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

Gap junctions are communication channels between adjacent animal cells.
These channels are composed of transmembrane proteins called connexins. Six connexin molecules form a hemichannel called a connexon .
A homomeric connexon comprises six copies of the same connexin protein, whereas a heteromeric connexon is formed by different connexin proteins.
The connexons can dynamically diffuse through the membrane. When one connexon on a cell membrane encounters another connexon on the adjacent cell, they pair up to form a complete channel.
Clusters of such channels form the gap junction plaques that allow the exchange of ions, secondary messengers, sugars, and other small molecules between cells.
The diversity of connexins and their combinations confers channel selectivity for specific molecules.
The transport of solutes is further regulated by the opening and closing of channels in response to various stimuli, such as voltage difference, calcium ion concentration, and pH.
For example, gap junctions in heart muscles respond to voltage differences and synchronize the flow of ions between groups of muscle cells, thus generating rhythmic contractions in the heart.

gap junctions

Gap Junctions

The cytoplasm of adjacent animal cells can exchange small molecules, ions, and secondary messengers via the communication channels which form the gap junctions. These junctions comprise a few hundred to thousands of molecular channels, each made of two halves, called the connexon hemichannel. A connexon is a hexamer of six transmembrane connexin proteins, which assemble radially, thus forming a pore or channel in the center. One connexon hemichannel docks with a corresponding connexon on the adjacent cell, completing the channel.
Gap Junction Dynamics
Connexins are translated by the ribosome on the rough endoplasmic reticulum and are cotranslationally inserted into the ER membrane. The monomers are then transported to the Golgi network, where they oligomerize. The hexameric connexons are transported from the trans-Golgi network to the plasma membrane via secretory vesicles. The connexons can freely move along the plasma membrane until they encounter other connexons, forming clusters. Thus a growing cluster has new connexons continually added to its periphery, forming a gap junction plaque. At the center of this plaque, old connexons are endocytosed and marked for degradation. Gap junctions are, therefore, dynamic assemblies with a constant turnover of connexons at the membrane.
Invertebrate Gap Junctions
Gap junctions in invertebrates have a similar structure to those in vertebrates; however, they comprise different proteins called innexins (invertebrate connexins). Though innexins have a similar transmembrane structure, they don&#39;t share sequence homology with connexins. They also differ from their vertebrate counterparts in requiring eight units to form an innexon hemichannel instead of six.
Counterparts in Plants
Unlike in animal tissues, where the membranes of adjacent cells are in direct contact, the cell walls in plant tissues prevent direct contact of adjacent plasma membranes. Intercellular communication and exchange of molecules thus occur via specialized junctions called the plasmodesmata. The membrane of one cell is continuous with that of the adjacent cell at these junctions, forming a tubular channel of about 20 to 40nm in diameter. Thus, the cytoplasm of adjacent cells is contiguous, allowing the regulated exchange of various small molecules.

The cytoplasm of adjacent animal cells can exchange small molecules, ions, and secondary messengers via the communication channels which form the gap ...

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JoVE Core

Cell Biology

Unit 1

Cell-Cell Interactions

KEY TERMS AND CONCEPTS

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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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

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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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