NANOS1 upregulates the production of MMP14 to promote tumour cell invasion. It is highly expressed in lung cancer, especially in invasive tumour cells; its expression correlates with tumour aggressiveness.
The first nitric oxide synthase to be identified was found in neuronal tissue (NOS1 or nNOS); the NOS (eNOS or NOS3) was the third to be identified. They were originally classified as "constitutively expressed" and "Ca2+ sensitive" but it is now known that they are present in many different types and that expression is regulated under specific physiological conditions.
In NOS1 and NOS3, physiological concentrations of Ca2+ in cells regulate the binding of calmodulin to the "latch domains", thereby initiating electron transfer from the to the moieties. In contrast, calmodulin remains tightly bound to the inducible and Ca2+-insensitive isoform (iNOS or NOS2) even at a low intracellular Ca2+ activity, acting essentially as a subunit of this isoform.