Figure 2.

Neuronal nitric oxide synthase (nNOS) protein expression, compartmentation and function in healthy cardiac myocytes

The diagram illustrates the localization of nNOS and target proteins and regulation. nNOS is located in the sarcoplasmic reticulum (SR), mitochondria, plasma membrane and possibly nucleus. nNOS interacts with ryanodine receptor (RyR), xanthine oxidoreductase (XOR), α-syntrophin [forming a macrocomplex with Na⁺ channel (SCN5a) and plasma membrane Ca²⁺-ATPase (PMCA4b)]. nNOS modifies the activities of various proteins either through S-nitrosylation (-SNO) or through PKA-dependent, cGMP/PKG-dependent phosphorylations of downstream proteins.