Related Experiment Video
Updated: Aug 3, 2026

07:51
Mesenteric Artery Contraction and Relaxation Studies Using Automated Wire Myography
Published on: September 22, 2011
G proteins and endothelium-dependent relaxations
1INSERM, Hôpital Lariboisière, Paris, France. cboulang@infobiogen.fr
Journal of Vascular Research
|May 1, 1997
Summary
Pertussis toxin reveals that G(i) proteins are crucial for nitric oxide (NO) release in endothelial cells. Impaired G(i) function in regenerated endothelium may lead to vasospasm and atherosclerosis.
Area of Science:
- Vascular Biology
- Cellular Signaling
- Endothelial Function
Background:
- Endothelial cells regulate vascular tone via relaxing factors like nitric oxide (NO).
- G proteins mediate receptor signaling to NO synthase (NOS) in endothelial cells.
- Pertussis toxin specifically targets and inhibits certain G proteins, primarily G(i).
Purpose of the Study:
- To investigate the role of G(i) proteins in mediating endothelium-dependent NO release.
- To determine the impact of pertussis toxin-sensitive pathways on vascular function.
- To explore the implications of impaired G(i) protein function in regenerated endothelium.
Main Methods:
- Utilized pertussis toxin to selectively inhibit G(i) proteins in porcine coronary arteries.
- Examined the release of NO in response to various endothelium-dependent vasodilators.
- Investigated endothelial cell cultures to assess G(i) protein function and receptor sensitivity.
Main Results:
- Pertussis toxin inhibited NO release evoked by specific agonists (e.g., serotonin, thrombin) but not others (e.g., bradykinin).
- Regenerated endothelium and cultured endothelial cells showed significantly reduced or absent NO release via pertussis-toxin-sensitive pathways.
- Abnormal G(i) protein function, rather than reduced presence, was implicated in the impaired NO release in cultured cells.
Conclusions:
- Both G(i) and G(q) proteins are involved in coupling receptor activation to endothelial Ca2+ increase and NO synthesis.
- Selective impairment of G(i) proteins in regenerated endothelium disrupts NO-mediated vasodilation.
- This disruption may contribute to vasospasm and the initiation of atherosclerosis.
More Related Videos
Related Concept Videos
G-protein Coupled Receptors
G-protein coupled receptors are ligand binding receptors that indirectly affect changes in the cell. The actual receptor is a single polypeptide that transverses the cell membrane seven times creating intracellular and extracellular loops. The extracellular loops create a ligand specific pocket which binds to neurotransmitters or hormones. The intracellular loops holds onto the G-protein.
Activation and Inactivation of G Proteins
Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
G-Protein Gated Ion Channels
GPCRs are primarily responsible for our sense of smell, taste, and vision. The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
Sensory organs,...
GPCRs Regulate Adenylyl Cylase Activity
Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
Two...
IP3/DAG Signaling Pathway
Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...
Nitric Oxide Signaling Pathway
Nitric oxide (NO), an inorganic gas, acts as a potent second messenger in most animal and plant tissues. NO diffuses out of the cells that produce it and enters the neighboring cells to generate a downstream response. NO synthase (NOS) catalyzes NO production by the deamination of the amino acid arginine. There are three isoforms of NOS. Endothelial cells have endothelial NOS (eNOS), nerve and muscle cells have neuronal NOS (nNOS), and macrophages produce inducible NOS (iNOS) upon exposure to...

