110 Signaling Examples

Summary

This video explains cellular signaling systems, focusing on two main types: intracellular receptors and cell surface receptors. Intracellular receptors respond to hydrophobic signals, like steroid hormones, that easily cross the plasma membrane, leading to gene transcription and altered cell behavior. In contrast, cell surface receptors interact with hydrophilic signals, triggering complex transduction pathways involving kinase cascades and second messengers like cyclic AMP and calcium ions. These mechanisms amplify signals and initiate various cellular responses, including metabolic changes and gene activation, showcasing the intricate processes that enable cells to communicate and react to their environment.

Takeaways

• 😀 Intracellular receptors are located in the cytosol or nucleus and interact with hydrophobic signals like steroid hormones.
• 😀 Signals like testosterone and estradiol can cross the plasma membrane to bind with intracellular receptors.
• 😀 The binding of a signal activates the receptor, initiating transcription of specific genes.
• 😀 In signaling via cell surface receptors, polypeptide signals cannot cross the plasma membrane and bind to receptors outside the cell.
• 😀 Cell surface receptors undergo conformational changes upon signal binding, propagating the signal internally.
• 😀 Transduction involves a series of changes to cellular proteins, resembling a 'Rube Goldberg' machine of signaling.
• 😀 Protein phosphorylation is a common mode of transduction that uses kinases to amplify signals through a cascade.
• 😀 Second messengers like cyclic AMP (cAMP) and calcium ions rapidly diffuse within the cell to activate target proteins.
• 😀 cAMP is produced from ATP and acts to activate protein kinase A, while calcium ions are released from the endoplasmic reticulum.
• 😀 The final cellular responses can include changes in metabolism or gene expression, influencing overall cell behavior.

Q & A

What are intracellular receptors, and where are they located?

Intracellular receptors are located inside the cell, either in the cytosol or the nucleus. They bind to hydrophobic signals that can easily cross the plasma membrane.

What type of signals typically bind to intracellular receptors?

Steroid hormones, such as testosterone and estradiol, are prominent examples of hydrophobic signals that bind to intracellular receptors.

What happens during the reception step of intracellular signaling?

The signal crosses the plasma membrane and binds to the receptor, activating it. If the receptor is in the cytosol, it moves to the nucleus; if it is already in the nucleus, it remains there.

Describe the transduction process for intracellular signaling.

In transduction, the activated receptor, now acting as a transcription factor, binds to specific enhancers in the DNA, initiating the transcription of specific genes.

What is the final outcome of signaling via intracellular receptors?

The final outcome is the production of new proteins that alter the cell's behavior as a response to the original signal.

What distinguishes signaling via cell surface receptors from intracellular receptors?

Cell surface receptors bind to signals (typically polypeptides) that cannot cross the plasma membrane, while intracellular receptors bind to hydrophobic signals that can.

What is the initial event that occurs when a signal binds to a cell surface receptor?

Binding of the signal to the extracellular portion of the receptor triggers a conformational change in the receptor's intracellular portion, propagating the signal inside the cell.

Explain the concept of a kinase cascade in cell signaling.

A kinase cascade is a series of events where one kinase activates another through phosphorylation, leading to the amplification of the signal. Each activated kinase can further activate multiple downstream kinases.

What are second messengers, and why are they important in signaling pathways?

Second messengers are small molecules or ions produced in response to receptor activation. They are crucial for rapidly diffusing within the cell and activating various enzymes, facilitating cellular responses.

Can you give examples of common second messengers mentioned in the transcript?

Two common second messengers are cyclic AMP (cAMP) and calcium ions (Ca²⁺). cAMP activates protein kinases, while calcium ions, released from the endoplasmic reticulum, activate various enzymes in the cytosol.

How do the final responses differ when signaling involves second messengers compared to kinase cascades?

When signaling involves second messengers, the activated proteins are typically enzymes that alter metabolism or cell structure. In contrast, kinase cascades often result in the activation of transcription factors that lead to changes in gene expression.