Endothelial NOS
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| Location (UCSC) | Chr 7: 150.99 – 151.01 Mb | Chr 5: 24.57 – 24.59 Mb | |||||||
| PubMed search | [3] | [4] | |||||||
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Endothelial NOS (eNOS), also known as nitric oxide synthase 3 (NOS3) or constitutive NOS (cNOS), is an
inflammatory diseases.[9]
eNOS is primarily responsible for the generation of NO in the platelet aggregation.[12]
Therefore, a functional eNOS is essential for a healthy cardiovascular system.
Structure and catalytic activities
eNOS is a dimer containing two identical monomers of 140 kD constituted by a reductase domain, which displays binding sites for
L-arginine.[13] The reductase domain is linked to the oxidase domain by a calmodulin-binding sequence.[14]
In the vascular endothelium, NO is synthesized by eNOS from L-arginine and molecular oxygen, which binds to the heme group of eNOS, is reduced and finally incorporated into L- arginine to form NO and
Function
eNOS has a protective function in the cardiovascular system, which is attributed to NO production. Regulation of the vascular tone is one of the best known roles of NO in the cardiovascular system. Once produced in endothelial cells, NO diffuses across the vascular smooth muscle cell membranes and activates the enzyme soluble guanylate cyclase (sGC), which catalyzes the conversion of guanosine triphosphate into cyclic guanosine monophosphate (cGMP).[21] cGMP, in turn, activates protein kinase G (PKG), which promotes multiple phosphorylation of cellular targets lowering cellular Ca2+ concentrations and promoting vascular relaxation.[22] NO exerts antiproliferative effects by cGMP-dependent inhibiting Ca2+ influx or by directly inhibiting the activity of arginase and ornithine decarboxylase, decreasing the generation of polyamides required for DNA synthesis.[23][24] NO also has antithrombotic effects that result of its diffusion across platelet membrane and sGC activation, resulting in inhibition of platelet aggregation.[25] Moreover, NO affects leukocyte adhesion to the vascular endothelium by inhibiting the nuclear factor kappa B (NF-κB), which induces vascular endothelial expression of chemokines and adhesion molecules.[26] In addition to these functions, NO produced by eNOS has antioxidant properties as it reduces superoxide anion formation as a result of NO-induced increases in the expression of superoxide dismutase, an antioxidant enzyme that catalyzes the conversion of superoxide anion to hydrogen peroxide.[27] Furthermore, part of antioxidants properties of NO is attributable to up-regulation of heme-oxygenase-I and ferritin expression, which reduce superoxide anion concentrations in blood vessels.[28]
Regulation
eNOS expression and activity are carefully controlled by multiple interconnected mechanisms of regulation present at the transcriptional, posttranscriptional, and posttranslational levels. Binding of transcription factors such as
promoter and DNA methylation represents an important mechanism of transcriptional regulation.[29] Posttranscriptionally, eNOS is regulated by modifications of the primary transcript, mRNA stability, subcellular localization, and nucleocytoplasmatic transport.[30] Posttranslational modifications of eNOS include fatty acid acylation, protein-protein interactions, substrate, and co-factor availability, and degree of phosphorylation. Importantly, eNOS is attached by myristoylation and palmitoylation to caveolae, a pocket-like invagination on the membrane rich in cholesterol and sphingolipids.[31] With the binding of eNOS to caveolae, the enzyme is inactivated due to the strong and direct interaction of eNOS with caveolin-1.[32] The binding of calcium-activated calmodulin to eNOS displaces caveolin-1 and activates eNOS. However, more recent studies have questioned the hypothesis that caveolin-1 directly binds to eNOS, as the region of the caveolin-1 protein proposed to bind to eNOS may be inaccessible due to its location in the plasma membrane. As a result, the specifics of how caveolin-1 interacts with eNOS to regulate eNOS activity are still unclear. [33] Moreover, eNOS activation is dynamically regulated by multiple phosphorylation sites at tyrosine, serine, and threonine residues.[13]
Clinical significance
Impaired NO production is involved in the
preeclampsia, diabetes mellitus, obesity, erectile dysfunction, and migraine. In this regard, a large number of studies showed that polymorphisms
in NOS3 gene affect the susceptibility to these diseases.
Although NOS3 is a highly polymorphic gene, three genetic polymorphisms in this gene have been widely studied: the single nucleotide polymorphisms (SNPs) g.-786T>C (where "g." denotes genomic change which results in a Glu298Asp change in the coded protein), located in NOS3 promoter and in exon 7, respectively, and the variable number of tandem repeats (VNTR) characterized by 27 bp repeat in intron 4.[34] The C allele for the g.-786T>C polymorphism, which results in reduced eNOS expression and NO production,[35] was associated with increased risk for hypertension,[36] preeclampsia,[37] diabetic nephropathy,[38] and retinopathy,[39] migraine,[40] and erectile dysfunction.[41] The presence of ‘Asp’ allele for the Glu298Asp polymorphism reduces eNOS activity,[42] and was associated with higher susceptibility to hypertension,[43][44] preeclampsia,[45] diabetes mellitus,[46] migraine,[40] and erectile dysfunction.[47][48] The VNTR in intron 4 affects eNOS expression,[49] and the susceptibility to hypertension,[36] preeclampsia,[37] obesity,[50] and diabetes mellitus.[46] Growing evidence supports the association of diseases with NOS3 haplotypes (combination of alleles in close proximity, within a DNA block). This approach may be more informative than the analysis of genetic polymorphisms one by one.[51] Haplotypes including the SNPs g.-786T>C and Glu298Asp and the VNTR in intron 4 affected the susceptibility to hypertension,[52][53][54][55] preeclampsia,[56] and hypertension in diabetic subjects.[57]
NOS3 variants may also affect the responses to drugs that affect NO signaling, such as statins, angiotensin-converting enzyme inhibitors (ACEi) and phosphodiesterase type 5 (PDE-5) inhibitors (PDE5i). Statin treatment was more effective in increasing NO bioavailability in subjects carrying the CC genotype for the g.-786T>C polymorphism than in TT carriers.[58][59] Hypertensive patients carrying the TC/CC genotypes and the C allele for the g.-786T>C polymorphism showed better antihypertensive responses to ACEi enalapril.[60] Likewise, patients with erectile dysfunction carrying the C allele for g.-786T>C polymorphism showed better responses to PDE-5 inhibitor sildenafil.[61][62] Together, these studies suggest that statins, ACEi and PDE-5 inhibitors may restore an impaired NO production in subjects carrying the variant allele/genotype for g.-786T>C NOS3 polymorphism, thus attenuating the cardiovascular risk. In addition to analysis of genetic polymorphisms individually, haplotypes including the SNPs g.-786T>C and Glu298Asp and the VNTR in intron 4 were shown to affect the responses to sildenafil in patients with erectile dysfunction.[61]
Notes
Wikidata Q38597218 . |
References
- ^ a b c GRCh38: Ensembl release 89: ENSG00000164867 – Ensembl, May 2017
- ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000028978 – Ensembl, May 2017
- ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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Further reading
- de la Monte SM, Lu BX, Sohn YK, Etienne D, Kraft J, Ganju N, Wands JR (2000). "Aberrant expression of nitric oxide synthase III in Alzheimer's disease: relevance to cerebral vasculopathy and neurodegeneration". Neurobiology of Aging. 21 (2): 309–19. S2CID 34155727.
- Shaul PW (2002). "Regulation of endothelial nitric oxide synthase: location, location, location". Annual Review of Physiology. 64: 749–74. PMID 11826287.
- Wu KK (May 2002). "Regulation of endothelial nitric oxide synthase activity and gene expression". Annals of the New York Academy of Sciences. 962 (1): 122–30. S2CID 20537144.
- Alp NJ, Channon KM (Mar 2004). "Regulation of endothelial nitric oxide synthase by tetrahydrobiopterin in vascular disease". Arteriosclerosis, Thrombosis, and Vascular Biology. 24 (3): 413–20. PMID 14656731.
- Tai SC, Robb GB, Marsden PA (Mar 2004). "Endothelial nitric oxide synthase: a new paradigm for gene regulation in the injured blood vessel". Arteriosclerosis, Thrombosis, and Vascular Biology. 24 (3): 405–12. PMID 14656742.
- Kawashima S, Yokoyama M (Jun 2004). "Dysfunction of endothelial nitric oxide synthase and atherosclerosis". Arteriosclerosis, Thrombosis, and Vascular Biology. 24 (6): 998–1005. PMID 15001455.
- Duda DG, Fukumura D, Jain RK (Apr 2004). "Role of eNOS in neovascularization: NO for endothelial progenitor cells". Trends in Molecular Medicine. 10 (4): 143–5. PMID 15162796.
PDB gallery | |
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![1p6m: Bovine endothelial NOS heme domain with (4S)-N-(4-amino-5-[aminoethyl]aminopentyl)-N'-nitroguanidine bound](/File:PDB_1p6m_EBI.jpg)
![2hx2: Bovine eNOS heme domain complexed with (4S)-N-{4-Amino-5-[(2-aminoethyl)-hydroxyamino]-pentyl}-N'-nitroguanidine](/File:PDB_2hx2_EBI.jpg)
