NOS1

NOS1 Full Name

nitric oxide synthase 1 (neuronal)

NOS1 Introduction

Nitric oxide synthase 1 (NOS1), commonly referred to as neuronal nitric oxide synthase (nNOS), is a constitutively expressed, calcium/calmodulin-dependent enzyme responsible for the endogenous synthesis of nitric oxide (NO). As a highly complex signaling molecule, NOS1 catalyzes the oxidation of the amino acid L-arginine to L-citrulline, releasing NO in the process. While predominantly localized within the central and peripheral nervous systems, NOS1 is also critically expressed in skeletal and smooth muscle tissues. In the central nervous system, the NO generated by NOS1 acts as a highly diffusible, atypical retrograde neurotransmitter. It modulates essential physiological processes, including synaptic plasticity, long-term potentiation (LTP), learning, and memory. At the molecular level, NOS1 is physically tethered to the NMDA glutamate receptor complex at the postsynaptic density via the scaffolding protein PSD-95, efficiently coupling neuronal activation and calcium influx to immediate NO production.

Figure 1. The neuronal nNOS/PSD-95/NMDA receptor complex and proposed mechanism of nNOS/PSD-95 inhibitors. (Source: Bach A, et al. 2015)

Despite its vital physiological roles, the dysregulation or sustained overactivation of NOS1 is deeply implicated in the pathogenesis of numerous severe neurological disorders. Under pathological conditions such as ischemic stroke, traumatic brain injury, or chronic neuroinflammation, massive calcium influxes cause NOS1 to produce neurotoxic levels of NO. This excess NO rapidly reacts with superoxide radicals to form peroxynitrite, a highly damaging reactive nitrogen species that induces severe oxidative stress, DNA damage, and mitochondrial dysfunction. Consequently, aberrant NOS1-driven excitotoxicity is a widely recognized contributing factor in the progression of major neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, and Huntington's disease.

Beyond the brain, defects in peripheral NOS1 function lead to significant myopathic and gastrointestinal phenotypes. In healthy skeletal muscle, NOS1 is anchored to the sarcolemma to regulate local blood flow during exertion. In Duchenne muscular dystrophy (DMD), this sarcolemmal localization is lost, severely impairing local vasodilation and exacerbating exercise-induced muscle ischemia and damage. Additionally, the targeted loss of NOS1-expressing inhibitory motor neurons in the enteric nervous system is the primary pathological mechanism underlying severe gastrointestinal motility disorders, such as achalasia and infantile hypertrophic pyloric stenosis.

Alternate Names for NOS1

NOS1; nitric oxide synthase 1 (neuronal); NOS; nitric oxide synthase, brain; nNOS; NOS type I; neuronal NOS; constitutive NOS; peptidyl-cysteine S-nitrosylase NOS1; bNOS; IHPS1; N-NOS; NC-NOS;

• 1. Bach A, et al. Biochemical investigations of the mechanism of action of small molecules ZL006 and IC87201 as potential inhibitors of the nNOS-PDZ/PSD-95-PDZ interactions. Sci Rep. 2015 Jul 16;5:12157.
  2. Zhou L, et al. Neuronal nitric oxide synthase: structure, subcellular localization, regulation, and clinical implications. Nitric Oxide. 2009 Jun;20(4):223-30.