Protein Kinase A pathway
Protein kinase A (PKA) is the major downstream effector of many hormones, including glucagon, epinephrine, vasopressin, and neurotransmitters. The figure below shows multiple actions of PKA, but note that no single hormone effectuates all these changes. Glucagon and epinephrine mediate most of them. The effect of PKA on Aquaporin 2 and K+-channel is not activated by glucagon or epinephrine, but by vasopressin and neurotransmitters, respectively!
| Abbreviation | Name | Function |
|---|---|---|
| AC | Adenylyl Cyclase | Activated by glucagon receptor, produces cAMP from ATP. |
| cAMP | Cyclic AMP | Activates Protein Kinase A |
| PKA | Protein Kinase A | Mediates the effects of mainly glucagon (in liver) and epinephrine (in muscle), but also vasopressin in the kidney and neurotransmitters in the brain |
| HSL | Hormone-sensitive lipase | A lipase found in adipocytes. Catalyses DAG -> MAG + FFA |
| AQP2 | Aquaporin 2 | A water channel in the kidney used for water reabsorption |
| ACC | Acetyl-CoA carboxylase | Catalyses Acetyl-CoA -> Malonyl-CoA, which inhibits β-oxidation |
| HMG-CoAR | HMG-CoA reductase | Catalyses the rate-limiting step of cholesterol synthesis |