What is the common second messenger increased by receptor activation linked to Gs proteins?

The common second messenger that is increased by receptor activation linked to Gs proteins is cyclic adenosine monophosphate (cAMP). When a Gs protein-coupled receptor is activated by a ligand, it undergoes a conformational change that activates the associated Gs protein. This process involves the exchange of GDP for GTP on the alpha subunit of the Gs protein, leading to the activation of adenylate cyclase.

Adenylate cyclase then catalyzes the conversion of ATP to cAMP. The increase in cAMP levels within the cell acts as a secondary messenger that activates various downstream signaling pathways, most notably protein kinase A (PKA). PKA subsequently phosphorylates target proteins, leading to a variety of physiological responses depending on the specific cell type and context.

Understanding this mechanism is critical because cAMP plays a central role in mediating the effects of many hormones and neurotransmitters, illustrating its importance in cellular signaling processes. This key action of Gs proteins and cAMP serves as a foundational concept in biochemistry and pharmacology related to receptor signaling pathways.