Name: cell-to-cell signaling via channels
Uploaded: 2026-08-26T08:20:48.315Z
Duration: 1 min 37 s
Channel: JoVE

Contact-dependent cell communication requires direct physical contact between neighboring cells. In juxtacrine signaling, a membrane-bound ligand on one cell binds to a membrane-bound receptor on an adjacent cell, as in the Notch&#x2013;Delta signaling pathway.In animal tissues, gap junctions are intercellular junctions that form direct communication channels between neighboring cells. Gap junctions are specialized protein channels that connect the cytoplasm of neighboring cells.These junctions allow selective small ions and water-soluble molecules to pass through, but exclude macromolecules, such as large peptides.Gap junctions are made of transmembrane connexin proteins. Six connexin proteins assemble to form a connexon. When one connexon on a cell membrane encounters another connexon on an adjacent cell, they create a complete continuous channel that can open and close.Similarly, in plants, the rigid walls of adjacent cells are connected by membrane-lined channels called plasmodesmata.Each plasmodesma allows molecules to move between cells mainly through the cytoplasmic sleeve, which is the space between the plasma membrane and the desmotubule. The desmotubule is continuous with the en

contact-dependent cell communication

Contact-Dependent Cell Communication

Contact-dependent cell communication, as the name suggests, requires that communicating cells be in direct contact with each other. This is achieved either through receptor-ligand interactions or by specialized cytoplasmic channels that allow the flow of small molecules between cells. In animal cells, channels called gap junctions facilitate contact-dependent signaling in certain tissues, whereas plasmodesmata perform a similar function in plants.Juxtacrine Signaling Juxtacrine signaling requires communicating cells to be in direct physical contact. Unlike endocrine or paracrine signaling, signaling molecules are not released into the extracellular environment. Instead, communication occurs through the binding of membrane-bound ligands to receptors on adjacent cells or through specialized cytoplasmic channels that directly connect neighboring cells. These channels allow the exchange of small molecules and ions. In animals, receptor&#x2013;ligand interactions, such as Delta&#x2013;Notch signaling, regulate cell differentiation during development.Gap Junctions In animal cells, gap junctions are formed when a set of six proteins called connexins arrange themselves to form a cylindrical structure within the plasma membrane. This cylindrical structure is called a connexon. When connexons of adjacent animal cells align, a channel forms between the two cells. The opening and closing of these channels is regulated by various enzymes. The selectivity of gap junctions allows a single cell to regulate communication with its neighbors and coordinate a complex multicellular response. For example, the gap junctions in cardiac muscles control the flow of ions in a rhythmic manner. This regulates the electrical signal that passes through the cells, allowing the heart muscles to contract and relax in coordination.Plasmodesmata In plants, contact-dependent signaling occurs through cytoplasmic channels called plasmodesmata. These channels pass through both the cell wall and the cell membrane.Unlike gap junctions, plasmodesmata are more flexible in allowing molecules to pass through. At the center of most plasmodesmata channels is a continuous endoplasmic reticulum tubule (ER) that runs between the two cells. This ER extension, called the desmotubule, is surrounded by the cytoplasmic sleeve. This sleeve permits the passive and active transport of molecules. However, for the transportation of larger molecules, like transcription factors, small RNA, or other nucleic acids and proteins, the plasmodesmata can dilate. Because of this ability, plasmodesmata play a key role in the spatial organization of cells and their fate. Unfortunately, this ability also permits viral infection to quickly spread between cells.

Contact-dependent signaling, as the name suggests, requires that communicating cells be in direct contact with each other. This is achieved either through ...

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Biology

Cellular Processes

Cell Signaling

KEY TERMS AND CONCEPTS

cell-to-cell signaling via channels

Cell-to-cell signaling can happen when neighboring cells are in direct contact. In this kind of communication, cells use receptor-ligand interactions or special cytoplasmic channels to move small molecules between them.

In animal cells, these channels are called gap junctions. They form when six proteins called connexins assemble into a cylindrical structure in the plasma membrane called a connexon. When connexons from two adjacent cells line up, a channel opens between the cells. Enzymes help control when these channels open and close. Gap junctions are selective, so a cell can control communication with nearby cells and help create a coordinated multicellular response.

A clear example appears in cardiac muscle. Gap junctions help control the movement of ions in a rhythmic way. This supports the electrical signal that moves through the tissue and helps heart muscle contract and relax in sync.

Plants use a similar system called plasmodesmata. These cytoplasmic channels pass through both the cell wall and the cell membrane. They are more flexible than gap junctions in the kinds of molecules they allow to pass.

Most plasmodesmata contain a continuous endoplasmic reticulum tubule that connects the two cells. This ER extension is called the desmotubule, and it is surrounded by the cytoplasmic sleeve. The sleeve allows passive and active transport of molecules. Plasmodesmata can also widen to move larger molecules, such as transcription factors, small RNA, and other nucleic acids and proteins. This makes them important for cell organization and cell fate, but it also allows viruses to spread quickly from cell to cell.

Cell-to-Cell Signaling via Channels

what is cell signaling?

How Cells Send and Receive Signals

Cell signaling lets cells send and receive messages from the environment and from other cells. Even with a protective membrane, cells need to detect changes and respond to them. Unicellular and multicellular organisms use signaling to stay coordinated and to react to outside cues. Cells often rely on receptor proteins in the membrane to sense information. Skin cells can respond to touch, and photoreceptors in the retina can detect light. Most cells respond to chemical signals such as hormones,...

internal receptors

Steroid Hormones and Intracellular Receptors

Steroid hormones and other small signaling molecules can pass through the cell membrane and bind to intracellular receptors inside the cell. These receptors are also called internal receptors. Many hydrophilic signals cannot cross the plasma membrane, so this pathway is used by signals that are small or hydrophobic. Nitric oxide, or NO, also uses this type of signaling. When a ligand, which is a signaling molecule, binds to a receptor in the cytoplasm or nucleus, the receptor changes shape.

Cell-to-cell signaling can happen when neighboring cells are in direct contact. In this kind of communication, cells use receptor-ligand interactions or special cytoplasmic channels to move small molecules between them. In animal cells, these channels are called gap junctions. They form when six proteins called connexins assemble into a cylindrical structure in the plasma membrane called a connexon. When connexons from two adjacent cells line up, a channel opens between the cells. Enzymes help...

autocrine signaling

Self-Signaling Cells in Immunity and Cancer

Autocrine signaling is a cell communication method in which a cell sends a signal to itself. The same cell releases an extracellular signaling molecule and also has receptors that can bind to that molecule. This lets the cell respond to its own message. In the immune system, this process is important for homeostasis, or keeping body conditions stable. A well-studied example is the macrophage, an immune cell that secretes cytokines such as interleukin-1, or IL-1. Macrophages also have membrane...

paracrine signaling

Local Cell Signaling in Blood and Healing

Local cell signaling helps cells communicate with nearby neighbors using released signaling molecules. These molecules act only over a short distance because they break down quickly or are inactivated if they are not taken up. This type of signaling supports processes such as nitric oxide signaling in blood vessels, neuron-to-neuron communication at synapses, blood clotting, tissue repair, and local allergic skin reactions. A clear example is nitric oxide signaling in blood vessels. The...

synaptic signaling

Chemical and Electrical Synapses

Neurons send signals across synapses, which are junctions between cells. These signals can excite or inhibit other neurons or target cells such as muscles. Most synapses are chemical. Some are electrical. Chemical synapses use action potentials, which are electrical impulses, to trigger the release of neurotransmitters. The sending neuron is the presynaptic neuron, and the receiving neuron is the postsynaptic neuron. An action potential travels along the axon and reaches the axon terminal,...

endocrine signaling

Hormones Travel to Distant Target Cells

Endocrine signaling uses hormones to send messages to target cells in other organs. Endocrine cells release these hormones into the circulatory system, which carries the signal through the body. Because the hormone reaches the whole organism, only cells with the right receptors respond. This kind of signaling usually acts slowly, but its effects last longer. Endocrine cells can use cell surface receptors or intracellular receptors, depending on the hormone. Cell surface receptors are...

bacterial signaling

Quorum Sensing in Bacteria

Quorum sensing lets bacteria coordinate behavior by sensing how many cells are nearby. Bacteria can signal inside the cell or between cells. When many bacteria act together, they can behave like a community and change gene expression as a group. This signaling starts with autoinducers, or AIs. Individual bacteria make AIs and release them across the cell membrane into the surrounding space. Some AIs diffuse out passively along a concentration gradient, while others are moved out by active...

yeast signaling

Yeast Cell Communication in Mating

Yeast cell communication helps control mating, colony growth, and other cell responses. Yeasts are single-celled organisms, but unlike bacteria, they are eukaryotes with a nucleus. Their signaling works much like cell signaling in other eukaryotic cells. A signal often begins when a ligand, such as a protein or small molecule released from a yeast cell, binds to a receptor on the cell surface. This binding activates second-messenger kinases, which then switch transcription factors on or off.

g protein-coupled receptors

GPCR Signaling Through G Proteins

G-protein coupled receptors, or GPCRs, start cell signaling after a ligand binds to the receptor. The receptor is a single polypeptide that crosses the cell membrane seven times. These membrane loops create an outside pocket that fits a specific ligand, such as a neurotransmitter or hormone. The inside loops connect to a G-protein.

enzyme-linked receptors

Trk Receptors in Cell Signaling

Trk receptors are enzyme-linked receptors that help cells respond to growth factors and some hormones. They belong to the receptor tyrosine kinase, or RTK, family. These receptors can trigger several signals inside a cell after they are activated. Neurotrophin receptors are one RTK group and include TrkA, TrkB, and TrkC, which are tropomyosin-related kinase receptors. TrkA binds nerve growth factor, neurotrophin-6, and neurotrophin-7. TrkB binds brain-derived neurotrophic factor, or BDNF, and...

ion channels

Ion Channels in Cells and Membranes

Ion channels are membrane proteins that help cells move ions across the plasma membrane. Ions such as sodium, potassium, and calcium move into and out of cells to maintain the electrochemical gradient. This gradient supports cell size and volume, nerve signaling, and gas and nutrient exchange. Ion channels are specialized integral membrane proteins that let specific ions pass down their electrochemical gradient. Their main job is to help keep the membrane potential, which is needed for cell...

what are second messengers?

Cell Signals That Use Second Messengers

Cell signals often use second messengers to carry messages inside the cell. Many receptor-binding ligands are hydrophilic, so they do not cross the cell membrane. Instead, the signal is relayed to an internal messenger that can spread the message farther. G-protein coupled receptors can activate the phosphoinositol pathway and the cyclic AMP, or cAMP, pathway. In the phosphoinositol pathway, the receptor activates phospholipase C. This enzyme hydrolyzes phosphatidylinositol biphosphate, or...

intracellular signaling cascades

Cell-Surface Receptor Signal Cascades

Cell-surface receptor signal cascades move information from outside the cell into the cytoplasm. This process is called signal transduction. It happens only with cell-surface receptors, because they cannot interact with most cell parts, such as DNA. Internal receptors are different. They can interact directly with DNA in the nucleus and help start protein synthesis. When a ligand binds to a receptor, the receptor changes shape. That shape change affects the receptor’s intracellular domain or...

key terms and concepts

Learn how direct cell contact enables signaling through gap junctions in animals and plasmodesmata in plants, including ion flow, transport, and viral spread.

Cell-to-Cell Signaling via Channels | JoVE K12

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Cell-to-Cell Signaling via Channels

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