G-protein coupled receptor

Definition

A g-protein coupled receptor (GPCR) is a large family of membrane proteins that play a critical role in cellular signaling by transmitting signals from outside the cell to the inside. They are involved in a variety of physiological processes and respond to a wide range of stimuli, including hormones, neurotransmitters, and environmental factors. GPCRs activate intracellular signaling pathways through the interaction with G-proteins, which relay the signal further into the cell, leading to various biological responses.

5 Must Know Facts For Your Next Test

1. GPCRs are one of the largest protein families in humans, comprising about 800 different receptors that mediate diverse functions.
2. They are involved in important processes such as vision, taste, smell, and immune responses, making them crucial for survival.
3. GPCRs work by undergoing a conformational change upon ligand binding, which activates associated G-proteins on the cytoplasmic side of the membrane.
4. There are several subclasses of GPCRs, including class A (rhodopsin-like), class B (secretin-like), and class C (metabotropic glutamate receptors), each with unique characteristics.
5. Many drugs target GPCRs due to their central role in signaling pathways; approximately 30-40% of all modern medicinal drugs act on these receptors.

Review Questions

• How do g-protein coupled receptors initiate signaling within cells after binding with ligands?
  • When a ligand binds to a g-protein coupled receptor, it causes a conformational change in the receptor. This change activates an associated G-protein by exchanging GDP for GTP. The activated G-protein then dissociates and interacts with other intracellular targets, propagating the signal further into the cell through various signaling pathways.
• Discuss the importance of g-protein coupled receptors in drug development and pharmacology.
  • G-protein coupled receptors are critical targets in drug development due to their involvement in numerous physiological processes and diseases. By understanding how these receptors function and interact with ligands, pharmaceutical companies can design specific drugs that either activate or inhibit GPCRs. This approach has led to the development of treatments for various conditions, including allergies, heart disease, and mental disorders, highlighting their significance in modern medicine.
• Evaluate the role of second messengers in g-protein coupled receptor signaling and how this influences cellular responses.
  • Second messengers play a vital role in amplifying and relaying signals initiated by g-protein coupled receptors. Once a GPCR is activated and interacts with G-proteins, these proteins can stimulate the production of second messengers like cyclic AMP (cAMP) or inositol trisphosphate (IP3). These molecules then trigger further downstream effects within the cell, such as changes in enzyme activity or gene expression. This amplification process allows for a rapid and coordinated cellular response to external stimuli.

Related terms

G-protein: G-proteins are molecular switches that transmit signals from activated GPCRs to target proteins inside the cell, mediating various signaling pathways.

Ligand: A ligand is a molecule that binds to a receptor, such as a GPCR, and triggers a response in the cell, often activating signaling pathways.

Second messenger: Second messengers are small molecules that propagate signals within the cell after a GPCR has been activated, facilitating cellular responses to external signals.