GPCR signaling truth

GPCR signaling truth

• A. GPCRs are ion channels that open upon ligand binding
• B. GPCRs convey signals to effector proteins such as adenylyl cyclase
• C. GPCRs are transcription factors that enter nucleus
• D. GPCRs hydrolyze ATP directly in cytosol

Answer: (B)

GPCR signaling relays the message from a ligand-bound receptor at the cell surface to intracellular effector proteins through heterotrimeric G proteins. When a ligand binds, the receptor promotes GDP to GTP exchange on the G alpha subunit, causing the G protein to dissociate into G alpha-GTP and G beta-gamma. These subunits then regulate downstream effectors such as adenylyl cyclase or phospholipase C. Activating adenylyl cyclase converts ATP to cyclic AMP, which starts a signaling cascade (for example, activating protein kinase A) and leads to the cellular response. This description captures how GPCRs function: they transmit signals to effector enzymes that generate second messengers. GPCRs are not ion channels themselves; ion channels are a different class of receptors that open directly upon ligand binding. GPCRs do not enter the nucleus as transcription factors to regulate gene expression; instead, the second messengers they modulate eventually influence transcriptional programs downstream. GPCRs also do not hydrolyze ATP directly in the cytosol; they regulate enzymes like adenylyl cyclase that use ATP to produce cAMP, but the receptor itself is not an ATPase.

GPCR signaling relays the message from a ligand-bound receptor at the cell surface to intracellular effector proteins through heterotrimeric G proteins. When a ligand binds, the receptor promotes GDP to GTP exchange on the G alpha subunit, causing the G protein to dissociate into G alpha-GTP and G beta-gamma. These subunits then regulate downstream effectors such as adenylyl cyclase or phospholipase C. Activating adenylyl cyclase converts ATP to cyclic AMP, which starts a signaling cascade (for example, activating protein kinase A) and leads to the cellular response. This description captures how GPCRs function: they transmit signals to effector enzymes that generate second messengers.

GPCRs are not ion channels themselves; ion channels are a different class of receptors that open directly upon ligand binding. GPCRs do not enter the nucleus as transcription factors to regulate gene expression; instead, the second messengers they modulate eventually influence transcriptional programs downstream. GPCRs also do not hydrolyze ATP directly in the cytosol; they regulate enzymes like adenylyl cyclase that use ATP to produce cAMP, but the receptor itself is not an ATPase.