Hydrogen sulfide signalling in the CNS - Comparison with NO.

Hydrogen sulfide (H2 S) together with polysulfides (H2 Sn , n > 2) are signalling molecules like NO with various physiological roles including regulation of neuronal transmission, vascular tone, inflammation and oxygen sensing. H2 S and H2 Sn diffuse to the target proteins for S-sulfurating their cysteine residues that induces the conformational changes to alter the activity. On the other hand, 3-mercaptopyruvate sulfurtransferase transfers sulfur from a substrate 3-mercaptopyruvate to the cysteine residues of acceptor proteins. A similar mechanism has also been identified in S-nitrosylation. S-sulfuration and S-nitrosylation by enzymes proceed only inside the cell, while reactions induced by H2 S, H2 Sn and NO even extend to the surrounding cells. Disturbance of signalling by these molecules as well as S-sulfuration and S-nitrosylation causes many nervous system diseases. This review focuses on the signalling by H2 S and H2 Sn with S-sulfuration comparing to that of NO with S-nitrosylation and discusses on their roles in physiology and pathophysiology.