How can G protein coupled receptors activate their effector system?

Many different mammalian cell-surface receptors are coupled to a trimeric signal-transducing G protein. As noted earlier, ligand binding to these receptors activates their associated G protein, which then activates an effector enzyme to generate an intracellular second messenger (see Figure 20-3a).

Do G proteins stimulate or inhibit effector proteins?

G-protein Function Activation of heterotrimeric G proteins by GPCRs leads to the formation of free α-GTP and βγ subunits that are able to interact with a diverse array of effector enzymes, ion channels, or both to stimulate or inhibit the activity of these effector proteins.

What is the advantage of G protein-coupled receptors?

G Protein-Coupled Receptors (GPCRs) transduce extracellular signals and activate intracellular pathways, usually through activating associated G proteins. Due to their involvement in many human diseases, they are recognized worldwide as valuable drug targets.

Where are heterotrimeric G proteins found in the nervous system?

Heterotrimeric G proteins are cytosolic, membrane-associated proteins that transduce neuromodulatory signals within autonomic, sensory, and central nervous system neurons.

Which is part of the G protein family?

The Gs family of heterotrimeric G proteins include two closely related α-subunits that couple receptors to adenylyl cyclase and generation of cyclic adenosine monophosphate (cAMP): Gsα (stimulatory) encoded by the GNAS gene at 20q13 and G olfα (olfactory) encoded by GNAL at 18p11 (Jones and Reed, 1989 ).

How are G proteins involved in ion channels?

Activated by G protein-coupled receptors embedded in the pre- and postsynaptic membranes of neurons, G proteins control the activities of ion channels and enzymes that generate intracellular second messenger molecules.