Caveolin-1 is a protein that in humans is encoded by the CAV1 gene. The scaffolding protein encoded by this gene is the main component of the caveolae plasma membranes found in most cell types. The protein links integrin subunits to the tyrosine kinase FYN, an initiating step in coupling integrins to the Ras-ERK pathway and promoting cell cycle progression. Nitric oxide synthases (EC 184.108.40.206) (NOSs) are a family of enzymes that catalyze the production of nitric oxide (NO) from L-arginine. NO is an important cellular signaling molecule, having a vital role in many biological processes. It is the intercellular signal that controls vascular tone (hence blood pressure), insulin secretion, airway tone, and peristalsis, and is involved in angiogenesis (growth of new blood vessels) and in the development of nervous system. It is believed to function as a retrograde neurotransmitter and hence is likely to be important in learning. Nitric oxide signalling is mediated in mammals by the calcium/calmodulin controlled isoenzymes eNOS (endothelial NOS) and nNOS (neuronal NOS); the inducible isoform iNOS is involved in immune response, binds calmodulin at all physiologically relevant concentrations, and produces large amounts of NO as a defense mechanism. It is the proximate cause of septic shock and may play a role in many diseases with an autoimmune etiology.