Receptors 101 ELM 2

• What are G Protein-Coupled Receptors (GPCRs) pivotal for?

  Transmitting signals to the cell's interior
• Why are GPCRs considered a diverse range of receptors?

  They serve specific and vital functions
• What is the general mechanism of GPCRs?

  • Link extracellular signals to intracellular pathways
  • Use G proteins as intermediaries
• How many GPCR sequences does the human genome encode?

  831 GPCR sequences
• Which family of GPCRs has over 600 members?

  Family A (Rhodopsin-like receptors)
• How many distinct G protein alpha subunits do humans possess?

  18 distinct alpha subunits
• How many beta and gamma subunits are present in human G proteins?

  5 beta and 12 gamma subunits
• What is the subunit composition of GPCRs?

  • Composed of alpha, beta, and gamma subunits
  • Lipid tails anchor G protein subunits to the membrane
• What does the alpha subunit of GPCRs bind in its resting state?

  GDP
• What happens to GDP during the activation cycle of GPCRs?

  It is replaced by GTP
• What is the role of activated G proteins in signaling?

  They activate target proteins and secondary messengers
• How is signaling terminated in GPCRs?

  GTP is hydrolyzed to GDP
• What occurs during agonist dissociation in GPCR signaling?

  Agonist dissociation occurs randomly
• What are the primary messengers involved in Gq signaling?

  • Diacylglycerol (DAG)
  • Inositol Triphosphate (IP3)
• What effect does Gq activation have on intracellular calcium levels?

  It increases intracellular calcium levels
• What enzyme cleaves PIP2 in Gq signaling?

  Phospholipase C (PLC)
• What role does IP3 play in Gq signaling?

  It opens a calcium channel in the ER
• What happens to calcium after it is released from the ER in Gq signaling?

  It can activate ryanodine receptors
• How does Protein Kinase C (PKC) become active?

  By binding calcium and DAG
• What does Gs do in its signaling pathway?

  Stimulates adenylyl cyclase, increasing cAMP levels
• What is the role of cAMP in Gs signaling?

  Activates Protein Kinase A (PKA)
• What does PKA do in response to cAMP levels?

  Modulates protein activity through phosphorylation
• What is the effect of Gi on adenylyl cyclase?

  Gi inhibits adenylyl cyclase, reducing cAMP levels
• What can the beta-gamma subunits of Gi do?

  Directly modulate membrane proteins
• What is the role of calcium ions in muscle contraction?

  Essential for actin and myosin interactions
• What proteins does calcium bind to for regulatory functions?

  Calmodulin and various other proteins
• How does cAMP influence Protein Kinase A (PKA)?

  It influences PKA activity through phosphorylation
• What effect does cAMP have on HCN channels in the heart?

  Modulates ion channel activity
• What are the key aspects of GPCR function and signaling pathways?

  • Integral roles in cellular communication
  • Activate diverse signaling pathways
  • Involve specific G proteins and secondary messengers
  • Critical for physiological regulation
• How does understanding GPCR signaling enhance therapeutic development?

  • Facilitates targeted therapies
  • Enhances grasp of biological processes