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

Las uniones celulares son grandes complejos multiproteicos que pueden unir las células a la matriz extracelular formando uniones célula-matriz, o actuar como puntos de contacto entre células vecinas en los tejidos para formar uniones célula-célula.
Las células suelen tener tres tipos principales de uniones célula-célula: uniones estrechas, de anclaje y de separación, cada una con una estructura y función distintas.
Consideremos el epitelio cilíndrico. Las uniones estrechas cerca de los ápices de estas células mantienen unidas las membranas plasmáticas adyacentes y funcionan como una barrera para el flujo de moléculas a través de los espacios intercelulares.
Debajo de esta porción apical hay dos tipos de uniones de anclaje: las uniones adherentes y las desmosomas.
Juntas, estas uniones de anclaje forman una red de citoesqueletos interconectada a través de las células que ayuda a resistir las fuerzas mecánicas.
El tercer tipo, las uniones gap, se dispersan por toda la membrana plasmática, particularmente hacia el extremo basal. Estas uniones actúan como canales de comunicación entre las células adyacentes, permitiendo el paso de moléculas e iones.

<ol>
	<li>Campbell, Hannah K., Jessica L. Maiers y Kris A. DeMali. "Interacción entre uniones estrechas y uniones adherentes". Investigación celular experimental 358.1 (2017): 39-44.</li>
	<li>Giepmans, Ben NG. "Uniones gap y proteínas que interactúan con conexinas". Investigación cardiovascular 62.2 (2004): 233-245.</li>
</ol>

descripción general de las uniones célula-célula

Overview of Cell-Cell Junctions

La compleja disposición tridimensional de las células en cualquier organismo multicelular se define y se mantiene mediante interacciones de las células entre sí y con la matriz extracelular. Las uniones célula-célula son estructuras especializadas donde los complejos multiproteicos de una célula interactúan con los complejos multiproteicos de otra célula. Estas uniones celulares se clasifican en tres tipos principales según su función: uniones de oclusión, de anclaje y de separación.

Uniones oclusivas o estrechas

Las uniones estrechas funcionan principalmente para impedir el movimiento de moléculas como el agua y los solutos a través de los espacios intercelulares. Están presentes como una serie de proteínas transmembrana que interactúan directamente con las mismas proteínas de la membrana adyacente. De este modo, mantienen las dos membranas plasmáticas muy cerca una de la otra, impidiendo el paso de moléculas. Las uniones estrechas también pueden ser selectivamente permeables, lo que permite el paso de iones de carga específica y bloquea otros.

Uniones de anclaje

Las uniones de anclaje mantienen unidas las células y proporcionan resistencia mecánica a la estructura del tejido. Forman puntos de contacto donde el citoesqueleto de una célula se ancla al de sus células vecinas mediante moléculas de adhesión transmembrana llamadas cadherinas. Existen dos tipos de uniones de anclaje:

<ol style="list-style-type: disc;">
	<li>uniones adherentes que unen el citoesqueleto de actina y</li>
	<li>desmosomas que unen los filamentos intermedios.</li>
</ol>

Por tanto, forman una extensa red citoesquelética que funciona de forma cooperativa para mantener la estructura y función del tejido.

Uniones gap

Las uniones en hendidura son canales de proteínas que facilitan la comunicación entre las células. Las proteínas transmembrana constituyentes forman un canal que une los citoplasmas de las células adyacentes y permiten el intercambio de moléculas e impulsos eléctricos. El movimiento de las moléculas está regulado por la apertura y cierre de las proteínas del canal. Por ejemplo, la señal de las contracciones rítmicas del corazón pasa de una célula a otra a través de las uniones hendidas del tejido del músculo cardíaco. Las células vegetales, sin embargo, no pueden intercambiar moléculas a través de uniones en hendidura debido a la pared celular. En cambio, forman canales de comunicación llamados plasmodesmos. Estos son poros revestidos de membranas que conectan las células a través de las paredes celulares de modo que el citoplasma de una célula es contiguo al de otra. Por tanto, existe libre circulación de solutos e iones a través de células vegetales conectadas por plasmodesmos.

Descripción general de las uniones célula-célula

La compleja disposición tridimensional de las células en cualquier organismo multicelular se define y mantiene mediante las interacciones de las células entre sí y ...

Education

Educación

JoVE Core

Cell Biology

Biología Celular

Unit 1

Unidad 1

Cell-Cell Interactions

Interacciones célula-célula

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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 Biología Celular ilustra procesos celulares complejos mediante completos vídeos animados fáciles de entender. Esta colección se centra en los componentes esenciales de las células y su funcionamiento, incluyendo los orgánulos y las membranas, el transporte celular y el metabolismo energético celular. Todo este material se complementa con los vídeos de científicos en acción, que muestran la aplicación de la biología celular en experimentos reales de investigación.

Cell Junctions in Tissues

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