Name: cell communication through gap junctions
Uploaded: 2023-04-30T11:55:54.000Z
Duration: 1 min 27 s
Channel: JoVE

Les jonctions lacunaires sont des canaux de communication entre des cellules animales adjacentes.
Ces canaux sont composés de protéines transmembranaires appelées connexines. Six molécules de connexine forment un hémicanal appelé connexon.
Un connexon homomérique comprend six copies de la même protéine connexine, tandis qu’un connexon hétéromère est formé par différentes protéines connexines.
Les connexons peuvent diffuser dynamiquement à travers la membrane. Lorsqu’un connexon sur une membrane cellulaire rencontre un autre connexon sur la cellule adjacente, ils s’apparient pour former un canal complet.
Des amas de ces canaux forment les plaques de jonction lacunaire qui permettent l’échange d’ions, de messagers secondaires, de sucres et d’autres petites molécules entre les cellules.
La diversité des connexines et de leurs combinaisons confère une sélectivité de canal pour des molécules spécifiques.
Le transport des solutés est en outre régulé par l’ouverture et la fermeture des canaux en réponse à divers stimuli, tels que la différence de tension, la concentration en ions calcium et le pH.
Par exemple, les jonctions lacunaires dans les muscles cardiaques réagissent aux différences de tension et synchronisent le flux d’ions entre les groupes de cellules musculaires, générant ainsi des contractions rythmiques dans le cœur.

<ol>
	<li>Laird, Dale W. « Cycle de vie des connexines dans la santé et la maladie. » Biochemical Journal 394.3 (2006) : 527-543.</li>
	<li>Bauer, Reinhard et al. « Communication intercellulaire : la famille multiprotéique de la drosophile innexine des protéines de jonction lacunaire. » Chimie et biologie 12.5 (2005) : 515-526.</li>
	<li>Sager, Ross E. et Jung-Youn Lee. « Plasmodesmata en un coup d’œil. » Journal de la science cellulaire 131.11 (2018) : jcs209346.</li>
</ol>

jonctions Écartées

Gap Junctions

Le cytoplasme des cellules animales adjacentes peut échanger de petites molécules, des ions et des messagers secondaires via les canaux de communication qui forment les jonctions écartées. Ces jonctions comprennent quelques centaines à des milliers de canaux moléculaires, chacun constitué de deux moitiés, appelés connexons hémi-canaux. Un connexon est un hexamère de six protéines connexines transmembranaires, qui s'assemblent radialement, formant ainsi un pore ou un canal au centre. Un connexon hémi-canal s'arrime à un connexon correspondant sur la cellule adjacente, complétant ainsi le canal.

Dynamique des Jonctions Écartées

Les connexines sont traduites par le ribosome sur le réticulum endoplasmique rugueux et sont insérées de manière cotraductionnelle dans la membrane du RE. Les monomères sont ensuite transportés vers le réseau de Golgi, où ils s'oligomérisent. Les connexons hexamériques sont transportés du réseau trans-Golgi vers la membrane plasmique via des vésicules sécrétoires. Les connexons peuvent se déplacer librement le long de la membrane plasmique jusqu'à ce qu'ils rencontrent d'autres connexons, formant des amas. Ainsi, un cluster en croissance a de nouveaux connexons ajoutés continuellement à sa périphérie, formant une plaque de jonction ecartée. Au centre de cette plaque, les anciennes connexons sont endocytosées et marquées pour leur dégradation. Les jonctions écartées sont donc des assemblages dynamiques avec un renouvellement constant des connexons au niveau de la membrane.

Jonctions Écartées des Invertébrés

Les jonctions écartées chez les invertébrés ont une structure similaire à celles des vertébrés ; cependant, ils comprennent différentes protéines appelées innexines (connexines d'invertébrés). Bien que les innexines aient une structure transmembranaire similaire, elles ne partagent pas d'homologie de séquence avec les connexines. Ils diffèrent également de leurs homologues vertébrés en ce qu'ils nécessitent huit unités pour former un hémi-canal innexon au lieu de six.

Homologues dans les Plantes

Contrairement aux tissus d'origine animale, où les membranes des cellules adjacentes sont en contact direct, les parois cellulaires des tissus végétaux empêchent le contact direct des membranes plasmiques adjacentes. La communication intercellulaire et les échanges de molécules se font ainsi via des jonctions spécialisées appelées plasmodesmes. La membrane d'une cellule est en continuité avec celle de la cellule adjacente au niveau de ces jonctions, formant un canal tubulaire d'environ 20 à 40 nm de diamètre. Ainsi, le cytoplasme des cellules adjacentes est contigu, permettant l’échange régulé de diverses petites molécules.

Jonctions Écartées

Le cytoplasme des cellules animales adjacentes peut échanger de petites molécules, des ions et des messagers secondaires via les canaux de communication qui forment l’espace ...

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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 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 connexon from one cell docks with a matching connexon from the neighboring cell to complete the channel.

Connexins are made on ribosomes attached to the rough endoplasmic reticulum. They are inserted into the ER membrane as they are made. The monomers then move to the Golgi network, where they oligomerize, or assemble into larger units. The hexameric connexons travel from the trans-Golgi network to the plasma membrane in secretory vesicles.

Once at the membrane, connexons can move freely until they meet other connexons. They cluster together and form a gap junction plaque. New connexons keep joining at the outer edge of the plaque. At the center, older connexons are endocytosed and marked for degradation, so gap junctions keep turning over over time.

Invertebrate gap junctions are similar in shape to vertebrate ones, but they use different proteins called innexins. Innexins are not sequence homologs of connexins, even though they have a similar transmembrane structure. They also form hemichannels with eight units instead of six.

Plants use plasmodesmata instead of gap junctions because their cell walls keep adjacent plasma membranes from touching directly. These junctions allow intercellular communication and the exchange of molecules between plant cells. The membrane of one cell continues into the next, forming a tubular channel about 20 to 40 nm wide. This makes the cytoplasm of neighboring cells continuous and allows the regulated movement of small molecules.

Cell Communication Through Gap Junctions

cell adhesion molecules - types and functions

cell-adhesion-molecules-types-and-functions

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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

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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

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

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tight junctions

Tight Junction Proteins and Cell Barriers

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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 gap junctions connect animal cells, how connexins build connexon channels, and how innexins and plasmodesmata support cell communication.

Cell Communication Through Gap Junctions | 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 Communication Through Gap Junctions

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