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

Die Adhärensverbindung ist eine Verankerungsverbindung, die Zellen in Geweben wie dem Epithel zusammenhält.
Adherens-Verbindungen sind große Multiproteinkomplexe, die aus drei Hauptproteinklassen bestehen - den adhäsiven Cadherinen, dem verankernden Aktin-Zytoskelett und den Linker-Cateninen.
Die Assemblierung der Adhären-Verbindungen beginnt mit der Polymerisation von Aktinmonomeren in der Nähe der Zellmembran zur Bildung von Ausstülpungen, die als Lamellipodien bezeichnet werden.
Wenn Lamellipodien von benachbarten Zellen nahe genug beieinander liegen, interagieren die Cadherine auf ihrer Oberfläche und lösen die Lokalisierung von mehr Cadherinen aus, wodurch sich Cluster bilden.
Diese Cluster werden durch Beta-, Alpha- und p120-Catenine stabilisiert, die dazu beitragen, mehr Cadherin-Catenin-Komplexe an die Anbaustelle zu rekrutieren.
Wenn sich die Kontaktzone zwischen den beiden Zellen ausdehnt, verschieben die Alpha-Catenine die Aktinpolymerisation von verzweigt zu unverzweigt und ordnen sie parallel zur Zellmembran an.
Diese Aktinfilamente verbinden sich dann mit Myosin, um kontraktile Bündel zu bilden und so eine reife Adhärensverbindung zu bilden.
Die Verbindung verbindet das Zytoskelett einer Zelle mit einer anderen, die durch die extrazellulären Wechselwirkungen von Cadherin-Molekülen zusammengehalten wird.

<ol>
	<li>Niessen, Carien M. und Cara J. Gottardi. "Molekulare Komponenten der Adhärensverbindung." Biochimica et Biophysica Acta (BBA)-Biomembranes 1778.3 (2008): 562-571.</li>
	<li>Baum, Buzz und Marios Georgiou. "Dynamik von Adhärentverbindungen bei der Etablierung, Aufrechterhaltung und dem Umbau des Epithels." Zeitschrift für Zellbiologie 192.6 (2011): 907-917.</li>
	<li>Mengaud, Jérôme, et al. "E-Cadherin ist der Rezeptor für Internalin, ein Oberflächenprotein, das für den Eintritt von L. monocytogenes in Epithelzellen benötigt wird." Zelle 84.6 (1996): 923-932.</li>
</ol>

adherens-kreuzungen

Adherens Junctions

Starke Kontaktpunkte zwischen benachbarten Zellen verankern sie untereinander und bilden Gewebe. Es gibt zwei Arten solcher Verankerungsverbindungen: adhärente Verbindungen und Desmosomen. Adherens-Verbindungen sind in Geweben wie Epithel und Endothel reichlich vorhanden und bilden eine kontinuierliche Adhäsionszone, die als Adhäsionsgürtel bezeichnet wird. In anderen Geweben, beispielsweise im Herzmuskel, erscheinen sie als Cluster und verbinden die Zellen, um eine koordinierte Herzmuskelkontraktion zu bewirken.

Adherens-Verbindungen sind dynamisch

Die Endothelzellen, die die Blutgefäße auskleiden, sind eng miteinander verbunden und bilden eine Barriere, die das Entweichen anderer Zellen und Moleküle aus dem Blutkreislauf in das umliegende Gewebe verhindert. Bei einer Immunantwort müssen die Leukozyten aus dem Blutkreislauf jedoch diese Barriere passieren und das Zielgewebe erreichen. Entzündungsmoleküle wie Histamine und Signalproteine wie der vaskuläre endotheliale Wachstumsfaktor (VGEF) lösen nachgelagerte Prozesse aus, wie etwa die Phosphorylierung und Internalisierung von Cadherinen, die auf der Endothelzelloberfläche vorhanden sind. Dies führt zur Auflösung der adhärenten Verbindungen und erhöht die Endothelpermeabilität, indem Lücken entstehen, die den Durchgang von Immunzellen und anderen Molekülen ermöglichen. Die Aufrechterhaltung und der Abbau adhärenter Verbindungen werden somit dynamisch als Reaktion auf bestimmte Reize reguliert.

Adherens-Verbindungen und Infektion

Infektionserreger wie Helicobacter pylori können in das Wirtsgewebe eindringen, indem sie die Adhäsionsverbindungen zerstören und sich durch die interzellulären Lücken bewegen. Diese Bakterien produzieren Proteasen, die die extrazelluläre Domäne von Cadherinen spalten und so zu einer Demontage der Verbindungsstelle führen. Zelloberflächen-Cadherine werden auch von Bakterien wie Streptococcus pneumoniae als Rezeptoren missbraucht, um sich an das Epithel der oberen Atemwege anzuheften.

Die eindrucksvollste Entführung wird jedoch vielleicht durch Listeria monocytogenes demonstriert. Dieses Bakterium exprimiert Zellwandproteine, die E-Cadherine anheften und die Rekrutierung von ɑ-, β- und p120-Cateninen an der Stelle auslösen. Diese Rekrutierung initiiert eine dynamische Aktinpolymerisation und bildet Membranvorsprünge, die die Bakterien in einem Prozess namens induzierte Phagozytose verschlingen. Das Bakterium gelangt so in eine nichtphagozytische Zelle und vermehrt sich im Wirt.

Adherens-Kreuzungen

Starke Kontaktpunkte zwischen benachbarten Zellen verankern sie aneinander und bilden Gewebe. Es gibt zwei Arten solcher Verankerungsverbindungen – Adhärene ...

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 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 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 Adhesion in Tissues and Infection

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