cell surface receptor signaling pathway

Definition

Target type: biologicalprocess

The series of molecular signals initiated by an extracellular ligand binding to a receptor located on the cell surface. The pathway ends with regulation of a downstream cellular process, e.g. transcription. [GOC:signaling]

Cell surface receptor signaling pathways are essential for cellular communication and coordination. They allow cells to respond to a diverse array of extracellular stimuli, including hormones, neurotransmitters, growth factors, and environmental cues. These pathways involve a series of events initiated by the binding of a ligand to its specific receptor protein located on the cell surface. This binding event triggers a cascade of intracellular signaling events that ultimately alter cellular functions, such as gene expression, metabolism, growth, differentiation, and apoptosis.

Here is a detailed overview of the process:

1. Ligand Binding: The signaling process begins with the binding of a ligand to its cognate receptor on the cell surface. This interaction is highly specific and often involves non-covalent bonds, such as hydrogen bonds, ionic interactions, and van der Waals forces.

2. Receptor Activation: Upon ligand binding, the receptor undergoes a conformational change, altering its structure and activating its signaling activity. This activation can involve dimerization of receptor subunits, phosphorylation of specific amino acid residues, or changes in protein-protein interactions.

3. Signal Transduction: The activated receptor initiates a cascade of intracellular signaling events, known as signal transduction. These events involve a series of proteins that relay and amplify the signal from the cell surface to the nucleus or other cellular compartments.

4. Second Messenger Production: In many signaling pathways, the activated receptor triggers the production of intracellular signaling molecules called second messengers. Common second messengers include cyclic AMP (cAMP), calcium ions (Ca2+), diacylglycerol (DAG), and inositol triphosphate (IP3). These second messengers can activate downstream signaling pathways and amplify the initial signal.

5. Protein Kinase Activation: Many signaling pathways involve the activation of protein kinases, enzymes that phosphorylate specific amino acid residues on target proteins. Phosphorylation can alter protein activity, localization, or interactions with other proteins.

6. Signal Amplification: The signal transduction cascade involves multiple steps of amplification, ensuring that a single ligand binding event can trigger a significant cellular response. Amplification can occur through the activation of multiple downstream signaling molecules or through the production of second messengers.

7. Signal Integration: Cells often receive multiple signals simultaneously. Signaling pathways can integrate these signals, allowing cells to respond appropriately to complex environmental cues. Integration can occur through convergence of different pathways on common signaling molecules or through the modulation of pathway activity by other signaling events.

8. Signal Termination: To maintain cellular homeostasis and prevent uncontrolled signaling, pathways have mechanisms for signal termination. Termination can involve dephosphorylation of proteins, degradation of second messengers, or inactivation of signaling proteins.

9. Cellular Response: Ultimately, the signal transduction pathway leads to a specific cellular response. This response can involve changes in gene expression, protein synthesis, cell growth, differentiation, migration, or apoptosis.

Examples of cell surface receptor signaling pathways include:

- G protein-coupled receptor (GPCR) signaling: This pathway involves seven-transmembrane receptors that activate G proteins, which in turn regulate the activity of downstream effectors, such as adenylyl cyclase or phospholipase C.

- Receptor tyrosine kinase (RTK) signaling: This pathway involves receptors with intrinsic tyrosine kinase activity. Upon ligand binding, RTKs become activated and phosphorylate themselves and other target proteins, triggering a cascade of signaling events that lead to cell growth, proliferation, and differentiation.

- Cytokine receptor signaling: This pathway involves receptors that bind to cytokines, which are signaling molecules that regulate immune responses and inflammation. Cytokine receptors activate downstream signaling pathways, such as the JAK-STAT pathway, leading to the production of transcription factors that alter gene expression.

- Integrin signaling: Integrins are transmembrane receptors that connect the extracellular matrix to the cytoskeleton. They play crucial roles in cell adhesion, migration, and differentiation. Integrin signaling involves activation of downstream signaling pathways, such as the focal adhesion kinase (FAK) pathway.

Cell surface receptor signaling pathways are highly regulated and complex processes that are essential for cellular function and organismal development. Dysregulation of these pathways can contribute to various diseases, including cancer, diabetes, and neurodegenerative disorders.'
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Compounds (3,216)