What primary signaling pathway is activated by G_q proteins?

What primary signaling pathway is activated by G_q proteins?

• A. Adenylyl cyclase inhibition
• B. Phospholipase C pathway
• C. Direct activation of ion channels
• D. PI3K-Akt pathway

Answer: (B)

G_q proteins primarily signal through the phospholipase C pathway. When a GPCR activates a G_q, the α subunit stimulates phospholipase C beta (PLCβ). PLCβ then hydrolyzes PIP2 in the membrane to generate IP3 and DAG. IP3 released into the cytosol opens IP3 receptors on the endoplasmic reticulum, releasing Ca2+ stores, while DAG stays in the membrane to activate protein kinase C. The combined rise in intracellular Ca2+ and PKC activity drives many cellular responses. Adenylyl cyclase inhibition is characteristic of G_i/o signaling, not G_q. The PI3K-Akt pathway is typically associated with receptor tyrosine kinases or GPCRs signaling through Gβγ or other routes rather than the canonical G_q–PLC axis. Direct activation of ion channels can occur in some GPCR pathways, but the defining pathway for G_q is the PLCβ–IP3/DAG cascade.

G_q proteins primarily signal through the phospholipase C pathway. When a GPCR activates a G_q, the α subunit stimulates phospholipase C beta (PLCβ). PLCβ then hydrolyzes PIP2 in the membrane to generate IP3 and DAG. IP3 released into the cytosol opens IP3 receptors on the endoplasmic reticulum, releasing Ca2+ stores, while DAG stays in the membrane to activate protein kinase C. The combined rise in intracellular Ca2+ and PKC activity drives many cellular responses.

Adenylyl cyclase inhibition is characteristic of G_i/o signaling, not G_q. The PI3K-Akt pathway is typically associated with receptor tyrosine kinases or GPCRs signaling through Gβγ or other routes rather than the canonical G_q–PLC axis. Direct activation of ion channels can occur in some GPCR pathways, but the defining pathway for G_q is the PLCβ–IP3/DAG cascade.