Name: cell adhesion in tissues and infection
Uploaded: 2023-04-30T11:55:15.000Z
Duration: 1 min 24 s
Channel: JoVE

La jonction adhérente est une jonction d’ancrage qui maintient les cellules ensemble dans des tissus tels que l’épithélium.
Les jonctions adhérentes sont de grands complexes multiprotéiques comprenant trois classes de protéines principales : les cadhérines adhésives, le cytosquelette d’actine d’ancrage et les caténines de liaison.
L’assemblage des jonctions adhérentes commence par la polymérisation des monomères d’actine près de la membrane cellulaire pour former des protubérances appelées lamellipodes.
Lorsque les lamellipodes des cellules voisines sont suffisamment proches, les cadhérines à leur surface interagissent et déclenchent la localisation de plus de cadhérines, formant des grappes.
Ces amas sont stabilisés par les caténines bêta-, alpha et p120, qui aident à recruter davantage de complexes cadhérine-caténine sur le site de croissance.
Au fur et à mesure que la zone de contact entre les deux cellules s’étend, les alpha-caténines déplacent la polymérisation de l’actine de ramifiée à non ramifiée et les disposent parallèlement à la membrane cellulaire.
Ces filaments d’actine s’associent ensuite à la myosine pour former des faisceaux contractiles, formant ainsi une jonction d’adhérents matures.
La jonction relie le cytosquelette d’une cellule à une autre, maintenu ensemble par les interactions extracellulaires des molécules de cadhérine.

<ol>
	<li>Niessen, Carien M., et Cara J. Gottardi. « Composants moléculaires de la jonction adhérente. » Biochimica et Biophysica Acta (BBA)-Biomembranes 1778.3 (2008) : 562-571.</li>
	<li>Baum, Buzz et Marios Georgiou. « Dynamique des jonctions adhérentes dans l’établissement, la maintenance et le remodelage de l’épithélial. » Journal de biologie cellulaire 192.6 (2011) : 907-917.</li>
	<li>Mengaud, Jérôme, et al. « E-cadhérine est le récepteur de l’internaline, une protéine de surface nécessaire à l’entrée de L. monocytogenes dans les cellules épithéliales. » Cellule 84.6 (1996) : 923-932.</li>
</ol>

jonctions adhérentes

Adherens Junctions

Des points de contact forts entre les cellules adjacentes les ancrent les unes aux autres, formant ainsi des tissus. Ces jonctions d’ancrage sont de deux types : les jonctions adhérentes et les desmosomes. Les jonctions adhérentes sont abondantes dans les tissus tels que l’épithélium et l’endothélium, formant une zone continue d’adhésion appelée ceinture d’adhésion. Dans d’autres tissus, comme le muscle cardiaque, ils apparaissent sous forme de groupes reliant les cellules pour produire une contraction coordonnée du muscle cardiaque.

Les Jonctions Adhérentes sont Dynamiques

Les cellules endothéliales tapissant les vaisseaux sanguins sont étroitement liées, formant une barrière qui empêche la fuite d’autres cellules et molécules de la circulation sanguine vers les tissus environnants. Or, lors d’une réponse immunitaire, les leucocytes issus du sang doivent traverser cette barrière et atteindre le tissu cible. Les molécules inflammatoires comme les histamines et les protéines de signalisation comme le facteur de croissance endothélial vasculaire (VEGF) déclenchent des processus en aval, tels que la phosphorylation et l'internalisation des cadhérines présentes à la surface des cellules endothéliales. Cela conduit au désassemblage des jonctions adhérentes et augmente la perméabilité endothéliale en créant des lacunes qui permettent aux cellules immunitaires et à d’autres molécules de passer. Le maintien et la rupture des jonctions adhérentes sont ainsi régulés de manière dynamique en réponse à des stimuli spécifiques.

Jonctions Adhérentes et Infection

Les agents infectieux comme Helicobacter pylori peuvent pénétrer dans le tissu hôte en perturbant les jonctions adhérentes et en se déplaçant à travers les espaces intercellulaires. Ces bactéries produisent des protéases qui clivent le domaine extracellulaire des cadhérines, provoquant ainsi le désassemblage des jonctions. Les cadhérines de la surface cellulaire sont également détournées en tant que récepteurs par des bactéries telles que Streptococcus pneumoniae pour adhérer à l'épithélium des voies respiratoires supérieures.

Cependant, le détournement le plus impressionnant est peut-être démontré par Listeria monocytogenes. Cette bactérie exprime des protéines de la paroi cellulaire qui fixent les E-cadhérines et déclenchent le recrutement des caténines ɑ, β et p120 sur le site. Ce recrutement initie une polymérisation dynamique de l'actine, formant des saillies membranaires qui engloutissent les bactéries dans un processus appelé phagocytose induite. La bactérie pénètre ainsi dans une cellule non phagocytaire et prolifère au sein de l'hôte.

Jonctions Adhérentes

De forts points de contact entre les cellules adjacentes les ancrent les unes aux autres, formant des tissus. Ces jonctions d’ancrage sont de deux types – adhérentes ...

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cell adhesion in tissues and infection

Adherens junctions are strong cell-to-cell anchors that help tissues stay connected. These anchoring junctions work with desmosomes, another type of junction that holds adjacent cells together. In many epithelial and endothelial tissues, adherens junctions form a continuous adhesion belt. In heart muscle, they often appear as clusters that help cells work together for coordinated contraction.

Adherens junctions are also dynamic, especially in the cells that line blood vessels. These endothelial cells form a barrier that normally keeps cells and molecules inside the bloodstream. During an immune response, leukocytes, or white blood cells, must cross this barrier to reach damaged tissue. Inflammatory molecules such as histamines and signaling proteins such as vascular endothelial growth factor, or VEGF, can trigger phosphorylation and internalization of cadherins on the endothelial cell surface. Cadherins are adhesion proteins that help cells stick together. When this happens, adherens junctions break down, permeability increases, and gaps open for immune cells and other molecules to pass through.

Some infections also take advantage of adherens junctions. Helicobacter pylori can disrupt these junctions by producing proteases that cut the extracellular part of cadherins. This breaks the junctions and helps the bacteria move through the spaces between cells. Other bacteria, such as Streptococcus pneumoniae, use cadherins as receptors to attach to the upper respiratory epithelium. Listeria monocytogenes uses a more complex strategy. It binds E-cadherins and recruits alpha-, beta-, and p120-catenins, which starts actin polymerization. This creates membrane protrusions that engulf the bacteria in induced phagocytosis, allowing it to enter a nonphagocytic cell and multiply inside the host.

Cell Adhesion in Tissues and Infection

cell adhesion molecules - types and functions

cell-adhesion-molecules-types-and-functions

Cell Adhesion Molecules in Tissues

Cell adhesion molecules help cells stick together and work as part of a tissue. They give multicellular organisms physical strength and also help cells send signals across the plasma membrane. These proteins are important for coordinated activity in tissues and organ systems. CAMs are grouped into four main families: integrins, cadherins, selectins, and immunoglobulin-like CAMs, or IgCAMs. Each family supports cell interactions in a different way. Some CAMs help cells attach firmly, while...

structure of cadherins

Cadherins in Cell Junctions and Disease

Cadherins are cell adhesion proteins that help cells stick together and build tissues. Their name comes from their calcium-dependent binding. Early examples were named E-cadherin, P-cadherin, and N-cadherin after the epithelial, placental, and neuronal cells where they were first found. Classical cadherins share similar sequences and structures. Other cadherins, including those involved in cell signaling, are grouped as non-classical cadherins. This diversity comes from multiple cadherin genes...

cadherins in tissue organization

Cadherins Guide Cell Sorting in Tissues

Cadherins help cells sort into the right tissues during development. They are a large superfamily of cell adhesion molecules, with more than 180 variants. Different tissues express specific cadherin combinations, which helps cells recognize and stick to the right neighbors. Cadherins usually bind to the same or a closely related cadherin on another cell. This is called homophilic binding. Because of this matching behavior, cells of the same type tend to group together and form clusters that...

catenins

Catenins in Cell Junctions and Signaling

Catenins help cells stay connected and also support signaling inside the body. These proteins act as linker proteins in cell junction complexes because they have multiple binding domains and flexible structures. Most catenins contain a protein sequence called the armadillo repeat, so they are also known as armadillo proteins. Alpha-catenin is the main exception. Catenins bind to cell adhesion molecules such as cadherins. They then connect cadherins to cytoskeletal proteins, and the exact link...

selectins

Selectins in Immune Cell Capture

Selectins help cells make short, temporary contacts during immune responses. They are cell adhesion molecules that bind carbohydrate ligands on other cells. These rod-like proteins have a long outside region and end in a lectin domain, which binds carbohydrates only when calcium ions are present. Three main selectins are known: L-selectin, P-selectin, and E-selectin. Their names reflect where they are found and how long they are. This tissue specificity helps explain why selectins act in...

immunoglobulin-like cell adhesion molecules

immunoglobulin-like-cell-adhesion-molecules

Ig-CAMs in Neural Growth and Disease

Ig-CAMs, or immunoglobulin-like cell adhesion molecules, are cell surface glycoproteins in the immunoglobulin superfamily. They contain immunoglobulin domains, and some also have fibronectin type III domains. Their Ig domains can be glycosylated to different degrees. These molecules can bind to the same kind of Ig-CAM or to other ligands, such as integrins. Most Ig-CAMs help cells stick together only for a short time. The nectin class is different because it helps form stable junctions,...

overview of cell-cell junctions

Cell Junctions in Tissues

Cell junctions help hold tissues together and let neighboring cells communicate. In multicellular organisms, the three-dimensional shape of tissues depends on interactions between cells and the extracellular matrix. Cell-cell junctions are specialized structures made of multi-protein complexes on one cell that connect with similar complexes on another cell. These junctions are grouped into three main types based on function: occluding, anchoring, and gap junctions. Tight junctions, also called...

adherens junctions

Adherens junctions are strong cell-to-cell anchors that help tissues stay connected. These anchoring junctions work with desmosomes, another type of junction that holds adjacent cells together. In many epithelial and endothelial tissues, adherens junctions form a continuous adhesion belt. In heart muscle, they often appear as clusters that help cells work together for coordinated contraction. Adherens junctions are also dynamic, especially in the cells that line blood vessels. These...

tension response at adherens junctions

How Adherens Junctions Sense Force

Adherens junctions help cells stay attached while they respond to mechanical force. These multi-protein complexes can adapt to tensile force and shear stress. When the force changes, mechanosensory proteins in the junction can change shape. This process is called mechanotransduction. Alpha-catenin is one of the main force-sensing proteins in adherens junctions. It is an allosteric protein, which means its shape affects how it works. Alpha-catenin has three VH, or vinculin homology, domains...

desmosomes

Desmosomes and Cell Anchoring

Desmosomes are cell junctions that anchor cells together. They are button-like structures that create an interlinked network of intermediate filaments across cells. This strong link helps tissues resist mechanical stress and maintain tissue integrity. Desmosomes are built from multiple proteins. Their core includes desmosomal cadherins, which are adhesion proteins that bind to cadherins on neighboring cells. The two desmosomal cadherins are desmogleins and desmocollins. These transmembrane...

tight junctions

Tight Junction Proteins and Cell Barriers

Tight junction proteins form seals between neighboring cells. These molecular barriers help stop fluids, ions, and other small solutes from leaking across body cavities and tissue compartments in multicellular organisms. They are an important part of cell barriers in places where controlled movement matters. The main tight junction proteins are claudin and occludin. Other proteins include tricellulin and JAM, which stands for junctional adhesion molecule. Most of these proteins are 4-pass...

gap junctions

Cell Communication Through Gap Junctions

Gap junctions let adjacent animal cells share small molecules, ions, and secondary messengers. These communication channels connect the cytoplasm of neighboring cells. They are built from many molecular channels, often from a few hundred to thousands in one junction. Each channel is made of two halves called connexon hemichannels. A connexon is a hexamer, meaning it is formed by six transmembrane connexin proteins. The six proteins arrange in a ring and create a pore in the center. One...

key terms and concepts

Learn how adherens junctions hold tissues together, open during immune responses, and can be disrupted by bacteria like H. pylori, S. pneumoniae, and Listeria.

Cell Adhesion in Tissues and Infection | JoVE K12

cell biology

JoVE Core Biologie cellulaire illustre les processus cellulaires complexes dans des leçons vidéos complètes mais faciles à comprendre. Cette collection se concentre sur les composants et fonctions essentiels de la cellule ; cela inclut les organelles et les membranes ainsi que le transport et le métabolisme énergétique cellulaire. Elle est complétée par nos vidéos de scientifiques à l'action qui démontrent l'application de la biologie cellulaire dans des expériences concrètes.

Cell Adhesion in Tissues and Infection

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