USMLE

Gq Signaling Pathway

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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

Summary

The Gq signaling pathway is a cell signaling pathway that starts with binding of a G-protein coupled receptor associated with a Gq protein subunit. This Gq protein subunit then stimulates the activation of PLC, or phospholipase C. PLC is an enzyme that breaks down a membrane phospholipid, PIP2, into two intermediates, diacylglycerol (DAG) and inositol triphosphate (IP3). DAG goes on to activate another enzyme, protein kinase C (PKC). The other intermediate produced, IP3, induces the release of calcium ions from the sarcoplasmic or endoplasmic reticulum. This influx of calcium causes smooth muscle contraction.

Key Points

  • Gq Signaling Pathway
    • Gq subunit → PLC (phospholipase C)
      • Binding to a Gq-coupled receptor causes activation of a Gq protein subunit, which then acts as a second messenger to activate phospholipase C (PLC)
    • PLC cleaves PIP2 → DAG (diacylglycerol) and IP3 (inositol triphosphate)
      • PIP2 is a cell membrane phospholipid which is cleaved by phospholipase C to form two intermediates: diacylglycerol (DAG) and inositol triphosphate (IP3)
      • DAG (diacylglycerol) → PKC (protein kinase C)
        • Protein kinase C (PKC) is activated by DAG, as well as by calcium ions released from sarcoplasmic reticulum under the influence of IP3
      • IP3 (inositol triphosphate) → opens calcium channels
        • Released calcium further stimulates PKC, and also induces smooth muscle contraction
        • Calcium influx → smooth muscle contraction