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

Le giunzioni gap sono canali di comunicazione tra cellule animali adiacenti.
Questi canali sono composti da proteine transmembrana chiamate connessine. Sei molecole di connessina formano un emicanale chiamato connexon .
Un connessione omomerico comprende sei copie della stessa proteina connessina, mentre un connessione eteromerico è formato da diverse proteine connessine.
I connessioni possono diffondersi dinamicamente attraverso la membrana. Quando un connessione su una membrana cellulare incontra un altro connettione sulla cellula adiacente, si accoppiano per formare un canale completo.
I gruppi di tali canali formano le placche di giunzione gap che consentono lo scambio di ioni, messaggeri secondari, zuccheri e altre piccole molecole tra le cellule.
La diversità delle connessine e delle loro combinazioni conferisce selettività di canale per molecole specifiche.
Il trasporto dei soluti è ulteriormente regolato dall'apertura e chiusura dei canali in risposta a vari stimoli, come la differenza di tensione, la concentrazione di ioni calcio e il pH.
Ad esempio, le giunzioni gap nei muscoli cardiaci rispondono alle differenze di tensione e sincronizzano il flusso di ioni tra gruppi di cellule muscolari, generando così contrazioni ritmiche nel cuore.

<ol>
	<li>Laird, Dale W. "Ciclo di vita delle connessine in salute e malattia". Giornale biochimico 394.3 (2006): 527-543.</li>
	<li>Bauer, Reinhard, et al. "Comunicazione intercellulare: la famiglia multiproteica Drosophila innexin di proteine della giunzione gap." Chimica e biologia 12.5 (2005): 515-526.</li>
	<li>Sager, Ross E. e Jung-Youn Lee. "Plasmodesmata a colpo d'occhio." Giornale di scienza cellulare 131.11 (2018): jcs209346.</li>
</ol>

giunzioni di gap

Gap Junctions

Il citoplasma delle cellule animali adiacenti può scambiare piccole molecole, ioni e messaggeri secondari attraverso i canali di comunicazione che formano le giunzioni comunicanti. Queste giunzioni comprendono da poche centinaia a migliaia di canali molecolari, ciascuno costituito da due metà, chiamati emicanale di connessina. Una connessone è un esamero di sei proteine connessine transmembrana, che si assemblano radialmente, formando così un poro o canale al centro. Un emicanale connessina si aggancia con un connessone corrispondente sulla cella adiacente, completando il canale.

Dinamica della giunzione gap

Le connessine vengono tradotte dal ribosoma sul reticolo endoplasmatico ruvido e vengono inserite in modo co-traduzionale nella membrana dell'ER. I monomeri vengono poi trasportati nella rete del Golgi, dove oligomerizzano. I connessioni esamerici vengono trasportati dalla rete trans-Golgi alla membrana plasmatica tramite vescicole secretorie. I connessioni possono muoversi liberamente lungo la membrana plasmatica finché non incontrano altri connessoni, formando cluster. Pertanto un cluster in crescita ha nuovi connessi continuamente aggiunti alla sua periferia, formando una placca di giunzione. Al centro di questa placca, i vecchi connessioni sono endocitati e contrassegnati per la degradazione. Le giunzioni comunicanti sono, quindi, insiemi dinamici con un ricambio costante di connessioni sulla membrana.

Giunzioni degli spazi tra gli invertebrati

Le giunzioni gap negli invertebrati hanno una struttura simile a quelle dei vertebrati; tuttavia, comprendono diverse proteine chiamate innexine (connexine degli invertebrati). Sebbene le connessine abbiano una struttura transmembrana simile, non condividono l'omologia di sequenza con le connessine. Differiscono anche dalle loro controparti vertebrati perché richiedono otto unità per formare un emicanale innexina invece di sei.

Controparti nelle piante

A differenza dei tessuti animali, dove le membrane delle cellule adiacenti sono in contatto diretto, le pareti cellulari dei tessuti vegetali impediscono il contatto diretto delle membrane plasmatiche adiacenti. La comunicazione intercellulare e lo scambio di molecole avvengono quindi tramite giunzioni specializzate chiamate plasmodesmi. La membrana di una cellula è continua con quella della cellula adiacente in corrispondenza di queste giunzioni, formando un canale tubolare di circa 20-40 nm di diametro. Pertanto, il citoplasma delle cellule adiacenti è contiguo, consentendo lo scambio regolato di varie piccole molecole.

Giunzioni di gap

Il citoplasma delle cellule animali adiacenti può scambiare piccole molecole, ioni e messaggeri secondari attraverso i canali di comunicazione che formano il gap ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Cell-Cell Interactions

Interazioni cellula-cellula

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

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Catenins in Cell Junctions and Signaling

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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 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 Communication Through Gap Junctions

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