G-protein coupled receptors

Definition

G-protein coupled receptors (GPCRs) are a large family of membrane proteins that play a critical role in cellular communication by transmitting signals from outside the cell to the inside. They are involved in various physiological processes, responding to a wide range of stimuli such as hormones, neurotransmitters, and environmental signals. Their ability to activate intracellular signaling pathways makes them essential for many biological functions.

5 Must Know Facts For Your Next Test

1. GPCRs are the largest family of membrane proteins in humans, with over 800 different types identified.
2. They are integral membrane proteins characterized by seven transmembrane helices that span the cell membrane.
3. When a ligand binds to a GPCR, it undergoes a conformational change that activates an associated G-protein, leading to signal transduction inside the cell.
4. GPCRs can activate multiple signaling pathways depending on the type of G-protein they interact with, such as Gs, Gi, or Gq.
5. Dysfunction or mutations in GPCRs are linked to various diseases, including cancer, heart disease, and neurological disorders.

Review Questions

• How do G-protein coupled receptors facilitate cellular communication upon ligand binding?
  • Upon binding a ligand, GPCRs undergo a conformational change that activates an associated G-protein inside the cell. This activated G-protein then interacts with other proteins or enzymes to initiate a cascade of intracellular signaling events. This process enables cells to respond to external signals quickly and effectively, coordinating various physiological responses.
• Discuss the role of second messengers in the signaling pathway initiated by G-protein coupled receptors.
  • Second messengers are crucial for amplifying and propagating the signals generated by activated GPCRs. When a GPCR is activated by its ligand, it can stimulate the production of second messengers like cyclic AMP (cAMP) or calcium ions. These second messengers then modulate various intracellular processes, leading to diverse physiological effects such as changes in gene expression or alterations in cell metabolism.
• Evaluate the implications of GPCR malfunction in relation to disease states and potential therapeutic targets.
  • Malfunction or mutations in GPCRs can have significant implications for health, as they are involved in numerous signaling pathways that regulate vital physiological functions. For example, aberrant GPCR activity is linked to diseases such as cancer and heart disease. Understanding these mechanisms opens avenues for targeted therapies that can either enhance or inhibit GPCR function to restore normal signaling and treat various conditions.

Related terms

Ligand: A molecule that binds to a receptor, triggering a biological response; in the case of GPCRs, ligands can be hormones, neurotransmitters, or other signaling molecules.

Second messenger: Intracellular signaling molecules released in response to the activation of GPCRs that propagate the signal within the cell, such as cyclic AMP (cAMP) or calcium ions.

Signal transduction: The process by which a cell converts an extracellular signal into an intracellular response, often involving GPCRs and subsequent signaling cascades.