cGMP Signaling
| Category | Mechanisms |
|---|---|
| Also known as | cyclic GMP pathway, PKG signaling |
| Last updated | 2026-04-14 |
| Reading time | 3 min read |
| Tags | mechanismsignalingsecond-messenger |
Overview
Cyclic GMP (cGMP) is a second messenger closely analogous to cAMP but with distinct synthesis, effectors, and physiology. It is produced by two families of guanylyl cyclase: soluble guanylyl cyclase (sGC), activated by nitric oxide, and particulate (membrane-bound) guanylyl cyclases, activated by peptide ligands such as atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and guanylin.
cGMP primarily acts through protein kinase G (PKG), cyclic-nucleotide-gated ion channels (important in photoreceptor and olfactory signaling), and phosphodiesterase modulation. Its physiological roles include vasodilation, platelet inhibition, natriuresis, phototransduction, and intestinal fluid balance. Disruption of cGMP signaling contributes to pulmonary hypertension, erectile dysfunction, heart failure, and constipation.
The therapeutic importance of cGMP has grown over recent decades. Drugs that raise cGMP — nitrates (vasodilators), PDE5 inhibitors (sildenafil, tadalafil), soluble guanylyl cyclase stimulators (riociguat), natriuretic peptide therapies (nesiritide), and guanylate cyclase-C agonists (linaclotide) — are established or emerging treatments for cardiovascular, renal, pulmonary, and gastrointestinal disease.
Mechanism / Process
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Stimulus delivery. cGMP production is initiated by one of two triggers: nitric oxide diffusing across membranes to activate sGC, or peptide ligands engaging particulate guanylyl cyclases on the plasma membrane.
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Cyclase activation. sGC, a heterodimer with a ferrous heme, is activated when NO binds the heme. Particulate cyclases are single-pass transmembrane receptors whose extracellular domain binds ligand and intracellular domain catalyzes cGMP synthesis from GTP.
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cGMP rise. Intracellular cGMP concentrations rise from low nanomolar to micromolar within seconds to minutes.
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Effector activation. cGMP activates PKG (serine/threonine kinase), gates cyclic-nucleotide-gated channels, and allosterically regulates specific phosphodiesterases.
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PKG phosphorylates substrates. Targets include IP3 receptor-associated proteins (modulating calcium release), myosin light chain phosphatase (relaxing smooth muscle), and BK channels.
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Cross-pathway effects. cGMP can inhibit cAMP-degrading PDE3 (increasing cAMP) or stimulate PDE2 (decreasing cAMP), producing pathway crosstalk.
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Termination. Phosphodiesterases PDE5, PDE6, PDE9, and others degrade cGMP. Inhibition of PDE5 (by sildenafil) prolongs cGMP action in vascular smooth muscle and corpus cavernosum.
Key Players / Molecular Components
- Soluble guanylyl cyclase (sGC). Heterodimeric, NO-activated.
- Particulate guanylyl cyclases. GC-A (ANP/BNP), GC-B (CNP), GC-C (guanylin/uroguanylin), GC-D through GC-G in sensory systems.
- Protein kinase G. PKG-I (alpha and beta isoforms, cytosolic and smooth muscle), PKG-II (membrane-anchored).
- Cyclic-nucleotide-gated channels. CNGA1 in photoreceptors, CNGA2 in olfactory neurons.
- Phosphodiesterases. PDE5 (vascular smooth muscle, corpus cavernosum), PDE6 (retina), PDE9 (brain, cardiomyocytes).
Clinical Relevance / Therapeutic Targeting
cGMP-raising drugs form a substantial therapeutic class. Organic nitrates (nitroglycerin) release NO and raise cGMP to relieve angina. PDE5 inhibitors (sildenafil, tadalafil, vardenafil) treat erectile dysfunction and pulmonary arterial hypertension. Riociguat is a direct sGC stimulator for pulmonary hypertension. Vericiguat activates sGC in heart failure with reduced ejection fraction. Nesiritide is recombinant BNP used for acute decompensated heart failure. Linaclotide and plecanatide target intestinal GC-C for chronic constipation and irritable bowel syndrome.
Peptides That Target This Pathway
- ANP (atrial natriuretic peptide) — activates GC-A to raise cGMP in kidney and vasculature.
- BNP (B-type natriuretic peptide) — co-target of GC-A, used therapeutically as nesiritide.
- CNP (C-type natriuretic peptide) — activates GC-B in bone growth and cartilage.
- Guanylin and uroguanylin — activate GC-C in intestinal epithelium.
- Linaclotide — synthetic guanylin analog for constipation.
Related Topics
Related entries
- Calcium Signaling— Calcium signaling is a universal intracellular communication system in which transient rises in cytoplasmic calcium concentration trigger diverse cellular responses including muscle contraction, neurotransmitter release, gene expression, and hormone secretion.
- Calcium Signaling— The use of calcium ion gradients as a universal intracellular second messenger controlling contraction, secretion, gene expression, and apoptosis.
- cAMP Signaling— The signaling pathway built around cyclic AMP, a second messenger generated by adenylyl cyclase that regulates diverse physiological processes through PKA and Epac.
- Nitric Oxide System— The nitric oxide system encompasses the enzymatic production, signaling, and regulatory functions of nitric oxide — a gaseous signaling molecule critical to vasodilation, immune defense, neurotransmission, and tissue protection.
- Second Messenger Systems— Small intracellular molecules that relay and amplify signals from receptors to downstream effectors, including cAMP, cGMP, IP3, DAG, and calcium.