Name: cell junctions in tissues
Uploaded: 2023-04-30T11:54:51.000Z
Duration: 1 min 14 s
Channel: JoVE

Les jonctions cellulaires sont de grands complexes multiprotéiques qui peuvent lier les cellules à la matrice extracellulaire en formant des jonctions cellule-matrice, ou agir comme points de contact entre les cellules voisines dans les tissus pour former des jonctions cellule-cellule.
Les cellules ont généralement trois principaux types de jonctions cellule-cellule : les jonctions serrées, les jonctions d’ancrage et les jonctions lacunaires, chacune ayant une structure et une fonction distinctes.
Considérons l’épithélium cylindrique. Les jonctions serrées près de l’apex de ces cellules maintiennent les membranes plasmiques adjacentes ensemble et fonctionnent comme une barrière à la circulation des molécules dans les espaces intercellulaires.
Sous cette partie apicale se trouvent deux types de jonctions d’ancrage : les jonctions adhérentes et les desmosomes.
Ensemble, ces jonctions d’ancrage forment un réseau cytosquelettique interconnecté entre les cellules qui aide à résister aux forces mécaniques.
Le troisième type, les jonctions lacunaires, sont dispersées dans toute la membrane plasmique, en particulier vers l’extrémité basale. Ces jonctions agissent comme des canaux de communication entre les cellules adjacentes, permettant aux molécules et aux ions de passer.

<ol>
	<li>Campbell, Hannah K., Jessica L. Maiers et Kris A. DeMali. « Interaction entre les jonctions serrées et les jonctions adhérentes. » Recherche expérimentale sur les cellules 358.1 (2017) : 39-44.</li>
	<li>Giepmans, Ben NG. « Jonctions lacunaires et protéines interagissant avec la connexine. » Recherche cardiovasculaire 62.2 (2004) : 233-245.</li>
</ol>

aperçu des jonctions cellule-cellule

Overview of Cell-Cell Junctions

L'arrangement tridimensionnel complexe des cellules dans tout organisme multicellulaire est défini et maintenu par les interactions des cellules entre elles et avec la matrice extracellulaire. Les jonctions cellule-cellule sont des structures spécialisées dans lesquelles les complexes multiprotéiques d'une cellule interagissent avec les complexes multiprotéiques d'une autre cellule. Ces jonctions cellulaires sont classées en trois types principaux en fonction de leur fonction : jonctions d'occlusion, d'ancrage et lacunaires.

Jonctions Obstruantes ou Serrées

Les jonctions serrées fonctionnent principalement pour empêcher le mouvement de molécules telles que l'eau et les solutés à travers les espaces intercellulaires. Ils sont présents sous la forme d’une série de protéines transmembranaires qui interagissent directement avec les mêmes protéines sur la membrane adjacente. Ainsi, ils maintiennent les deux membranes plasmiques à proximité l’une de l’autre, empêchant ainsi le passage des molécules. Les jonctions serrées peuvent également être sélectivement perméables, permettant aux ions spécifiques d’une charge de se déplacer, tout en bloquant les autres.

Jonctions d’Ancrage

Les jonctions d’ancrage maintiennent les cellules ensemble et confèrent une résistance mécanique à la structure tissulaire. Ils forment des points de contact où le cytosquelette d’une cellule est ancré à celui des cellules voisines via des molécules d’adhésion transmembranaire appelées cadhérines. Il existe deux types de jonctions d’ancrage :

<ol style="list-style-type: circle;">
	<li>adhère aux jonctions qui relient le cytosquelette d'actine et</li>
	<li>desmosomes qui relient les filaments intermédiaires.</li>
</ol>

Ainsi, ils forment un vaste réseau du cytosquelette qui fonctionne de manière coopérative pour maintenir la structure et la fonction des tissus.

Jonctions Écartées

Les jonctions lacunaires sont des canaux protéiques qui facilitent la communication entre les cellules. Les protéines transmembranaires constitutives forment un canal reliant les cytoplasmes des cellules adjacentes et permettent l’échange de molécules et d’impulsions électriques. Le mouvement des molécules est régulé par l'ouverture et la fermeture des canaux protéiques. Par exemple, le signal des contractions rythmiques du cœur est transmis de cellule en cellule via les jonctions lacunaires du tissu musculaire cardiaque. Cependant, les cellules végétales ne peuvent pas échanger de molécules via des jonctions lacunaires à cause de la paroi cellulaire. Au lieu de cela, ils forment des canaux de communication appelés plasmodesmes. Ce sont des pores tapissés de membranes reliant les cellules à travers les parois cellulaires de telle sorte que le cytoplasme d’une cellule soit contigu à celui d’une autre. Ainsi, les solutés et les ions circulent librement à travers les cellules végétales reliées par des plasmodesmes.

Aperçu des Jonctions Cellule-Cellule

L’arrangement tridimensionnel complexe des cellules dans tout organisme multicellulaire est défini et maintenu par les interactions des cellules les unes avec les autres et ...

Education

Enseignement

JoVE Core

Cell Biology

Biologie cellulaire

Unit 1

Unité 1

Cell-Cell Interactions

Interactions cellule-cellule

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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 occluding junctions, stop water and solutes from moving through the spaces between cells. They do this with transmembrane proteins that match and bind to the same proteins on the adjacent cell membrane, keeping the two membranes close together. Tight junctions can also be selectively permeable, so some charge-specific ions can pass while others are blocked.

Anchoring junctions give tissues mechanical strength by holding cells together. They create contact points where the cytoskeleton of one cell attaches to the cytoskeleton of a neighboring cell through transmembrane adhesion molecules called cadherins. Two main forms are adherens junctions, which link actin filaments, and desmosomes, which link intermediate filaments. Together, these connections build a strong cytoskeletal network that supports tissue structure and function.

Gap junctions are channels that let cells communicate with each other. Their transmembrane proteins form a passage between the cytoplasms of adjacent cells, allowing molecules and electrical impulses to move across. The channels can open and close to control movement. In cardiac muscle, gap junctions help pass the signal for rhythmic heart contractions from cell to cell.

Plant cells do not use gap junctions because of the cell wall. Instead, they connect through plasmodesmata, which are membrane-lined pores that pass through the cell walls. These channels link the cytoplasm of one plant cell to another, allowing solutes and ions to move freely between them.

Cell Junctions in Tissues

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 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

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...

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 tight junctions, anchoring junctions, and gap junctions help cells stay connected, strengthen tissues, and pass signals in animals and plants.

Cell Junctions in Tissues | 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 Junctions in Tissues

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