enzyme-linked receptor protein signaling pathway

Definition

Target type: biologicalprocess

The series of molecular signals initiated by an extracellular ligand binding to a receptor on the surface of the target cell, where the receptor possesses catalytic activity or is closely associated with an enzyme such as a protein kinase, and ending with the regulation of a downstream cellular process, e.g. transcription. [GOC:mah, GOC:signaling, ISBN:0815316194]

Enzyme-linked receptor protein signaling pathways are intricate processes that allow cells to respond to a diverse array of external stimuli, such as hormones, growth factors, and neurotransmitters. These pathways involve a cascade of events initiated by the binding of a ligand to a specific receptor protein embedded in the cell membrane. The binding event triggers a series of molecular interactions and modifications, ultimately leading to changes in cellular behavior, gene expression, and downstream signaling pathways. Here's a detailed description of the process:

1. **Ligand Binding and Receptor Activation:**
- The process begins with a specific ligand, often a protein or a small molecule, binding to its cognate receptor on the cell surface.
- This binding event induces a conformational change in the receptor, activating its enzymatic activity.

2. **Initiation of Intracellular Signaling Cascade:**
- The activated receptor, acting as an enzyme, triggers a cascade of intracellular signaling events.
- This cascade typically involves phosphorylation of specific proteins, which act as molecular switches, turning signaling pathways on or off.

3. **Signal Amplification and Relay:**
- Many enzyme-linked receptors exhibit intrinsic kinase activity, meaning they can add phosphate groups to other proteins.
- This phosphorylation event can activate downstream signaling molecules, which in turn can activate even more molecules, resulting in signal amplification.
- These signaling molecules often act as messengers, relaying the signal from the cell surface to the interior of the cell.

4. **Transcriptional Regulation and Gene Expression:**
- The intracellular signaling cascade ultimately influences gene expression, often by activating or inhibiting transcription factors.
- Transcription factors bind to specific DNA sequences, regulating the transcription of target genes.
- This regulation of gene expression leads to changes in protein synthesis and cellular functions.

5. **Diverse Cellular Responses:**
- Enzyme-linked receptor signaling pathways are highly diverse and can lead to a wide range of cellular responses, including:
- Cell growth and proliferation
- Differentiation and development
- Metabolism and energy production
- Immune responses
- Apoptosis (programmed cell death)

6. **Examples of Enzyme-Linked Receptors:**
- Receptor tyrosine kinases (RTKs): Involved in growth factor signaling, cell differentiation, and proliferation.
- Receptor serine/threonine kinases: Involved in developmental processes, stress responses, and cell cycle control.
- G protein-coupled receptors (GPCRs): Although not strictly enzyme-linked, they are often coupled to intracellular signaling pathways that involve enzyme activation.

7. **Regulation and Feedback Mechanisms:**
- Enzyme-linked receptor signaling pathways are tightly regulated to ensure proper cellular function.
- Feedback mechanisms, both positive and negative, are crucial for controlling the duration and intensity of signaling events.
- These mechanisms prevent excessive or inappropriate signaling, maintaining cellular homeostasis.

In summary, enzyme-linked receptor protein signaling pathways are fundamental to cellular communication and function. They allow cells to sense and respond to their environment, regulating a wide range of cellular processes. The intricate nature of these pathways, involving multiple signaling molecules and complex regulatory mechanisms, highlights the complexity and sophistication of cellular communication.'
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Proteins (5)

Compounds (275)