cycle Progression in Keratinocyte Sheets via Cell-Cell Adhesion and Rac1

Regulations of cell motility and proliferation are essential for epithelial development and homeostasis. However, it is not fully understood how these cellular activities are coordinated in epithelial collectives. In this study, we find that keratinocyte sheets exhibit time-dependent coordination of collective cell movement and cell cycle progression after seeding cells. Cell movement and cell cycle progression are coordinately promoted by Rac1 in the “early phase” (earlier than ∼30 h after seeding cells), which is not abrogated by increasing the initial cell density to a saturated level. The Rac1 activity is gradually attenuated in the “late phase” (later than ∼30 h after seeding cells), leading to arrests in cell motility and cell cycle. Intact adherens junctions are required for normal coordination between cell movement and cell cycle progression in both early and late phases. Our results unveil a novel basis for integrating motile and proliferative behaviors of epithelial collectives.

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Cell motility and cell cycle progression in keratinocyte sheets are temporally coordinated

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Rac1 promotes both cell motility and cell cycle progression in keratinocyte sheets

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Arrest of cell motility and cell cycle is associated with Rac1 deactivation

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Adherens junction is required for coordinating cell motility and cell cycle

CD99-PTPN12 Axis Suppresses Actin Cytoskeleton-Mediated Dimerization of Epidermal Growth Factor Receptor

Simple Summary

The epidermal growth factor receptor (EGFR) is activated through growth factor-dependent dimerization accompanied by functional reorganization of the actin cytoskeleton. Lee et al. demonstrate that CD99 activation by agonist ligands inhibits epidermal growth factor (EGF)-induced EGFR dimerization through impairment of cytoskeletal reorganization by protein tyrosine phosphatase non-receptor type 12 (PTPN12)-dependent c-Src/focal adhesion kinase (FAK) inactivation, thereby suppressing breast cancer growth.

Abstract

The epidermal growth factor receptor (EGFR), a member of ErbB receptor tyrosine kinase (RTK) family, is activated through growth factor-induced reorganization of the actin cytoskeleton and subsequent dimerization. We herein explored the molecular mechanism underlying the suppression of ligand-induced EGFR dimerization by CD99 agonists and its relevance to tumor growth in vivo. Epidermal growth factor (EGF) activated the formation of c-Src/focal adhesion kinase (FAK)-mediated intracellular complex and subsequently induced RhoA-and Rac1-mediated actin remodeling, resulting in EGFR dimerization and endocytosis. In contrast, CD99 agonist facilitated FAK dephosphorylation through the HRAS/ERK/PTPN12 signaling pathway, leading to inhibition of actin cytoskeletal reorganization via inactivation of the RhoA and Rac1 signaling pathways. Moreover, CD99 agonist significantly suppressed tumor growth in a BALB/c mouse model injected with MDA-MB-231 human breast cancer cells. Taken together, these results indicate that CD99-derived agonist ligand inhibits epidermal growth factor (EGF)-induced EGFR dimerization through impairment of cytoskeletal reorganization by PTPN12-dependent c-Src/FAK inactivation, thereby suppressing breast cancer growth.

Histamine-induced biphasic activation of RhoA allows for persistent RhoA signaling

The small GTPase RhoA is a central signaling enzyme that is involved in various cellular processes such as cytoskeletal dynamics, transcription, and cell cycle progression. Many signal transduction pathways activate RhoA—for instance, Gα_q-coupled Histamine 1 Receptor signaling via Gα_q-dependent activation of RhoGEFs such as p63. Although multiple upstream regulators of RhoA have been identified, the temporal regulation of RhoA and the coordination of different upstream components in its regulation have not been well characterized. In this study, live-cell measurement of RhoA activation revealed a biphasic increase of RhoA activity upon histamine stimulation. We showed that the first and second phase of RhoA activity are dependent on p63 and Ca²⁺/PKC, respectively, and further identified phosphorylation of serine 240 on p115 RhoGEF by PKC to be the mechanistic link between PKC and RhoA. Combined approaches of computational modeling and quantitative measurement revealed that the second phase of RhoA activation is insensitive to rapid turning off of the receptor and is required for maintaining RhoA-mediated transcription after the termination of the receptor signaling. Thus, two divergent pathways enable both rapid activation and persistent signaling in receptor-mediated RhoA signaling via intricate temporal regulation.

The small GTPase RhoA is a central signaling enzyme that is involved in various cellular processes such as cytoskeletal dynamics, transcription, and cell cycle progression. This study shows that histamine induces biphasic activation of RhoA via two divergent signaling pathways, allowing for intricate regulation of cellular processes.

Interplay between actomyosin and E-cadherin dynamics regulates cell shape in the Drosophila embryonic epidermis

Precise regulation of cell shape is vital for building functional tissues. Here, we study the mechanisms that lead to the formation of highly elongated anisotropic epithelial cells in the Drosophila epidermis. We demonstrate that this cell shape is the result of two counteracting mechanisms at the cell surface that regulate the degree of elongation: actomyosin, which inhibits cell elongation downstream of RhoA (Rho1 in Drosophila) and intercellular adhesion, modulated via clathrin-mediated endocytosis of E-cadherin (encoded by shotgun in flies), which promotes cell elongation downstream of the GTPase Arf1 (Arf79F in Drosophila). We show that these two mechanisms do not act independently but are interconnected, with RhoA signalling reducing Arf1 recruitment to the plasma membrane. Additionally, cell adhesion itself regulates both mechanisms - p120-catenin, a regulator of intercellular adhesion, promotes the activity of both Arf1 and RhoA. Altogether, we uncover a complex network of interactions between cell-cell adhesion, the endocytic machinery and the actomyosin cortex, and demonstrate how this network regulates cell shape in an epithelial tissue in vivo.

Palmitoylated Proteins in Dendritic Spine Remodeling

Activity-responsive changes in the actin cytoskeleton are required for the biogenesis, motility, and remodeling of dendritic spines. These changes are governed by proteins that regulate the polymerization, depolymerization, bundling, and branching of actin filaments. Thus, processes that have been extensively characterized in the context of non-neuronal cell shape change and migration are also critical for learning and memory. In this review article, we highlight actin regulatory proteins that associate, at least transiently, with the dendritic plasma membrane. All of these proteins have been shown, either in directed studies or in high-throughput screens, to undergo palmitoylation, a potentially reversible, and stimulus-dependent cysteine modification. Palmitoylation increases the affinity of peripheral proteins for the membrane bilayer and contributes to their subcellular localization and recruitment to cholesterol-rich membrane microdomains.

ROCK1 inhibitor stabilizes E-cadherin and improves barrier function in experimental necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of newborns. Although incompletely understood, NEC is associated with intestinal barrier dysfunction. E-cadherin, an adherens junction, is a protein complex integral in maintaining normal barrier homeostasis. Rho-associated protein kinase-1 (ROCK1) is a kinase that regulates the E-cadherin complex, and p120-catenin is a subunit of the E-cadherin complex that has been implicated in stabilizing the cadherin complex at the plasma membrane. We hypothesized that E-cadherin is decreased in NEC and that inhibition of ROCK1 would protect against adherens junction disruption. To investigate this, a multimodal approach was used: In vitro Caco-2 model of NEC (LPS/TNFα), rap pup model (hypoxia + bacteria-containing formula), and human intestinal samples. E-cadherin was decreased in NEC compared with controls, with relocalization from the cell border to an intracellular location. ROCK1 exhibited a time-dependent response to disease, with increased early expression in NEC and decreased expression at later time points and disease severity. Administration of ROCK1 inhibitor (RI) resulted in preservation of E-cadherin expression at the cell border, preservation of intestinal villi on histological examination, and decreased apoptosis. ROCK1 upregulation in NEC led to decreased association of E-cadherin to p120 and increased intestinal permeability. RI helped maintain the stability of the E-cadherin-p120 complex, leading to improved barrier integrity and protection from experimental NEC.NEW & NOTEWORTHY This paper is the first to describe the effect of ROCK1 on E-cadherin expression in the intestinal epithelium and the protective effects of ROCK inhibitor on E-cadherin stability in necrotizing enterocolitis.

p120-catenin-dependent collective brain infiltration by glioma cell networks

Diffuse brain infiltration by glioma cells causes detrimental disease progression, but its multicellular coordination is poorly understood. We show here that glioma cells infiltrate the brain collectively as multicellular networks. Contacts between moving glioma cells are adaptive epithelial-like or filamentous junctions stabilized by N-cadherin, β-catenin and p120-catenin, which undergo kinetic turnover, transmit intercellular calcium transients and mediate directional persistence. Downregulation of p120-catenin compromises cell-cell interaction and communication, disrupts collective networks, and both the cadherin and RhoA binding domains of p120-catenin are required for network formation and migration. Deregulating p120-catenin further prevents diffuse glioma cell infiltration of the mouse brain with marginalized microlesions as the outcome. Transcriptomics analysis has identified p120-catenin as an upstream regulator of neurogenesis and cell cycle pathways and a predictor of poor clinical outcome in glioma patients. Collective glioma networks infiltrating the brain thus depend on adherens junctions dynamics, the targeting of which may offer an unanticipated strategy to halt glioma progression.

An LTR Retrotransposon-Derived Long Noncoding RNA lncMER52A Promotes Hepatocellular Carcinoma Progression by Binding p120-Catenin

Long terminal repeat (LTR) retrotransposons are a major class of transposable elements, accounting for 8.67% of the human genome. LTRs can serve as regulatory sequences and drive transcription of tissue or cancer-specific transcripts. However, the role of these LTR-activated transcripts, especially long non-coding RNAs (lncRNA), in cancer development remains largely unexplored. Here, we identified a novel lncRNA derived from MER52A retrotransposons (lncMER52A) that was exclusively expressed in hepatocellular carcinoma (HCC). HCC patients with higher lncMER52A had advanced TNM stage, less differentiated tumors, and shorter overall survival. LncMER52A promoted invasion and metastasis of HCC cells in vitro and in vivo. Mechanistically, lncMER52A stabilized p120-catenin and triggered the activation of Rho GTPase downstream of p120-catenin. Furthermore, we found that chromatin accessibility was crucial for the expression of lncMER52A. In addition, YY1 transcription factor bound to the cryptic MER52A LTR promoter and drove lncMER52A transcription in HCC. In conclusion, we identified an LTR-activated lncMER52A, which promoted the progression of HCC cells via stabilizing p120-catenin and activating p120-ctn/Rac1/Cdc42 axis. LncMER52A could serve as biomarker and therapeutic target for patients with HCC. SIGNIFICANCE: A novel long noncoding RNA lncMER52 modulates cell migration and invasion via posttranslational control of p120-catenin protein stability. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/5/976/F1.large.jpg.

Rebalancing of actomyosin contractility enables mammary tumor formation upon loss of E-cadherin

E-cadherin (CDH1) is a master regulator of epithelial cell adherence junctions and a well-established tumor suppressor in Invasive Lobular Carcinoma (ILC). Intriguingly, somatic inactivation of E-cadherin alone in mouse mammary epithelial cells (MMECs) is insufficient to induce tumor formation. Here we show that E-cadherin loss induces extrusion of luminal MMECs to the basal lamina. Remarkably, E-cadherin-deficient MMECs can breach the basal lamina but do not disseminate into the surrounding fat pad. Basal lamina components laminin and collagen IV supported adhesion and survival of E-cadherin-deficient MMECs while collagen I, the principle component of the mammary stromal micro-environment did not. We uncovered that relaxation of actomyosin contractility mediates adhesion and survival of E-cadherin-deficient MMECs on collagen I, thereby allowing ILC development. Together, these findings unmask the direct consequences of E-cadherin inactivation in the mammary gland and identify aberrant actomyosin contractility as a critical barrier to ILC formation.

Ezrin Orchestrates Signal Transduction in Airway Cells

Ezrin is a critical structural protein that organizes receptor complexes and orchestrates their signal transduction. In this study, we review the ezrin-meditated regulation of critical receptor complexes, including the epidermal growth factor receptor (EGFR), CD44, vascular cell adhesion molecule (VCAM), and the deleted in colorectal cancer (DCC) receptor. We also analyze the ezrin-meditated regulation of critical pathways associated with asthma, such as the RhoA, Rho-associated protein kinase (ROCK), and protein kinase A (cAMP/PKA) pathways. Mounting evidence suggests that ezrin plays a role in controlling airway cell function and potentially contributes to respiratory diseases. Ezrin can participate in asthma pathogenesis by affecting bronchial epithelium repair, T lymphocyte regulation, and the contraction of the airway smooth muscle cells. These studies provide new insights for the design of novel therapeutic strategies for asthma treatment.

Getting a grip on adhesion: Cadherin switching and collagen signaling

Epithelial-mesenchymal transition (EMT) is a developmental biological process that is hijacked during tumor progression. Cadherin switching, which disrupts adherens junctions and alters cadherin-associated signaling pathways, is common during EMT. In many tumors, substantial extracellular matrix (ECM) is deposited. Collagen is the most abundant ECM constituent and it mediates specific signaling pathways by binding to integrins and discoidin domain receptors (DDRs). The interaction of the collagen receptors results in activation of signaling pathways that promote tumor progression including an induction of the cadherin switching. DDR inhibitors have demonstrated anticancer therapeutic efficacy preclinically by inhibiting the collagen signaling. Understanding how collagen signaling impacts cellular processes including EMT and cadherin switching is of great interest especially given the strong interest in stromal targeted therapies for desmoplastic cancers.

Dynamic microtubules drive fibroblast spreading

When cells with a mesenchymal type of motility come into contact with an adhesive substrate they adhere and start spreading by the formation of lamellipodia. Using a label-free approach and virtual synchronization approach we analyzed spreading in fibroblasts and cancer cells. In all cell lines spreading is a non-linear process undergoing isotropic or anisotropic modes with first fast (5–20 min) and then slow (30–120 min) phases. In the first 10 min cell area increases 2–4 times, while the absolute rate of initial spreading decreases 2–8 times. Fast spreading depends on actin polymerization and dynamic microtubules. Inhibition of microtubule growth was sufficient for a slowdown of initial spreading. Inhibition of myosin II in the presence of stable microtubules restored fast spreading. Inhibition of actin polymerization or complete depolymerization of microtubules slowed down fast spreading. However, in these cases inhibition of myosin II only partially restored spreading kinetics. We conclude that rapid growth of microtubules towards cell margins at the first stage of cell spreading temporarily inhibits phosphorylation of myosin II and is essential for the fast isotropic spreading. Comparison of the fibroblasts with cancer cells shows that fast spreading in different cell types shares similar kinetics and mechanisms, and strongly depends on dynamic microtubules.

Summary: Cell spreading is a non-linear process. The fast spreading phase depends on dynamic microtubules (MTs). Rapid growth of MTs towards the cell membrane promotes the temporal relaxation of acto-myosin contractility.

αE-catenin is a candidate tumor suppressor for the development of E-cadherin-expressing lobular-type breast cancer

Although mutational inactivation of E-cadherin (CDH1) is the main driver of invasive lobular breast cancer (ILC), approximately 10-15% of all ILCs retain membrane-localized E-cadherin despite the presence of an apparent non-cohesive and invasive lobular growth pattern. Given that ILC is dependent on constitutive actomyosin contraction for tumor development and progression, we used a combination of cell systems and in vivo experiments to investigate the consequences of α-catenin (CTNNA1) loss in the regulation of anchorage independence of non-invasive breast carcinoma. We found that inactivating somatic CTNNA1 mutations in human breast cancer correlated with lobular and mixed ducto-lobular phenotypes. Further, inducible loss of α-catenin in mouse and human E-cadherin-expressing breast cancer cells led to atypical localization of E-cadherin, a rounded cell morphology, and anoikis resistance. Pharmacological inhibition experiments subsequently revealed that, similar to E-cadherin-mutant ILC, anoikis resistance induced by α-catenin loss was dependent on Rho/Rock-dependent actomyosin contractility. Finally, using a transplantation-based conditional mouse model, we demonstrate that inducible inactivation of α-catenin instigates acquisition of lobular features and invasive behavior. We therefore suggest that α-catenin represents a bona fide tumor suppressor for the development of lobular-type breast cancer and as such provides an alternative event to E-cadherin inactivation, adherens junction (AJ) dysfunction, and subsequent constitutive actomyosin contraction. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

p120-catenin is required for regulating epidermal proliferation, differentiation, and barrier function

p120-catenin (p120) is an important regulator in the function and stability of E-cadherin. However, the role of p120 in the epidermis is unclear. Previous studies have shown that globally knockout of p120 caused increased epidermal proliferation but little changes in epidermal differentiation and permeability. In the present study, we generated a conditional knockout mouse model and examined epidermal proliferation, differentiation and permeability. The results showed that conditional knockout of p120 in the epidermis caused not only increased epidermal proliferation but also decreased epidermal differentiation and increased permeability. These data suggest that p120 is required for suppressing epidermal proliferation, promoting epidermal differentiation and maintaining permeability barrier function of the epidermis.