glucagon receptor activity

Definition

Target type: molecularfunction

Combining with glucagon and transmitting the signal across the membrane by activating an associated G-protein; promotes the exchange of GDP for GTP on the alpha subunit of a heterotrimeric G-protein complex. [GOC:mah, GOC:signaling, PMID:22438981]

Glucagon receptor activity is a critical molecular process that plays a vital role in regulating glucose homeostasis. The glucagon receptor (GCGR), a G protein-coupled receptor (GPCR), is expressed primarily in the liver, where it mediates the actions of glucagon, a peptide hormone produced by the pancreas. Upon binding of glucagon to its receptor, a cascade of intracellular signaling events is triggered, ultimately leading to the activation of downstream effector molecules.

The initial step in this process involves the conformational change of the GCGR upon glucagon binding. This conformational change activates the receptor's intracellular domain, allowing it to interact with heterotrimeric G proteins. Specifically, the GCGR couples to Gαs proteins, stimulating the production of cyclic adenosine monophosphate (cAMP) by adenylyl cyclase. cAMP then acts as a second messenger, activating protein kinase A (PKA).

PKA, in turn, phosphorylates various downstream targets, including key enzymes involved in glucose metabolism. One of the primary targets of PKA is glycogen synthase, which is responsible for the synthesis of glycogen. Phosphorylation of glycogen synthase by PKA inhibits its activity, leading to a decrease in glycogen synthesis.

Furthermore, PKA also phosphorylates and activates glycogen phosphorylase, the enzyme responsible for the breakdown of glycogen. This activation results in an increase in glycogenolysis, the process of releasing glucose from glycogen stores.

The actions of glucagon receptor activity on glycogen metabolism ultimately lead to an increase in blood glucose levels. In addition to its effects on glycogen metabolism, glucagon receptor activity also stimulates gluconeogenesis, the process of synthesizing glucose from non-carbohydrate precursors. This occurs through the activation of key enzymes involved in gluconeogenesis, such as phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase.

In summary, glucagon receptor activity is a complex molecular process that involves a cascade of intracellular signaling events, leading to the activation of downstream effector molecules. These events ultimately result in an increase in blood glucose levels through the regulation of glycogen metabolism and gluconeogenesis. This process is essential for maintaining glucose homeostasis and providing the body with a readily available source of energy.'
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Proteins (2)

Compounds (9)