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

As cateninas são um grupo diversificado de proteínas adaptadoras que participam da adesão célula-célula.
As cateninas têm vários domínios de ligação que se ligam a caderinas, componentes do citoesqueleto e várias proteínas reguladoras do citoesqueleto. Assim, eles ligam o citoesqueleto com caderinas nos locais de adesão celular.
Enquanto algumas cateninas, como a placoglobina e a placofilina, ajudam a estabelecer conexões estáveis entre as caderinas e os filamentos intermediários, outras, como alfa e beta-cateninas, organizam dinamicamente o citoesqueleto de actina na membrana plasmática.
A organização dos filamentos de actina começa com a ligação da beta-catenina ao domínio citosólico de uma molécula de caderina. Em seguida, a alfacatenina se liga à beta-catenina.
Outra catenina, p120, também se liga a esses complexos e regula a estabilidade das caderinas na membrana.
À medida que alguns complexos de caderina-catenina se agrupam, as alfa-cateninas se dissociam e formam dímeros citosólicos.
Esses dímeros de alfa-catenina interagem fortemente com a actina filamentosa e ajudam a organizar os feixes de actina, fornecendo força ao citoesqueleto aos locais de adesão celular.

<ol>
	<li>Perez-Moreno, Mirna e Elaine Fuchs. "Cateninos: impedindo que as células tenham seus sinais cruzados." Célula de desenvolvimento 11.5 (2006): 601-612.</li>
	<li>Lua, Randall T. "Via Wnt / β-catenina." STKE da Ciência 2005.271 (2005): cm1-cm1.</li>
</ol>

cateninas

Catenins

As cateninas são caracterizadas por múltiplos domínios de ligação e estruturas dinâmicas que lhes permitem funcionar como proteínas ligantes em complexos de junção celular. Todas as cateninas, exceto a α-catenina, contêm uma sequência proteica característica chamada repetição de tatu e, portanto, também são chamadas de proteínas tatu. Cateninas em junções celulares As cateninas ligam-se a moléculas de adesão celular, como as caderinas, e ligam-nas a diferentes proteínas do citoesqueleto, dependendo do tipo de junção celular. Na junção aderente, o citoesqueleto de actina é organizado dinamicamente pelas cateninas alfa, beta e p120, direta ou indiretamente. Por exemplo, a α-catenina liga-se diretamente à F-actina, enquanto a p120 regula a polimerização da actina via Rho GTPases. Nos desmossomos, entretanto, os filamentos intermediários são organizados pelas interações de cateninas especiais chamadas placoglobina e placofilina com outras proteínas, como a desmoplacina. β-catenina e sinalização celular Além de se ligar às caderinas nas junções celulares, a β-catenina também pode funcionar na sinalização celular, como a via Wnt. Nessa via, a ligação de uma molécula sinalizadora Wnt ao receptor da superfície celular, denominado frizzled, desencadeia uma cascata que aumenta a concentração de β-catenina no citoplasma. Isto permite que a β-catenina se transloque para o núcleo, se ligue a fatores de transcrição e regule a expressão do gene alvo. Ao contrário de outras cateninas que possuem diversas variantes específicas de tecidos entre organismos, apenas uma única variante de β-catenina é encontrada em vertebrados. Esta variante é composta por uma sequência de aminoácidos altamente conservada em todas as espécies de vertebrados. p120-catenina e plasticidade sináptica Os complexos caderina-catenina são uma parte importante da plasticidade sináptica – o fortalecimento e enfraquecimento das conexões sinápticas envolvidas na memória. Por exemplo, a p120 está envolvida na estabilização dos receptores de glutamato na membrana sináptica, mantendo assim a potenciação a longo prazo. Ela também está envolvida na estabilização das caderinas neurais, prevenindo sua endocitose e promovendo o agrupamento de caderinas nas junções sinápticas. Demonstrou-se que a regulação negativa da p120 previne a adesão entre os neurônios pré e pós-sinápticos.

Cateninas

As cateninas são caracterizadas por múltiplos domínios de ligação e estruturas dinâmicas que lhes permitem funcionar como proteínas ligantes em complexos de junções celulares. ...

Education

JoVE Core

Cell Biology

Biologia Celular

Unit 1

Unidade 1

Cell-Cell Interactions

Interações Célula-Célula

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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

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 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 - Biologia Celular ilustra processos celulares complexos em vídeos de animação fáceis de entender e, ao mesmo tempo, abrangentes. Esta coleção foca nos componentes e funções essenciais das células, incluindo organelas e membranas, transporte celular e energia celular. É complementado por vídeos de Cientistas em ação que demonstram a aplicação da biologia celular em experimentos de pesquisa do mundo real.

Catenins in Cell Junctions and Signaling

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