Angiotensin II causes vasoconstriction by activating which intracellular signaling pathway in vascular smooth muscle?

Angiotensin II causes vasoconstriction by activating which intracellular signaling pathway in vascular smooth muscle?

• A. Gq protein signaling with phospholipase C activation
• B. Gi protein signaling with inhibition of adenylyl cyclase
• C. Gs protein signaling with activation of adenylyl cyclase
• D. G12/13 protein signaling with RhoA activation

Answer: (A)

Angiotensin II induces vasoconstriction in vascular smooth muscle primarily through the AT1 receptor, which couples to Gq/11 proteins. Activation of Gq/11 stimulates phospholipase Cβ, leading to production of IP3 and DAG. IP3 releases calcium from the sarcoplasmic reticulum, raising intracellular Ca2+; Ca2+ binds calmodulin and activates myosin light-chain kinase, driving cross-bridge cycling and contraction. DAG activates PKC, further modulating contraction and calcium sensitivity. While other pathways like G12/13-RhoA can sustain contraction, the immediate vasoconstrictive signaling here is via Gq-PLC activation, making this the best choice.

Angiotensin II induces vasoconstriction in vascular smooth muscle primarily through the AT1 receptor, which couples to Gq/11 proteins. Activation of Gq/11 stimulates phospholipase Cβ, leading to production of IP3 and DAG. IP3 releases calcium from the sarcoplasmic reticulum, raising intracellular Ca2+; Ca2+ binds calmodulin and activates myosin light-chain kinase, driving cross-bridge cycling and contraction. DAG activates PKC, further modulating contraction and calcium sensitivity. While other pathways like G12/13-RhoA can sustain contraction, the immediate vasoconstrictive signaling here is via Gq-PLC activation, making this the best choice.