Medicine & USMLE

Gs / Gi Pathway

General Pharm
  1. Gs / Gi Pathway
  2. Gq Signaling Pathway
  3. Alpha-1 (Adrenergic) Receptors
  4. Alpha-2 (Adrenergic) Receptors
  5. Beta-1 (Adrenergic) Receptors
  6. Beta-2 (Adrenergic) Receptors
  7. Beta-3 (Adrenergic) Receptors
  8. M1 (Muscarinic) Receptors
  9. M2 (Muscarinic) Receptors
  10. M3 (Muscarinic) Receptors
  11. D1 (Dopamine) Receptors
  12. D2 (Dopamine) Receptors
  13. H1 (Histamine) Receptors
  14. H2 (Histamine) Receptors
  15. V1 (Vasopressin) Receptors
  16. V2 (Vasopressin) Receptors


The Gs and Gi pathways are important cell signalling pathways activated when a ligand binds to a G-protein coupled receptor, with a variety of downstream effects. These pathways both operate through the second messenger cAMP.

When a ligand binds to a Gs-coupled receptor, the Gs subunit is activated and stimulates the synthesis of cAMP. Conversely if a Gi subunit is activated, it inhibits the synthesis of cAMP. cAMP in turn stimulates PKA, an important kinase enzyme with two downstream effects. First, PKA inhibits MLCK by phosphorylating it, and second, PKA increases calcium levels in the heart by phosphorylating calcium channels.