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Current Biology : CB Nov 2023Various functions within our bodies require the generation and maintenance of compartments with distinct compositions, which in turn necessitate the formation of...
Various functions within our bodies require the generation and maintenance of compartments with distinct compositions, which in turn necessitate the formation of semipermeable cellular diffusion barriers. For example, the blood-brain barrier protects the brain by allowing only specific molecules to pass through. Another instance is the intestinal barrier, which allows the uptake of essential nutrients, while restricting the passage of pathogenic molecules and bacteria. Breakdown of such barriers causes various pathologies, such as brain or retinal edema, or diarrhoea. Epithelia and endothelia are the most common barrier-forming cells. Individual cells in such barriers are held together by cell-cell adhesion structures - also known as intercellular junctions - that are essential for barrier formation and maintenance. Here, we will focus on the structure and assembly of tight junctions (TJs) and their functions as barriers, but will refer to other adhesive structures crucial for barrier regulation such as adherens junctions (AJs) and focal adhesions to the extracellular matrix (ECM) (Figure 1A,B). We will also discuss additional functions of TJs in cell surface polarity and the regulation of gene expression, cell function, and cell behaviour.
Topics: Tight Junctions; Intercellular Junctions; Cell Adhesion; Adherens Junctions; Brain
PubMed: 37935122
DOI: 10.1016/j.cub.2023.09.027 -
The Journal of Clinical Investigation Nov 2019Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with rising incidence. Diseased tissues are heavily vascularized. Surprisingly, the pathogenic impact... (Clinical Trial)
Clinical Trial
Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with rising incidence. Diseased tissues are heavily vascularized. Surprisingly, the pathogenic impact of the vasculature in IBD and the underlying regulatory mechanisms remain largely unknown. IFN-γ is a major cytokine in IBD pathogenesis, but in the context of the disease, it is almost exclusively its immune-modulatory and epithelial cell-directed functions that have been considered. Recent studies by our group demonstrated that IFN-γ also exerts potent effects on blood vessels. Based on these considerations, we analyzed the vessel-directed pathogenic functions of IFN-γ and found that it drives IBD pathogenesis through vascular barrier disruption. Specifically, we show that inhibition of the IFN-γ response in vessels by endothelial-specific knockout of IFN-γ receptor 2 ameliorates experimentally induced colitis in mice. IFN-γ acts pathogenic by causing a breakdown of the vascular barrier through disruption of the adherens junction protein VE-cadherin. Notably, intestinal vascular barrier dysfunction was also confirmed in human IBD patients, supporting the clinical relevance of our findings. Treatment with imatinib restored VE-cadherin/adherens junctions, inhibited vascular permeability, and significantly reduced colonic inflammation in experimental colitis. Our findings inaugurate the pathogenic impact of IFN-γ-mediated intestinal vessel activation in IBD and open new avenues for vascular-directed treatment of this disease.
Topics: Adherens Junctions; Adult; Aged; Animals; Antigens, CD; Cadherins; Endothelial Cells; Female; Humans; Imatinib Mesylate; Inflammatory Bowel Diseases; Interferon-gamma; Male; Mice; Mice, Knockout; Middle Aged
PubMed: 31566580
DOI: 10.1172/JCI124884 -
Nature Aug 2020The ability of the skin to grow in response to stretching has been exploited in reconstructive surgery. Although the response of epidermal cells to stretching has been...
The ability of the skin to grow in response to stretching has been exploited in reconstructive surgery. Although the response of epidermal cells to stretching has been studied in vitro, it remains unclear how mechanical forces affect their behaviour in vivo. Here we develop a mouse model in which the consequences of stretching on skin epidermis can be studied at single-cell resolution. Using a multidisciplinary approach that combines clonal analysis with quantitative modelling and single-cell RNA sequencing, we show that stretching induces skin expansion by creating a transient bias in the renewal activity of epidermal stem cells, while a second subpopulation of basal progenitors remains committed to differentiation. Transcriptional and chromatin profiling identifies how cell states and gene-regulatory networks are modulated by stretching. Using pharmacological inhibitors and mouse mutants, we define the step-by-step mechanisms that control stretch-mediated tissue expansion at single-cell resolution in vivo.
Topics: Adaptor Proteins, Signal Transducing; Adherens Junctions; Animals; Base Sequence; Cell Cycle Proteins; Cell Differentiation; Cell Self Renewal; Chromatin; Chromatin Assembly and Disassembly; Clone Cells; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; Gene Regulatory Networks; Hydrogels; Mechanotransduction, Cellular; Mice; Mice, Transgenic; Mitogen-Activated Protein Kinase Kinases; Mutation; RNA, Messenger; RNA-Seq; Single-Cell Analysis; Skin; Stem Cells; Trans-Activators; Transcription Factor AP-1; Transcription, Genetic; YAP-Signaling Proteins
PubMed: 32728211
DOI: 10.1038/s41586-020-2555-7 -
Biophysical Reviews Oct 2019Tight junctions (TJ) play a central role in the homeostasis of epithelial and endothelial tissues, by providing a semipermeable barrier to ions and solutes, by... (Review)
Review
Tight junctions (TJ) play a central role in the homeostasis of epithelial and endothelial tissues, by providing a semipermeable barrier to ions and solutes, by contributing to the maintenance of cell polarity, and by functioning as signaling platforms. TJ are associated with the actomyosin and microtubule cytoskeletons, and the crosstalk with the cytoskeleton is fundamental for junction biogenesis and physiology. TJ are spatially and functionally connected to adherens junctions (AJ), which are essential for the maintenance of tissue integrity. Mechano-sensing and mechano-transduction properties of several AJ proteins have been characterized during the last decade. However, little is known about how mechanical forces act on TJ and their proteins, how TJ control the mechanical properties of cells and tissues, and what are the underlying molecular mechanisms. Here I review recent studies that have advanced our understanding of the relationships between mechanical force and TJ biology.
PubMed: 31586306
DOI: 10.1007/s12551-019-00582-7 -
Nature Aging Sep 2023The age-related decline in the ability of the intestinal barrier to maintain selective permeability can lead to various physiological disturbances. Adherens junctions...
The age-related decline in the ability of the intestinal barrier to maintain selective permeability can lead to various physiological disturbances. Adherens junctions play a vital role in regulating intestinal permeability, and their proper assembly is contingent upon endocytic recycling. However, how aging affects the recycling efficiency and, consequently, the integrity of adherens junctions remains unclear. Here we show that RAB-10/Rab10 functionality is reduced during senescence, leading to impaired adherens junctions in the Caenorhabditis elegans intestine. Mechanistic analysis reveals that SDPN-1/PACSINs is upregulated in aging animals, suppressing RAB-10 activation by competing with DENN-4/GEF. Consistently, SDPN-1 knockdown alleviates age-related abnormalities in adherens junction integrity and intestinal barrier permeability. Of note, the inhibitory effect of SDPN-1 on RAB-10 requires KGB-1/JUN kinase, which presumably enhances the potency of SDPN-1 by altering its oligomerization state. Together, by examining age-associated changes in endocytic recycling, our study sheds light on how aging can impact intestinal barrier permeability.
Topics: Animals; Adherens Junctions; Aging; Biological Transport; Caenorhabditis elegans; Intestines; Caenorhabditis elegans Proteins; JNK Mitogen-Activated Protein Kinases
PubMed: 37640905
DOI: 10.1038/s43587-023-00475-1 -
Current Biology : CB May 2020Neurons are highly specialized cells equipped with a sophisticated molecular machinery for the reception, integration, conduction and distribution of information. The... (Review)
Review
Neurons are highly specialized cells equipped with a sophisticated molecular machinery for the reception, integration, conduction and distribution of information. The evolutionary origin of neurons remains unsolved. How did novel and pre-existing proteins assemble into the complex machinery of the synapse and of the apparatus conducting current along the neuron? In this review, the step-wise assembly of functional modules in neuron evolution serves as a paradigm for the emergence and modification of molecular machinery in the evolution of cell types in multicellular organisms. The pre-synaptic machinery emerged through modification of calcium-regulated large vesicle release, while the postsynaptic machinery has different origins: the glutamatergic postsynapse originated through the fusion of a sensory signaling module and a module for filopodial outgrowth, while the GABAergic postsynapse incorporated an ancient actin regulatory module. The synaptic junction, in turn, is built around two adhesion modules controlled by phosphorylation, which resemble septate and adherens junctions. Finally, neuronal action potentials emerged via a series of duplications and modifications of voltage-gated ion channels. Based on these origins, key molecular innovations are identified that led to the birth of the first neuron in animal evolution.
Topics: Animals; Biological Evolution; Neurons; Synapses; Synaptic Transmission
PubMed: 32428501
DOI: 10.1016/j.cub.2020.04.008 -
Trends in Cell Biology May 2023The cell-cell connections in adherens junctions (AJs) are mediated by transmembrane receptors, type I cadherins (referred to here as cadherins). These cadherin-based... (Review)
Review
The cell-cell connections in adherens junctions (AJs) are mediated by transmembrane receptors, type I cadherins (referred to here as cadherins). These cadherin-based connections (or trans bonds) are weak. To upregulate their strength, cadherins exploit avidity, the increased affinity of binding between cadherin clusters compared with isolated monomers. Formation of such clusters is a unique molecular process that is driven by a synergy of direct and indirect cis interactions between cadherins located at the same cell. In addition to their role in adhesion, cadherin clusters provide structural scaffolds for cytosolic proteins, which implicate cadherin into different cellular activities and signaling pathways. The cluster lifetime, which depends on the actin cytoskeleton, and on the mechanical forces it generates, determines the strength of AJs and their plasticity. The key aspects of cadherin adhesion, therefore, cannot be understood at the level of isolated cadherin molecules, but should be discussed in the context of cadherin clusters.
Topics: Humans; Cadherins; Cell Adhesion Molecules; Adherens Junctions; Actins; Actin Cytoskeleton; Cell Adhesion
PubMed: 36127186
DOI: 10.1016/j.tcb.2022.08.007 -
Journal of Cellular Physiology Jun 2023The microtubule cytoskeleton plays a critical role in a variety of cellular activities, and its structures and functions have been extensively studied. However, little... (Review)
Review
The microtubule cytoskeleton plays a critical role in a variety of cellular activities, and its structures and functions have been extensively studied. However, little is known about cell differentiation-related microtubule remodeling, its regulatory mechanisms, and its physiological functions. Recent studies have shown that microtubule-binding proteins as well as cell junctions, such as desmosomes and adherens junctions, are involved in the remodeling of microtubules in response to cell differentiation. In addition, the microtubule-organizing activity and structural integrity of centrosomes undergo dramatic changes during cell differentiation to promote microtubule remodeling. Here we summarize recent advances revealing the dynamic changes in microtubule organization and functions during cell differentiation. We also highlight the molecular mechanisms underlying microtubule modeling in differentiated cells, focusing on the key roles played by microtubule-binding proteins, cell junctions, and centrosomes.
Topics: Adherens Junctions; Cell Differentiation; Centrosome; Cytoskeleton; Microtubules
PubMed: 36960617
DOI: 10.1002/jcp.31011 -
Tissue Barriers Oct 2023Tight junctions (TJs) are the most apical components of junctional complexes in epithelial and endothelial cells. Barrier function is one of the major functions of TJ,... (Review)
Review
Tight junctions (TJs) are the most apical components of junctional complexes in epithelial and endothelial cells. Barrier function is one of the major functions of TJ, which restricts the ions and small water-soluble molecules from passing through the paracellular pathway. Adherens junctions (AJs) play an important role in cell-cell adhesion and cell signaling. Gap junctions (GJs) are intercellular channels regulating electrical and metabolic signals between cells. It is well known that TJ integral membrane proteins, such as claudins and occludins, are the molecular building blocks responsible for TJ barrier function. However, recent studies demonstrate that proteins of other junctional complexes can influence and regulate TJ barrier function. Therefore, the crosstalk between different cell junctions represents a common means to modulate cellular activities. In this review, we will discuss the interactions among TJ, AJ, and GJ by focusing on how AJ and GJ proteins regulate TJ barrier function in different biological systems.
Topics: Tight Junctions; Epithelial Cells; Endothelial Cells; Intercellular Junctions; Adherens Junctions
PubMed: 36220768
DOI: 10.1080/21688370.2022.2133880 -
The Journal of Cell Biology Jul 2023The mechanisms that regulate the spatial sorting of nonmuscle myosins-2 (NM2) isoforms and couple them mechanically to the plasma membrane are unclear. Here we show that...
The mechanisms that regulate the spatial sorting of nonmuscle myosins-2 (NM2) isoforms and couple them mechanically to the plasma membrane are unclear. Here we show that the cytoplasmic junctional proteins cingulin (CGN) and paracingulin (CGNL1) interact directly with NM2s through their C-terminal coiled-coil sequences. CGN binds strongly to NM2B, and CGNL1 to NM2A and NM2B. Knockout (KO), exogenous expression, and rescue experiments with WT and mutant proteins show that the NM2-binding region of CGN is required for the junctional accumulation of NM2B, ZO-1, ZO-3, and phalloidin-labeled actin filaments, and for the maintenance of tight junction membrane tortuosity and apical membrane stiffness. CGNL1 expression promotes the junctional accumulation of both NM2A and NM2B and its KO results in myosin-dependent fragmentation of adherens junction complexes. These results reveal a mechanism for the junctional localization of NM2A and NM2B and indicate that, by binding to NM2s, CGN and CGNL1 mechanically couple the actomyosin cytoskeleton to junctional protein complexes to mechanoregulate the plasma membrane.
Topics: Adherens Junctions; Cell Membrane; Cytoskeletal Proteins; Cytoskeleton; Myosins; Tight Junctions
PubMed: 37204781
DOI: 10.1083/jcb.202208065