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

Gap Junctions sind Kommunikationskanäle zwischen benachbarten tierischen Zellen.
Diese Kanäle bestehen aus Transmembranproteinen, den Connexinen. Sechs Connexin-Moleküle bilden einen Halbkanal, der als Connexon bezeichnet wird.
Ein homomeres Connexon besteht aus sechs Kopien desselben Connexin-Proteins, während ein heteromeres Connexon von verschiedenen Connexin-Proteinen gebildet wird.
Die Connexons können dynamisch durch die Membran diffundieren. Wenn ein Connexon auf einer Zellmembran auf ein anderes Connexon auf der benachbarten Zelle trifft, paaren sie sich zu einem vollständigen Kanal.
Cluster solcher Kanäle bilden die Gap-Junction-Plaques, die den Austausch von Ionen, sekundären Botenstoffen, Zuckern und anderen kleinen Molekülen zwischen Zellen ermöglichen.
Die Vielfalt der Connexine und ihrer Kombinationen verleiht der Selektivität der Kanäle für bestimmte Moleküle.
Der Transport von gelösten Stoffen wird weiter reguliert durch das Öffnen und Schließen von Kanälen als Reaktion auf verschiedene Reize, wie z. B. Spannungsdifferenz, Kalziumionenkonzentration und pH-Wert.
Zum Beispiel reagieren Gap Junctions im Herzmuskel auf Spannungsunterschiede und synchronisieren den Ionenfluss zwischen Gruppen von Muskelzellen, wodurch rhythmische Kontraktionen im Herzen erzeugt werden.

<ol>
	<li>Laird, Dale W. "Lebenszyklus von Connexinen in Gesundheit und Krankheit." Biochemisches Journal 394.3 (2006): 527-543.</li>
	<li>Bauer, Reinhard, et al. "Interzelluläre Kommunikation: die Drosophila-Innexin-Multiproteinfamilie von Gap-Junction-Proteinen." Chemie und Biologie 12.5 (2005): 515-526.</li>
	<li>Sager, Ross E. und Jung-Youn Lee. "Plasmodesmen auf einen Blick." Zeitschrift für Zellwissenschaft 131.11 (2018): jcs209346.</li>
</ol>

gap junctions

Gap Junctions

Das Zytoplasma benachbarter tierischer Zellen kann über die Kommunikationskanäle, die die Gap Junctions bilden, kleine Moleküle, Ionen und sekundäre BotenSubstanzenaustauschen. Diese Verbindungen bestehen aus einigen hundert bis tausenden molekularen Kanälen, die jeweils aus zwei Hälften bestehen und als Connexon-Hemikanal bezeichnet werden. Ein Connexon ist ein Hexamer aus sechs Transmembran-Connexin-Proteinen, die sich radial anordnen und so in der Mitte eine Pore oder einen Kanal bilden. Ein Connexon-Halbkanal dockt an ein entsprechendes Connexon der angrenzenden Zelle an und vervollständigt so den Kanal.

Gap-Junction-Dynamik

Connexine werden vom Ribosom auf dem rauen endoplasmatischen Retikulum translatiert und kotranslational in die ER-Membran eingefügt. Anschließend werden die Monomere zum Golgi-Netzwerk transportiert, wo sie oligomerisieren. Die hexameren Konnexone werden über sekretorische Vesikel vom Trans-Golgi-Netzwerk zur Plasmamembran transportiert. Die Connexons können sich frei entlang der Plasmamembran bewegen, bis sie auf andere Connexons treffen und Cluster bilden. Auf diese Weise werden an der Peripherie eines wachsenden Clusters ständig neue Verbindungen hinzugefügt, die eine Gap-Junction-Plakette bilden. Im Zentrum dieser Plakette werden alte Connexons endozytiert und für den Abbau markiert. Gap Junctions sind daher dynamische Anordnungen mit einem konstanten Wechsel von Verbindungen an der Membran.

Gap Junctions für Wirbellose

Gap Junctions bei Wirbellosen haben eine ähnliche Struktur wie bei Wirbeltieren; Sie bestehen jedoch aus verschiedenen Proteinen, die Innexine (Connexine der Wirbellosen) genannt werden. Obwohl Innexine eine ähnliche Transmembranstruktur haben, weisen sie keine Sequenzhomologie mit Connexinen auf. Sie unterscheiden sich auch von ihren Wirbeltier-Gegenstücken dadurch, dass sie acht statt sechs Einheiten benötigen, um einen Innexon-Halbkanal zu bilden.

Gegenstücke in Pflanzen

Anders als in tierischen Geweben, wo die Membranen benachbarter Zellen in direktem Kontakt stehen, verhindern die Zellwände in pflanzlichen Geweben den direkten Kontakt benachbarter Plasmamembranen. Die interzelluläre Kommunikation und der Austausch von Molekülen erfolgen somit über spezielle Verbindungsstellen, die sogenannten Plasmodesmen. An diesen Verbindungsstellen ist die Membran einer Zelle mit der der benachbarten Zelle verbunden und bildet einen röhrenförmigen Kanal mit einem Durchmesser von etwa 20 bis 40 nm. Somit ist das Zytoplasma benachbarter Zellen zusammenhängend und ermöglicht den regulierten Austausch verschiedener kleiner Moleküle.

Das Zytoplasma benachbarter tierischer Zellen kann kleine Moleküle, Ionen und sekundäre Botenstoffe über die Kommunikationskanäle austauschen, die die Lücke bilden ...

Education

Lehre

JoVE Core

Cell Biology

Zellbiologie

Unit 1

Einheit 1

Cell-Cell Interactions

Zell-Zell-Interaktionen

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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

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catenins

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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

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overview of cell-cell junctions

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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...

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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

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 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 Zellbiologie veranschaulicht komplexe zelluläre Prozesse in leicht verständlichen und dennoch umfassenden animierten Videolektionen. Diese Sammlung konzentriert sich auf die wesentlichen Bestandteile und Funktionen von Zellen, einschließlich Organellen und Membranen, Zelltransport und Zellenergie. Ergänzt wird sie durch Videos von Wissenschaftlern in Aktion, die die Anwendung der Zellbiologie in realen Forschungsexperimenten demonstrieren.

Cell Communication Through Gap Junctions

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