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

As junções comunicantes são canais de comunicação entre células animais adjacentes.
Esses canais são compostos de proteínas transmembranares chamadas conexinas. Seis moléculas de conexina formam um hemicanal chamado conexon .
Um conexon homomérico compreende seis cópias da mesma proteína conexina, enquanto um conexon heteromérico é formado por diferentes proteínas conexina.
Os conexons podem se difundir dinamicamente através da membrana. Quando um conexon em uma membrana celular encontra outro conexon na célula adjacente, eles se emparelham para formar um canal completo.
Aglomerados de tais canais formam as placas de junção comunicante que permitem a troca de íons, mensageiros secundários, açúcares e outras pequenas moléculas entre as células.
A diversidade de conexinas e suas combinações confere seletividade de canal para moléculas específicas.
O transporte de solutos é ainda regulado pela abertura e fechamento de canais em resposta a vários estímulos, como diferença de tensão, concentração de íons cálcio e pH.
Por exemplo, as junções comunicantes nos músculos cardíacos respondem às diferenças de voltagem e sincronizam o fluxo de íons entre grupos de células musculares, gerando contrações rítmicas no coração.

<ol>
	<li>Laird, Dale W. "Ciclo de vida das conexinas na saúde e na doença." Jornal Bioquímico 394.3 (2006): 527-543.</li>
	<li>Bauer, Reinhard, et al. "Comunicação intercelular: a família multiproteica Drosophila innexin de proteínas de junção comunicante." Química e biologia 12.5 (2005): 515-526.</li>
	<li>Sager, Ross E. e Jung-Youn Lee. "Plasmodesmata em resumo." Jornal de ciência celular 131.11 (2018): jcs209346.</li>
</ol>

junções comunicantes

Gap Junctions

O citoplasma de células animais adjacentes pode trocar pequenas moléculas, íons e mensageiros secundários através dos canais de comunicação que formam as junções comunicantes, ou junções gap. Essas junções compreendem de algumas centenas a milhares de canais moleculares, cada um feito de duas metades, chamados de hemicanal de conexão. Um conexônio é um hexâmero de seis proteínas conexinas transmembranares que se agrupam radialmente, formando assim um poro, ou canal, no centro. Um hemicanal de conexão se acopla a uma conexão correspondente na célula adjacente, completando o canal. Dinâmica das Junções Comunicantes As conexinas são traduzidas pelo ribossomo no retículo endoplasmático rugoso e são inseridas co-translacionalmente na membrana do RE. Os monômeros são então transportados para a rede de Golgi, onde oligomerizam. Os conexônios hexaméricos são transportados da rede trans-Golgi para a membrana plasmática através de vesículas secretoras. Os conexônios podem mover-se livremente ao longo da membrana plasmática até encontrarem outros conexônios, formando aglomerados. Assim, um aglomerado crescente tem novos conexônios continuamente adicionadas à sua periferia, formando uma placa de junções comunicantes. No centro desta placa, conexônios antigos são endocitados e marcados para degradação. As junções comunicantes são, portanto, conjuntos dinâmicos com uma renovação constante de conexônios na membrana. Junções comunicantes de invertebrados As junções comunicantes em invertebrados têm uma estrutura semelhante às dos vertebrados; no entanto, eles compreendem diferentes proteínas chamadas inexinas (conexinas de invertebrados). Embora as inexinas tenham uma estrutura transmembrana semelhante, elas não compartilham uma homologia de sequência com as conexinas. Eles também diferem de seus equivalentes vertebrados por exigirem oito unidades para formar um hemicanal innexon em vez de seis. Homólogos em Plantas Ao contrário dos tecidos animais, onde as membranas das células adjacentes estão em contato direto, as paredes celulares dos tecidos vegetais impedem o contato direto das membranas plasmáticas adjacentes. A comunicação intercelular e a troca de moléculas ocorrem, portanto, por meio de junções especializadas chamadas plasmodesmos. A membrana de uma célula é contínua com a da célula adjacente nessas junções, formando um canal tubular com cerca de 20 a 40 nm de diâmetro. Assim, o citoplasma das células adjacentes é contíguo, permitindo a troca regulada de várias moléculas pequenas.

Junções Comunicantes

O citoplasma de células animais adjacentes pode trocar pequenas moléculas, íons e mensageiros secundários através dos canais de comunicação que formam a lacuna ...

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

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

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

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

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 - 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.

Cell Communication Through Gap Junctions

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