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

Cell junctions are large, multi-protein complexes that can link cells to the extracellular matrix forming cell-matrix junctions, or act as contact points between neighboring cells in tissues to form cell-cell junctions.
Cells typically have three main types of cell-cell junctions - tight, anchoring, and gap junctions, each with a distinct structure and function.
Consider the columnar epithelium. The tight junctions near the apices of these cells hold adjacent plasma membranes together and function as a barrier to the flow of molecules through the intercellular spaces.
Below this apical portion are two types of anchoring junctions&#8212; the adherens junctions and desmosomes.
Together, these anchoring junctions form an interconnected cytoskeletal network across cells that helps to resist mechanical forces.
The third type, gap junctions, are dispersed throughout the plasma membrane, particularly towards the basal end. These junctions act as communication channels between adjacent cells, allowing molecules and ions to pass through.

overzicht van cel-celverbindingen

Overview of Cell-Cell Junctions

De complexe driedimensionale rangschikking van cellen in elk meercellig organisme wordt gedefinieerd en in stand gehouden door interacties van cellen met elkaar en de extracellulaire matrix. Cel-celverbindingen zijn gespecialiseerde structuren waarbij de multi-eiwitcomplexen op de ene cel interageren met de multi-eiwitcomplexen op een andere cel. Deze celverbindingen worden op basis van hun functie ingedeeld in drie hoofdtypen: occluderende, verankerende en gap-junctions.

Afsluitende of strakke verbindingen

Strakke kruispunten functioneren voornamelijk om de beweging van moleculen zoals water en opgeloste stoffen door de intercellulaire ruimtes te voorkomen. Ze zijn aanwezig als een reeks transmembraaneiwitten die rechtstreeks interageren met dezelfde eiwitten op het aangrenzende membraan. Ze houden de twee plasmamembranen dus dicht bij elkaar, waardoor de doorgang van moleculen wordt voorkomen. Strakke kruispunten kunnen ook selectief permeabel zijn, waardoor ladingsspecifieke ionen er doorheen kunnen bewegen, terwijl andere worden geblokkeerd.

Verankerende kruispunten

Verankeringsverbindingen houden cellen bij elkaar en zorgen voor mechanische sterkte aan de weefselstructuur. Ze vormen contactpunten waar het cytoskelet van de ene cel is verankerd aan dat van de aangrenzende cellen via transmembraanadhesiemoleculen die cadherines worden genoemd. Er zijn twee soorten ankerverbindingen:

<ol style="list-style-type: disc;">
	<li>Hecht verbindingen aan die het actine-cytoskelet met elkaar verbinden</li>
	<li>desmosomen die de tussenliggende filamenten met elkaar verbinden.</li>
</ol>

Ze vormen dus een uitgebreid cytoskeletnetwerk dat samenwerkt om de weefselstructuur en -functie te behouden.

Gap-verbindingen

Gap-junctions zijn eiwitkanalen die de communicatie tussen cellen vergemakkelijken. De samenstellende transmembraaneiwitten vormen een kanaal dat de cytoplasma's van aangrenzende cellen met elkaar verbindt en maakt de uitwisseling van moleculen en elektrische impulsen mogelijk. De beweging van moleculen wordt gereguleerd door het openen en sluiten van de kanaaleiwitten. Het signaal voor ritmische samentrekkingen van het hart wordt bijvoorbeeld van cel naar cel doorgegeven via de gap-junctions in het hartspierweefsel. Plantencellen kunnen echter vanwege de celwand geen moleculen uitwisselen via gap-junctions. In plaats daarvan vormen ze communicatiekanalen die plasmodesmata worden genoemd. Dit zijn met membraan omzoomde poriën die de cellen via de celwanden verbinden, zodat het cytoplasma van de ene cel grenst aan dat van een andere cel. Er is dus een vrije beweging van opgeloste stoffen en ionen door plantencellen die met elkaar verbonden zijn door plasmodesmata.

Overzicht van cel-celverbindingen

The complex three-dimensional arrangement of cells in any multicellular organism is defined and maintained by interactions of cells with each other and ...

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JoVE Core

Cell Biology

Celbiologie

Unit 1

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Cell-Cell Interactions

Cel-celinteracties

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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 Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Cell Junctions in Tissues

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