Name: cell signaling cascades inside cells
Uploaded: 2021-04-07T12:11:59.000Z
Duration: 1 min 43 s
Channel: JoVE

Intracellular signaling pathways relay and amplify extracellular signals into the cell interior.Several signaling pathways, such as the cyclic AMP, MAPK/ERK, and IP3/DAG pathways, transmit and amplify signals. These signals can change gene expression or cell metabolism.For example, the cyclic AMP signaling pathway can be activated by external ligands, such as adrenaline, that bind to transmembrane G protein-coupled receptors, or GPCRs.Ligand binding changes the shape of the GPCR, allowing it to interact with and activate a G protein on the inside of the cell.Then, the GDP on the G&#x3B1; subunit is replaced by GTP, allowing the G&#x3B1; subunit to separate from the G&#x3B2;&#x3B3; dimer.The activated G&#x3B1; subunit stimulates the enzyme adenylyl cyclase, which converts ATP into cyclic AMP, or cAMP.Once activated, adenylyl cyclase produces many cAMP molecules. As a result, the signal is amplified.cAMP acts as a second messenger and activates cytosolic protein kinase A, or PKA, by causing its regulatory and catalytic subunits to separate.PKA uses ATP to phosphorylate many target proteins, including transcription factors that regulate gene expression.

intracellular signaling cascades

Intracellular Signaling Cascades

Once a ligand binds to a receptor, the signal is transmitted through the membrane and into the cytoplasm. The continuation of a signal in this manner is called signal transduction. Signal transduction only occurs with cell-surface receptors, which cannot interact with most components of the cell, such as DNA. Only internal receptors can interact directly with DNA in the nucleus to initiate protein synthesis. When a ligand binds to its receptor, conformational changes occur that affect the receptor&#x27;s intracellular domain. Conformational changes of the extracellular domain upon ligand binding can propagate through the membrane region of the receptor and lead to activation of the intracellular domain or its associated proteins.After the ligand binds to the cell-surface receptor, the activation of the receptor&#x27;s intracellular components sets off a chain of events that is called a signaling pathway or a signaling cascade. In a signaling pathway, second messengers&#x2013;enzymes&#x2013;and activated proteins interact with specific proteins, which are then activated in a chain reaction that eventually leads to a change in the cell&#x27;s environment, such as an increase in metabolism or specific gene expression. The events in the cascade occur in a series like how a current flows in a river. Interactions that occur before a certain point are defined as upstream events, and events after that point are called downstream events.Signaling pathways can get very complicated very quickly because most cellular proteins can affect different downstream events, depending on the conditions within the cell. A single pathway can branch off toward different endpoints based on the interplay between two or more signaling pathways, and the same ligands are often used to initiate different signals in different cell types. This variation in response is due to differences in protein expression in different cell types. Another complicating element is signal integration of the pathways, in which signals from two or more different cell-surface receptors merge to activate the same response in the cell. This process can ensure that multiple external requirements are met before a cell commits to a specific response.The effects of extracellular signals can also be amplified by enzymatic cascades. At the initiation of the signal, a single ligand binds to a single receptor. However, activation of a receptor-linked enzyme can activate many copies of a component of the signaling cascade, which amplifies the signal.This text is adapted from <a href="https://openstax.org/books/biology-2e/pages/9-2-propagation-of-the-signal">Openstax, Biology 2e, Section 9.2: Propagation of the Signal</a>.

Once a ligand binds to a receptor, the signal is transmitted through the membrane and into the cytoplasm. The continuation of a signal in this manner is ...

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Education

JoVE Core

Molecular Biology

Unit 2

Cell Signaling Pathways

KEY TERMS AND CONCEPTS

cell signaling cascades inside cells

Cell signaling cascades inside cells relay messages from one molecule to the next. These pathways help a cell respond to a signal in a controlled way. The signal is often carried through a series of steps, which can amplify the original message.

A signaling cascade may involve a receptor at the cell surface and molecules inside the cell that pass the message along. Each step can trigger the next step in the chain. This makes the response specific and allows the cell to act on the signal at the right time.

In many cases, these cascades include small signaling molecules and proteins that change activity after receiving a signal. Some pathways are fast, while others lead to longer-lasting changes in cell behavior. Together, they help explain how cells process information and respond to their environment.

Cell Signaling Cascades Inside Cells

notch signaling pathway

Notch Cell Communication and Gene Control

Notch signaling is a conserved cell-to-cell communication pathway in animals. It is unusual because the Notch protein acts as both the receptor and the main signaling molecule. The pathway was first linked to a mutant wing shape in Drosophila melanogaster, where changes in the Notch gene caused a serrated, or "notched," wing margin. The Notch gene was later shown, in 1985, to encode a transmembrane surface receptor. Signaling starts when the Notch receptor on one cell directly binds the Delta...

canonical wnt signaling pathway

Wnt Signals in Development and Disease

Wnt signaling helps cells communicate during development and in adult tissues. The Wnt proteins were first discovered nearly four decades ago in genetic studies of body pattern defects in Drosophila. One gene was named wingless, or wg, because of the fly phenotype it caused. Around the same time, Harold Varmus found that a murine tumor virus activated the mammalian wg homolog, Int-1, and this activity led to tumor formation in mice. The gene family was later called Wnt, a name built from...

hedgehog signaling pathway

Hedgehog Signaling in Growth and Disease

Hedgehog signaling helps guide organ development and tissue balance in both invertebrates and vertebrates. The Hedgehog gene was first identified because it affected the growth of disorganized, hair-like bristles in Drosophila, which looked like hedgehog spines. In mammals, the pathway includes Sonic Hedgehog (Shh), Desert Hedgehog (Dhh), and Indian Hedgehog (Ihh), which each carry out specialized roles in development. Mammalian Hedgehog signaling also depends on the primary cilium, a...

nf-&#954;b-dependent signaling pathway

NF-κB in Immune Defense and Disease

NF-κB is a transcription factor that helps control immune defense and inflammation in animals. It was discovered in 1986 in the lab of Nobel laureate Professor David Baltimore because of its interaction with the immunoglobulin light chain enhancer in B-cells. Since then, researchers have shown that NF-κB regulates the expression of more than 100 genes. Many of the genes controlled by NF-κB support innate and adaptive immune responses. They also help drive inflammatory responses. In this way,...

internal receptors

Internal Receptors and Hormone Signals

Internal receptors are proteins inside a cell that bind signaling molecules. These receptors help certain hormones send messages after they pass through the cell membrane. Because the receptor is internal, the signal acts from within the cell rather than at the surface. Many internal receptors respond to steroid hormones. These hormones can cross the membrane and reach the receptor inside the cell. Once the hormone binds, the receptor can help trigger a response that changes cell activity. <br...

circadian rhythms and gene regulation

Light Control of the Biological Clock

Light helps control the biological clock by shaping circadian rhythms. These 24-hour cycles affect how cells, body systems, and behavior stay in sync with day and night. In animals, this timing system helps regulate complex physiology. The study of circadian rhythm began in 1935, when German zoologists Hans Kalmus and Erwin Bünning found it in Drosophila melanogaster, the fruit fly. The molecular basis stayed unclear for decades. In 1984, Jeffrey C. Hall, Michael Rosbash, and Michael W. Young...

what is cell signaling?

Cell Signaling in Cell Communication

Cell signaling is a key part of cell communication. It helps cells send, receive, and respond to signals so they can work together. A signal starts when a cell releases a molecule. Another cell detects that molecule with a receptor, which is a protein that binds the signal. This binding begins a signaling pathway inside the cell. The pathway carries the message through the cell in a process called signal transduction. In the end, the cell produces a response. That response can change cell...

autocrine signaling

Autocrine Cell Communication

Autocrine cell communication is a signaling process in which a cell sends a message to itself. In this pathway, the cell releases a signaling molecule and also has receptors that can detect that same molecule. This makes the cell both the sender and the receiver. Autocrine signaling is common in cell communication and is often grouped with cytokine signaling. Cytokines are small signaling proteins that help cells communicate, especially in immune responses and growth control. In autocrine...

paracrine signaling

Local Cell Communication in Tissues

Paracrine signaling is a form of local cell communication in tissues. In this process, one cell releases chemical signals that affect nearby target cells. Because the signal stays close to where it is made, paracrine signaling helps cells coordinate responses within a limited area. These signals do not travel far through the body. Instead, they move through the space around neighboring cells and bind to specific receptors on target cells. This nearby action makes paracrine signaling different...

endocrine signaling

Hormones in Endocrine Signaling

Endocrine signaling uses hormones to send messages through the body. These signals travel through the bloodstream from one cell or gland to another target cell. The target cell responds only if it has the right receptor to detect the hormone. This type of cell communication helps coordinate many body functions at a distance. Because the signal moves through the blood, the source and the target do not need to be close together. Endocrine signaling is a key way cells regulate activity in other...

what are second messengers?

Cell Signals and Second Messengers

Second messengers are small molecules that help cells pass along signals after a receptor is activated. They carry the message inside the cell and help start a response to the outside signal. This signaling step is important in cell communication. It helps the signal move from the cell membrane to targets deeper inside the cell. Second messengers make that relay possible and help the cell respond in a controlled way. Common second messengers include cyclic AMP, calcium ions, and inositol...

Cell signaling cascades inside cells relay messages from one molecule to the next. These pathways help a cell respond to a signal in a controlled way. The signal is often carried through a series of steps, which can amplify the original message. A signaling cascade may involve a receptor at the cell surface and molecules inside the cell that pass the message along. Each step can trigger the next step in the chain. This makes the response specific and allows the cell to act on the signal at the...

g-protein coupled receptors

G-protein Receptors in Cell Signaling

G-protein coupled receptors help cells receive and pass along signals. These membrane receptors sit in the cell membrane and respond when a ligand binds to them. A ligand is a molecule that fits and attaches to a receptor. When a ligand binds, the receptor changes shape. That shape change activates a G protein inside the cell. The G protein then helps start the signal inside the cell. These receptors are important because they connect outside signals to inside responses. They are a major part...

enzyme-linked receptors

How Enzyme-Linked Receptors Signal

Enzyme-linked receptors help cells respond to signals outside the cell. They are a major class of cell-surface receptors, and they work by triggering enzyme activity after a signal binds. Many enzyme-linked receptors are receptor tyrosine kinases. When a signaling molecule binds, the receptor changes shape and activates its enzyme side. This starts a signaling step inside the cell that can affect cell behavior. These receptors are important in cell communication. They help carry messages from...

non-canonical wnt signaling pathways

Wnt Pathways That Guide Cell Position

Wnt signaling helps guide early embryonic development and later life processes in animals. It is controlled by Wnt proteins, which can trigger different intracellular pathways depending on which receptors and co-receptors they bind. These signals support organ formation in the embryo and help maintain neuronal and blood stem cells. The non-canonical Wnt pathways are the β-catenin independent routes. They are more diverse and less well characterized than the canonical Wnt/β-catenin pathway. Two...

key terms and concepts

Learn how intracellular signaling cascades pass messages inside cells, amplify signals, and help cells respond in specific ways with clear high school biology language.

Cell Signaling Cascades Inside Cells | JoVE K12

molecular biology

JoVE Core Molecular Biology showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

Cell Signaling Cascades Inside Cells

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