Name: cell signaling pathways and responses
Uploaded: 2023-04-30T11:38:51.000Z
Duration: 1 min 23 s
Channel: JoVE

Cells use a variety of signaling mechanisms to coordinate cellular processes and communicate with other cells. A signaling pathway is initiated when a signaling molecule called a ligand binds to its target receptor.
Paracrine signaling occurs when a secreted ligand targets the neighboring cells. Whereas, autocrine signaling occurs when the ligand targets the same cell that released it.
In a juxtacrine or contact-dependent signaling pathway, a ligand remains bound to the cell surface and interacts directly with the receptors on adjacent cells. Small soluble ligands may also directly flow between cells via gap junctions in the plasma membrane.
Multicellular organisms coordinate cellular behavior over a long distances. In endocrine signaling, hormones travel to different body parts through the bloodstream.
Synaptic signaling between neurons is a specialized form of long-range signaling. At the synaptic junction, the axon terminal of a neuron secretes ligands called neurotransmitters to communicate with target cells.
Additionally, quorum sensing is carried out by some bacterial communities to react together by sensing a critical concentration of signaling ligands.

overview of cell signaling

Overview of Cell Signaling

Despite the protective membrane that separates a cell from the environment, cells need the ability to detect and respond to environmental changes. Additionally, cells often need to communicate with one another. Unicellular and multicellular organisms use a variety of cell signaling mechanisms to communicate with the environment.
Cells respond to many types of information, often through receptor proteins positioned on the membrane. For example, skin cells respond to and transmit touch information, while photoreceptors in the retina can detect light. Most cells, however, have evolved to respond to chemical signals, including hormones, neurotransmitters, and many other types of signaling molecules. Cells can even coordinate different responses elicited by the same signaling molecule.
Typically, cell signaling involves three steps: (1) reception, (2) transduction, and (3)&#160; response. In most signal reception, a membrane-impermeable molecule, or ligand, causes a change in a membrane receptor; however, some signaling molecules, such as hormones, can cross the membrane to reach their internal receptors. The membrane receptor can then send this signal to intracellular messengers, transducing the message into a cellular response. This intracellular response may include changes in transcription, translation, protein activation, and other responses.
Unicellular organisms such as bacteria can use a type of cell signaling called quorum sensing to detect their concentration in a colony and generate coordinated responses. Eukaryotic cells can release ligands that target the same cell that produced the signal (autocrine signaling) or neighboring cells (paracrine signaling). Signals can even be sent over long distances, as in the case of some hormones, and produce responses in distant cells, called endocrine signaling. Contact-dependent signaling describes physical pathways created between neighboring cells through which cytoplasmic signals can rapidly pass. Nervous system cells can generate rapid responses through a specialization of cell signaling called synaptic signaling.

Despite the protective membrane that separates a cell from the environment, cells need the ability to detect and respond to environmental changes. ...

Education

JoVE Core

Cell Biology

Unit 1

Principles of Cell Signaling

KEY TERMS AND CONCEPTS

cell signaling pathways and responses

Cell signaling pathways help cells detect changes and respond to their environment. Cells also use signaling to communicate with other cells. Both unicellular and multicellular organisms rely on these signaling systems to share information.

Cells often receive messages through receptor proteins on the cell membrane. Skin cells can respond to touch, and photoreceptors in the retina can detect light. Most cells respond to chemical signals such as hormones and neurotransmitters, and the same signal can trigger different responses in different cells.

Cell signaling usually follows three steps: reception, transduction, and response. During reception, a ligand, or signaling molecule, binds to a receptor. In many cases, the ligand cannot cross the membrane, but some hormones can enter the cell and bind to internal receptors. The receptor then passes the message to intracellular messengers, which carry out transduction and lead to a cellular response.

The response can include changes in transcription, translation, protein activation, and other cell activities. Bacteria also use cell signaling through quorum sensing, which helps them detect how crowded the colony is and coordinate their actions. In eukaryotes, signaling can be autocrine, paracrine, endocrine, contact-dependent, or synaptic. Autocrine signals act on the cell that released them, paracrine signals act on nearby cells, endocrine signals travel long distances, contact-dependent signals pass through direct cell connections, and synaptic signaling allows rapid communication in the nervous system.

Cell Signaling Pathways and Responses

Cell signaling pathways help cells detect changes and respond to their environment. Cells also use signaling to communicate with other cells. Both unicellular and multicellular organisms rely on these signaling systems to share information. Cells often receive messages through receptor proteins on the cell membrane. Skin cells can respond to touch, and photoreceptors in the retina can detect light. Most cells respond to chemical signals such as hormones and neurotransmitters, and the same...

types of signaling molecules

Cell Signals That Travel Between Cells

Cell signals that travel between cells carry information in multicellular organisms. These signaling molecules can be small peptides, nucleotides, steroids, fatty acid derivatives, or dissolved gases such as nitric oxide. Some signals act near the cell that released them, while others move over long distances. Other signals stay on the cell surface and work only when cells make contact. Some signaling proteins need extra processing before they can act. Peptide and protein signals are made as...

types of receptors: cell surface receptors

types-of-receptors-cell-surface-receptors

Cell Surface Receptors and Signal Relay

Cell-surface receptors help cells detect signals outside the cell and relay them inward. They are also called transmembrane receptors because they sit in the cell membrane and span the plasma membrane. A ligand is the molecule that binds to the receptor, and it does not need to enter the cell to trigger a response. These receptors are membrane-anchored, integral proteins. They have three main parts. The extracellular domain binds the ligand outside the cell, the transmembrane domain passes...

types of receptors: internal receptors

Steroid Hormone Signaling with Intracellular Receptors

Steroid hormones and other small signaling molecules can enter the cell and bind intracellular receptors. These receptors are found in the cytoplasm or the nucleus. Because the ligands are hydrophobic, they can cross the plasma membrane, unlike many hydrophilic signals. When a ligand binds an intracellular receptor, the receptor changes shape and becomes active. The active receptor can work like a transcription factor. It binds to specific DNA sites and can increase or decrease the...

assembly of signaling complexes

Protein Docking in Cell Signaling

Protein docking helps cells build signaling complexes that pass messages inside the cell. These multiprotein complexes form through protein-protein interactions at the cytoplasmic side of transmembrane receptors. They can also include enzymatic and non-enzymatic proteins linked to the receptor. Together, they help activate and spread intracellular signals that control cell functions. Cell signaling often depends on interaction domains, which are protein parts that recognize specific binding...

interactions between signaling pathways

Cross-Talk in Cell Signaling Pathways

Cell signaling pathways often cross-talk with one another. This means one pathway can influence another instead of acting alone. Cells use these linked pathways to combine signals from the environment and respond in a controlled way. One common pattern is convergence. In convergence, two separate signaling pathways meet at the same functional unit. That unit may be a single protein or a protein complex. The final response can be different from, or stronger than, the response from either...

amplifying signals via second messengers

Cell-Surface Receptors and Second Messengers

Cell-surface receptors use second messengers to carry signals into the cell. Many receptor-binding ligands are hydrophilic, so they do not cross the cell membrane. Instead, they bind to receptors on the outside of the cell and pass the message to the cytoplasm. G protein-coupled receptors can activate the phosphoinositol pathway and the cAMP pathway. In the phosphoinositol pathway, the receptor activates phospholipase C. This enzyme splits phosphatidylinositol biphosphate, or PIP2, into two...

amplifying signals via enzymatic cascade

Turning Off Amplified Cell Signals

Cell signaling depends on both signal amplification and signal shutoff. When a ligand binds to a cell-surface receptor, the receptor changes shape inside the cell. That change can activate an enzyme function or let the receptor bind other molecules. In many signal transduction pathways, one ligand can trigger many downstream targets, so the signal is amplified. Proteins that pass the signal are often phosphorylated, which means a phosphate group is added at one or more sites. This modification...

diversity in cell signaling responses

Cell Signaling Response Speed and Patterns

Cell signaling responses can differ in both pattern and speed. A cell’s function and communication depend on outside signals, internal signaling pathways, and the response that follows. Different cell types do not use the same set of signaling parts. Receptors are selective for their matching ligands, but once activated, they can affect DNA transcription, protein synthesis, and metabolism. Some signaling systems produce graded responses. In a graded response, the cell output changes in...

cell signaling feedback loops

How Cells Balance Signal Strength

Cell signaling is controlled by feedback loops that connect a cell’s output back to its input. Positive feedback and negative feedback help keep signaling systems working in the right range. These loops are especially important when cells need to respond quickly and then adjust that response. Negative feedback loops act as output limiters in many signaling systems. After an input signal starts a response, the response rises quickly until it reaches a threshold. Beyond that point, the negative...

cell signaling in plants

Plant Receptor Kinases and Growth Signals

Plant receptor kinases help cells communicate and control growth, flowering, fruiting, and activity in roots, shoots, and leaves. These signals also help plants respond to changing environmental conditions. Plant signaling works differently from animal signaling, so the receptors used in plants are not the same as those commonly found in animals. Plants mainly use enzyme-linked receptors. In animals, the largest class of cell-surface receptors is the G-protein coupled receptor, or GPCR.

plant hormones

Plant Hormones and Growth Signals

Plant hormones are chemical signals that help control growth and development in plants. They allow different parts of a plant to communicate and respond to changes in the environment. The main plant hormones include auxin, gibberellins, cytokinins, abscisic acid, and ethylene. Each one has a different role, but they often work together to shape how a plant grows, matures, and reacts to stress. Auxin helps direct plant growth, while gibberellins support stem elongation and seed germination.

key terms and concepts

Learn how cells receive signals, pass them through receptors and messengers, and produce responses through autocrine, paracrine, endocrine, and synaptic signaling.

Cell Signaling Pathways and Responses | 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 Signaling Pathways and Responses

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