Name: catenins in cell junctions and signaling
Uploaded: 2023-04-30T11:55:07.000Z
Duration: 1 min 23 s
Channel: JoVE

Catenins are a diverse group of adapter proteins that participate in cell-cell adhesion.
Catenins have multiple binding domains that bind cadherins, cytoskeletal components, and various cytoskeletal regulator proteins. Thus, they link the cytoskeleton with cadherins at the cell adhesion sites.
While some catenins, such as plakoglobin and plakophilin, help establish stable connections between cadherins and the intermediate filaments,others, such as alpha- and beta-catenins, dynamically organize the actin cytoskeleton at the plasma membrane.
The organization of actin filaments begins with the binding of beta-catenin to the cytosolic domain of a cadherin molecule. Following this, alpha-catenin binds to the beta-catenin.
Another catenin, p120, also tethers to these complexes and regulates the stability of cadherins on the membrane.
As a few cadherin-catenin complexes cluster together, the alpha-catenins dissociate and form cytosolic dimers.
These alpha-catenin dimers interact strongly with the filamentous actin and help organize actin bundles, thus providing cytoskeletal strength to the cell adhesion sites.

catenins

Catenins

Catenins are characterized by multiple binding domains and dynamic structures that allow them to function as linker proteins in cell junction complexes. All catenins, except &#945;-catenin, contain a characteristic protein sequence called the armadillo repeat and are therefore also called armadillo proteins.
Catenins in Cell Junctions
Catenins bind to cell adhesion molecules such as cadherins and link them to different cytoskeletal proteins depending on the type of cell junction. At the adherens junction, the actin cytoskeleton is dynamically organized by the alpha-, beta-, and p120-catenins, both directly or indirectly.&#160;For example, &#945;-catenin binds directly to F-actin, whereas p120 regulates actin polymerization via Rho GTPases.&#160;At desmosomes, however, the intermediate filaments are organized by the interactions of special catenins called plakoglobin and plakophilin with other proteins such as desmoplakin.
&#946;-catenin and Cell Signaling
In addition to binding cadherins at cell junctions, &#946;-catenin can also function in cell signaling such as the Wnt pathway. In this pathway, the binding of a Wnt&#160; signal molecule to the cell surface receptor, termed&#160; frizzled, triggers a cascade that increases &#946;-catenin concentration in the cytoplasm. This allows &#946;-catenin to translocate to the nucleus, bind to transcription factors, and regulate the target gene expression. Unlike other catenins that have several tissue-specific variants across organisms, only a single variant of &#946;-catenin is found in vertebrates. This variant is composed of a highly conserved amino acid sequence across all vertebrate species.
p120-catenin and Synaptic&#160; Plasticity
The cadherin-catenin complexes are an important part of synaptic plasticity - the strengthening and weakening of synaptic connections involved in memory. For example, p120 is involved in the stabilization of glutamate receptors on the synaptic membrane, thus maintaining long-term potentiation. It is also involved in the stabilization of neural cadherins by preventing their endocytosis and promoting cadherin clustering at synaptic junctions.&#160;Downregulating p120 has been shown to prevent adhesion between the pre-and postsynaptic neurons.

Catenins are characterized by multiple binding domains and dynamic structures that allow them to function as linker proteins in cell junction complexes. ...

Education

JoVE Core

Cell Biology

Unit 1

Cell-Cell Interactions

KEY TERMS AND CONCEPTS

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 depends on the type of cell junction. At adherens junctions, alpha-catenin, beta-catenin, and p120-catenin help organize the actin cytoskeleton. Alpha-catenin binds directly to F-actin. p120 helps control actin polymerization through Rho GTPases.

At desmosomes, catenins help organize intermediate filaments instead of actin. In this case, special catenins called plakoglobin and plakophilin interact with other proteins such as desmoplakin. These interactions help build strong cell connections in tissues that need mechanical support.

Beta-catenin also has a signaling role in the Wnt pathway. When a Wnt signal molecule binds to the frizzled receptor on the cell surface, a cascade raises beta-catenin levels in the cytoplasm. Beta-catenin can then move into the nucleus, bind to transcription factors, and regulate target gene expression. In vertebrates, only one beta-catenin variant is found, and its amino acid sequence is highly conserved across species.

p120-catenin also plays an important role in synaptic plasticity, which is the strengthening and weakening of synaptic connections involved in memory. It helps stabilize glutamate receptors on the synaptic membrane and supports long-term potentiation. p120 also stabilizes neural cadherins by preventing their endocytosis and by promoting cadherin clustering at synaptic junctions. When p120 is downregulated, adhesion between pre- and postsynaptic neurons is reduced.

Catenins in Cell Junctions and Signaling

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

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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 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

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

Explore how catenins link cadherins to the cytoskeleton, support Wnt signaling, and help strengthen synapses in high school biology.

Catenins in Cell Junctions and Signaling | 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.

Catenins in Cell Junctions and Signaling

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