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Gq Signaling Pathway

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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