The cGMP system: components and function.

The cyclic guanosine monophosphate (cGMP) signaling system is one of the most prominent regulators of a variety of physiological and pathophysiological processes in many mammalian and non-mammalian tissues. Targeting this pathway by increasing cGMP levels has been a very successful approach in pharmacology as shown for nitrates, phosphodiesterase (PDE) inhibitors and stimulators of nitric oxide-guanylyl cyclase (NO-GC) and particulate GC (pGC). This is an introductory review to the cGMP signaling system intended to introduce those readers to this system, who do not work in this area. This article does not intend an in-depth review of this system. Signal transduction by cGMP is controlled by the generating enzymes GCs, the degrading enzymes PDEs and the cGMP-regulated enzymes cyclic nucleotide-gated ion channels, cGMP-dependent protein kinases and cGMP-regulated PDEs. Part A gives a very concise introduction to the components. Part B gives a very concise introduction to the functions modulated by cGMP. The article cites many recent reviews for those who want a deeper insight.