Nitric oxide synthase 2 (inducible)

Nitric oxide synthase, inducible is an enzyme which is encoded by the NOS2 gene in humans and mice.^[5]

Genetics

Three related pseudogenes are located within the Smith-Magenis syndrome region on chromosome 17. Alternative splicing of this gene results in two transcript variants encoding different isoforms.^[6]

Location

Nitric oxide synthase is expressed in epithelial cells of the liver, lung and bone marrow. It is inducible by a combination of lipopolysaccharide and certain cytokines.^{[citation needed]}

Function

Nitric oxide is a reactive free radical mediating in neurotransmission, antimicrobial and antitumoral activities.^{[citation needed]} In mice, the function of Nos2 in immunity against a number of viruses, bacteria, fungi, and parasites has been well characterized, whereas in humans the role of NOS2 has remained elusive and controversial.^[7] Nos2 is important for protective immunity against CMV.^[8]

Autosomal recessive NOS2 deficiency has been described in mice. They lack the gene encoding nitric oxide synthase 2 (Nos2) and are susceptible to murine CMV infection.^[11]

In February 2020, the same autosomal recessive, complete NOS2 deficiency was described in a human. A 51-year-old previously healthy person died after 29 months of progressive CMV infection due to respiratory failure secondary to CMV pneumonitis, CMV encephalitis, and hemophagocytic lymphohistiocytosis. Whole-exome sequencing on genomic DNA from his blood showed he had homozygous variants in five genes. The only loss-of-function variant was a homozygous frameshift mutation in nitric oxide synthase 2. This condition is extremely rare, occurring in fewer than 1 per million persons.^[8]

References

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