termination of signal transduction

Definition

Target type: biologicalprocess

The signaling process in which signal transduction is brought to an end rather than being reversibly modulated. [GOC:mtg_signal]

Termination of signal transduction is a crucial process that ensures proper cellular function and prevents overstimulation. It involves the cessation of signaling events initiated by extracellular stimuli, ensuring that cellular responses are tightly regulated and transient. Here's a detailed description of the process:

1. **Receptor Deactivation:** Receptors, the initial points of signal reception, can be deactivated through several mechanisms:
* **Phosphorylation/Dephosphorylation:** Receptor activity can be modulated by phosphorylation or dephosphorylation by specific kinases and phosphatases. This alters the receptor's conformation, reducing its affinity for the signal molecule.
* **Internalization:** Receptors can be internalized into the cell through endocytosis, removing them from the cell surface and preventing further signaling. This process can be ligand-dependent, meaning the signal molecule itself triggers internalization, or independent, occurring through constitutive mechanisms.
* **Desensitization:** Some receptors undergo desensitization after prolonged exposure to a signal. This involves a change in the receptor's conformation that makes it less responsive to subsequent stimuli.

2. **Second Messenger Deactivation:** Second messengers, such as cAMP, cGMP, and calcium ions, play critical roles in signal transduction pathways. Their levels need to be tightly controlled to ensure appropriate cellular responses.
* **Enzymes:** Specific enzymes are responsible for breaking down second messengers. For example, phosphodiesterase hydrolyzes cAMP and cGMP, reducing their levels.
* **Calcium pumps:** Active transport mechanisms like calcium pumps remove calcium ions from the cytoplasm, restoring basal levels.

3. **Protein Deactivation:** Signaling proteins downstream of receptors are often activated by phosphorylation.
* **Phosphatases:** Specific phosphatases remove phosphate groups from activated proteins, rendering them inactive.
* **Protein Degradation:** Signaling proteins can be degraded by proteasomes, a cellular machinery responsible for protein breakdown, thus terminating the signaling cascade.

4. **Feedback Inhibition:** Many signal transduction pathways exhibit feedback inhibition, where downstream components negatively regulate upstream components. This can be achieved through:
* **Direct inhibition:** A signaling protein directly interacts with and inhibits an upstream component.
* **Indirect inhibition:** A downstream protein triggers the production of a molecule that inhibits an upstream component.

5. **Signal Diffusion:** The signaling molecule itself may diffuse away from the receptor, reducing its concentration and decreasing its ability to bind to other receptors.

The precise mechanisms of termination vary depending on the specific signaling pathway involved. However, all these processes work in concert to ensure that signal transduction is tightly regulated, transient, and responsive to changes in the cellular environment. These mechanisms are critical for maintaining cellular homeostasis and preventing aberrant signaling, which can lead to disease.'
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Proteins (3)

Compounds (329)